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EGG-SSRE-9926

November 12, 1991

TECHNICAL REPORT

EVALUATION OF EPRI DRAFT

REPORT NP-7065 - REVIEW

OF NRC/INEL GATE VALVE

TEST PROGRAM

Prepared for the

U.S. NUCLEAR REGULATORY COMMISSION
EGG-SSRE-9926

November 12, 1991

EVALUATION OF EPRI DRAFT

REPORT NP-7065 - REVIEW OF NRC/INEL

GATE VALVE TEST PROGRAM

Robert Steele, Jr.

John C. Watkins

Kevin G. DeWall

NRC Technical Monitors

E. J. Sullivan

T. G. Scarbrough

G. H. Weidenhamer

Idaho National Engineering Laboratory

EG&G Idaho, Inc.

Idaho Falls, Idaho 83415

Prepared for

Technical Assistance Management Section

Office of Nuclear Reactor Regulation

and Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, D.C. 20555

Under DOE Contract No. DE-AC07-761D01570

FIN Nos. L1525 and A6857
EXECUTIVE SUMMARY

This'report documents an INEL 'evaluation of EPRI Draft Report NP-7065,

'Review of'NRC/INEL Gate Valve Test Program," (hereinafter referred to as the

'EPRI report). The EPRI report is critical of the NRC/INEL gate valve test

program and is being used by some utilities as a riationalelfor discounting the

applicability of the INEL gate'valve test'dati. Our' purpose in this review is

- to'resolve the comments of the review team sponsored by EPRI and provide strong

technical bases for areas of agreement a'nd disagreement between the INEL and EPRI

positions. . ; . , r -

' Areas of disagreement between EPRI and the NRC/INEL include predictable

versus nonpredictable' valve :performance, motor-operator sizing 'equations,

typicality of the test hardware,'-applicability of the Phase I and 'the Phase II

test conditions,'assess nnt of valve responseas 'indicated in the measured stem

force,-and the validity'of the NRC documents issued relating to valve testing.

The INEL tested 5-degree flexwedge gate valves. Selection of test valves

was based on surveys of 'equipment 'instalied in nuclear service. Not every

variation produced by-evreiy'vavne manufacturer'was'tested;"however, among the six

valves with seven internal configurations, most of the design features (except

the double-disc design mentioned in the EPRI report) of most of the wedge gate

valves used in"'Generlic Issue 87 nuclear' service were tested.-The'majority of the

valVes that were tested exhibited nonpredictable performance because'they were

unable to close'without damag~e when subjected to the design basisttest loadings. , ~~~~~~I d ;-_J& ' ,' * ; ,

The"EPRI report states that the iimaanufacturers of the'valve-'tested in the

NRC/INEL' piogram hav6iproduced 'valves with'*other design features. It'further

sugg~ests t hat valves with other design' features might perform diffeiently than

' those tiest~e'd in the NRC/INEL'program.' Test experience'indicates that 'the design

feature that has the greatest effect on whether internal 'damage occur's is bodyguide to disc-guide clearance. Large clearances allow the disc to tip

-'excessively dulring clorsure against high loads, resulting in damage to the guides,

disc,"'and seats'. 'Th6eNRC/INEL test results', considered together'with the results

iii
a

of other similar test programs, indicate-that most of the design variations the

EPRI report refers to (single/double disc, thick/thin disc,

hardfaced/nonhardfaced disc guide, etc.) have little effect on the capability of

a valve to perform under Generic Issue 87 loads. These. other similar test

programs tested design variations not tested by NRC/INEL. The EPRI Marshall PORV

and block valve test program performed after TMI resulted in about an even split

between capable and noncapable valves. The double disc gate valve represented

one of the noncapable valves. European testing prior to their development of new

valve designs found similar problems. The threshold disc loading levels where

current valve designs begin to perform nonpredictably are not known.

NRC/INEL testing has shown that the standard industry motor operator sizing

equation used to determine the stem force requirements of a flexwedge gate valve

is incomplete regardless of the disc area term or the disc factor used. This is

because the standard industry equation puts all of the missing terms, including

sliding friction, into an area-specific disc factor that serves as a multiplier.

As such, we disagree with the disc factors that the EPRI report implies the

industry can use in their MOV analyses. EPRI's NMAC equation is a more effective

tool, but it, too, fails to account for the effects of fluid conditions, and it

may. estimate overly high loads for the motor operator if conservative disc

(friction) factors are used.

The EPRI report questions whether the test conditions were applicable to

Generic Issue 87 valves. The typicality of the test hardware was established

prior to procurement by surveys of the hardware installed in nuclear plants; the

test conditions, while not perfect in every case, provided representative Generic

Issue 87 line break conditions for representative Generic Issue 87 valves.

Although the blowdown conditions are not directly applicable to all safetyrelated valves, performance curves developed from a test program that includes

blowdown conditions are applicable not only to Generic Issue 87 valves, but to

other safety-related valves as well.

Reading the trace on a data plot of the measured stem force to draw

inferences about valve response can at times appear to be more of an art than a

science. For a predictable valve, that portion of the closure stroke that occurs

iv
just-after flow isolation, when the disc is riding fully on the seats, is very

well defined on a stem force trace and represents the maximum closing loading for

such a valve. The sliding friction (INEL correlation or the EPRI-NMAC equation)

or disc factor (industry equation) used to size a motor operator for a valve must

be based on a correct identification of this point.

The INEL analyses of the Phase I and Phase II test results were not

complete at the time of the EPRI review. At that time, we were trying to analyse

the test results using standard industry equations. What we observed was a

random variation in the analysis results when we solved for the disc factor. We

were later able to correlate the randomness in the results to fluid subcooling

and pressure effects. It was not until we quit trying to fit the data to the

standard industry equation that we were able to make significant progress in the

analysis of the test results.

The NRC documents reviewed in the EPRI report have some omissions in the

description of circumstances, but after two years of additional analyses, the

conclusions presented in the documents are still valid.

We hope that the analyses and results presented in this report will help

the nuclear power industry resolve any confusion surrounding the NRC/INEL Gate

Valve Research Program. We also hope the material presented in this report will

provide additional insights for EPRI in their upcoming MOV Performance Prediction

Program.

,. V
U

-

vi
CONTENTS

EXECUTIVE SUMMARY ...................

* rvsfll~r,. rme..rslr,-r-.

..II

A6RN'JUWLLUbfUML1Ib. . . . . . . . . . . . . . . . . . . . . . . . . . .

iii

xi

'ABBREVIATIONS . . . . ... . . . . . . . . . . . . xii

E . . . . ..

f I. .1

.

1. INTRODUCTION ... ................

2. BACKGROUND INFORMATION . . . . . . . ' .. 3

3. TECHNICAL ISSUES . . . . . . . ... . . . . . . . . . . .

3.1 Applicability of Results . . . . . . . . . . . .

3.2 Applicability of Test Conditions

3.2.1 Valve Inlet Pressure . . ... . . . . . 3.2.2 Multiple Closures . . . . . . . . . . . . 3.2.3 Blowdown Closure Tests .. ,3.2.4 Blowdown Opening Tests

3.2.5 Normal Flow Tests . . . . . . . . . . . . 3.2.6 No Flow Tests . i. . . . .. . . .

3.2.7.Nitrogen Flow. . .....

. .

. . .

. . . . . .

. . . .

. . . .

7

7

13

13

19

19

21

22

25

27

3.3 Applicability of. Test Hardware ;,. . . . . ..'. . I.-. . . .;I . 28

3.3.1 DifferentValve Designs .-. . . 3.3.2 Valve 1 . . . 3.3.3 DamagedHardware .' .:. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

28

30

- 36

3.4 Assessment of.Test Results .:. . . . . . . . . . . . .-. . ., 37

3.4.1 Identification-of Valve Positions ..

3.4.2 Apparent Disc Factor . . . . . . . . . . 3.4.3 AverageDisctFactor . . . ;...... .

3.4.4 Linear Contact Stress Model . . . . . . . .. . . . . . 3.4.5 Valve Anomalous-Behavior;During.Closure .... . .

3.4.6 Nitrogen Flow Through Valves . . . . . . . . . . . . .

4. CONCLUSIONS .... ....... ....... .......

APPENDIX A - Paragraph by Paragraph review of EPRI Draft Report NP-7065

APPENDIX B - Sections 1, 2, and 3 of NUREG/CR-5558, "Generic Issue 87:

Flexible Wedge ,Gate ,Valve, Test? Program, Phase.:-II Results and

Analysis," January 1991. . . . . . . . . . . . . . . . . . . . . .

37

46

'53

55

56

61

69

A-1

B-1

I vii
a

APPENDIX C - J. C. Watkins, R. Steele, K. G. DeWall, "NRC Test Results and

Operations Experience Provide Insights for a New Gate Valve Stem

Force Correlation," Nineteenth Water Reactor Safety Information

Meeting, October 1991 ...................... . C-l

APPENDIX D - INDUSTRY GATE VALVE SIZING SHEETS . . . . . . . . . . . . . D-1

APPENDIX E - PHASE I AND II INSTRUMENTATION DIAGRAMS AND ACCURACIES . . . E-1

FIGURES

1. Page 1 of the INEL April 18, 1990 NRC Experts Meeting Handout . . . . 8

2. Page 2 of the INEL April 18, 1990 NRC Experts Meeting Handout . . . . 9

3. Background page from the INEL April 18, 1990 NRC Experts Meeting

Handout ...... . . . . . . . . . . . ... ........ . 10

4. Objectives listed in the INEL April 18, 1990 NRC Experts Meeting

Handout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5. Objectives (continued) listed in the INEL April 18, 1990 NRC Experts

Meeting Handout . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6. Isometric drawing of a typical Mark I RWCU supply line . . . . . . . 15

7. Isometric drawing of the Phase II 6-in test loop . . . . . . . . . . 16

8. Drawing of the Phase II 6-in test loop . . . . . . . . . . . . . . . 17

9. Isometric drawing of a typical Mark II RWCU supply line . . . . . . . 18

10. INEL correlation for tests with less than 700F subcooled fluid . . . 23

11. INEL correlation for tests with 700F or greater subcooled fluid . 24

12. INEL correlation and results from selected utility tests . . . . . . 26

13. Photograph of the entire Valve A disc after the Phase I tests . . . . 32

14. Closeup photograph of the Valve A disc after the Phase I tests . . . 33

15. Closeup photograph of the Valve 1 disc after the Phase II tests . . . 35

16. Stem force for Valve 2 during Step 25 of Test 1 . . . . . . . . . . . 42

17. Selected upstream pressures for Valve 2 during Step 25 of Test 1 . 43

viii
18. Downstream dynamic pressure for Valve 2 during Step 25 of Test 1 . . 44

19. Disc factor for Valve 2 closing on line break flow, effect of

subcooling at 1000 psig .... . . . . ...... . . . . . . . . 51

20. Disc factor for Valve 2 closing on line break flow, effect of pressure

at 100I Fsubcooling .. . ....... . . . . . . ....... . 52

21. Stem force history of Valve A closing against 1000 psi, 10F subcooled

fluid at full flow conditions .... . . . ..... . . . . . . . 59

22. Schematic drawing of the Phase I test loop . . . . . . . . . . . . . 62

23. Flow meter differential pressure trace for Test 3 of Valve A,

Phase I ..... . . . . . . . . ..... . . . . . . . . . . . . 63

24. Pressure traces for Test 3 of Valve A, Phase I . . . . . . . . . . . 63

25. Flow meter differential pressure trace for Test 2 of Valve A,

Phase I ...... . . . . . . . . . . . . . . . . . . . . . . .. 65

26. Pressure traces for Test 2 of Valve A, Phase I . . . . . . . . . . . 65

TABLES

1. Phase II gate valve test data assessment . . . . . . . . . . . . . . 39

2. Reassessment of the design basis tests . . . . . . . . . . . . . . . 49

ix
a

--

x
*1

ACKNOWLEDGMENTS

The authors would like to thank MPR.Associates for providing a magnetic

copy of the EPRI report., Having the ,EPRI report in this format allowed us to

more easily and accurately reproduce the textjfor our paragraph by paragraph

review, thus ensuring that there were-no-msae in our presentation of the

content of the EPRI report. We,woul d al so 1i ke to thank EPRI for, allowing us to

reproduce the figures and tablesfrom their report. With thefigures and the

tables from the UpI report included, the reader. can better, understand the

material being discussed. The_ applicable.figures and tables (except the

Section 4 material which has not been reproduced) follow each of the sections

contained in Appendix A.

xi
a

ABBREVIATIONS

ACRS NRC's Advisory Committee on Reactor Safety

ANSI Americal National Standards Institute

ASME American Society of Mechanical Engineers

BWR Boiling Water Reactor

EPRI Electric Power Research Institute

GI Generic Issue

GL Generic Letter

HPCI High Pressure Coolant Injection

INEL Idaho National Engineering Laboratory

KWU Kraftwerk Union AG (German architect-engineer)

MOV Motor-operated valve

NMAC Nuclear Maintenance Application Center

NRC Nuclear Regulatory Commission

NRR NRC Office of Nuclear Reactor Regulation

PORV Power Operated Relief Valve

PWR Pressurized Water Reactor

RCIC Reactor Core Isolation Cooling

RES NRC Office of Nuclear Regulatory Research

RWCU Reactor Water Cleanup

xii
.; . EVALUATION i OF.;EPRI DRAFT

REPORT NP-7065 - REVIEW OF NRC/INELGATE VALVE TEST PROGRAM

1. .1 INTRODUCTION k . . . . Ii.

For the past several years, the Idaho National, Engineering Laboratory

(INEL) has been performing motor-operated -valve (MOV) ,research, under, the

sponsorship of the U.S. Nuclear Regulatory Commission (NRC). The-purpose-of this

research is to assess the capability of motor-operated gate-valves commonly

installed in boiling water reactor (BWR) high pressure coolant injection (HPCI)

and reactor core isolation cooling (RCIC) steam supply lines and reactor water

cleanup (RWCU) systems to close under postulated line break isolation conditions.

The research included two full-scale qualification and line break flow isolation

test programs using typical, RWCU and HPCI gate'valves. .In response to the valve

performance observed in the test programs,.-INELsand NRC raised,,.several issues

addressing potential problems for, MOVs. in these specific BWR systems and-for

nuclear power plant MOVs ingeneral. - -

In response to the issues raised by the results of the NRC/INEL test

programs, the Electric Power Research Institute (EPRI) sponsored a review of the

INEL gate valve testing (hereinafter referred to as an EPRI effort). The results

of the EPRI effort have been published in EPRI Report NP-7065 (Prepublication

Copy), "Review of NRC/INEL Gate Valve Test Program," January 1991 (hereinafter

referred to as the EPRI report). The EPRI report is critical of the NRC/INEL

gate valve test program and is being used by some utilities as a rationale for

discounting the applicability of the NRC/INEL test results.

At the request of the NRC Offices of Nuclear Reactor Regulation (NRR) and

Nuclear Regulatory Research (RES), the INEL reviewed the EPRI report. The

results of that review are presented in this INEL report. We evaluated the

content of the EPRI report, addressed the conclusions, and responded to specific

concerns expressed in the report, especially where problems or disagreements were

1
apparent. Our purpose is to resolve the comments in the EPRI report and provide

strong technical bases for areas of agreement and disagreement between the INEL

and EPRI positions.

The EPRI report addresses three major subjects: (1) a review of early INEL

publications of test results, (2) a report on the NRC-sponsored posttest valve

inspection and measurement' effort, and' (3) recommendations for the EPRI MOV

Performance Prediction Program. Our review is limited to the first subject. We

accept the EPRI' report's documentation of the posttest valve inspection and

measurement effort as an accurate representation of what took place. The EPRI

report's recommendations relative to the EPRI test program do not require our

review in this format.

In Section 2 of this report, we present background information pertinent

to an understanding of the subject. In Section 3, we extract the major technical

issues contained in the EPRI report, organize them in a logical manner, and

discuss each of them from the INEL viewpoint. Our conclusions of the review of

the EPRI report are presented in Section 4. The various appendices provide

supporting information for our review; of special note is Appendix A, which

contains a paragraph by paragraph review of the EPRI report.

2
2. BACKGROUND INFORMATION

-. : ..., . . . : ~ ~ ~~~ . '~ ~~~~~~~~~~~~~~~~~~~~~~~~

.

The INEL, under the sponsorship of the.NRCOffice of Nuclear-Regulatory

Research, is performing-.motor-operated valve research to, contribute to the

resolution of specific generic safety issues and to develop and improve industry

mechanical equipment qualification,, .operation,- and, maintenance consensus

standards. This effort includes a research program that qualified six full-scale

motor-operated gate valves to ANSI/ASME B16.41 and then. tested .each at the

design-basis conditionsfor containment-isolation valves installed in BWR RWCU

process lines and HPCI turbine steam. supply. lines. . The valves- were

parametrically tested at pressures, temperatures, :and flow conditions above, at,

.and.below the worst-case conditions~that could be experienced in the RWCU process

lines and the HPCI turbine steam supply lines as a result of a~downstream pipe

*break.outside containment. One of.the RWCU was also tested at -alves saturated

steam flow conditions to provide insights for the RCIC turbine steam supply line

containment isolation valves, as part of the same generic issue.

A.. .- r -;* ,-,

- The purpose-of this testing was to provide technical input to the NRC

effort regarding Generic Issuej(GI)-87, .."Failure of the HPCI'Steam Line Without

Isolation.". GI-87 also applies to-theRCIC and RWCU-isolation valves.; The test

program has also provided information applicable to the implementation of Generic

Letter (GI) 89-10,, "Safety-Related (Motor-Operated Valve Testing and

Surveillance." . - '; . '. . .

i - -, .lt ,; s ',,

INEL has conducted two sets of experiments for the GI-87 research program.

In Phase I, two full-scale RWCU valves, typical of those used in operating

. plants, were tested with ,high -energy. water. The; testplan for.-Phase I was

reviewed by the NRC, valve vendors, and NRC's Advisory Committee.on. Reactor

Safety (ACRS). The results of the Phase I program were reported in NUREG/CR5406, "BWR Reactor, Water Cleanup-, System Flexible-Wedge GatelIsolation Valve

Qualification and High Energy Flow-,Interruption -Test.";,-Thetest.-results were

unexpected; they challenged the validity of many gate valve design rules. As we

analyzed these unexpected test results; we realized Ain retrospect, that the test

facility and instrumentation were marginal, -the 'two-valve.sample was small, and

3
F

the data from one valve were less useful because.the valve sustained damage as

a result of the high flow'loading. Because of these shortcomings, some experts

in the industry did not accept the results as having general applicability. As

,a result, the NRC determined that a larger Phase' II program was necessary. Both

phases of the test program are more completely explained in Appendix B.

In the Phase II program; the NRC increased the number of valves to six,

representative of those installed in both the' HPCI and RWCU systems. The

Phase'll program benefitted from the lessons learned during the Phase I program

and included tests on an RWCU valve that would be applicable to RCIC valves. The

test plan for Phase II was reviewed by the NRC staff, EPRI, utilities, valve

vendors, and diagnostic equipment vendors. The INEL developed its own advanced

instrumentation and data acquisition system, and a different test facility with

greater capacity was selected. However, we know from experience that 'it is

impossible to anticipate every possible contingency. The EPRI report highlights

some of the lessons we learned from the Phase II testing.

The results of the Phase II program (including the Phase I work) were

presented to the public in (1) NRC Technical Report EGG-SSRE-8970, "Generic

Issue-87 Flexible-Wedge Gate Valve Test Program' Phase II Data Report," dated

March 1, 1990, (2) "GI-87 Gate Valve Test Program Results Review and Issue

Identification," presented at the Second NRC Valve Experts Review Group Meeting,

Bethesda, MD, April 18, 1990, and (3) NUREG/CR-5558, "Generic Issue 87: Flexible

Wedge Gate Valve Test Program, Phase II Results and Analysis." NUREG/CR-5558 was

published at the same time as the EPRI report (January 1991) and was not included

in their review.

In response to the INEL gate valve tests, the NRC has issued the following

documents:

NRC Information Notice No. 89-88, "Recent NRC-Sponsored Testing of MotorOperated Valves," December 26, 1989

NRC Information Notice No. 90-40, "Results of NRC-Sponsored Testing of

Motor-Operated Valves," June 5, 1990

4
' Generic Letter 89-10, Supplement 3, "Consideration of the Results of NRC-

'-''Sponsored Tes'ts of Motor-Operated Vilves," Octbbeir'25, 1990.

To support licensee response to the issues raised in these documents, EPRI

sponsored an independent'rev'iew-of the NRC/INEL.Gate Valve Test program. The

review was performed by MPR Associates with assistance 'from an industry

inspection team and oversight from the EPRI MOV Performance Prediction Program

TechnicaiiAdvisory 'Group'.'The subjectEPRI report'd cuments'the results of that

review. -

The technical 'issues"'extiracted'from the EPRI report fall into two major

categories: the-'EPRI report expresses concern about the applicability of some

of the NRC/INEL test program results,- an'd'many 'conclusions produced by the EPRI

assessment of the data differ from the preliminary conclusions of the NRC and the

INEL. It should be noted that the EPRV1'report` was' based' on the very early gate

valve work: the Phase I NUREG, the Phase II data report, and the April 18, 1990

NRC public meeting. The Phase'! NUREG"(NUREG/CR-5406j'asked mo're questions than

it answered. The Phase II data report (EGG-SSRE-8970) contained eight volumes

' of1 data traces without'any analyses.' -The April' 18th meeting was a general

overview of the test results specific to GI-87 and some of the other interesting

insights observed during the testing. We took great care at the April 18th

meeting to point out that'the analysis of thtedata'had just begun and that we

were only-pointing out inconsistencies 'Letween observedztest results and the

industry precepts 'that were 'origiially 'used -to' size 'valve operators in the

plants. The purpose of the experts meeting was to review the results to date and

to obtain' input'on 'further analysis.-'The EPRI-spdiisored'review of the NRC/INEL

valve test results might' have been 'more e'ffective had 'it occurred later, after

we had analyzed'the Phase' II data mo'r'e thbroughly."

-; A * ; , X, 5 ; \ * ; , '1 - .

As stated in their Yeport":'the"objectives'-o6fthe EPRI review were to

1. "Deve7op an understanding of the scope and applicability of the test

results both for valves installed in the specific BWR systems under

study and to industry 11OVs in general."

5
W

. 2. "Document detailed information on thetest valves, such that the

test results and implications to specific valves could be

evaluated."

3. "Document the principal results of the test program, including

observed valve behavior."

4. "Develop lessons learned from these tests to better plan the EPRI

MOV Performance Prediction Program."

S. mHdentify, generally, gate valve design details which need to be

properly addressed to obtain satisfactory performance under severe

b7owdown isolation conditions."

EPRI's scope in this review was identified as

1. Oa detailed posttest inspection of the valves tested,"

2. "an assessment of the applicability of the valve designs tested to

industry MOVs,"

3. "a limited assessment of the applicability of the conditions tested

both to design basis conditions for the BWR systems under study and

to design basis conditions for industry valves in general, and"

4. "a detailed review of the test data, using primarily published data

plots, focusing on determination of the "apparent disk factor"

implied by the data for all valve strokes performed with

differential pressure and relating these results to the conditions

tested and valve internal damage sustained."

6
3. TECHNICAL ISSUES

3.1 Applicability of Results

The EPRI report expresses concern about the-.applicability of the test

conditions, the test hardware, and the test results to a wide range of industry

applications. The EPRI report does not review the additional-subjects, e.g.

electrical, training, or diagnostic testing portions of our published data.

Instead, the review concentrates on-the valve and thermal hydraulic portions of

the NRC/INEL test programs.

Several statements in the EPRI;,report indicate that we were not careful

enough in defining the applicability of the results 'of the early work. For

example, the EPRI report- states; "It is expected that. the potential for

sustaining-damage such as gouging/michining of valve internals and/or plastic

deformation of valve interna7s is -only significant under very high flow

(b7owdown) conditions where significant DP exists in mid-stroke. Specifically,

such damage and the attendanthigh disk factors would not be expected for the

vast majority of industry valves.' Most industry .va7veis -are in pumped flow

systems and, depending on the system frictional losses, would be expected to

develop significant differential pressures only whenthe valve disk is on or very

near the seats." We have always tried to make it clear that our full scale

testing applied specifically to that small percentage of'BWR MOVs that have

design basis requirements to close during blowdown conditions," and we have never

stated otherwise.

At the time EPRI reviewed our work, the most conclusive INEL document was

the April 18, 1990 NRC experts-meetinghandout. Figures 1 and 2 are the first

two pages of that handouts, and they cle'arly-,show that we intended to talk

primarily about GI-87 at-this meeting. Figure 3, the background page, brings up

GL 89-10; however, Figures 4 and 5 show that- only our seventh objective

specifically discusses GL'89-10. This-objective refers to correlating the data

for in situ testing and extrapolation, which we have since accomplished (see

Appendix C). The bulk of the thermal-hydraulic data presented, pertinent to the

7
GI-87 Gate Valve Test

Program Results Review

And Issue Identification.

Technical presentations by:

R. Steele, K.G. DeWall, and J.C. Watkins

USNRC Technical Monitors

G.H.Weidenhamer

Roy Woods

Second NRC Valve Experts

Review Group Meeting

Bethesda, MD

April 18,1 990

I l

Idaho

National

Engineering

Laboratory

Figure 1. Page 1 of the INEL April 18, 1990 NRC Experts Meeting Handout

I, t I a
I

Purpose of the Presentation

Providethe Review Group and the audience

with a review of the work to date on the

N RtC; GI 87 Gate Valve Test Program -

.; 2 44OO-.

Figure 2. Page 2 of the INEL April 18, 1990 NRC Experts Meeting Handout
Background

* This presentation is based on the results and

analysis of Phase I and Phase 11 qualification

and, high energy flow interruption gate valve tests

performed to provide technical insights for the

NRC effort regarding Generic Issue-87 (GI-87),

"Failure of HPCI Steam Line Without Isolation."

* The results will also be applicable, in part,

to the implementaion of Generic Letter 89-10

(GL-89-10), "Safety-Related Motor-Operated

Valve Testing and Surveillance."

Fcf2 ,.A4 05xMH

Figure 3. Background page from the INEL April 18, 1990 NRC Experts Meeting Handout

t. . .... *

10
The objectives of the Test Programs included the following:

1-.' Determine the valve stem force requird to: - .. close typical RWCU,:RCIC, and HPCI system ^-' fisolation.-valves at typical operating conditions

and under blowdown conditions.

2. Compare valve closing. loads to.opening loads

at various system conditions.

3. Evaluate valve closure force components, such

.asdisc friction, packing drag, stem rejection load, and fluid dynamics.

I '.-A

Wor42u-N4.1I

Figure 4. Objectives listed in the INEL April 18, 1990 NRC Experts Meeting Handout.
Objectives (continued)

4. Meas.ure the. effects of temperature, pressure, and valve design on valve closing and, opening loads.

5. Evaluate the terms and variables in the present

standard valve and motor operator sizing equations.

6. Provide detailed, information to assist in the

NRC effort regarding GI-87.

7. Correlate the data for development of a methodology

for in situ motor-operated valve testing, supporting

the implementation of Generic Letter 89-10.

".02ts-0490012

Figure 5. Objectives listed in the INEL April 18, 1990 NRC Experts Meeting Handout.

F ~ ~ ~ ~ ~ ~ ~ ~ ; ~ ~ ~ ~ . U
EPRI review, was related.to GI-87. We also mentioned that for the 10-in.,valves .; -A .!a *1i' . "'.K.-. t -K.

we-tested-the-unseatingiloads were'-not the highest-opening'-Ioads %ie'encountered

and that even our.low flow data -did 'not support the standard motor-operator

sizing practices of the'industry. '

3.2 Applicability of Test Conditions'

With regard to the applicability of the test conditions relative to both

GI-87 and GL 89-10, two issues need to be recognized. First, it should be

established that the GI-87-valves:areia subset-of the GL 89-10:valves, and they

are specifically-identified in Supplement.3-to,:.the generic letter.- Second, the

additional concerns of GL.89-10,-such as-motor operator sizing, switch.;setting,

-and in-plant to design basis test-extrapolation, cannot be'ignored. Although the

GI-87 blowdown test conditionsido not apply directly to'other valves:designed for

lower loads,- the understanding of valve-.behavior. provided by the GI-87 test

results does address GL:89-10 concerns.

3.2.1 Valve Inlet Pressure. .The .EPRI -report states, -"The DP versus stroke

- behavior for valves with b7owdown design basis conditions in nuclear power plants

-would be..dependent on the details of p7ant-unique piping configuration. The

..piping configuration -is :important because systems. with: high overall7flow

resistance would have more flow pressure losses in the system and less DP across

the valve during mid-stroke. Less severe DP in mid-stroke is more favorable to

,valve-performance, because the valveidisk is not joaded as-heavily while it is

,sliding on the. guides and transitioning- to the, seat. The NRC/INEL test

conditions were more severe in this regard, since. system flow resistance was

7ower.iinjthe tests than in.artypica7lBWR.(see table be7ow). -"

13
p

System BWR Resistance and Basis INEL Test Resistance and Basis

RWCU 32.9 (net K from reactor 1.6 (Phase 1) 2.7 (Phase 2)

vessel to first isolation (net K from pressure tank to

valve, based on 6" pipe) isolation valve, based on 6" pipe)

HPCI 1.5 (net K from reactor 0.6 (net K from pressure tank to

vessel to first isolation isolation valve, based on 10" pipe)

valve, based on 10" pipe)

The opposite was our concern: did we have too much line loss in the test

loop to model the less complicated plant piping systems? Figure 6 is an

isometric drawing of a Mark I RWCU supply line, Figure 7 is an isometric drawing

of the Phase II 6-in. test loop, and Figure 8 provides the dimensions of the

Phase II-test loop. The test loop has about twice the-line losses of a Mark I

RWCU supply line. In contrast, Figure 9 is an isometric drawing of a much more

complicated Mark II RWCU supply line, where the line losses have a greater effect

on the pressure profile at the valve. It is easy to see that line losses in

these systems vary significantly from plant to plant. To address the issue of

line losses, we established, within facility limitations, the test target

pressures at the valves. The parametric testing at higher and lower pressures

provided an adequate range of pressure histories to account for any creditable

line loss scenario.

Conclusion: The valve inlet test pressure conditions were applicable to the GI87 valve subset. The parametric testing bounded the worst case

conditions and was useful in developing a correlation (see

Appendix C) that can be used once a utility has determined the

design basis conditions for a given valve and determined that the

valve design is predictable. (A predictable valve is defined as a

valve that can close under design basis conditions without

sustaining internal valve damage that would cause an unexpected

increase in the stem force necessary to close the valve.)

14
Reactor Water Clebanup High Energy Lines

Mark -I

Conl'aiment -'eok

,'Isolation .'r ,,61a

FCV-69-2

(outside)

Containment - ., ,,.Penetration

Containment

Isolation

.z * ' . ' . . . / FCV-69-1

:,. * * , ' , _ id / ~~~~~~~~~~~~~~~(Inside)

Normally open., 3' 4

; '.' . manual valve

* - 69-500

MG' 102 10

IFigure 6. Isometric drawing of a typical Mark I RWCU supply line.
SIEMENS

Valve Test Facility VPE

157 bar

Saturated steam. water. mixture

Blowdown from an accumulator

22 m3

approx. 200 kg / s

E321

Siemens AG - Bereich KWU

Figure 7. Isometric drawing of the Phase II 6-in test loop.

16
I

P2 - [~~~~~~~~jV VD~ VD I tDI rS _ 1 ~~~~~~~ m . =:--- ~~~~~~~~~~~~PS PDP DS

't0^''T -I ' ' '' f. M M M ?''TiT

Design pressure: 160 bar

Simplified.flow scheme of-the valve test rig VPE

pool

Figure 8. Schematic drawing of the Phase II 6-in test loop.
Reactor Water Cleanup High Energy Lines

Mark II

Nonsalety

Valve

G33MOV030B

Containment

Isolalion

Outside

G33MOV034

Containment

Isolation

Inside

G33MOV033

Nonsalety

Valve

G33MOV03 1

MG102 109

Figure 9. Isometric drawing of a typical Mark II RWCU supply line.

I. I

A
3.2.2 Multiple Closures. The EPRI report points out that GI'-87 valves need to

close only once at design basis conditions when it states "11OVs in the RCIC, HPCI

and RWCU systems are only required to isolate a. break once. Because of the

potential for valve damage under b7owdown-'conditions, on7y the first b7owdown

isolation closure test for each valve design is considered potentially applicable

to valves installed in-these systems." We agree, and we designed the research

programs so that in every case (with the exception of Valve A), the first

blowdown was the nominal design basis pressure and temperature test for the valve

:being tested. -'Four of the six -valves tested in 'Phase II sustained internal

damage due'to high disc loadings during their design basis test. Thus, their

performance is referred to as nonpredictable. A nonpredictable valve is defined

as a valve that sustains internal valve'damag, such as galling, machining of

surfaces, or plastic deformation, during closure, such that the stem force

reflects more than simple sliding friction. We performed the additional

parametric tests primarily on the'predictable valves, to'obtain sufficient data

to evaluate'industry sizing methods "and to'evaluate -val'Ve performance under a

range of loadihgs. The' parametrictestsiwere-'necessary, 'be'cause it'is not

possible to define performance curves- fribma ''sin'gle ditat point.''

*The first blowdown test for'Valve Ain Phase I was not at'the design'basis

conditions.-Due to facility start-up problems, we tested Valve A'at- the design

-basis pressure but at less than design-basis temperature-(500F subcooled instead

of 100F). The INEL test engineer mide :this decision'to avoid losing a week of

test facility time. We did not expect the'results that we6btained:from Valve A

.(the- valve was damaged 'during the test), -and .'in light of those -results, it is

easy to question the decision in hindsight., -

Conclusion: For seven-of the eight valves tested during-Phase I'andPhise'II,

the.-nominal design-basis test wasiperformed-first to evaluate-the

: - * ability of -the valves-tb close once._:Thelmultiple closures after

the initial design.basiste-st were defined in.the approved;test plan

and were applicable to the research program.

! ~ ~ ~ ~ ~ ~ , . ,4 I -.', . - ,. . -, ,j , ; .*- . -;, -

-3.2.3 Blowdown-Closure Tests. -Several;:statements.in-the EPRI-report indicate

that the blowdown conditions simulated in tests performed by the INEL are not

19'
*.

applicable to all safety-related valves in nuclear service. For example, the

EPRI report states:

"Applicability of B7owdown Conditions to Overall Valve PoDulation

- the NRC/INEL b7owdown closure test conditions are directly

applicable to a small portion of the MOV population - about 4X of

BWR valves and none of PWR valves.

- dependent on plant-unique configurations and 'design-basis"

interpretation, the NRC/INEL b7owdown closure test conditions might

be potentially applicable to additional valves (up to 15% for BWRs

and 9% for PWRs).

- the. NRC/INEL b7owdown opening conditions are not generally

applicable to valve design basis conditions in nuclear power

plants."

Applicability of the blowdown test conditions to all of the safety related

valves was never intended by any of the INEL reports. What we have learned for

5-degree flexible wedge gate valves is that when the on-the-seat normalized

normal loading achieves a minimum threshold, the response of the valve becomes

very repeatable (provided the valve does not experience damage). We have

established this minimum threshold level at 400 lbf/in2. As such, if the

normalized normal loading is above this threshold, the INEL correlation (see

Appendix C) will bound the, maximum valve stem loading from very low flows to

blowdown conditions. The INEL correlation was developed from the results of our

normal and low flow closure testing and our design basis blowdown closure

testing. The development of the correlation is explained in Appendix C, which

is a copy of our most recent paper presented at the Nineteenth Annual Water

Reactor Safety Information Meeting. We are currently working with selected

utilities to assess whether this correlation can be used with even lower test

loadings, thereby encompassing nearly all 5-degree flexible wedge gate valves

addressed by GL 89-10. Thus, in this indirect way, the NRC/INEL test results are

applicable to valves other than GI-87 valves.

Conclusion: The blowdown tests provide data for the worst case loadings. To

build complete valve performance curves, one must have the worst

20
-- - case loading; as -'well gas lesser loadings to determine'Aif a

relationship existsin the data and to establish the limits of that

relationship. Although. blowdown" conditions' are not directly

applicable to all safety-related valves, performance curves

developed from a testprogram that includes blowdown conditions are

applicable~to GL 89-1O. '-'-''

3.2.4 Blowdown'Opening Tests. 'x The EPRI report states that "in general, nuclear

power plant valves do not ;have -to -open against design basis b7owdown opening

conditions such:as tested in'these'NRC/INEL-tests. However, some valves need to

open in systems where the flow rate may be significant as the valve opens, and

there could be the potential for this type of behavior. Accordingly, to the

'extent this phenomenon-is die'to' fof7 effects, 'it would need to be adequately

accounted form invalve opening 'applications. 'For most nuc7ear-power plant

valves, which face opening-conditionsi.far less severe than the NRC/INEL b7owdown

conditions, -this effect is not expected to be as strong as observed in' the

NRC/INEL tests."''

' We~performed normal flow openings, "no flow openings,' and maximum flow

openings. The"EPRI report expresses some concern about the'value-'of the'blowdown

opening tests.' We'have never quoted a safety function for i valve to initiate

blowdown flow, except perhaps for the PORV-block valve. However, not all systems

in a nuclear plant are pumped systems- :Some 'are connected to large vessels where

momentary to slightly more sustained high' flows could .be anticipated -upon

opening, depending on the downstream volume.

The results 'of these'te'sts' do show'some interesting responses and-yield

:insights into'the phenom'ena-affectingrvalve performance.` :Thus;,the:results of

-. these tests became'very useful :to us in the overallIanalysis. In particular, we

observed that!the largest-stem force didinot 'always -occuir'-'at 'unseating, as

typically assumed by the industry. NWe do not yet'know the p'ointatithichflow

begins to-.be;a!significant..contrtibutor,'to opening.loads;. However, even.the

rapidly decaying flow:forces observed--during -the large-valve:no-flow opening

tests, were sufficient to.produce the. largest stem forces after.'the :valve.. was

partially open. If such a response can so easily be obtained, we hesitate to

21
.

term it "unusual behavior" as the EPRI report has. The INEL will continue to

assess the results of the opening tests and will hopefully be able to better

quantify valve opening response at a later date.

Conclusion: The blowdown opening tests provided very important information. The

highest opening stem forces do not always occur during unseating,

and the resultant flow during opening can have a significant effect

on the stem force. We do not yet know the point at which flow

becomes a factor in valve opening. These test results may be useful

to licensees in determining the extent of bypass for the opening

torque switch.

3.2.5 Normal Flow Tests. Regarding the NRC/INEL normal flow tests, the EPRI

report states, "the INEL normal flow conditions are quite unlike typical gate

valve conditions in power plants. Although great care should be used in

interpreting and applying results of these tests, it is expected that some data

would be useful in valve evaluations. However, the evaluations described in

Sections 5 and 6 show little or no meaningful information could be obtained at

the point of flow "isolation" (due to very low DP) and that disk factors

determined at other points (between isolation and seating for example) gave

suspicious results (i.e., they were substantially out of agreement with other

tests). Until these data are studied in more detail, it does not appear stem

forces or disk factors determined from the data plots should be directly applied

to nuclear power plant valves."

We agree that not all of the tests provided useful information. However,

the purpose of the normal flow tests was not simply:to duplicate the normal flow

conditions for a given valve in a plant, but instead to provide data that could

be used to characterize valve behavior in general. In those normal flow tests

where we were able to establish an on-the-seat normalized normal loading greater

than 400 lbf/in2, the results contributed to the correlation shown in Figures 10

and 11. Since completing the correlation, we have been working with utilities

that are performing differential pressure testing with proven diagnostic

measurement equipment. We have been able to analyze some pumped low flow

22
L.

Less Than 700 FtSubcooled Fluid

O7 , I ; .,-, . , , . , . 

07% -100 - *Valve 3

,c W l \ "'A Valve 5 .4-~~~~~~~~~~~~~~~~~N

-200 .. Valve A

_Valve B

c' -300

-~J

,C -400 Thinflm mmay. *

not apply.,

-500

.N

~ -600 E

Z -700

-8 00... .'....'*..'''

0. 200 400 600 800 1,000 1,200 1,400 .1,600

.- -- Normalized Normal Load (Ib f in2) I I

Figure 10. INEL correlation for tests with less than 70°F subcooled fluid. M455 kqd-I091 -22
700F or Greater Subcooled Fluid

0 . . . . . . I . .- - .- . . . . . . . . .. . . . a . . .

NC:

-

-0

-J0)

C1

-o

C)

~0

N

EL.

To0

-100

-200

-300

-400

-500

-600

-700

-800

0 200 400 600

Normalized

800 1,000 1,200

Normal Load (Ibf/in2)

1,400 1,600

Figure 11. INEL correlation for tests with 700F or greater subcooled fluid. M455 kigw-1091-23b

I
differential pressure tests where the on-the-seat normalized normal loading did

not reach the 400 lbf/in2 cutoff. One utility tested one 4-in., seven 8-in., and

one'12-in. gate valve at pressures from 80 to 200 psig. A second utility tested

four gate valves (one each at 3, 6, 10, and 12 in.) at pressures from 70 to

150 psig. All of the testing was done at fluid conditions greater than 700F

subcooled.- Figure 12 shows the result of that analysis and how'the valves fit

the correlation. .- _' - _' ' - -- '-''--' -' ' ' - ' 

Conclusion: We believe that when the results of our nrormal'flow testing and the

normal flow testing by others, with proven'diagn6stic measurement

equipment, are properly used, they -may be applicable for

" characterizing the response of predictable gate valves. Many valves

..-cannot be design'basis tested in situ. If a utility can determine

that a valve design is predictable, low flow in situ testing could

be used to validate that the valve is responding in.a manner similar

to valves tested by'Ithe INEL. If such a similarity can be shown,

the INEL correlation'can be used to bound the design basis loads for

that particular valve.

3.2.6 No-Flow. Tests. Regarding the NRC/INEL no-flow tests, the'EPRI report

states that- 'the presence of an initially:-depressurized downstream volume

actually permitted a brief period of flow -- much less than one second for cold

conditions, about one second for hot water conditions (6" valves) and several

seconds for steam conditions (10" valves). The longer duration for the hot

conditions is'attributed to the flashing two-phase flow or steam inrush flow as

the valve initially opens and starts to pressurize the downstream volume. For

10" va7ves -tested in steam, these "no flow" tests actually established several

seconds of -b0owdown-like conditions. As discussed earlier, opening against

blowdown flow is not a condition applicable to most gate valves in nuclear power

plants, and thus 10" hot "no-flow" tests are not directly applicable to most

industry MOVs." . -

The leakage tests and the cold ind hot cyclic no-flow tests were part of

the ANSI/ASME B16.41 valve qualification tests.; A no-flow test with a

25
70°F or Greater Subcooled Fluid 0 ,x,= , I .

C

.0

-0

*0

CU

0

-4

ci)

C

en

la

.N

E

0

Z

-100

-200

-300

-400

-500

-600

-700

04orQ

-800

0 200 400 600

Normalized

800

Normal

1,000

Load (lbf

1,200

/in2)

1,400 1,600

W54 to 0691-14

Figure 12. INEL correlation and results from selected utility tests

t I I I
. pressurized fluid upstream of the~valve'will produce a-momentary motion'of the

* -fluid when the ivalveis opened.,.This phenomenon will be more pronounced if the

fluid is-'highly compressible. :The-term-"no flow"! is not an attempt to ignore

this momentary'phenomenon, but rather to distinguish these tests from tests with

sustained-forced flow. ;Note that during the.no-flow;tests, there was no flow at

the discharge end of the test facility.,

.These tests were performed:because the NRC wanted to be assured that the

.valvessubjected to design basis flowrinterruption tests -would have passed the

nuclear valve qualification tests. The tests were applicable-for what they'were

intended. The no-flow tests (and normal flow tests) performed before and after

,each blowdown were designed to represent possible in-plant-performance tests and

:were performed to -obtain -data for possible extrapolation analysis. We were

hoping :to find something in the collected data that.could.indicate how the valves

- might perform at design basis blowdown conditions. - To date we'have not been able

to predict valve performance-using data.from no-flow tests.' Theonly major point

we gained from this qualification:data~was the difference -in response of the

valves going from cold to hot cycling. The EPRI report suggests some possible

reasons for this difference.

Conclusion: The ANSI/ASME B16.41 valve qualification tests demonstrated that

- ., 'most-of thefvalves used in the INEL:test:program.would-have passed

, * ,,- the standard qualification test used by the industry. The fact.that

* ,some of thefvalves.were damaged during designibasis-blowdown--tests

-.* .,. after having passed.the standard qualification-test has' caused the

ASME to take another look at the qualification standard.

.. A, k~~~~~~~ -i. t... . -,,, o, ,,,.,,

,,,3.2.7 Nitrogen-Flow.,The,.EPRI report~points-out that some of the Phase-I tests

,had nitrogen.-flowing through-the valves. This was-,an unfortunate facility

. problem. .The EPRI.report-also points out that dry nitrogen might-increase the

friction factor of a valve. Flow of a nitrogen/steam mixture did occur, but not

dry nitrogen flow. Our review of the video tapes of the Phase I blowdown tests

clearly, shows -that water vapor was -being discharged during .:all the tests,

*including those where nitrogen flowwas.,involved.r-Figures -10Oand 11 show -all the

on-the-seat sliding versus normal loads for the Phase I and Phase II valves (the

27
a

friction factor is defined as the sliding load divided by the normal load, or the

slope of the solid line on each of these figures). Two of the Valve A tests in

Figure 10 (darkened circles) had nitrogen flow through the valve; these two data

points lie near a normalized normal loading of 400 lbf/in2. As can be seen, the

on-the-seat sliding versus normal loads for these Valve A tests line up well with

those of all of the rest of the valves. This comparison indicates that the

nitrogen/water vapor mixture did not affect the on-the-seat performance of the

valves. This issue is discussed in depth in Section 3.4.6, and the thick

film/thin film lubrication discussion in Appendix C provides further insight into

the observed behavior.

Conclusion: Dry nitrogen flow did not occur. Where flow of a nitrogen/steam

mixture occurred, the analysis of the on-the-seat performance of the

valves shows that-the presence of some nitrogen did not increase the

friction between the disc and the seat. Even if the Phase I results

with nitrogen flow were excluded, there would be no change in the

conclusions presented to date.

3.3 Applicability of Test Hardware

3.3.1 Different Valve Designs. The EPRI report states that all of the tested

valves, except Valve 1 in Phase II, are representative of valves in nuclear

service. We discuss the exception in Section 3.3.2 of this report. The EPRI

report also points out that the manufacturers have provided other designs to the

power plants and suggests that these other designs may perform differently than

those we tested. This statement might lead the reader to infer that other design

variants might perform adequately. Most of the design variants listed in the

EPRI report were tested as part of the INEL program. The major design variant

that was not tested was- the double disc gate valve; however, this design was

tested by EPRI in an earlier program.

In that program, conducted in 1980, EPRI tested PORVs and block valves at

the Duke Power Marshall Steam Station. The block valves were 3- and 4-in. gate

28
valves tested at near blowdown conditions, with the PORV providing an orifice to

full flow. The tests were basically uninstrumented, go/no-go tests. Two

manufacturers, Velan and Anchor/Darling, were common between the EPRI/Marshall

and the INEL tests. In the EPRI/Marshall test, the Velan flexwedge gate valve

closed, but the Anchor/Darling double disc gate valve did not close with the

originally sized operator, requiring a seat design change and a larger operator

prior to retest. -No public domain data are available to indicate why the

Anchor/Darling valve failed, what stem force was required to close each valve,

or how~the results compare to industry calculations..-

In addition to the NRC/INEL and EPRI/Marshall tests, full-scale design

basis testing has been performed in Great Britain and Germany. In NRC

Information Notice No. 90-72, "Testing of Parallel.Disc Gate Valves-in Europe,"

the NRC discusses the British-and German experience in full-scale testing of

parallel disc gate valves. ,That testing resulted in internal damage to the gate

valves, including abrasion and galling of the disc and seat sliding surfaces.

Because of this damage, significantly more stem force was required to close the

valves than would be predictedusing the standard industry equations. ; Their

early parallel disc gate valve research provides results similar to the, results

of NRC/INEL testing. In later testing, after significant design changes, both

the English and the Germans have developed-predictable gate valve designs, albeit

at a higher friction factor than istypically used in the U.S. 7

The EPRI report suggests that valves with different designs (machined

and/or hardfaced guides, as-cast/machined and welded body guides, thinner/thicker

discs) will perform differently than .those testedjin the .NRC/INEL program. As

for hardfacing, there was no difference in the NRC/INEL tests, inthe performance

between * .n .Valve z....- B with hardfaced discguides cgides,a and Valv Valve 2.(same 2 (same; valve),,with non- - . . .. K...

hardfaced disc guides. As for thinner discs, Valve 3, the Walworth valve, was

a600,71b class valve with a thin disc. The on-seat performance waslthevsame as

with the thick-disc valves. The as-cast body guides may have.some effect on

valve performance (higher frictions). We did not test every design variant of

every manufacturer. However, the valves we tested represented most of the

different variations in design possibilities,.except for the double.disc design

noted. The one design feature that has the greatest effect on valve operability

29
is body-guide/disc-guide clearance. Large clearances allow the disc to tip

excessively during closure under high flow loads, resulting in damage to the

disc, guides, and seats.

Conclusion: The valve designs tested in the NRC/INEL test program are typical of

most flexwedge gate valves installed in GI-87 nuclear applications.

There are no solid test results in the public domain to indicate

that any of the other valve designs referred to in the EPRI report

would perform any better than those tested in the test programs

mentioned above. The INEL believes that any valve design should be

tested before being placed in nuclear safety service.

3.3.2 Valve 1. Several statements in the EPRI report express concern about the

representativeness of Valve 1. For example, the EPRI report states that

"Anchor/Dar7ing indicates that Valve 1 is not representative of Anchor/Darling

valves supplied to the nuclear industry. Specifically, the Valve 1 downstream

disk hardfacing is thinner and the edge sharper than Anchor/Dar7ing requires in

their manufacturing process. These conditions are considered detrimental to

valve performance. Valve 1 was refurbished between Phase 1 and Phase 2 of the

NRC/INEL tests. The atypical condition of the disk hardfacing could have been

the result of this refurbishment which was not performed by Anchor/Dar7ing. Test

results for Valve 1 are not considered applicable to typical Anchor/Darling

valves meeting the manufacturer's hardfacing and manufacturing requirements."

The EPRI report further states that "After the Phase 1 test program,

Valve A was refurbished to be used as Valve I in the Phase 2 test program. The

refurbishment was performed by Crane Valve Services. Unfortunately, this

refurbishment was not performed in accordance with the Crane nuclear Q/A program,

and the avai7ab7e'records are minimal. It is not possible to tell from the

records what operations were carried out in the refurbishment." The EPRI report

concludes that -'Anchor/Dar7ing has determined that Valve 1 is not representative

of Anchor/Darling valves and that data from Valve 1 tests are not applicable to

Anchor/Dar7ing valves in nuclear power plants. The observed configuration of

Valve 1 could have been the-result of the disk face being machined down during

refurbishment at Crane. Such'a process could thin the existing Ste7lite layer

30
and remove an existing bevel at the edge. Unfortunately, available documentation

is not sufficient to evaluate this hypothesis, although it is plausible."

It is important to note that both Phase II Anchor/Darling valve

refurbishments (Valves 1 and 4) were performed by Crane-Aloyco. The EPRI report

states that "Valve 4 is an Anchor/Dar7ing 10-inch flexible wedge gate valve with

an ANSI class pressure rating of 900 7bs. This valve was fabricated by

Anchor/Darling in 1982 for Hope Creek Unit 2, which was subsequently canceled.

The figures and-information.in Section 4 and Appendix D of this report show the

Valve 4 configuration. This valve had machined guide slots in the carbon-steel

disk, cast guide rails in the carbon-steel body, and Ste7lite hardfacing on the

disk and seat faces.' Anchor/Dar7ing indicates that Valve 4 is similar in design

features -to a large population of 'flexible wedge-gate valves they have

manufactured and supplied to nuclear power plants."-

The refurbishments were performed at Crane-Aloyco because Anchor/Darling

proposed an unrealistic schedule to refurbish the valves. The work at CraneAloyco was performed through their engineering department at the suggestion of

Crane-Aloyco. Standard shop work would not have assured us that original design

features important to assessing valve performance would-have been maintained.

We are completely satisfied with the work done at Crane-Aloyco.

Figures 13 and 14 are photographs of the Valve A disc taken after the

Phase I tests. These photographs show the condition of the seating surface and

the sharp edge discussed later in this section. The valvewwas manufactured for

the Phase I test 'program by Anchor/Darling, and to quote 'the' EPRI report,

"Anchor/Darling indicates 'that-Va7ve A is similar in'design features to a large

popu7ation'of.flexible wedge gate valves they have manufactured and supplied to

nuclear power-.p7ants.".' Valves 'supplied to nuclear.power plants with similar

design",features-to 'Valve A ~wouldctherefore be expected to-perform in a similar

fashion when exposed to similar conditions. '-Valve-A performed unpredictably in

the Phase I test 'prog-r'amrdue to iGternal damage caused by the flow loadings.

After the Phase I tests and in preparation for the Phase II program,

Valve A was refurbished by Crane Valve Services, Crane-Aloyco, Inc. and

31
-

.

Figure 13. Photograph of the entire Valve A disc after the Phase I tests

.
wwh

Figure 14.'Closeup photbgraph'of the Valve A disc after th06Phase'I tests':

14-,Clo p ~ .. . .e, > . . .. .
U.

redesignated Valve 1 for Phase II. The work scope for this purchase order is

correctly quoted in the EPRI report on page 3-3 as follows:

'Inspect Anchor/Darling valve - 6", 900 pound, Valve serial No. E-A345-1-1

and refurbish. In addition, manufacture a new stem nut for an SMB-0

Limitorque Motor Operator. Refurbishment will require disc and seat

repair. The downstream disc face and body seat were previously damaged in

testing."

Numerous telephone discussions between INEL and Crane-Aloyco controlled the

refurbishment process, which included repeated directions forbidding Crane-Aloyco

from any work that was not previously agreed on. We were fully aware of how

important it was that the work leave the original design features intact.

Postwork conversations with Crane-Aloyco have assured INEL that no refurbishment

work was performed other than that agreed to. Crane-Aloyco did not modify the

undamaged upstream disc surface of Valve A, which became the downstream surface

of Valve 1.

Ih the Phase II testing, Valve A was designated Valve 1 to help separate

test results between the two test programs. The valve was installed in the

system with its flow direction reversed from Phase I so that the downstream disc

surface and valve body seat ring would be original Anchor/Darling surfaces.

Reversing the flow direction through the valve does not impact the test results,

as such valves have bidirectional application. The Anchor/Darling 6-in. valve

was disassembled immediately after the Phase II testing to verify that the Crane

refurbished surface was not downstream. As verified by INEL and NRC, the

original Anchor/Darling surface was in the proper downstream orientation.

Figure 15 is a photograph of the same surface after Phase II, again showing the

sharp edge that the EPRI report identified as atypical of Anchor/Darling disc

configurations. The photographs and the posttest verifications provide clear

evidence that the-downstream seat and disc on the Anchor/Darling 6-inch valve

tested in Phase II were original Anchor/Darling configurations.

Conclusion: All of the evidence shows that Valve 1 is representative of hardware

delivered by the manufacturer to the INEL, under the premise of

being representative of their hardware delivered to the nuclear

34
I &'.

"i -z . . I 

. ., I I i i

w

C,'

Figure is. Closeup photograph of the Valve i disc after the Phase II tests .. \
.

industry. Posttest examinations showed that Valves 1 and 4.had

exactly the same failure mechanisms when subjected to design basis

flow.

3.3.3 Damaged Hardware. After the Phase I tests we were criticized for not

performing valve inspections between tests and for further testing damaged

hardware. Valve inspections between tests were considered for the Phase II test

program, but we later decided against them because of cost. Experience had shown

us that valve damage can be detected through a sensitive stem force measurement.

Using such measurements during the Phase II testing, we were able to detect every

occurrence of valve damage. This valve damage was subsequently confirmed during

posttest inspections.

We might explain here in more detail why we did not perform inspections

between tests during the Phase II testing. Our test program was primarily a hot

test program. A large expenditure of time and resources went to heating the

large volumes of water used to test these valves. These volumes could not be

held at temperature for long periods of time because. of the associated labor and

energy costs. A hot water or steam test gets a valve very hot. Once a valve is

heated, it needs 16 to 24 hrs to cool before an inspection could be performed.

Such a delay is expensive. The INEL method of detecting valve damage worked,

allowing the tests to be conducted with available funds.

Some valves were tested after damage was detected; we tested Valves 5 and 6

after damage was detected in the first blowdown closure of each. Further testing

was performed because we believed that additional information supporting the

objectives of the test program could be obtained, such as understanding the

difference between mid-stroke performance and on-the-seat performance, and this

was our last chance at testing the large valves during this test program. The

additional information was useful in the development of the INEL stem force

correlation, the,'analysis of marginally sized motors, and the analysis of

predictable/nonpredictable valve behavior.

Conclusion: We used a sensitive stem force measurement to detect valve damage.

Although damage occurred to valves 5 and 6, we continued-to test

36
- I them. ,The additional ,testing performed with these damaged valves

,, provided'-some useful information. For `allt the predictable

(undamaged) valves, the 'on-the-seat stem forces were the highest

stem forces measured. Some of the nonpredictable valves, where high

stem forces from guide daimiage occurred during the stroke, recovered

once they reached the final seating part of the stroke.- Properly

used, these data can help us understand valve performance. Our

biggest challenge 'for-future, testing will be determining which Jo ~~~- i, , i

valves are nonpredictable and at what disc loadings they become

nonpredictable.'

3.4 Assessment of Test Results,

The' EPRI report'Is'analyses 'of the' INEL test data are based largely on two

separate issues: identification of-the po'sition of the valve at which to assess

performance, and the assessment' of apparent disc factor. The following

discussion first addresses these' two issues, then addresses additional issues

discussed in the EPRI report, such as an average disc factor, the linear contact

stress model, anomalous'valve behavior during closure strokes, and the effect of

nitrogen flowing through' a valve.

3.4.1 Identification of Valve'Positions. The EPRI report identified four valve

positions at which to assess valve response. ' These four positions were

identified as zero stem position, flow isolation, wedging, ,andthe position at

which'the miaximum u m 'sem- force occurred. We have evaluated each in light of our

assessment of -the -test results, in light 7of how'the' EPRI report actually defines

'each positioin,' and how each was used in~the analyses'ofithe INEL test data. The

EPRI'report states:' -

-- (1) "'At zero 'stem position, is-indicated. by''the_ "Va7ve-Stem Position"

: data p7ot. IINEL reported that, for Phasef2 testing, this position

'indicator was calibrated'before testing 'so'that ityould read zero

-,'.when the disk-comp7et'ely coveredsthe f7ow'area' Valve stem position

information is not interpretab7e in 'this way ''for Phase 1 testing.

Note that the interpretation of stem position is subject to

hysteresis effects due to the stem/disk clearance (i.e., for a given

stem position, the disk can be at either of two locations, depending

37
a

on whether the stem is pushing or pulling the disk). Therefore,

zero stem position may not always represent the instant that a

"true" seal between disk and seat is made."

We recognize that a slight hysteresis effect exists; however, our concern

is more fundamental. For test repeatability purposes during the Phase II

testing, we set each stem position indicator such that it read zero when the disc

initially covered the visual flow area as viewed down the pipe and through the

valve. At this point in the valve closure stroke, the flow is not isolated

because the disc is not riding totally on the seats. The fluid is able to flow

between the upstream seat and the disc, under the disc, and between the disc and

the downstream seat. However, since the disc completely covers the visual flow

area, the area term in the standard industry equation has reached its maximum.

In its discussion on the effect of hysteresis, the EPRI report associates zero

stem position with true flow isolation when it states that "zero stem position

may not always represent the instant that a "true" seal between disk and seat is

made." We have never stated that a zero stem position relates to actual flow

isolation. In fact, we recognize that it does not. The INEL assessment of the

Phase II test data used to develop the INEL correlation, as shown in Table 1,

consistently shows stem positions at flow isolation not at our designated zero

position, but instead somewhere between zero and final wedging. No useful

information will be determined from the zero stem position, except that the area.

term in the standard industry equation is at its maximum.

(2) "At flow isolation (or unisolation). For closing strokes, isolation

was generally identified as the point when downstream static

pressure fell to. zero. For opening strokes, isolation (or

unisolation) was identified as the point when downstream pressure

increased above zero. This method did not work for normal flow

tests, where a downstream orifice was used to.control f7ow-and

resulted in the downstream pressure remaining at a high level beyond

valve closure, (i.e. the DP was small). Further, it appears dynamic

pressure (which is measured with a tap facing the flow as opposed to

a flush tap which is used to measure static pressure) may be a more

sensitive indicator of true isolation. The exact determination of

flow isolation should be studied more carefully in a long-term

evaluation of the test data."

38
Table 1. '- Phase II gate valve test data'assessment

- I . . . . . 1. . .I . .

Force (lb,) _ Pressure (psi) I r, I I

-: Test

Valve Numb(

2 1

2 1

2 6b

2 6b

2 6b

2 6bl

2 6a

2 6a

2 6a

2 6a1

2 6al

.2 6c

2 6c

2 6c

2 6c

2 2

2 2

2 2

'2 i 3

2 '3

3, 1

3 1

3,. la

3 la

3 5

3 5

5 1

S i

'S la'

S Stem , , -- -

,r Step

25

26

18

25

26

26

18

25

26

.25

26

13

18

25

26

i8

25

26

25

26

25

26

25

2. 26,

25

26

25

Position

-7.34

-7.38

-7.10

-7.26

-7.08

-7.22

-7.54

-7.37

-7.14

-7.07

-7.35

-7.13

-7.08

-7.29

-7.39

-7.46

-7.06

-7.12

-7.10

-7.27

-7.13

-7.30

-7.17

-7.33

-7.18

-7.23

-7.47

-7.28

-7.21

i-7.33

Stem Normal.

12929

13578

10477

12173

12453

13654

7880

7859:

7703

8688

.8866

15626

987

1021

571

888

953

1031

413

r To^( S50

548

, i,609

633

952

Sliding .,Up

-424 959.6

-447 1002.4

-332 887.5

-404 856.4

'409' ' 922.4

-451 990.6

-254 601.7

-260 !.525.5

.-254' '; 524.7

-288 585.7

-294 603.1

-490 1414.6

-464 1431.2

-510 1276.3

-533 1317.7

-528 1215.7

-422 1056.1

'-424-' 1027.6

15046,,, 970, -, r: ~_ t. I 3 ; J i . -I '' I 

, 15798 1315 i i . i;~, . i, -:7 . ,,i

16452 1359

16083 1234

Delta

948.5

980.3

540.6

851.3

915.8

989.6

389.7

'526.5

524.5

'582.8

606.7

907.9

927.8

1268.3

1310.8

1186.4

1052.5

'1024.3

753.2

890.8

237.0

861.0

909.1'

893.8

1106.8

1136.2

876.8.

810.9

1021.3

981.2

--Subcooled

Fluid (°F)

11.5

16.3

95.9

36.2

36.0

48.4

91.9

18.8

'10.9

42.5

39.0

124.4

115.4

47.0

39.7

9.5

9.0

-8.4

- 371.7

388.6

' 17.2

5.9

7.5

7.1

7.3

, . 11.0

*9.6

6.9

5.6

7.7

'13096

13079'

12751'

;14512

4355

8628

10804

11032

12235

,13281

24756

22547

30474

'29045

1091

1063-

793

'936

247

887

,., 942-

928 -

~1144

1177. .-. r

904

835

1055

1013

-438'

-496

'-13

-298

- -- 386

--396,

-435

-477

-336

-304

-421

-400

746.4

'886.7

1012.0

856.1

-915.1

894.4,

1117.4

1140.4

879.9

813.0

1026.3

985.7'

i

S la -'26'

- 39
.

Flow isolation is the most meaningful stem position at which to assess the

response of a predictable-valve as it closes. At flow isolation, the disc is

riding fully on the valve body seats, and the upstream pressure, the bonnet

pressure, and the under the disc pressures should equalize since there is no flow

through the valve. The differential pressure should be close to its maximum,

depending on how fast the downstream pressure decays, and the disc area term is

still at its maximum. For a predictable valve, this is also the point where the

stem force is the highest prior to wedging. We agree with the EPRI report that

flow isolation is a position at which the performance of the valve should be

assessed.

The EPRI report-interprets flow isolation during a closure stroke as "the

point when downstream static pressure fell to zero." For opening strokes,

"isolation was identified as the point when downstream pressure increased above

zero." The discussion recognizes the coarseness of this measurement and suggests

that the "dynamic pressure . . . may be a more sensitive indicator of true

isolation." This definition of flow isolation, based on either a static or a

dynamic downstream pressure, can be misleading. The downstream pressure is based

on a number of phenomena and may not always be indicative of disc position.

Phenomena which may adversely affect using the downstream pressure to identify

disc position include leakage through the valve, the pressure and temperature of

both the upstream and the downstream fluid, the net expansion of the fluid in the

downstream piping, the resistance to flow in the downstream piping, and the

ability of the instrumentation to detect small changes in pressure levels.

The flow isolation assessment performed by the INEL recognized these

limitations and included a study to relate the position of the disc or stem to

the valve body seats to more accurately identify true flow isolation. From this

study, we realized that true flow isolation coincides with a very pronounced

region in the stem force trace of a predictable valve. True flow isolation can

also be observed in some of the pressure instrumentation, such as a convergence

of the upstream, the, bonnet, and the under the disc pressures or in the

downstream dynamic pressure, provided the valve does not leak excessively. Note,

however, that the usefulness of the pressure readings is limited by the

sensitivity of the instrumentation.

40
. By way of example, Figures 16 through 18 show the stem force, the upstream,

bonnet, and under-the-disc pressure, and the downstream dynamic pressure

histories for Valve 2 Test 1 Step 25. Also shown on each of these figures is the

point identified as flow isolation as shown on Table 6-1 of the EPRI report and

the point used by the INEL to assess the response of the valve.

What we observe is that-at that point-identified as flow isolation in the

EPRI report, the upstream pressure is higher than either the bonnet or the underthe-disc-pressure. This difference'Kin the pressures indicates flow through the

valve; the valve has not yet isolated the flow. Conversely, the'point identified

as flow isolation by the INEL is past the point where the pressures converge,

reflecting a region on the stem force history where the stem force levels off

just before wedging. After the pressures converge, the downstream dynamic

pressure continues to decay and finally stabilize, as shown in Figure 18. The

point identified in the EPRI report as "flow isolation occurs before the

downstream dynamic pressure falls to zero.

While it is true that downstream dynamic.pressure is a better indication

of flow isolation than downstream static pressure, we have found the plateau on

the stem force trace (Figure 16) to be the best indicator of flow isolation, as

confirmed by the convergence of the three valve pressures and by',the decay of the

'downstream dynamic pressure. For predictable valves, this plateau represents the

-,maximum force before wedging. The point identified in the EPRI report as flow

isolation typically lies before this plateau rather than on it, thus yielding too

low a value for the stem force necessary to achieveitrue flow isolation.

Most of the'apparent disc factors presented in the EPRI report for flow

Kisolationa'are too low, primarily because they are based on stem force values

-measured before isolation, when the disc was still riding on the guides. This

issue is discussed in more detail in Section 3.4.2.

(3):---f i"At~wedging,-as identified-from the stem-force plots. For closing

-strokes, wedging was identified as the instant just prior to the

-:'essentia77y vertica7 section' of the-' stem force plot which

'corresponds to a rapid increase'in stem force. For opening strokes, : J ~'; ' ' I".

.., .. - .r 41 ,
0

-5,000

%-o

.0

LE

U)

-10,000

-15,000

-20,000

-25,OOCI

20 21 22 23 24 25 26

Time (s)

27 28 29 30 31 32

Figure 16. Stem force for Valve 2 during Step 25 of Test 1. M475 icw-i 191-03

r 1, I
A

. i I "I I , I I t, I

1,000

950

0',

I.rn

C',

0~

900

850

800

750

-700

21 22 23 24 .. . .. . * .7

5. . I 2 

25 -;,

Tim'e, (s)

27 28 29 30 31

Figure 11. Selected upstream pressures for Valve 2 during Step 25 of Test 1.

M475 lew-1 191 -01
125 . -- _ _ _ _ _

Ln X EPRI

10 .... ............. I N E L

0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ . . ..-i-.......-....... ........ !............. .... .......-.......-..-.. .

CU - L.

Li ~~~~~~5 ...... ... ..... -

EE

rd

VI~~~~~~~

4-)-2

21 23 25 27 29 31

Time (s)

Figure 18. Downstream dynamic pressure for Valve 2 during Step 25 of Test 1.

I. U
wedging was identified by the plateau immediately after the initia7

"cracking" peak'on'the stem force plot." y a

The EPRI report has'defined the wedging position in the closing direction

as "'the instant just"prior to the essentia77y'vertica7 section of the stem force

plot which corresponds 'to a'rapid iincrease in stem force." Using such a

definition to assess the stem force'requirements of a gate valve should ensure

that'true flow isolation has occurred 'for a predictable valve. As such, this is

an appropriate point' in the 'valve closure' stroke at which to assess valve

performance'.

However, as shown in Figure 6-4 and Table 6-1 of the EPRI report, the

apparent disc factor for'Valve"2 during Step 25 of Test 6B was calculated with

a stem force (13,000 ibb) that was on the'"essentia77y vertical section of the

stem force p7ot," rot just prior to it. While using a stem force on the vertical

section will yield'a higher'(and thus a more consiervai ve) apparent disc factor,

we are more concerned with the care used in assessing the INEL test results. We

have not determined whether this type of error occurred for any of the other

wedging'positions assessed in Table 6'1 of-'the EPRI.report.

(4) "At maximum stem force (excluding cracking peak) regardless of disk

.'position. 'This value is the highest' stem force during the stroke.

On some stem force plots, this coincided with one of the three

points mentioned above. On others, there was a maximum stem force

which occurred at a time other than isolation, wedging, or zero stem

position indication."

This point is applicable for assessment of predictable valves in the

closing direction, assuming that the stem force just prior to wedging is used.

For predictable valves, experience shows that the maximum stem force just prior

to wedging occurs when the disc is riding fully on the seats, after true flow

isolation has occurred. However, the analyst must use care to ensure that the

results from nonpredictable valves do not bias the results. Information at the

point the stem force maximizes is also useful in assessing the response of a

valve opening against a flow load.

45
I

W

Conclusion: The valve positions specified by the EPRI report for evaluating the

INEL test data are either incorrectly applied or else do not

consistently provide useful information. For the closing direction,

the stem force levels off shortly after'the disc begins riding on

the seats and flow has been isolated. For predictable valves, this

plateau is where the maximum load prior to wedging occurs. The

sliding friction (INEL correlation or the EPRI-NMAC equation) or the

disc factor (industry equation) used to size a valve must be based

on a correct identification of this point and on the resulting

loads. Other analyses may be interesting, but are not always

useful.

3.4.2 Apparent Disc Factor. According to the EPRI report, the EPRI effort

included "a detailed review of the test data, using primarily published data

plots, focusing on determination of the "apparent disk factor" implied by the

data for all valve strokes performed with differential pressure and relating

these results to the conditions tested and valve internal damage sustained."

The EPRI review included calculation of apparent disc factors and presented

the results as follows: "Apparent disk factors (disk factor implied by measured

DP and thrust using standard industry equation) required to achieve flow

isolation on. the first blowdown closure stroke of each test valve are shown

below."

46
-:-;Summary of First B'7owdown Isolation'Tests

-~ Sze Te., .:,.-st ,......................... Atparent,

Size Test DP at Disk Applicability

Valve Manufacturer ,in) No. -Fluid Isolation ' Factor to Similar

(psi) for Flow Industry

.______ ___________________ .__________ ' , :*.... ...... solat ion' Valves*

^ Anchor/Darlinq 6 Nitrogen . 5 '0.63 . P Potentially

Velan 6 -: t 1000 0.35. , Applicable

Anchor/Darling 6 1-1-25 .: Hot . 870 Valve V NIA ' Not

Water (0.86) Applicable

Velan 6 2-1-75 Hot 940 0.33 . Applicable

Wa lworth.: -1-25 . Hot' 870 > 0.19 ' APPl1cable

Water

.4 Anchor/Darling 10 4-1-25 Steam 700 0.49 Apolicable

5 Powell 10 5-I-25 Steam 880 0.44 Applicable

6 Velan 10 6-1-25 Steam 1000 0.42 Potentially

., ..' -. . . , -Applicable ., hiIndicates app7icabi7ity of't'est result (apparent disk factor) to valves in

-systems requiring blowdown iso7ation.' Test-4is considered applicable if

both valve design details and test conditions are representative of some

industry valves.

The EPRI report also states that Ithese data are considered potentially

app7icable only to similar valves insta77ed 'in 'the BWR systems under study or

other similar valves having as a design' basis function the isolation of b7owdown

flows under the range'of conditions tested." ' *~~~ -? -a,f. 

The apparent disc factors at flow isolation, as listed in the EPRI table

shown above, are based on Table 6-1 of the EPRI report. Enough information is

presented in Table'-6-1 determine how these'apparent disc factors were derived.

Columns three,"fo\ur,' and eight T'abli 6-1 contain g'eneric vilve 'information,

whereas' c'olumns 'five,' nine', and eleven 'contain test-specific information

necessary to calculate the apparent disc factor at-fIow isolation, as listed in

column thirteen of the table.

The INEL reassessed each test using the apparen' disc factor equation

47
a

presented in Section 5 of the EPRI report and recalculated the apparent disc

factor using the INEL identification of the stem force necessary to isolate flow

in each test (as explained in Section 3.4.1), the corresponding pressure and

differential pressure at the time of flow isolation, and the packing drag

measured during the-test series. The results of these recalculations, and the

data used, are presented in Table 2. As can be seen, there is a considerable

difference between the apparent disc factors presented in the EPRI report and the

apparent disc factors calculated by the INEL. Most of the EPRI report disc

factors are significantly lower than the INEL disc factors.

Most of the difference is caused by the fact that the values for stem force

used in the EPRI report analysis are too low; the EPRI report analysis does not

correctly identify the point of true flow isolation. This issue is discussed at

length in Section 3.4.1. The remaining difference is the result of revised

estimates of the upstream pressure and the differential pressure at flow

isolation. None of the difference is a product of the use of a smaller disc area

term: in our reassessment of the EPRI calculations, we used the same disc area

term that the EPRI calculation used, that is, the mean seat area, not the orifice

area.

Based on the results of Table 6-1, the EPRI report states that the

"Disk/seat friction coefficients may be slightly higher than typically assumed

values of 0.3. A value of 0.4 appears sufficient to cover friction phenomena

based on the NRC/INEL tests." Based on the recalculated results shown in

Table 2, the disc factor typically exceeds 0.4, and recommendations to use a disc

factor of 0.4 are not warranted.

A more fundamental concern, however, is the fact that the EPRI analysis

uses the standard industry equation in its assessment of valve performance. In

our early analyses of the NRC/INEL test results, we, too, tried to use the

standard industry equation, and we found it inadequate.

We were initially puzzled by the scatter in the disc factor data produced

in our early analyses of the NRC/INEL data. It became obvious that the range of

48
Table 2. Reassessment of the design basis tests

i! ..

.1

Isolation Stem Force _ARarent Disc Factor

* t I'I I . ;

Test

Number '

A-3-5

1-2-25

B-2-5

2-1-25'

2-2-25

2-3-25

2-6A-25 -

2-6A1-25

2-6B-25

2-6B3i-25

2-6C-25

3-1-25

3-1A-25

3-5-25

4-1-25

5-1-25

-:. 5-lA-25

6-1-25

6-lA-25

6-lB-25

EPRI Actual

.1I

Ibl. 6-1 Tisolation

9000 5347

19500 22900-

12500 ' 13833

10400 12929

9000 13096

5200 . 12751

5300 7859

6000 8688

8800 12173

9200 13700

12200 -15798

5900 4355

7000 10804

9100 12235

23800 16100

28000 24756

26500 :30474

28000 28200

I

EPRI

Tbl. 6-1

0.63

v.. 0so * 0.86

: 0.35

0.33

: 0.23

0.15'-

0.29

0.29

0.31;--

0.29

0.28

0.19'

-0.23

0.26

0.49

0.44

0.34

0.42

Actual

Isolation

0.36

1.05

0.43

0.45

0.40

0.59

0.50

0.50

,0.48

0.48

0.40'

0.48

0.43

0.40

0.30 '-

0.39

' 0.42

0.41

0.35;

0.36

* , . . - , 

'- ' Notes

Nonpredictable ,

Nonpredictable'

I

- ! I I

Nonpredictable

Nonpredictable

Nonpredictable

Nonpredictable

-

; -~ --I. K.

ri

" 32000 -

. 19000

;,

- - 29366

. , 25233

: 0.40

t .- 0.26 f ,- , 1 - , I .

I i . . , .-., ., :

1. Valve failed to close during the test.'-' ! - - * I.~~~~~~~~~~~~~~~~~~~~~~~~~~

: . - 1, I .

I k :"" "

; - , , - , r- , , - ,

C. *. * . C -

I .- i 1: , : 'I', 

j, . . , f , - al

1, i : I.,

- 49
IF

the disc factor (from 0.40 to 0.59 for Valve 2, for example) was greater than

could be reasonably attributed to random scatter. Our effort to discover a

pattern to the scatter produced the results shown in Figures 19 and 20.

Figure 19 shows disc factor data for Valve 2 closing against four different

fluid conditions, steam to cold water. In this particular figure, we used the

valve orifice area for the disc area term as it represents the least conservative

use of this term by the industry. For predictable valves, the plateau between

isolation and wedging represents the highest stem force in the closing stroke

prior to wedging. We selected the mid point of the plateau as being indicative

of the stem force required to isolate flow through a valve. Figure 19 clearly

shows that the disc factor varies with the degree of subcooling, with steam

conditions producing the lowest disc factor and cold water producing the highest.

Figure 20 shows disc factor data for Valve 2 closing against three

different pressures with the same degree of subcooling. A pattern in the data

scatter is evident. Surprisingly, the disc factor is higher with lower

pressures, and lower with higher pressures.

These results were unexpected, and the subsequent analysis performed by the

INEL, as described in more detail in Appendix C, defined the force balance on the

disc and a new correlation for assessing valve performance. During the

development of the correlation, we discovered that the standard industry equation

does not account for the pressure effects and fluid condition effects described

above, and does not account for valve design characteristics that are acted upon

by the differential pressure. One of these effects is the result of the angle

of the downstream seat, which lies approximately 5 degrees from vertical.

Appendix C presents a complete discussion of these effects.

Thus, what came out of the work was a realization that the standard

industry equation is incomplete. Pressure effects and fluid subcooling effects

are not accounted for, and some of the internal forces acting on the disc are

missing, in effect causing these missing forces to be accounted for in the one

component of the equation that is not specifically tied to a real quantity, the

disc factor. In addition, we realized the definition of the disc area term is

50
I.

0.0

-0.2 LTo

40-

0

co

._-I II 0

-0.3

-0.4

-0.5

-0.6

-15 -10 -5 0 5 10 15 20

I

Stem position MS9 RS0910 (% of travel)

Figure 19. Disc factor for Valve 2 closing on line break flow, effect of subcooling at 1000 psig.
L0

CO,

C-)

Co

0.0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

UL

-15 -10 -5 0 5 10 15

Stem position (% of travel)

20

MS291 I1S-0491.09

Figure 20. Disc factor for Valve 2 closing on line break flow, effect of pressure at 100OF subcooling.

q. a
'not ttindardized;;`several definitions exist, making it even more difficult to

- develop results with'wide' ap licability.

Using the'standard industry equation,' regardless of-how the disc area term

is 'defined, and solving for the'`dis'c factor 'will not result'in 'a 'value for the

sliding friction. The result is a disc factor that puts all of the terms missing

in the standard industry equation ,including sliding friction, into a multiplier.

Assessing the NRC/INEL test 'rsults' with' the EPRI-NMAC-equation would have

provided results much closer to th6 results shown in Appendix C.

Conclusion: The disc factors'derived by'the' EPRI report analyses are typically

-too low,;" mostly because; the analysis incorrectly identified the

point' of flow isolation' and 'consequently used too low a val`e for

the stem force. The sugg'estion in the EPRI report that the'industry

use a disc factor of 0.4 'in the standardindustry equation cannot be

supported irrespective of the disc area term used. The INEL is also

concerned'that the'standard 'industry equation' is incomplete. As

such, we believe that :the"-INEL correlation or like' methodology

should be-used to estimnatethe maximum *stem force requirements of a

''flexwedge gate valve whose'opertional characteristics are

considered to be'predictable at the'valve's'design basis'pressure

and temperature.' We 'consider lthe;INEL- ctorrelation to be a

;significant'improvement over the standard industry'equation and its

use of a disc factor toL account'for margins and missing variables.

3.4.3 Average Disc Factor."" The'EPRI effort"calculated'the--apparent disc factor

for a number of the Phase I and Phase II closure strokes where the disc sliding

on the seat anDeared to be'the dominant load phenomenon (rather than-machining

or shaping of surfaces). Theseare presented 'in Table`6- 'ofIthe EPRI report,

along with a summary of selected p'arameters'during each test. EPRI describes its

evaluation as follows: "Based on evaluating a7l of the b7owdown c1osure and

J'opening strokes'in'nthis' manner,' average apparent disk 'factors due 'to sliding

friction for each va7ve were determined. Table 6-3 summarizes the average disk

factors for blowdown conditions when sliding of the disk on the seat is

occurring.- As''shb9wn!4in this table,' the values are between 0.28 and 0.41 for

53
41

closing strokes, and are between 0.25 and 0.40 for opening strokes, with the

exception of Valve 2 at 0.47. If data for wedging of Valve 2 are considered, the

average apparent disk factor is as high as 0.52; however, as mentioned

previously, it appears additional surfaces were coming into play during wedging

and the apparent disk factor does not necessarily represent true friction'.

We have not performed a detailed review of this table. As discussed in

Section 3.4.2, the methodology used to determine the apparent disc factor is

inadequate, and the analyses used a point incorrectly assumed to be flow

isolation (see Section 3.4.1). Note also that the high disc factors for Valve 2

listed in Table 6-1 are from 1000F subcooled tests. As explained in Appendix C,

subcooling greater than about 700F can cause the disc factor to be high in

analyses using the standard industry equation. Some of the high apparent disc

factors for Valve 2 are more likely a product of fluid conditions effects than

of additional surfaces coming into play.

We do not recommend the use of the standard industry equation either for

operator sizing or for analysis of test data. However, if the standard equation

is used, an average disc factor is less likely than a maximum disc factor to lead

the analyst to a result that conservatively bounds the stem force requirements

of a valve. The INEL assessment of the data from the closing tests, as presented

in Appendix C, was not possible until we investigated all of the forces acting

on the disc just prior to wedging. Rather than averaging the disc factor, we

suggest that a follow-on analyses include:

(1) separately assess the opening and closing tests,

(2) use an equation that considers the effects of pressure and

differential pressure on all components of the valve design and

determine true sliding friction, not a disc factor,

(3) use only those test conditions representative of the disc actually

sliding on the seats, and

(4) include the effects of fluid subcooling and fluid pressure.

54
Conclusion: Using the- standard industry equation 'and averaging the.resultant

. disc.factors will.continue to yield inconclusive results. Without

a more rigorous assessment of the data,- it is not possible to

quantify-phenomena that affect the ability of-the disc to slide on

the valve body seats.

-.3.4.4 Linear Contact Stress Model. In an 'effort to correlate the observed

response of the valves tested,.-the EPRI report introduces a linear contact stress

model and attempts to evaluate valve application severity and the effect it has

.on the apparent disc factor. The model plots the apparent disc factor for each

valve tested against 'the linear contact stress.;. The EPRI report presents a

* series of eight figures, Figures 6-28 through 6-35, one for each valve tested in

Phase I and Phase II. Each figure contains the 'results'of both opening and

closing strokes and testing using both blowdown and normal flow conditions.

Based on this study, EPRI concludes that "there appears to be no clear

correlation of strokes. overal7 or for a particular subset of strokes. It appears

.that linear stress, by itself, 4s not necessarily an adequate valve severity

evaluation parameter for separating va7vesinto,"7ight7y loaded" and "heavily

loaded" classes."

TheINEL assessment of the.. closing' tests, .as presented in Appendix C,

concluded that a load dependent response does.exist. This response was observed

for both the Phase.IVand the Phase JI closure testing. We suspect that the EPRI

effort-did not demonstrate a *load.dependent:response because

(1) It used the standard industry equation-(with-aidisc area based on

the mean seat diameter),,which does not accurately identify all the

.forces acting on.,the valve disc just prior-to wedging and is thus

incomplete; -the EPRI-NMAC equation would have provided better

results.

(i) Fluid subcooling and differential pressure phenomena are embedded in

-,the results and cannot adequately -be identified -by solving for an

: apparent disc factor.term only.. .;^

:55
a

-(3) For one of the valves, the EPRI effort uses, a disc factor based on

dimensions from the manufacturer's drawings for part of the

assessment and a disc factor based on as-measured dimensions for

another part, thereby obscuring any embedded'trends.

(4) The EPRI report uses a linear stress correlation that is either not

complete and not structured properly (currently based on the nominal

valve diameter) to reveal the trends being sought.

(5) The apparent disc factor used for this study mixes isolation,

wedging, and the maximum disc factor. The true trends available

from the data may be obscured, since not all the values are based on

true disc to seat sliding friction.

(6) Both opening and closing tests were assessed together. We have not

assessed the results of the opening tests as yet, but the test

results indicate that other phenomena are involved during opening

and as such, combining opening and closing tests may not be

appropriate.

Conclusion: The linear stress model used by EPRI does not provide the desired

result. We believe the INEL methodology is more rigorous in

assessing valve closing loads; this methodology does demonstrate a

load and fluid phenomena dependency. The suggestions offered here

might be useful to EPRI analysts in their effort to obtain useful

results, both in understanding the NRC/INEL data and in evaluating

the EPRI MOV Performance Prediction Program. It should also be

noted that we are addressing only predictable valves; to date,

nonpredictable valve performance has not been quantified by either

the INEL or by EPRI.

3.4.5 Valve Anomalous Behavior During Closure. The EPRI report assesses the

appearance of wear and damage to each valve tested by the INEL to determine

whether the damage was responsible for any anomalous performance during the

56
blowdown tests, and thus, whether the'testing from that valve should be used to

assess valve response in general. Identifiable wear and damage to the disc seat,

body seats, disc guide, and body:guides of each valve for the Phase II -and to the

Valve B disc from Phase-I testing are'described in Table'6-2 of the EPRI report,

along with -an assessment 'of whether the conditions -noted' could have caused

anomalous behavior. Generally, they,-conclude'that damage tothe disc guide, the

body -guides, the disc'seat, and the body seats directly affects whether a valve

is considered to.be predicable or nonpredictable.- Such nonpredictable behavior

can result in-high!stem forces and-high apparent disc'factors.

The EPRI report express'es:-concern that "the inspection was carried out at

the conclusion of-the test program after numerous strokes-had been performed on

-each valve. ;'Because.-there were no inspections during the test-sequence, it is

not possible to precisely reconstructi^the:darmage scenarios."" -The apparent

concern, among other things, :is'that we have used-the test results-of damaged

valves and thereby biased the resultant disc factors. It was not our intent,

during the INEL testing, to visually Inspect-the internals of each valve

following each blowdown test. S-It was :our intent to use our sensitive'stem force

-measurement-to provide insight to valve damage'during the .tests. We-used this

method to assess valve damage, and'subsequent posttest' inspections confirmed the

relationship between an unusual stem force response and valve damage. Based on

the posttest inspections-and the-stem-force -traces,.we have made'an -assessment

of-each valve and any limitations in the resultant test'data, as -noted below.

The EPRI inspection team did not inspect the Phase I valves,- as both had

been refurbished for the Phase II testing. They were able to inspect the Valve B

disc -as 'itrhad been.replaced prior.-to the;Phase II testing. '-A complete

;inspection of the Phased Ivalves'was-performed by the INEL along with official

record photographs-ofteach'valve's condition. The posttest inspection results

of Valves A-and B are'the INEL's.alone. v '

Valve A - This valve performed unpredictably during mid stroke, evidenced

* by damage to the disc and valve:body guides.:;However, once the disc began

-:riding on ithe .valve body: seats, the valve responded-in a predictable

manner (see Figure 21). We used selected Valve A' test results in the

*-' 57
a

* development of the INEL correlation.

Valve B - This valve performed predictably during the Phase I testing,

just as it did during the Phase II testing, even though a different disc

was installed in the valve. The Phase I disc had hardfaced disc guides

representative of later Velan valves. The Phase II disc had nonhardfaced

guides representative of earlier Velan valves. There was no abnormal wear

on Valve B. All Valve B results, except the 1400 psi parametric test

which did not completely close, were used in the INEL correlation. The

valve failed to seat during the 1400 psi test, not because of damage to

the valve, but because the torque switch was not set high enough, even

though it was set higher than what the manufacturer recommended. We

observed that the motor operator suffered from what the industry-has

termed the rate of loading effect. This effect is one of the subjects of

our 1991 research update to be published later this year.

Valve 1 - This valve was badly damaged and did not completely close during

the initial design basis blowdown test sequence. No additional blowdown

test sequences were performed with this valve. We did not use the results

from this valve in developing the INEL correlation.

Valve 2 - This valve was cycled a number of times under blowdown

conditions. As a result, more indications of disc to guide and seat wear

were evident. However, there were no indications of abnormal or

detrimental wear.

EPRI has identified disc to valve body wear due to rotation of the disc as

one possible abnormality with this valve. This valve sustained by far the

largest number of cycles under load. In light of the large number of

valve cycles, we believe that the identified markings reflect normal wear

for the test conditions the valve was subjected to.

The appearance of such wear on a valve is not surprising. None of the

valves have any mechanism to prevent the disc from rotating relative to

58
.1 I

0

'C.,

0

* LLE

U)

C,)

>: Phase 'l, 6-In. RWCU system valve, nonhardfaced disc guldes, line break flow, comparing actual versus predicted thrust.

-Valve ATest 2. Step 5. 1000 psi. 5300F (100F Subcooled)

-, ,,Te t , :.

10000, . '- . .

0

.-0

-10000

n'

t0

. . I

-200000

-30000

0 6 10 15 20 25

Time (s)

30 35

S211 KGD-0490-03

Figure 21. Stem force history of Valve A closing against 1000 psi, 10F subcooled fluid at full flow conditions.
In

the pipe center line, other than resistance from the stem and by disc

contact with the guides. We have no reason to suspect that any rotation

of the disc in Valve 2 is more pronounced than in any other valve. In

fact, the limited lateral clearance between the disc and the guide would

minimize any rotational tendencies of the disc and prevent aggressive

contact angles from occurring. In addition, the methodology employed by

the INEL to assess valve response indicates that the behavior of Valve 2

during the testing was quite typical of the behavior of the other

predictable valves tested. Valve 2 data were used in the development of

the INEL correlation.

Valve 3 - The high loadings on the guide caused it to deform and allowed

the disc to ride on the seat instead of the guides. As a result, more

disc and body seat wear was observed. Otherwise, the valve responded

predictably and was typical of the other predictable valves tested. Data

from these tests, when the disc was riding on the seats, were used in the

development of the INEL correlation.

Valve 4 - This valve was badly damaged during the initial design basis

blowdown test sequence. No additional blowdown test sequences were

performed with this valve. We did not use the results from this valve in

developing the INEL correlation.

Valve 5 - The high loadings that occurred during the initial design basis

blowdown test resulted in disc tippage and an interference between the

disc and the seat. This behavior did not appear during subsequent

testing, as the material interface had been removed during the initial

design basis blowdown test. The behavior of this valve during those

subsequent tests was typical of the behavior of other, undamaged valves.

Therefore, results from those subsequent tests were used in developing the

INEL correlation.

Valve 6 - Damage to this valve consisted of disc and seat damage, guide

damage, and a bent guide. We initially attempted to use the results of

design basis testing measured when the disc first started to ride on the

60
seats, hoping to avoid the results of abnormal interferences between the

bent guide and the disc and the seats. However, upon further assessment

of the response of this valve during design basis blowdown testing, we

decided not to use any of the results from this valve in developing the

INEL correlation.

It should also be noted that the results of the posttest inspections were

such that, had additional tests been in order, we would have continued to test

Valves 2 and 3, which were the undamaged or minimally damaged valves on which we

performed multiple test cycles. As-we stated earlier'in the report, we 'continued

testing Valves 5 and 6 knowing they were damaged. Thus, we conclude that our

damage detectiofn methodology'based'on careful reading of the stem force trace was

successful.

Conclusion: Having assessed the wear and damage of each of the Phase I and II

valves, we believe that the sensitive stem force measurement used to

assess valve damage was correct for our test program. Based on the

damage each of these valves sustained and their respective stem

force trace, we used most of the results of Valves A, 2, and 3,

selected results from Valves B and 5, and none of the results from

Valves 1, 4, and 6 in developing the INEL closing stem force

correlation. r '

3.4.6 Nitrogen Flow Through Valves. The Phase I test loop at Wyle Laboratories

in Huntsville,-- Alabama- is shown in *Figure 22. The water accumulator was a

450 ft3 tank (3,366 gal) that discharged from the bottom. The nitrogen for the

gas blanket entered through the top. The EPRI report expresses concern that a

number of Phase I tests included nitrogen flow and states that "a complete

transition from water to nitrogen flow appeared to occur on the first b7owdown

stroke of Valve A (Test 3 Step 5)."

Our assessment of Phase I Test 3 Step 5 indicates that Valve A closed on

a nitrogen/steam 'mixture for 'the :la st 'two thirds of the blowdown stroke.

Figures 23 and 24 show pressure traces for this test. Figure 23 shows the

61
Blowdi

F iW Test Specimen

'own [1f Xy1 ie

6 I n.i6 In . 11

10 In. 10 In. 2 PIP pip

Waler tank X -]

10 In. Flojimeter

pipe~~~~~~~~~~

2011. It

0-3043

Figure 22. Schematic drawing of the Phase I test loop.

62
A-w

7 145: PHASEI.2.DPI.- .

7

4 0.

FE@ 40. 0

_

p

S

i

d

20.9 ,30.8

..2 , 0

10. .

f -.rf-7

_. , ->, . ,'

1 , . 1 . .

10.0 -. 15.0 : 20. O-

,-; Sees -;

25.0 . 3 . -. a

Figure 23. Flow meter-differential pressure trace for Test 3 of-Valve A, Phase.I.* -.

------- Pa>- as~l ----- .2. - -- -- --

;1400. 0-

E P H .~~ A S k E I- B - - -- - - - - - - - - -- - - - - - - - - - - - - - - - - -

14,,:.-, ._ ____

1 . 2 a-- a 0 -- - - - - - - _ _ _ _ _ _ _ __-_-_- 

P 00 00o~ 6__ | ____________ a_ 

v - ------- _

v ;' 0. 5.0 10.0- ;- 15. , 20.0 . 25.0 30.0; :.

-S-ec-s---- - - .------------- -

.~~~~- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -..............

-Figure 24. Pressure traces for Test 3 of Valve A, Phase I.
a

venturi flow meter differential pressure and, at 8 seconds, shows the disturbance

pointed to in the EPRI report. Figure 24 shows that at this same time, the valve

upstream static pressure increases, the valve differential pressure increases,

the valve downstream static pressure decreases, and the exit pipe static pressure

decreases.

The influence of nitrogen entrainment can be seen in a number of other

instrument readings as well. Valve body accelerometers show dramatic increases

in amplitude at the point where a nitrogen/steam mixture begins to pass through

the test valve. Analysis of the video tape recordings shows a marked change in

the visual shape and consistency of the exhaust, and an audible change in

exitnoise can be heard. Differential pressure transducers at the venturi flow

meter and test valve exhibit large changes in signal magnitude when a

nitrogen/steam mixture passes; however, 'the flashing of the slightly subcooled

water to steam and associated choke planes moving through the system can produce

a similar effect. In addition, flow meter measurements were used to calculate

an integrated flow for each test for comparison to the known accumulator volume.

Collectively, the response of the instruments provide positive evidence that a

transition from water to a nitrogen/steam mixture occurs at this point in Test 3

Step;5. In all cases where nitrogen flow was observed, all of the above

indications were present.

The EPRI report identifies other tests where "some nitrogen may have been

passed through the blowdown pipe and test valve during the stroke without a

complete transition from water to nitrogen occurring." One of these tests is

Test 2 for Valve A. Figures 25 and 26 show pressure traces for the Phase I

Test 2 first blowdown stroke (compare with Figures 23 and 24). Figure 25 shows

the flow meter differential pressure for this test and indicates a large

disturbance at about 23.5 seconds. The EPRI report identifies this as an

indication that nitrogen-entrained water was flowing. However, the other

pressure traces, shown in Figure 26, show a different response than was observed

during Test 3 Step 5. During Test 2, the valve upstream pressure, the downstream

pressure, the exit pressure, and the valve differential pressure all decrease at

the time of the flow meter disturbance. This indicates a drop in pressure

throughout the system, consistent with water flashing to steam upstream of the

64
20.0 - 25.0 .3. 0 I 0.0 -. : 18.0 1. w ISecs -. -

Figure 25. Flow meter differentialpressure trace for Test:2 of Valve A, Phase I;

I IMMH PtJIlSEl. l . P2-. - - * .. Ul am

0.0 5.0 i, 10. 15.80 20.0 25.0 Figure 26, Pressure traces for Test 2 of V A , P ae s - S,, s 

Figure 26. Pressure traces for Test 2 of Valve A, Phase I.
M

valve test section. The valve accelerometers do not show dramatic increases in

amplitude as was observed in Test 3, nor do video tape recordings reveal the same

trends. All of this taken together supports the conclusion that a water/steam

mixture was present throughout the valve cycle with no nitrogen entrainment.

Fluid volume calculations also support this conclusion. During Test 2, the

maximum flow (7,500 gpm) was measured at 15 psid (Figure 25), and the flow

'decreases somewhat linearly to zero 26 seconds later. The total consumed water

inventory for Test 2 was approximately 1,625 gal, slightly less than half of the

total accumulator inventory. The water level in the accumulator was over 8 feet

at the end of the test. Flow rate was about 2000 gpm when the disruptionpointed

out in the EPRI report occurred. This corresponds to an in-tank fluid velocity

of about 0.09 ft per second. It is unlikely that nitrogen would enter the

discharge with the water over 8 ft deep in the tank.

Our Phase I test plan was written to allow optional valve cycles under

blowdown conditions when the test engineer determined that water remained in the

accumulator after the primary blowdown closure. The primary blowdown closure was

designated Step 5, and the optional stroke was identified as Step 6 (opening) and

Step 7 (closing). Because of our inexperience with the Wyle test loop, we had

nitrogen/steam flow during several of these valve strokes. From the analysis

described above, we conclude that nitrogen/steam flow occurred in three of our

Step 5 closures: Valve A Test 3, Valve A Test 6, and Valve B Test 5. We saw

nitrogen/steam flow in four of our optional Step. 6 and 7 strokes: Valve A

Test 2, Valve A Test 7, Valve B Test 2, and Valve B Test 3. This matches the

information given in Table 2-1 of the EPRI report. However, analysis of all

instrumentation channels, as described above, shows that there was no

nitrogen/steam flow for the tests listed in Table 2-2 of the EPRI report. All

of the valve cycles listed in Table 2-2 of the EPRI report closed under

water/steam flow.

Section 3.2.7 provides additional information on nitrogen flow through the

valves.

Conclusion: We have assessed the Phase I tests and concur that the seven tests

66
listed in Table 2-1 of the EPRI report included nitrogen (nitrogen

entrainment in steam, not slugs of dry nitrogen). However, the

eight tests listed in Table 2-2 of the EPRI report did not. Those

tests had flow of water/steam mixture.

67
I

U

68
4. CONCLUSIONS

The'most important question raised by the INEL testing is how to determine

whether or not a valve will perform predictably. Although the EPRI report

suggests that valves with different disc designs might perform differently, the

INEL, EPRI Marshall, and European testing have all shown that a large number of

the valves tested performed unpredictably. The threshold level where current

valve designs begin to perform unpredictably needs to be determined and accounted

for.

The industry's traditional stem force equation used to size motor operators

is incomplete regardless of the disc area term or the disc factor used. This is

because the disc factor includes other terms along with sliding friction. As

such, we disagree with the suggested disc factors presented in the EPRI report

and suggest that a more rigorous analysis approach be used.

The typicality of the test hardware and the test conditions, while not

perfect in every case, provided representative Generic Issue 87 operating

conditions for evaluating representative Generic Issue 87 valves. Although the

EPRI report questions whether the test conditions were applicable to GI-87

valves, the research bounded the worst case conditions and has provided a

correlation that can be used once the design basis conditions for a valve are

known and the valve's predictable behavior established.

For a predictable valve, that portion of the closure stroke that occurs

just after flow isolation, when the disc is riding fully on the seats, is very

well defined on a stem force versus time trace and represents the maximum loading

for such a valve. The sliding friction (INEL correlation or the EPRI-NMAC

equation) or disc factor (industry equation) used to size a valve must be based

on a correct calculation of this point. Determination of this point and the

corresponding final stem force will help utilities evaluate performance margins

and/or establish that the valve is representative of the valves tested by the

INEL for predictable extrapolation purposes.

69
a

. The NRC documents reviewed in Appendix A (Section 8) of this report have

some omissions in the description of circumstances, but after two years of

additional analyses, the conclusions presented in the documents are still valid.

70
APPENDIX A

PARAGRAPH BY PARAGRAPH REVIEW OF

EPRI DRAFT REPORT NP-7065

This section of the report represents a paragraph by paragraph review of

the Summary Section and Sections 1 through 8 of EPRI Draft Report NP-7065. The

left hand column presents the original EPRI text as received from MPR Associates

and all references to figures, tables or appendices pertain to the EPRI report.

The right hand column presents the INEL evaluation of the EPRI text and all

references to figures, tables or appendices pertain to this report unless

otherwise stated. The applicable figures and tables follow each section (except

the Section 4 material which has not been reproduced).

A-1
SUMMARY

Under NRC sponsorship. the Idaho National Engineering Laboratory (INEL)

conducted a test program to assess the capability of motor-operated gate

valves commonly installedIn;BVR HPCI.)RCIC and RVCU systems to close

under postulated blowdown Isolation conditions. The results of the test

program have beenwsummarized by INEL1in test reports and presentations

(References 1 2 and 7). Based on the valve performance observed in the

test program. several Issues have been raised by INEL and NRC regarding

potential implications to MOVs In these specific BVR systems and to

nuclear power plant HOVs in general. However, utilization of the

NRC/INEL 'data 'to assess these Implications has been hindered by the

absence of sufficient pre-and post-test hardware characterization and by

a lack of detailed documentation on test facility configuration.

instrumentation and measurement uncertainty.

This comment on the INEL test program is not valid. The NRC sponsored

a one week, five man effort to assist EPRI in evaluating the posttest

condition of the hardware. This EPRI report, criticizing the lack of

posttest hardware characterization, contains the results of the NRC/EPRI

evaluation. The pretest configuration was verified by the valve

manufacturers; however, this information may be considered proprietary.

EPRI has access to the same information we have. The test facility

configurations have been published in each of our reports.

Instrumentation accuracies have always been available upon request.

Appendix E contains a copy of the Wyle Laboratories instrumentation

equipment sheet from the Phase I testing. The INEL load cells were

calibrated before and after both test programs and their accuracies

remained constant throughout, at 0.4X of full scale (40,000 lbs). The

Phase 11 instrumentation is the same is we are currently using in the

diagnostic test. validation except for the pressure and temperature

measurements.,

We used a large number of various pressure transducers in Phase 11. All

were strain gage type-and most were manufactured by Statham. All were

calibrated by the INEL standards laboratory prior to testing. Overall

pressure transducer accuracies were better than 2.0% of reading.

Thermocouples were expendable items, and each valve required a different

length thermocouple to properly place it in the flow stream.

Thermocouple response time will influence accuracies (steady state versus

transient). Steady state accuracies were i 10F. -

S-I
Appendix E contains our end to end, 99X confidence level. data

acquisition system and instrumentation accuracies for the diagnostic test

system. There are two exceptions to this list. Torque spring position

was measured by a HOVATS THO, and on Valves 3, 4. 5. and 6 stem force was

measured by General Physics load washers instead of stem-mounted load

cells. Valves 1 and 2 had both the stem-mounted load cell and the load

washers, with acceptable agreement between instruments. Additional

Information on the accuracy of the load washers can be obtained from the

developer at Point Beach Nuclear Power Station.

Finally, the calibration lab at the INEL Is continually audited by the

U.S. government and outside agencies. It has recently been audited by

Portland General Electric and Gulf States Utilities. and no problems were

found.

In response to this need, EPRI sponsored an independent review of the

NRC/INEL Gate Valve Test Program (Phases 1 and 2). The review was

carried out by HPR Associates with assistance from an industry inspection

team and with oversight from the EPRI NOV Performance Prediction Program

Technical Advisory Group.

The objectives of the review were to:

- Develop an understanding of the scope and applicability

of the test results both for valves installed in the

specific BWR systems under study and to industry IOVs in

general.

- Document detailed information on the test valves, such

that the test results and implications to specific

valves could be evaluated.

- Document the principal results of the test program.

Including observed valve performance.

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1 I1
- Develop lessons learned from these tests to better plan

the EPRI.MOV Performance Prediction Program.

- . Identify.-generally, gate valve design details which

,need to be properly addressed to obtain satisfactory

performance under severe blowdown isolation conditions.

The scope of the review included:

a detailed post-test inspection of the valves tested.

an assessment of the applicability of the valve designs

tested to Industry HOVs,

a limited assessment of the applicability of the

conditions tested both to design basis conditions for

the BWR systems under study and to design basis

conditions for industry valves in general, and

a detailed review of the test data, using primarily

published data plots, focusing on determination of the

"apparent disk factor" implied by the data for all valve

strokes performed with differential pressure and

relating these results to'the conditions tested and

valve internal damage sustained.'- ,...I ' ' 'ti . ', -: . -: '' .

; i :: '- * ., . . ... .

Overall, the INEL test program has provided a substantial quantity of MOV

differential pressure test data. This information has, allowed the

development of Insights on gate valve performance primarily under

blowdown isolation conditions. However, because of the specific approach

and conditions of these tests, their application to specific plant HOVs

requires detailed and careful evaluation of the test configuration, test

conditions and test results. The following summarizes key findings of

this review.: - - - . .

APPLICABILITY OF NRC/INEL TEST.CONDITIONS.

Blowdown Closure Tests .

- Blowdown closure :tests are applicable-to gate valves We agree, blowdown test conditions are applicable only to valves that

S-3
having a design basis requirement to Isolate under

blowdown flow conditions. A small fraction (less than

5X) of safety-related HOVs in the nuclear industry are

in this category.

HOVs in the RCIC. HPCI and RWCU systems are only

required to Isolate a break once. Because of the

potential for valve damage under blowdown conditions.

only the first blowdown isolation closure test for each

valve design Is considered potentially applicable to

valves installed in these systems.

The first blowdown closure test performed on Valve A

included nitrogen (rather than hot water) flow during

the last 60X of the valve stroke. Several of the

subsequent blowdown isolations for Valves A and 8

(Phase 1) showed evidence of some nitrogen passage

during the tests. Nitrogen flow isolation is not a

design condition of any industry NOV in a RCIC. HPCI or

RWCU system.

have a design basis requirement to isolate under these conditions. The

exact percentage of valves in this category is unknown to us.

The EPRI report points out that the GI-87 valves need to close against

pipe break flow only once. We agree, and that is why we designed the

test program so that in every case (with the exception of Valve A) the

first blowdown was the design basis test for that valve. Four of the six

valves in Phase II responded nonpredictably in their design basis tests.

The following parametric tests were performed to provide information on

performance across a wide range of pressures and fluid conditions.

We disagree with the number of Phase I tests The EPRI Report challenged

because of nitrogen flow. The EPRI Report claims seven tests with dry

nitrogen and eight with some nitrogen entrainment. Our analysis in

Section 3.4.6 of this report shows that only three of the primary

blowdown closure strokes for Phase I saw nitrogen entrainment. Four

other tests saw no nitrogen entrainment during the primary closure but

experienced nitrogen entrainment during the subsequent optional blowdown

open/close strokes. Evidence does not support dry nitrogen flow during

any Phase I test.

We agree that nitrogen flow is not a design condition for HPCI. RCIC. or

RWCU valves. However, when one analyzes on-the-seat valve performance

using the INEL correlation. one finds no difference between steam and the

steam/nitrogen mixture.

In all blowdown tests, there was significant valve DP

during mid-stroke, although there was considerable

variation among the test valves in this regard. It

appears large DP during mid-stroke is characteristic of

blowdown conditions and not of normal flow conditions to

which most HOVs are exposed. The mid-stroke DP affects

Section 3.2.1 contains a complete analysis of this EPRI comment. We

agree that piping systems can influence the pressure seen at the valve.

The Hark I System shown in 3.2.1 has less resistance than the test loops.

The point should be to establish the design basis requirement for any

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t1' I U11
valve performance and susceptibility to damage. Typical

BWRJ RVCU and HPCI systems have higher overall system

flow resistances than the NRC/INEL 6" and 10" loops.

respectively. Thus. valve DP during mid-stroke would be

less in actual BVR systems compared to NRC/INEL tests,

which would' tend to make valve performance more

favorable. Assessment of applicabilIty of'specific INEL

tests to plant valves/systems requires a detailed

comparison of the expected plant DP versus stroke

behavior to that developed during the INEL test (beyond

the~scope of this effort). -

Slowdown Opening Tests

- Blowdown opening (unisolation of break flow) generally

does not correspond to a design basis condition for

industry MOVs. Some applicability may exist for a very

limited number of NOVs, I.e.. PORY block valves.

valve and then calculate the line losses.

Ye have never quoted a safety function for i valve to initiate blowdown

flow. The results of these tests do show some Interesting responses and.

yield Insights into the phenomena effecting valve performance. We do not

know when flow begins to be a significant contributor to opening loads.

The facts, however, remain: the highest stem forces do not always occur

during unseating, and flow during opening can have a significant effect

on opening stem forces. ,.-. " , I , %:,

I I I

"Normal Flow" Closing and Opening Tests

- Because of the test system configuration, the "normal

flow" conditions in the NRC/INEL tests resulted' In

negligible differential pressures for Sof the 8 valves

tested (A, B. 4, 5 and 6). Data from these S tests

would be applicable to those valves which operate under

low differential pressures, but provide little insight

into valve disk/seat friction under high DP.

It was not our intent to duplicate every possible DP condition in our

test program, but rather to simulate a range of DP conditions and then

develop, from the results, a workable understanding of valve behavior.

It is true that the results from tests with very low DP were not as

useful to us as some of the other results. However, those normal flow

tests during which we were able to establish an on-the-seat normalized

normal loading greater than 400 lb/in2 contributed to the correlation

shown in.Figures 10 and 11 (Section 3.2.5). Since then we have been

working with utilities that are performing differential pressure testing

with proven diagnostic measurement equipment. We have analyzed some

pumped low flow differential pressure tests where the on-the-seat

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normalized normal loading did not reach the 400 lb1/in2 cutoff. One

utility tested one 4-in., seven 8-in., and one 12-in. gate valve at

pressures of 80 to 200 psig. A second utility tested four gate valves

(one each at 3. 6. 10. and 12 in.) at pressures of 70 to ISO psig. All

of the testing was done at fluid conditions greater than 70F subcooling.

Figure 12 (Section 3) shows the result of that analysis. We believe that

when the results of our testing are properly used to understand the

response of a gate valve, they are applicable.

Although moderate differential pressures were developed

during tests of 3 of 8 valves (1. 2 and 3), an unusual

behavior of DP with stroke observed during these tests

makes assessment of these data extremely difficult.

Further evaluation of these data is planned. Until more

detailed assessment is performed.results of these tests

should not be applied to HOVs in nuclear power plants.

Quantitative information on flow rate in normal flow

tests is not in the published NRC/INEL data. Hence, an

evaluation of applicability of flow rates has not been

performed.

For the reasons discussed above, we found these data, too, quite

valuable.

Flow rate data for every test in Phase I was published in NUREGICR-5406.

Volume 11, Data Report. Figure 2 of NUREG/CR-5406 is the flow rate

versus DP calibration of the flow meter, and the fourth plot (DPi) for

each test shows fluid flow versus time for that test. Phase 11 flow

rates were published in Phase 11 data report. EGG-SSRE-8970. for those

tests with flow rates within the calibrated range of the KWU flowmeters.

"No-Flow" Openino Tests

- Tests performed ostensibly under "no-flow" conditions

actually resulted in a brief period of flow as the valve

opened. Some useful information on disk friction is

obtained from these tests prior to flow initiation. In

addition, the "no-flow" tests performed on the 6-inch

valves under both hot and cold water conditions resulted

in DP versus stroke behavior similar to that expected

for typical power plant pumped flow systems. Hence, it

appears these data are potentially applicable to a wide

range of applications. Also, these tests provide a

basis for comparing performance between blowdown

The leakage and the cold and hot cyclic no-flow tests were part of the

ANSI 816.41 valve qualification tests. The NRC wanted to be assured that

the valves subjected to design basis flow Interruption tests would have

passed the nuclear valve qualification tests. The tests were applicable

for what they were intended. The no-flow tests (and normal flow tests)

performed prior to and after each blowdown were designed to represent

possible in plant performance tests and were performed to obtain data for

possible extrapolation analysis. We were hoping to find something in the

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,. .

I
'I.,

conditions and milder conditions. However. hot 'noflow" tests performed on 10-inch valves developed

blowdown-like conditions for the first few seconds of

the stroke. Therefore. these tests would have very

limited-potential applicability, I.e.. only to valves

required to open against blowdown flow conditions.

collected data that could indicate how the valves would perform at design

basis blowdown conditlons. To date we have not been able to predict

valve performance using no-flow data.

The EPRI Report suggest that our designation of these tests as no-flow

tests is a misnomer. Our use of this term was based on the fact that

during these tests. there was no flow at the discharge end of the test

facility.

APPLICABILITY OF NRC/INELJTEST VALVES

INEL tested two 6-Inch flexible wedge'gate valves (Valves A and B) in the

Phase I program. INEkitested three 6-inch flexible wedge gate valves

(Valves 1. 2 and 3) and three 10-Inch- flexible wedge gate valves (Valves

4, 5 and 6) in the Phase 2 program. Valves A and B were refurbished and

re-used as Valves:I and-2 In Phase 2. Based on inspectiors'of Valves I

through 6 and discussion with the manufacturers:

- Anchor/Darling indicates that Valve I is not

representative of Anchor/Darling valves supplied to the

nuclear industry. Specifically, the Valve 1 downstream

disk hardfacing is thinner and-the edge sharper than

Anchor/Darling requires in their manufacturing process.

These conditions ire considered detrimental to valve

performance.! Valve l was refurbished between Phase 1

and Phase 2 of, the NRC/INEL, tests. The atypical

condition:of:the disk hardfacing could have been the

result of this refurbishment which was not 'performed by

Anchor/Darling.. Test results for Valve I are not

considered applicable'to typical Anchor/Darling valves

meeting the manufacturer's hardfacing and manufacturing

requirements.

Valve I was manufactured for the test program by Anchor/Darling and

originally tested as Valve A in Phase 1. As the EPRI report states,

"Anchor/Darling indicatea that Valve A to similar in design features to

a large population of flexible wedge gate valves they have manufactured

and upplied to nuclear power plants.' Afterithe Phase I tests and in

preparation for the Phase 11 program. Valve A was refurbished by Crane

Valve Services, Crane-Aloyco, Inc.

In the Phase 11 testing. Valve A was designated Valve I to help separate

test results between the two test programs. The valve was installed in

the system with flow direction reversed from Phase I so that the

downstream disc surface and valve body seat ring were original

Anchor/Darling surfaces. Thus, the performance of Valve I is

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representative of hardware delivered by the manufacturer to the INEL,

under the premise of being representative of their hardware delivered to

the nuclear Industry. A more complete discussion of this issue is

presented in Section 3.3.2 of this report.

All other valves tested (A, B. 2. 3. 4, 5 and 6) appear

to be representative of some gate valves produced by the

respective manufacturers. Specifically, they are

representative of valves with the same design features.

However, gate valves with different design features have

been provided in significant quantity to nuclear power

plants, particularly by Anchor/Darling (manufacturer of

Valves A and 4) and Velan (manufacturer of Valves 8 2

and 6). The NRC/INEL test valve designs are not the

same as these other valve designs.

Detailed applicability of test valve results to nuclear

power plant valves is dependent on internal valve

dimensions. Dimensions are available for Valves 1

through 6 from the industry inspection effort. Detailed

dimensions are available for Valves A and B for those

surfaces which were not reworked between Phases I and 2;

dimensions for surfaces which were reworked are

available only as nominal dimensions from manufacturer

drawings. This limitation hinders the use of these

data.

Because all of the valves were damaged to some extent

during the test sequence, at some point the

configuration was no longer applicable to nuclear power

plant valves. Because mid-test inspections were not

carried out, it cannot be known precisely when this

point occurred.

Together, the six valve designs tested by the INEL are representative of

most flex wedge gate valves used in nuclear power plants. The EPRI

report points out that the manufacturers have provided other designs to

the power plants and suggests that these other designs may perform

differently than those we tested. Experience from NRC/INEL testing and

from other similar testing Indicates otherwise. Section 3.3.1 presents

a complete discussion of this issue.

Hore is known about the dimensions of the Phase I and HI valves than is

known about most of the valves in nuclear power plants. The valve

designs are representative of actual nuclear power plant hardware

delivered by these manufacturers.

Valve Inspections between tests were considered for the Phase HI test,

but we later decided against them because of cost factors. Experience

had shown us that valve damage can be detected through a sensitive stem

thrust measurement. Using this method during the Phase HI testing, we

were able to detect every occurrence of valve damage.

OBSERVED VALVE PERFORMANCE UNDER BLOWDOWN CLOSURE CONDITIONS

Apparent disk factors (disk factor implied by measured DP and thrust The disc factors derived by the EPRI analyses are typically too low.

S-8

t ' '.1
using standard industry equation) required to achieve flow isolation on

the first blowdown closure stroke of each test valve are shown below.

Section 3.4.2 of this report addresses this issue.

Summary of First Blowdown Isolation Tests

Apparent

Size Test- DP at Disk Applicability . Valve Manufacturer (in) No. Fluid Isolation Factor, to Similar

(psi) for Flow Industry

* ^ . Isolation Valves*

A' 'Anchoi/Darling 6 A-3-5 Nitrogen 510 0.63 Potentially

. - Applicable I

i B ! Velan - 6 B-2-5 Hot 1000 ' 0.35 Applicable

..UWater .

1 Anchor/Darling . 65< 1-1-25- Hot 870 Valve N/ANot

Water - (0.86) . - Applicable

2 Velan 6 2-1-25 Hot 940 0.33 Applicable _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _W _ a te r_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

3 Walworth 6 -3-1-25 Hot e 870 0.19 Applicable __________ __________W ___________ ater_ _ _ _ _ _ _ _

4 Anchor/Dariing 10 4-1-25 Steam 700 0.49 Applicable

5 Powell 10 5-1-25 Steam 880 0.44 Applicable

Velan 10 6-1-25 Steam 1000 0.42 Potentially

Applicable

* Indicates applicability of test result (apparent disk factor) to valves in systems requiring blowdown isolation. Test is considered applicable

if both valve design details and test conditions are representative of some industry valves.

These data are considered potentially applicable only to similar valves We do not consider the information contained in this table to be valid;

installed in the BWR systems under study or other similar valves having the stem position chosen by EPRI for flow Isolation was in error.

as a design basis function the isolation of blowdown flows under the Section 3.4.3 explains our position on this issue. Also. the apparent

range of conditions tested. disc factors are based on the mean seat diameter, which is not always

used by industry.

S-9
The EPRI report attempts to limit the applicability of the INEL testing

to specific valves in specific systems under specific conditions. The

INEL test program was designed to test a representative sample of valves

to produce data that would contribute to an understanding of valve

performance. Our assessment of these data has resulted In a correlation

that can be used to bound the closing stem thrust of a predictable 5-

degree flexible wedge gate valve. This correlation Is applicable to a

wide range of conditions and systems. Provisions are included for

determining whether a given valve is typical of the valves tested by the

INEL and whether the INEL correlation can be used for that valve.

As previously discussed, the internal dimensions of Valve I are not

typical of valves supplied by the manufacturer and as a result the disk

factor implied by the data is not considered applicable to industry

valves.

Similarly, review of the data and observed damage for Valve 6 indicates

that significant deformation of the body guide rails apparently occurred

on the first hot cycle "no flow" opening test (at 1200 psi). This stroke

had blowdown-like conditions for the first few seconds, which is unlike

typical non-blowdown nuclear power plant systems. It appears the brief

blowdown-like conditions may have caused the damage. Therefore. it

appears all blowdown closure strokes for this valve were performed with

pre-existing damage and, as a result, the direct applicability of the

disk factor implied by the data to Industry valves is unknown. Although

the direct applicability of the blowdown closure test is unknown, It

would be expected that a blowdown closure stroke would have bent

undamaged body guides in a similar manner as did the opening test,

potentially resulting in similar valve performance as shown in the table

for Valve 6.

Section 3.3.2 of this report addresses this issue.

Damage to this valve consisted primarily of bent guides (abnormal seating

behavior) and damaged seats, guides, and disc (nonpredictable mid-stroke

behavior). We initially attempted to use the results of design basis

testing from that portion of the stroke where the disc first started to

ride on the seats, hoping to avoid the influence of the nonpredictable

behavior and yet avoid the results of abnormal interferences caused by

bent guides. However, upon further assessment of the response of this

valve during design basis blowdown testing, we decided not to use any of

the results from this valve in developing the INEL correlation. Note,

however, that the fact that the valve experienced damage when subjected

to its design basis conditions is a significant result.

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t. I
r.I I.

Further, the test conditions for Valve A on the first blowdown closure

stroke were atypical (N2 versus water) of those for industry valves, and

as a result,'the direct applicability of the disk factor' implied by the

data to industry'valveis unknown. Although the effect of nitrogen flow

is unknown. 'the presence of gas versus liquid flow would not nominally

be expected to significantly affect disk tilting and resulting

gouging/machining.' Therefore, the performance for Valve A shown in the

table is considered potentially representative of performance under water

flow conditions. *

With the'exception of the qualifiers discussed above, the disk factors

shown above should be ~taken' as an lndlcation~ of performance which can

potentially occur for'similar valve'designs and blowdown closure

conditions. It should be noted that disk factors for valves which

sustained substantial internal damage (Valves A, 1. 4, 6 and to a limited

extent 5) might be expected to vary considerably from the values

indicated.

Section 3.4.6 addresses the issue of nitrogen flow.

As discussed in detail in Sections 3.4.1 and 3.4.2 of this report, the

INEL disagrees with the dIsc factors recommended by EPRI in their report.

In particular.' the disc factors listed for flow isolation were taken from

a valve position prior to isolation, and thus they are not conservative.

The mean seat area was not generally used for calculating stem force when

the valve operators were originally sized, and the standard industry

equilon is incomplete.

GENERAL OBSERVATIONS

Effect of Stroke Historv

On all valves. appirenttdisk factors increased from in initial low level

(0.1 to 0.2) to a higher stable "plateau" level (above 0.3) when the

valve was first stroked at elevated temperature. Some data also

indicated an increase in disk factor with repeated strokes at cold

temperatures. Potential causes for this behavior include:

- removal of residual machining oil from valve internal

'surfaces.

- removal of an oxide layer on valve internal surfaces,

S-lI
and

- mechanical wear (microscopic or macroscopic) of valve

internal surfaces.

In the NRC/INEL tests. disk factor in cold tests performed after hot

tests remained at the stable level. Hence. information on valve

performance at hot conditions could be obtained from cold tests performed

after exposure to hot conditions. This is contrary to NRC and INEL

conclusions which indicate valves need to be tested at temperature to

obtain meaningful performance information.

Although some information can be obtained from cold tests, to date we

know of no way to determine if a valve is predictable except by testing

at design basis conditions. The normal flow testing we performed would

not have told us that four of the six valves tested in Phase II would

respond nonpredictably during their design basis tests.

As for sliding friction, we still see a temperature dependence for valve

performance. Through further analysis we have determined that valves

should be tested at conditions which produce similar sliding surface

lubrication (i.e.. thin-film lubrication). Fluid subcooling is an

important parameter In this behavior. See Appendix C for additional

information.

Behavior Beyond Slidincz Friction

During blowdown testing of some valves (A, 1. 4, 6 and to a limited

extent 5) significant internal damage occurred indicating that the disk

was not sliding on the guide/seat surfaces. Instead, the disk tilted in

the direction of flow and aggressively engaged body guide rails and

seats, resulting in gouging and machining. Valves sustaining such damage

generally had higher apparent disk factors which are not considered

representative of those expected under sliding friction conditions.

In addition, the body guides in Valve 6 were bent in the direction of

flow. It appears this bending first occurred during a "hot cycle" no-flow

opening test. As previously mentioned, blowdown-like conditions existed

for the first few seconds of this test and may have caused the damage.

We agree that stem forces required to close nonpredictable valves are not

representative of stem forces required to close predictable valves.

We agree that the Valve 6 body guides were bent during the first hot

cycle DP opening test. The portion of the guides that bent corresponds

with the last 8X of the valve closure cycle. Because of this, Valve 6

did not exhibit the normal closing plateau in the force trace when

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i, ' 1

I
i

This damage resulted in pinching of the disk on subsequent tests which

would not' be Indicative of sliding behavior. This damage is attributed

to the lack of sufficient structural support for the lower portion of the

body guides in this particular valve design.

It is expected that the potential for sustaining damage such as

gouging/machining of valve internals and/or plastic deformation of valve

internals is only significant under very high flow (blowdown) conditions

where significant DP exists in mid-stroke. Specifically, such damage and

the attendant high disk factors would not be expected for the vast

majority of industry valves." Most industry valves are in pumped flow

systems and. depending on the system frictional losses, would be expected

to develop significant differential pressures only whe the vailve disk . * 9 .1 i i - i !.- ; * r ! . i .1 ". t I 1 . I t ' ~ . '~ j , s-L; . .; I

Is on or very near the seats.'

Slidinq Friction Behavior '

sliding on the seat as seen in all other Phase I and 1I valves. For this

reason we were unable to use Valve 6 data in the INEL stem force

correlation. The other 92X of each Valve 6 stroke is not influenced by

the bent guides, and that information is applicable for analysis of

nonpredictable behavior and high mid-stroke loads during blowdown opening

cycles.

The damage'noted in these valves occurred during design basis blowdown

testing. The severity of the loadings contributed to the damage.

However, we currently have no way to assess a given loading or to

determine'whether valve damage will occur without testing the valve at - * ; * ., '

its design basis conditions. We have never suggested that all Industry

valves include blowdown conditions in their design bases.

, ; ,,, , Jo * ,, , * - .. *

_. I. r1 . I

All tests'were revieweidto identify' priods of the test during which

sliding friction was the predominant behavior. Apparent disk factors for

sliding friction generally were in the 0.1 to 0.4 range. Sliding

friction is representative of the behavior 'expected for most industry

valves, l e., valve' in pumped flow systems; This result Is generally

consistent with industry practice.

.. ... ~~ ~ . . , .. i .. ,. . ;. . ..

The only significant exception to this result was Valve 2'which hid a

significantly higher apparent disk factor (0.5 to 0.6) when the disk was

in the region between isolation and wedging, both on opening and closing.

This' result is attributed tothe involvement of additional surfaces (disk

* *, -,- -; ,- , ,. A.S ''

As discussed previously, we take exception with the methods used in the

EPRI report to evaluate apparent disc factors. The range quoted (0.1 to

0.4) is not supported by the data, and the use of mean seat diameter was

not the common practice in operator sizing. See Section 3.4.2 for

additional information.

Using appropriate analytical methods, Valve E and 2 test data provide onthe-seat disc friction values similar to the other valves' on-the-seat

disc friction. See Appendix C for the analysis method. The discussion

of Valve 2 in Section 3.4.5 addresses the possible effects of lateral

S-13
slot lateral contact with body guide) in this region. Indications of

similar performance were also observed on Valve 6. However. disk factors

were only slightly above 0.4.

Apparent disk factors for Sliding friction conditions in blowdown tests

showed good agreement with those in simpler 'no-flow" opening tests.

This result Indicates that as long as anomalous behavior (beyond

friction) is avoided. valve performance can be predicted or extrapolated

across a range of differential pressure conditions.

disc rotation.

We agree with this concept, but only under our stated constraints and

using an appropriate analytical method. Data supports extrapolation of

performance for predictable. 5-degree flexible wedge gate valves, in the

closing direction, using the INEL correlation. We know of no data

available to justify extending this concept to other valve designs.

Thrust Increase during Blowdown Opening

After initial unwedging and for a significant period afterward (I10 secs) an increase in required stem -thrust was observed on some

blowdown opening tests. This behavior is generally attributed to a

reduction in pressure below the disk due to high flow "Bernoulli"

effects. In at least one case (Valve 6), such behavior was potentially

the result of previously sustained valve damage (bent body guide).

As previously discussed, with the possible exception of PORV block

valves, blowdown opening Is not a design basis requirement for Industry

MOVs.

We believe this phrase should read "after initial unseating" not

"unwedging." After unwedging we see a period where the disc is sliding

on the seat and flow is still isolated. Only after unseating do we see

an increase in stem force caused by the high flow pressure loadings.

Valve 6 behavior during blowdown opening is not the result of the bent

body guide. The bent guides would cause high stem forces after hammer

blow due to the pinching of the guides. The stem forces would gradually

decrease until the disc passed from the bent portion of the guides.

Instead we see a large increase in stem force at unseating and the onset

of flow. The blowdown opening data for Valve 6 is not the result, even

partially, of bent body guides.

We agree.

PERSPECTIVE ON NRC/INEL CONCLUSIONS

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I, - I~~
i

In general, although the results of this test program do have potential

Implications for specific valves in specific systems. some of the NRC and

INEL conclusions documented to date imply data applicability beyond what

is warranted. A detailed perspective on each NRC and INEL conclusion is

presented in Section 8.

Aftertwo years of additional in-depth data analysis with extensive peer

review, we still find that almost all of the conclusions stated in the

NRC/INEL documents quoted in Section 8 of the EPRI report are correct.

See our comments in Section 8 for exceptions.

r ~- . t . it :,..-, 

RECOMMENDED FURTHER INEL TEST PROGRAM EVALUATION * C * *; ;" ' ! ' "- : ' I -

Further investigation isrecommended in the following areas: ! !t ' ' z 1 . :_ t -. '. " i'S j . , 

-INEL digital data should be examined to: . ..

Comment on this section is beyond the scope of this review.

. =- confirm values obtained from plots. .'' ' .~ .' ' "' up? '' .* - ' - . : '

further assess details of "normal flow" tests

-,-; , further assess test system and flow effects on ,.- ¢valve-performance. 2 ---hi At .

- A detailed measurement accuracy evaluation should be

obtained from INEL-. , , .

- *. DetalIs on Instrument calibration methods and frequency

should be obtained from INEL-.

- Detailed valve dimensions from the inspection should be

used to develop and evaluate a model for predicting

disk/guide/seat interaction and potential for damaging

behavior.

A correlation of measured surface roughness and iron

content values with observed valve performance should be

made.

LESSnNS LEARNED FOR EPRI NOV PERFORMANCE.PREDICTION PROGRAM

Based on this review of the NRC/INEL data and the valve inspection

activities, several01insights were gained which should be considered in

the EPRI MOV PerformancePrediction Program as follows:

Comnent on the EPRI MOV Performance Prediction Program is beyond the

scope of this review.

S-IS
Test hardware (valves and operators) should be

extensively characterized riLor to-testing. Information

should be obtained and documented according to

procedures. and should include dimensional measurements,

photographs.. and performance information such as motor

characteristics, spring pack stiffness. etc.

The hardware vendors should be involved with the test

program to lend immediate information on valve set up.

performance, dimensional characteristics, Inspection

interpretations. etc.

- Flow loop testing should generally progress from less

severe to more severe conditions.

- Valves should be Internally inspected between strokes to

check for. damage. .

- Flow loops for testing should cover conditions typical

of nuclear, power. plant systems containing applicable

MOVs. Further, the systems should have configurational

and operational flexibility so that ranges of parameters

(e.g.. flow, pressure) can be covered in the tests.

- The NOV performance prediction methodology should

incorporate insight on valve performance gained from the

NRC/INEL tests..

- Separate effects elements for friction testing should

investigate the stroke/temperature history effect and

the effect of iron content.

- Separate effects analyses and flow loop tests to cover

flow effects (Bernoulli effect) on valve stem force

should be included.

- Testing to reproduce and explain the NRC/INEL Valve 2

behavior (unusually, high disk factor near wedged

position) is warranted.

KEY VALVE DESIGN CHARACTERISTICS

Several aspects of valve design which appear to be Important to achieving Comment on this section is beyond the scope of this review. However, we

optimal and repeatable valve performance under severe blowdown isolation caution the reader that not all of these statements are fully supported

S-16

P 1 I1
j

conditions were qualitatively identified through this review, by data.

Disk-to-Guide Clearance (fore. aft and lateral)

These clearances should be large enough to eliminate the

potential for binding (observed particularly in the

lateral direction in the NRC/INEL tests) yet not so

large as to allow significant disk tilting in the

direction of flow.

Guide Slat and Guide Rail Surface Finish

A smooth flat surface appears to be favorable. As-cast.

unmachined surfaces appear to aggravate the severity of

internal valve damage.

Edge Configuration of Disk Guide Slots. Disk and Body

Hardfacing on Seats

Sharp edges appear to increase the potential for

gouging/machining of internal surfaces. Rounded or

beveled edges appear to be more favorable.

Body Guide Rail Length

Guide rails should be of sufficient length to allow a

smooth transition of the disk from guide to seat without

significant disk tilting.

Disk Guide Slot Length

Disk guide slots should be long enough to adequately

constrain disk tilting and provide adequate load bearing

area.

Body Guide Rail Support.

Guide rails should be adequately supported throughout

their length to minimize the potential for plastic

deformation in the direction of flow.

- Guide Slot-and Rail Hardfacing

Hardfacing of body guide and disk slots would appear to

be beneficial although sufficient data was not obtained

,., S

S-17
from this program to fully evaluate this aspect.

Hardfacing Iron Content.

Iron dilution from base metal into the hardfacing

material may degrade the hardfacing's friction and wear

properties. Hardfacing procedures which require

application of several layers of hardfacing to the disk

and body seat base metal and control of hardfacing

thickness during subsequent machining should minimize

the potential for significant iron dilution.

S-18

! ; II I 4a
Section 1

INTRODUCTION

BACKGROUND

Two phases of testing of motor operated gate valves have been performed

by Idaho National Engineering Laboratory (INEL) under the sponsorship of

the United States Nuclear Regulatory Commission (NRC). Phase I testing

was performed during 1988 on two 6Finch valves (referred to as Valves A

& B) intended' to represent typical BWR Reactor'Water Clean-up (RWCU)

supply line-isolation valves. Phase'2'testing was performed during 1989

on six valves -- three 6-inch valves (referred to as Valves 1, 2 and 3)

and three 10-inch, valves (referred to -as' Valves 4. 5 and 6). These

valves were intended to represent typical 8WR RWCU. High Pressure Codlint

Injection (HPCI) steam supply and Reactor Core Isolation Cooling (RCIC)

steam supply isolation valves. The NRC/INEL tests covered high energy

blowdown flow conditions (intended to simulate pipe break conditions) and

selected lower flow conditions.

INEL and NRC have published conclusions and recommendations based on the

results of these tests. These-conclusions and recomnendatlons'(and their

appropriate source documents) are described in this report. The most

significant conclusions made by NRC and INEL-are that the-gate valves

which were tested required stem forces greater than predicted by existing

industry sizing equations.-and that some of the valves showed unexpected

behavior which is attributed to valve internal damage. These conclusions

are based strongly on-the observed results under the severe blowdown

conditions. Based on these tests, NRC has indicated concerns with NOV

performance in nuclear power plants.

No INEL comnents are appropriate for this section.

1-1
This report presents results of a short-term, EPRI-led effort to

independently evaluate the NRC/INEL tests. The objectives of this effort

are discussed below.

OBJECTIVES

The objectives of this effort are as follows:

- Develop an independent understanding of the scope, results and

implications of the NRC/INEL tests so that utilities

(particularly BWR s) can effectively deal with.NRC concerns.

Develop information needed to help interpret and explain NOV

performance in the NRC/INEL tests, so that the implications to

specific valves in nuclear power plant systems can be evaluated.

- Identify areas where detailed evaluation of the NRC/INEL data

should be pursued.

- Identify needed and desired elements of the EPRI NOV Performance

Prediction Program based on NRC/INEL test results.

- Identify, generally, valve design features

properly addressed to obtain satisfactory

severe blowdown isolation conditions.

Because of the short-term nature of this effort, the

as described below.

which need to be

performance under

scope was limited,

SCOPE OF EFFORT

The scope of this effort included:

- Evaluation of the applicability of the NRC/INEL blowdown test

1-2

I* . I
conditions to design basis conditions of valves in nuclear power

plants.

Scoping evaluation of NRC/INEL data (using published data

plots), with particular emphasis on determining "apparent disk

factor"1 for all valve strokes performed with differential

pressure (DP) and relating these results to the test conditions.

Inspection of NRC/INEL Phase 2 valves to obtain valve

configuration and other information to support evaluating the

test results and their applicability to nuclear power plant

valves.

Evaluation of likely causes for observed valve behavior.

General assessment of Implications for the EPRI NOV Performance

Prediction Program.

Because of the short-term nature of this task, it was not possible to

completely resolve the technical is'uesin these areas. In many places

this report identifies additional questions or areas where more detailed

evaluation is required.

ORGANIZATION OF REPORT

Section 2 presents a discussion of the applicability of test conditions

used In NRC/INEL. tests to the design basis:conditions of valves in

nuclear power plants. This section-incorporates work-presented tofthe

NRC in March 1990 (Reference 3). Section 3 discusses the applicability

of. the valves used in the NRC/INEL tests to valves in- nuclear power

plants.

. 4 .,

1-3
Section 4 describes the activities covered in the inspection of the

NRC/INEL valves and the results from the inspection. Section 5 describes

the methods and data used in the review of NRC/INEL data and the approach

used in the analysis of the data. Section 6 discusses the evaluation of

valve performance in the NRC/INEL tests based on the test data review and

inspection results. Section 7 discusses recommendations for future

efforts as a result of the findings of this work. Section*8 presents a

discussion of insights this effort has yielded on existing NRC and INEL

conclusions.

1. Apparent disk factor is the disk factor determined from the data

using the standard industry gate valve thrust equation. See Section S.

1-4

? 11 I~ I a
J

Section 2

APPLICABILITY OF TEST CONDITIONS

USED IN NRC/INEL TESTS

TYPES OF TEST CONDITIONS

In general. there were three types of test conditions used for valve

strokes with differential pressure (DP) in the NRC/INEL tests. These are

described in the table below.

Type General Procedure DP Behavior'

No Flow Upstream side pressurized and DP rapidly dissipated asdownstream

(Open strokes downstream depressurzed; valve volume pressurized. .-

only) opened.

Normal Flow Flow established using pump (Phase.) ODP increased as valve closed and then..

(Close and open or orifice (Phase 2); valve stroked dissipated as valve opened. In most

: strokes] ; . closed then opened; - cases this OP wais very small at'ill l

. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ times.

Blowdown - Flowsestablished'using quick-opening r DP increased as valve closed and thenl

(Close and open device; valve stroked closed and then decreased as valve opened. In all .

strokes) - ; partially opened and re-closedcases this OP was substantial .,.,, .. , .. ..., ..- ,, -e.,.- of-;, . _,, , , throughout the stroke.:

" '' '' I' ''' D ''!. ,, . , ., . , 

. I..

,,;I -I t . -'7

. 1. -i ! : - : - - ,

Figures 2-1 through 2-4 show sample-time histories of'selected valve

strokes-;; Each`figure Includes A ciurve of upstream pressure; valve

differentiallpressure and'stem position. These graphs were constructed

using digital data files provided by INEL.

- Flgure 2-1 shows data for a no-flow stroke (6-inch valve

with hot water conditions).

Figure 2-2. shows 'dataifor a blowdown closure stroke

(10-inch valve with steam conditions).

I I

2-1
Figure 2-3 shows data for a closure/opening cycle under

normal steam flow conditions for a 10-inch valve.

Figure 2-4 shows data for a closure/opening cycle under

normal hot water flow conditions for a six-inch valve.

The valve DP behavior throughout the stroke differs considerably between

these selected strokes. -To permit the data from several valve strokes

to be effectively compared. normalized DP (DP/upstream pressure) versus

normalized stroke position (% open) was plotted. Figures 2-5. 2-6 and

2-7 show comparisons of several valve strokes under no-flow, normal flow

and blowdown conditions, respectively. Once again. these data are from

digital data files provided by INEL. except for data for Valves A-and B

on Figure 2-7. which are taken from data plots from Reference 1. Each

graph also includes a curve representing the DP/stroke behavior for a

typical NOV in a six-inch, cold water pumped system in a nuclear power

plant, based on data from Toledo Edison.- The applicability of each type

of INEL test condition to design basis conditions for valves in nuclear

power plants is discussed separately below.

We are not surprised at the differences in DP behavior shown in

Figures 2-1 through 2-4. However, we are concerned about the use of

normalized DP (DPl/upstream pressmua). The pressure under the disc acts

on the valve stem through the valve disc to produce the stem rejection

load (piston effect), one differential pressure (upstream and downstream

disc surfaces) loads the disc producing disc drag, and another

differential pressure (top and bottom disc surfaces) provides additional

rejection type loads. These differential pressure forces produce the

primary loadings on a valve irrespective of whether the flow has been

isolated. The DP used by the EPRI report is simply the difference

between the upstream and downstream pressure measurements. As such, the

ratio of DP divided by upstream pressure does not represent real valve

loading, nor does it represent all the components that load a valve.

Comparisons of this ratio between tests does not even provide insight on

test severity. Consider, for example, that a low-pressure test with an

upstream pressure of 75 psig and a differential pressure of 60 psid has

a normalized DP of 0.8, while a high-pressure test with an upstream

pressure of 1500 psig and a differential pressure of 600 psid has a

normalized DP of 0.4.

In the no flow test (Figure 2-1) and low flow tests (Figures 2-3 and

2-4). upstream pressure remains essentially constant for the complete

valve cycle. Here the EPRI report normalized DP can be thought of as

merely expressing DP as a percentage of initial pressure. Packing drag

and sten rejection forces are significant in low flow applications; these

are not represented by normalized DP. Where upstream pressure holds

constant, normalized OP may be proportional to the forces acting on the

2-2

I II ~ ~
disc, but not related to the total stem force.

In blowdown'tests (Figure 2-2), upstream pressure drops with flow and may

not fully recover to its pretest value, even at closure. With the

upstream, bonnet, and under disc pressure changing independently. the

normalized DP is not proportional to disc forces. Packing drag and stem

rejection forces are once again not represented, although they are less

significant in blowdon tests. The actual ratio of DP to upstream

pressure can be affected by many conditIons, including upstream pressure,

flow rate, flow medium (water or steam), flow restriction (upstream or

downstream of the valve), subcooling (with the possibility of flashing),

direction of valve actuation (opening or' cloing), and rate of valve

actuation. Comparisons of such ratios, 'such as those shown in EPRI's

Figures 2-5 through 2-7.'are not useful indicitori of DP behavior unless

it is known that all those conditions are the same for the tests being

compared. Even then, it Is unlikely that such ratios will provide the

analyst any useful Information.

. I . .j : .- , :

. . I . I I . .- . !. I 11

I - I 1.! I

, I. 1 - 1, , f;

APPLICABILITY OF BLOVDOVNCCONDITIONS i T

The blowdown test conditions used in' the NRC/INEL tests were first

evaluated to determine what type of conditions were achieved and how thisw

would compare to design basis' blowdown conditions in nuclear power

plants. Then, the blowdown test conditions were compared to the ': , I - I ; , I , . * .. Il i,- ,. -

population of nuclear power plant valves to determine the overall - . , . r .. . , . . * . . a ..

applicability of these types of flow conditions. These evaluations are

discussed below.

range 'o'i -Biow-own,`,Co,- -A'itions' -:t

I  ! . .. I .  I

; .Jo

. . - I I., !'' I 1- . .

. Figure 24 shows norIIzed DP vs. stroke behavior for blowdowns of four I . . - I- . 11 - I;. . .I L i .. I . . I II

Normalized DP is not a valid method for evaluating valve loading. and

2-3
of the 6-inch valves (A. B. 1. and 2) and for one of the 10-inch

valves (4). The conditions were similar for the 10-inch valves. so it

is only necessary to show one curve. As shown, however, there was quite

a variation of conditions for the 6-inch valves. Important points

gathered from this evaluation are summarized below.

1. Blowdown conditions for 10-inch valves were the most severe in

terms of the differential pressure loading during mid-stroke.

Specifically the DP was about 60% of the upstream pressure as

the valve started to close, increased to over 80% of upstream

pressure as the valve closed halfway and then to 100% of

upstream pressure at flow isolation. These conditions would be

expected to more strongly load the guide surfaces (i.e.. during

mid-stroke) in comparison to most of the 6-inch valve strokes.

2. The conditions for the first blowdown stroke of Valve A were

much more erratic and more severe during midstroke than other

blowdown strokes for six-inch valves. As discussed more

extensively below, it appears this blowdown had nitrogen flow

for a significant portion of the valve stroke. The passage of

the water/nitrogen front and subsequent nitrogen flow are

believed to have caused the particular DP behavior.

3. Blowdown conditions for 6-inch valves, even when tested in the

same loop, showed considerable differences. For example. Valves

I and 2 showed significantly different behavior during midstroke (Figure 2-7). Although some of this behavior may be

attributable to valve flow resistance differences, It appears

more likely there were differences in the way the test facility

operated. Valve 3. although not shown, started off with a DP

comparisons between tests based on normalized DP are not appropriate as

discussed above.

The 10-inch valves are representative of HPCI steam supply isolation

valves. OP during stroke is representative of GI-87 type closures.

Valve 2 (6-inch) was tested with steam (GI-87 RCIC application) and

produced similar DP loadings. The DP and stroke relationship of valves

in a steam environment is expected to differ from valves in hot water

with flashing environments.

Discussion of nitrogen flow during the first blowdown test using Valve A

is presented in Section 3.4.6 of this report. During this test, upstream

pressure started at 1000 psig but dropped severely during the valve

closure. The normalized DP ratio shows what appears to be very high

loading, when in fact final upstream pressures and maximum DPs were only

on the order of 400 psi. Here again, normalized DP does not represent

real valve loading.

Figure 2-7 in the EPRI report actually shows that without a significant

loss in upstream pressure. Valves I (A) and 2 (E) show different but very

reproducible behavior between Phases I and It. Note how the Valve I and

A traces lie almost on top of one another. The same is true for Valve 2

and 8. Recall that Phase I and 11 used different test facilities with

completely different piping configurations. The EPRI report's argument

for a difference in how the facilities operated as the cause of the

2-4

v. , . a I. I a
behavior similar to Valve 2 and then suddenly "switched" during

mid-stroke'to a'behavior similar to Valve 1.: The root cause for

the differentnbehaviors is not known.`

In sumnsary, a wide range of DP versus stroke behavior is observed in the

NRC/INEL valve tests. The DP versus stroke behavior can significantly

influence valve performance because itiaffects how strongly the disk is

bloaded while it is still sliding on the guides and trinsitioning to the

seat.; The DP versus stroke behavior for valves with blowdown design

basi'sconditiotns in:'nu1ear power plants would be dependent on the

details of ptant-unique piping configuration. The piping configuration

is important becaute systems with high overall flow resistance would have

more flow pressuire losses in the system and less DP across the 'vlie

during mindstroke. Cess' severe DP in_!mid-stroke is more favorable to

vale performaniice because the valve disk is not loaded as heavily wh ile

it is sliding on the guides and tnsiti ing to the seat. The`NRC/iNEL

test conditionhs were more severe' in this regard since system flow

'reistance' wi' loe -in theI te'stisthan in a typical BWR' (see table

below). - - -K- , *v*-....

difference between valve responses is not supported by the data.

As previously discussed. normalized DP is not a valid method for

evaluating valve loading, and comparisons between tests based on

normalized DP are not appropriate.

As discussed in Section 3.2.1, a Hark I RVCU supply line would typically

have only half the line losses of the Phase It test loop. Conditions for

a Hark I would therefore be more severe. A Hark 11 RWCU supply line

would have greater line losses.

System BFR Resistance and Basis INEL Test Resistance and Basis

RWCU. 32.9 (net K from reactor vessel to-. 1.6 (Phase.1) 2.7 (Phase 2) (net K from

first isolation valve. based on 6" pressure tank to isolation valve, based on 6 -pp}- Mpipe) e -

HIt 1.5 (net K from reactor vessel to 0.6 (net K from pressure tank to isolation valve.

first isolation valve, based on10" based on 10" pipe)

pipe)

a ,;- 11 .-. , , 1 ., -8- I . .

Nitrogen Flow through Valves I

In Phase I tests, an accumulator with a nitrogen overpressure was used

. . .. . .. . ..... 

Ve disagree with EPRI's conclusion that flow through any of the Phase I

2-5
to provide the blowdown flow. In some of the blowdown isolation strokes.

it appears the flow was entirely nitrogen during the latter part of the

stroke. In others. it appears there may have been significant nitrogen

entrainment. These conclusions were inferred from the data plots. as

discussed below.

A complete transition from water to nitrogen flow appeared to occur on

the first blowdown stroke of Valve A (Test 3 Step 5). Figure 2-8 shows

the OP across the upstream flowmeter and across the test valve. At a

time of about 8 seconds, the flowmeter DP drops sharply. After about one

second. it rises again. If a water/nitrogen interface passed through the

system, the flowneter at the upstream end of the system would first show

a sharp drop as the fluid density dropped. Then, as the water slug in

the system was accelerated and ejected from the system, the DP would

Increase, first gradually (during acceleration) and then sharply (at

ejection). This behavior is seen on the flowmeter DP plot in Figure 2-8.

At the test valve location, which is further downstream, DP would be

expected to increase as the water slug was accelerated, drop as the

nitrogen arrived at the valve and then increase as the slug cleared.

This is consistent with' the observed behavior, although the times are not

as sharply defined. This could be due to a blending of nitrogen and

water as it flowed downstream. Nonetheless; it appears that after about

10 to 14 seconds,' when the valve was about 30-45% closed, only nitrogen

was flowing through the valve. The valve stem force plot, also shown In

Figure 2-8. shows that substantial forces developed only in the last onehalf of the valve stroke, i.e.. when nitrogen flow was occurring.

While the presence of dry nitrogen can result in higher friction factors

on valve parts, the effects of nitrogen flow versus saturated water flow

are not known for these tests. Table 2-1 identifies the valve blowdown

strokes from Phase;I where It appears nitrogen flow replaced water flow

valves was ever entirely nitrogen. Nitrogen entrainment did occur in

seven out of 24 full flow strokes.'

Section 3.4.6 of this report discusses our analysts to determine when

nitrogen flow occurred. Qry nitrogen flow did not occur during any of

the Phase I tests.

The tests identified in Table 2-1 experienced nitrogen entrainment, not

dry nitrogen flow.

2-6

t. ' I. ~AI 
at some point in the stroke, and the approximate stroke position where

this ' took' place. '" The' Information In this table Is based 'on' data

interpretation as discussed above.

In other strokes of the Phase;ltesting. it appears some nitrogen may

have been passed through the blowdown pipe and test valve during the

stroke without a complete transition from water to nitrogen occurring.

Figure 2-9 shows the flowmeter DOPand valve DP for the second blowdown

stroke of Valve A (Test 2 Step 5). At a time of about 22 seconds, a

significant'disruptIo66 or'the' flowmiyeter P Is' seen.' TheDP drops tozero, remains'there for aboutjone 'second, and then oscillates Sharply.

A slug of nitrogen being passed at about the same velocity as water would

give'rlse to a temporary low-flowmeter'DP. The disturbance is seen

slightly lateroat the valve (23-26 sec) as a somewhat attenuated DP

variation. This behavior began when the valve was about 60% closed and

seemed to settle out as the valve went to the fully closed position. The'

stem thrust trace for 'this valve is also shown on Figure 2-9.

Significant stem forcei ncrease occurred during the Iast 35X of the

stroke. i e., when nitrogen flow was occurring. .ok. I.e.. wh-n*nit 0 .

The effects of passing slugs of nitrogen through the system on valve

performance'are'not'known for these tests. Table 2-2 Identifies the

valve blowdown strokes from Phase I where it appears nitrogen slugs may

have been passed through the system, and the approximate stroke position

where this took place. The'informatioi in this table is based on data

interpretation as discussed above.

Overall, the'-presence of 'nitrogen' (continuous' or in slugs) does not

appear to be directly applicable to blowdown isolation design basis

conditions for valves in nuclear power plants.

In the test referred to here (Valve A, Test 2, Step 5). only one half of

the water volume in the accumulator was consumed. Ve see no way that

slugs of nitrogen could pass down through approximately eight feet of

standing water'to enter the ping system. Video recordings and other

system instrumentation support the' conclusion that no nitrogen flow

occurred during this test. ' ' .

All of the tests identified in Table 2-2 closed on water flashing to

steam (water/steam slug flow) without nitrogen entrainment.

Section 3.2.7 of this report discusses the effect of nitrogen and water

vapor mixture on the valve's on-the-seat performance. Valve A's on-theseat data are included in our Figures 10 and 11. The Valve A data line

up well with data from all the rest of the. Phase I and II valves. Note

2-7
also that there is nothing in the EPRI reports' Figure 2-8 to indicate

that nitrogen entrainment had any effect on the measured stem force.

Applicabilitv of Blowdown Conditions to Overall Valve Population

Two methods were used to evaluate applicability of blowdown conditions:

a valve loading severity evaluation and a condition-similarity

evaluation.

Valve Loadinc Severity. The valve loading severity evaluation examined

the contact force and contact stress between the valve disk and seat as

indicative of loading severity. This approach was studied because many

valve applications involve smaller valves and/or lower differential

pressures than the INEL tests; both of these parameter effects lead to

lower contact forces and stresses and would be intuitively expected to

yield improved sliding interaction. Contact force is defined as

Contact force * (DP) x (A)

where A - nominal area * 1D2/4 where D is the nominal valve diameter.

This analysis using nominal valve diameter contradicts the EPRI methods

used in Section 5. where mean seat diameter is used. We agree with the

use of mean seat diameter and question the use here of nominal diameter.

Several valves of the same nominal size can have widely varying mean seat

diameters.

Because of lack of detailed Information about valve-specific seat contact

widths, contact stress was evaluated in accordance with a "linear stress'

parameter.

Linear stress - (DP) x (A)/(C)

where C * nominal circumference - O. This parameter is the force per

un t length of circumference between disk and seat.

During 1989, an NOV population data base was established by MPR for EPRI

It may be true for the EPRI data base that valve-specific seat

information is unavailable. However, the information is available for

the NRC/INEL valves. The EPRI report contains the results of the

NRC/EPRI posttest characterization of the Phase I and II test hardware,

including the valve-specific seat information.

We agree that the Phase I and 11 blowdown conditions are applicable to

2-8

: I I
.9

(see. for example. Reference 4). The data base covered about 10X of the

safety related NOV's in U. S.' nuclear power plants, or over 1500 valves.

This data base was eviluited to 'select all *of the gate valves for which

the' design bifs DP was known, which provided i sample of 404 valves.

These 474jvilves represent 44X of the 9i3 gite valves In the database.

Figures 2-10Oandt2-11 show this population' In teims of contact load and

linear strss respectively. Also shown on these graphs are the RWCU and

HPCI steam isolition' valve conditions bised' on the 6" and 10" valve

conditiohi uied In the NRC/INEL: testi. These graphs "show'that the

majority 'of gate valves 6perite with much lower contact forces And

stresses than existed for the' NRC/INEL test conditlons. Hence -it was

concluded that the 6ondIfIoni covered in the NRC/INEL blowdown tests.

expressed in terms of contact loid 'and stress, apply to only a small

fraction' of the valves in Kuclear power plants. -

Condition Similarity. One of the unique features of a blowdown condition

is thait substantial DP across the valve exists throughout the valve

stroke (see Figure 2-7). For most valve applications, which do not cover

blowdoim conditions, DP Is relatively small except near or at the closed

position of the stroke. These'conditions are Judged to be more favorable

to reliable valve performance since the valve will not be heavily loaded

while the disk Issiding on the guideior transitionIng to the seat

ring. Accordingly a brief study of the number of gate valves which

would be expected to face blowdown' isolation conditions within their

design basis was carried out. This was done by reviewing system drawings

and talking to-cognizant utility:system engineers. The results are

presented in Table 2-3. From these results, it is concluded that:

- the NRC/INEL blowdown closure test conditions are directly

applicable to a small-portion of the NOV population - about 4%

of BWR valves and none of PWR valves.

- dependent on plant-unique configurations and "design-basis"

Interpretation, the NRC/INEL blowdown closure test conditions

61-87 valves. The application of blowdown conditions to all of the

safety-related valves in all of the plants was never intended or stated

in any of our reports or presentations.

A, ,, .1 . *,--.. , "I ;;I I . t

:. ~ ~ , ~ ~~~ . 1 I . . I ., . I: 1

2-9
might be potentially applicable to additional valves (up to 15%

for BWRs and 9% for PWRs).

- the NRC/INEL blowdown openina. conditions are not generally

applicable to valve design basis conditions in nuclear power

plants.

We have never quoted a safety function for a valve to initiate blowdomn

flow, except perhaps for the PORV block valve.

APPLICABILITY OF NORMA. FLOW CONDITIONS

Because -of the testing method used in the NRC/INEL tests, unique

differential pressure behavior was observed during the normal flow valve

strokes. Basically.-two types of-behavior were observed, which are

called "Very Low OP Behavior" and "Changing DP Behavior with Hysteresis"

in this report. These behaviors and their direct applicability are

discussed below.

Very Low DP Behavior

Normal flow tests for Valves A, BS 4, 5 and 6 In the NRC/INEL tests were

carried out in such a way that the valve DP was very small ('100 psi)

throughout the test. -This occurred because a low-head pump was used for

Valves A and B and a large downstream accumulator volume (which didn't

significantly depressurize as the valve was stroked closed and then open)

existed for Valves 4, 5 and 6. Under these conditions, the system

configuration, stroke tinm and hold time (between closing and opening

strokes) Influenced the DP. Detailed comparison to nuclear power plant

systems was beyond the-scope of this effort. As a result of the low DP

In these tests, n useful disk factor Information was obtained from these

strokes (see Sections 5 and 6). These tests show that for valve

conditions where DP Is a negligible load compared to packing and piston

effect loads, the valve can be stroked to full seat contact with the stem

load remaining at essentially the running load. This favorable

As shown in Section 3.2.5 of this report, much of the low DP data were

useful in that they helped provide an understanding of valve performance.

2-10

rt ' . I 1~~~~~~~~~~~ I~~~~~
yy

conclusion may apply to some systems in nuclear power plants. For most

fmotor'operated gate valves in nuclear power plants, the BP builds up in

the last portion of the closing stroke, usually to a value which is not

negligible in terms of overall valvi'load. Accordingly, the conditions

for normal fiow strokes'for Valves A, D, 4, 5 and 6 In the NRC/INEL tests

are not applicable to most nuclear power plant valves. Furthermore these

tests do' not provide useful quantitative information on valve

performance.'

Chanqinq DP Behavior with Hysteresis'

Normal flow tests for Valves 1, 2 and 3 achieved moderate DPs (several

hundred psi) but did so In a'unique time history fashion. Specifically,

during closure strokes.' the DP'started to build just before the flow

isolated and then continued to buld as thedisk moved to wedging (hard

seat contat

ct) 'After the disk seated and valve motion std'ped, 'P

continued to build. As the opening stroke started, OP continued to build

slightly as the'disk moved off the sett'and then rapidly dissipated as

the fl6w area was opened'(see Figure 2-6). This behavior, which was

different opening than closing (hysteresis), was due to the presence of

a moderate size accuzmu'lator volume'downstream of the test valve.1 Under

these conditions, DP is sensitive to system configuration, stroke time

And hold time (between close and open strokes). 'This type of behavior

miy be applicable to some nuclear power plant systems. 'However,.this

type 'of DP condition would not be expected in typical nuclear power plant

NOV gate valve applicitions, which are typically in pumped systems.

Based on discussions with utility personnel'and reviewof limited utility

data, we find that typically the DoP is constant at its maximum value (not

changing) while the disk' moves from isolation'to hard seat,' and that

there is vefy' little hysteresis.' Accordingly, 'the INEL normal flow

conditions ire quite unlike typical gate valve conditions in power .- . . o - !

Hysteresis describes "the phenomenon exhibited by a system in which the

reaction of a system to changes is dependent upon its past reactions to

change." Whether the OP behavior of the NRC/INEL piping system is

attributed to hysteresis or to some other characteristic is not ,~: .;~ I.: ..- . ~. . ,

important.

It was not our intention to precisely duplicate specific in-plant

conditions during the NRC/INEL tests, but rather to obtain data that

could be used to characterize valve behavior in general. Thus, what is

important here is the actual DP at the valve for a specific point in the

valve cycle. As discussed in Section 3.2.5 of this report, the data from

these tests provide useful information with regard to a valve's on-theseat performance.

2-11
plants. Although great care should be used in Interpreting and applying

results of these tests, It is expected that some data would be useful in

valve evaluations. 'However.- the evaluations described in Sections 5 and

6 show little or no meaningful information could be obtained at the point

of flow "Isolation" (due to very low DP) and that disk factors determined

at other points (between isolation and seating for example) gave

suspicious results (i.e., they were substantially out of agreement with

other tests). Until these data are studied in more detail, it does not

appear stem forces or disk factors determined from the data plots should

be directly applied to nuclear power plant valves.

APPLICABILITY OF NO-FLOW CONDITIONS

Tests with "no-flow" conditions covered opening strokes only. In these

tests, the presence of an initially depressurized downstream volume

actually permitted a brief period of flow -- much less than one second

for cold conditions, about one second for hot water conditions (6"

valves) and several seconds for steam conditions (10" valves). The

longer duration for the hot conditions is attributed to the flashing twophase flow or steam inrush flow as the valve initially opens and starts

to pressurize the downstream volume. For 10 valves tested In steam.

these "no flow' tests actually established several seconds of blowdownlike conditions. As discussed earlier, opening against blowdown flow is

not a condition applicable to most gate valves In nuclear power plants.

and thus 10" hot "no-flow" tests are not directly applicable to most

industry MOVs.

The leakage and the cold and hot cyclic no-flow tests were part of the

ANSI/ASHE B16.41 valve qualification tests. The tests were applicable

for what they were Intended. Section 3.2.6 provides additional

information on this Issue.

The condition of a very brief initial period of flow followed by a

prolonged period of no-flow during the opening stroke may be applicable

to some MOVs but is not the same as the design basis conditions of most

safety-relaited MOV's in nuclear power plants. Typically valves have the

2-12

I
I . PA

greatest flow when the valve is full open. Even though the test

condition is not directly applicable to typical valve design basis.

conditions, the DP profile for cold tests and for 6" valve hot tests

somewhat resembles that for opening a typical valve in a pumped system

(Figure 2-5). Accordingly, these tests provide data.which may be

potentially applicable to gate valves under a wide range of conditions.-

since the loading on the disk as a function-of. stroke position is

similar. This result also suggests that a simplified in-plant test

method in which the valve is opened after the upstream has been

pressurized with a hydro pump may provide meaningful nfrmation for many

valves.

. .. - . ' f. ..

. .. _ . . . . . . . . .

2-13
Table 2-1

PHASE 1 BLOWDOWN CLOSURE STROKES

WHERE NITROGEN FLOW APPARENTLY

REPLACED WATER FLOW

Valve/Test/Step | X Closed at Nitrogen I ____________________________ Flow Initiation

A-3-5 28

A-2-7 30

A-6-S 2

A-7-7 55

B-2-7 48

B-3-7 70

B-5-5 59

Table 2-2

PHASE 1 BLOWDOWN CLOSURE STROKES

WITH APPARENT PARTIAL NITROGEN ENTRAINMENT

Valve/Test/Step | X Closed at Nitrogen

J Flow Initiation

A-2-5 59

A-S-S 62

A-9-5 14

A-10-7 93

A-li-S 10

B-2-5 10

B-3-5 52

B-4-7 72

2-14

i.. I I
Table 2-3

SUMMARY OF GATE VALVES EXPOSED TO

BLOVDOON ISOLATION CONDITIONS

WITHIN DESIGN BASIS

CRITERIA:

2. Motor-Operated -

2. Gate Valve

3. High Energy Blowdown Isolation Within Design Basis Function

* An applicable valve had to meet all three criteria.

.:- , i:

Reacior Type ; Minimum Extent | Possible'Additions to

i of Applicability Apicabilt (May be beyond n -I . . '<~~~~~~~~~~~~Design Basis)-

BVR 6 valves/unit Up to 20 valves/unit

(about 41 of MOVs) (about-I5% of MOVs)

These are lines connected to the" These are lines connected to the - s - - primary system and penetrating primary system and penetrating..'

: :: containment, with normally open MOV's containment. but MOVs are

and no check valves. normally closed or there are

check valves.

.PVR Primary'System 0 valves/unit 2 to 3-valves/unit.

In many units, no MOV Isolation on (2X of MOVs)

primary system required within design PORV block valves, let- down

basis. Isolation capability may be line MOVs on some units.

.:________________:____ implied or desired on some valves.

PWR Secondary System 0 valves/unit Up to IO valves/unit

Nominally, no MOV isolation on (7X of MOVs)

secondary side required within design Lines with check valves (e.g.

basis. Isolation capability may be feed lines) or lines attached to

implied or desired on some valves. main steam pipes.

.,

I.We have requested, but not been provided with, drawings and detailed Information to allow this "system effect" to be independently calculated. I "I

2-15
1200 .6

UPSTREAM PRESSURE I

1000 5

800 ._ _ ~VALVE STEM____/

a \ 800 ~~~~~~POSITION 4~~~~~~~~~ C.)-

z

I I ~~~~~~~z

a. 600- 3

D by ' / ~~~~~~~~DATA FROM VALVE 2

cO 400 ITEMPERATUREt520F 2

w

200 -- - 1 >

DIFFERENTIAL PRESSURE.

0 . 0

-200 .,,,, ,,I II,,,I,,I I I I -

0 5 10 15 20 25 30 35

TIME (SECONDS)

PRESSURE, DP, AND POSITION HISTORIES

FOR NO-FLOW OPENING TEST

FIGURE 2-1
1200

1000

I

0~

a:

800

600

400

l

I i

I

I

I

_. i

t

i

- Ii I

I i

I

1 *. !

-UPSTREAM-PRESSURE -

- - -DIFFERENTIAL -- PRESSURE---

.. _ .. . .. \_VVALVE STEM_

* ~~~POSMON -

8

7

6 ---

w

0 5 z

4* j

. 0

3 a-

. w

2 :-i

1 >

0

-1

'200- _ g _ _

I

II

IDATA FROM VALVE 4 V

TEST ISTEP 25 -

TBMPERATURE 485FI: . . . . . . . . . . . . . . . . . . . . . . . . I . . .

0 5 '-'10 ,-115 20 25 30 L 35

I TIME (SECONDS)

"PRESSURE,-'DP 'AND POSI-IONHISTORIES

FOR' BLOWDOWN 'CLOSI NG 'TEST

FIGURE 2-2
In

*1200

1000

800

I

.C,

IC',

wu

0 a

600

400

-\_ . -S. UPSTRM PRESSURE...

\ - VALVE STEM;

POSITION

- . i.*--i-

*~ I ;

A -

I

i

i

.. I __ _... - II

i

6 ,

5 z

z

0 4

0~

CO

t3E

2 Lu

-1

1>

8

7

-

200

0

-200

/ DIFFERENTIAL L

I ~~~~~~~~~~~~~~~~I

A@ k/ A, i DATA FROM VALVE 4

TEST I STEP 18

TEMPERATURE=555 F

IJ J L ~~~~~~~~~~~~~~~~~

0

-1

0 10 20 30 40 50 60

- TIME (SECONDS)

PRESSURE, DP, AND POSITION HISTORIES

FOR NORMAL FLOW TEST--10-INCH VALVE

FIGURE 2-3
6

UPSTREAM PRESSURE .

1000 \ r_5

8DIFFERENT I __ __

800 -- iPRESSURE' 4I

IL 600 *\ ° --/I-3 

RN MAL FOW TETliNCHDATA FROM VALVE2

200 __._-lTEST-1STEP18:_ - VALVE STEM |\./j / TEMPERATURE=525F - POSITION >

0., 10 - 20 o.30 40 50 60 70

TME (SECONDS)

wPRESSURE,- - DPj:AND POSI~O -HISTORIES - ^ --.- FQRNO MAL FLOW TEST.6-lNCH VALVE ..FIGURE 24
1

wu

cr_

C,

wo

co

cf) 0L

EL

D

i

I

I

i

i

I

I

i

I

i

T,

0.8

0.6

0.4

0.2

i i

I

i

i I

I

10-INCH VALVE

* _ HOT NO-FLOW TEST

-(NRC/INEL)

6-INCH VALVE

COLD NO-FLOW-TEST-

(NRC/INEL)

VALVE IN PUMPED SYSTEM

(TOLEDO EDISON)

6-INCH VALVE -- ' HOT NO-FLOW TEST

(NRC/INEL) - ~~~~1*

- -t

= ~~~~~~~~~~~~~~~~~~~~~~~~~~II

, 9 9 9 1~~~~~~~

-0

-0.2

P 1 _1Fi

i I~~~~

i~~~~~~

I I I I I . . I . . . . . .

. . . . .

-20 0 20 40 60 80 100

STROKE POSITION (% OPEN)

NORMALIZED DP VS. STROKE FOR NO-FLOW

TESTS AND VALVE IN PUMPED SYSTEM

FIGURE 2-5
I

I

I '

I

I

I1

II

i

II

\\ i .. - --- i-

*I

I

)All . - -

LLI w

CC

U)

LLI

CL

I0

0]

0

0.8

0.6

0.4

0.2

* ________ I: _ __ __ _

-I 1 - - 6-INCH VALVE

.1 < 4- NORMAL FLOW TEST' - (NRC/INEL)

I' *N.1" l .*

- ^ \\ t I t -. ,VALVE IN PUM

\rE- r Ii

..

I

I . .

I

'-I'-. _ -11~ I -|-vo0v0-1 1: 

0

-0.2

10-INCH VALVE

NORMAL FLOW TEST

i(NRC/INEL) I

i

PED SYSTEM

EDISON)J' -

; - - "

I

I

-. 1 - I I

I I

. . . I .

- I!

I . I -1

. . . . . . . . . . . . . . . . . . .  - . I . . . . .

-20;-- I 20g. 40 60

- STROKE POSITION (% OPEN)

80- 100

NORMALIZED;DP VS. STROKE FOR- NORMAL

.FLOW TESTS 'AND VALVE. IN PUMPED. qSYSTEM

-FIGURE 2-6

9
6-INCH VALVE (A)

FIRST BLOWDOWN

/e(PHASE 1 NRC/INfEL)

_10INCH VALVE (4)

-1R"\ , B~~~~~LOWDOWN

(PHASE 2 NRC/INEL)

w

sr 0.8 t19-- -- \------

w

Q 0.6 6-iNCH VALVE (1)

ffi e l ; \\ \ \ \ ~~~~~~~~~~~~IAE 2 NRC/INE)

6-4NCH VALVE (A) SECOND BLOWDOWN

&(PHASE.NRC/INEL) *-

VALVE IN 8i'NCH VALVEN(B)/

PUMPED SYS LLOWDWWI 

EO .ISON 1/NE NRC/INEL) (PHASE 2 

PUMPED SYSTEM A 6ENCH VALVE (2)T

FIGURSN) , I(PE 2 NRC/IN-)7

-0.2 . . ., ,., . ., ,,,I 

-20 0 20. 40 60 80. 100

STROKE POSITION'(% 6OPEN)

,NORMALIZED DP VS. STROKE -FOR BLOWDOWN

TESTS AND VALVE IN PUMPED SYSTEM

I.FIGURE 2-7-

.
MPR ASSOCIATES . F-140-49-97

11/8/90

0.

tu

-J

L6.

0-%

cm

CLn

CL.

-

LJ

LU

50

40

30

20

10

0

-10

- 600

0 10 : 20 30

TIME(SEC)

40

400

200

0

:-200

0 20 30

TIME(SEC)

40

U-

-DJo

CCDl

U. :D

L&

-j

0

-10000

-20000

-30000 t

L

'-ioooo E

0 - - - - - - - - - - - - - - - - - - -

10 " 20

TIME(SEC)

; 30 40

..FLOWMETER DP,,'VALVE.DP. AND;STEM FO.RCE

FOR FIRST VALVE A BLOWDOWN CLOSING STROKE

FIG U RE 2-8
MPR ASSOCIATES

F-140-49-98

11/8/90

0-

C6

U)

C- ta.

0

-J

fob

to

CD

-

a.

0

La

-J

u- U)

..

25

20

15

10

5

0

-5

-10

1200

1000

800

600

400

200

0

-200

0 F

TIME(SEC)

TIME(SEC)

U-

-J

ULU,,

Ln

.u

Zi=

-A

.10000

-20000

-30000

-40000 .I . . , . . . . .I . -. -. . . . . . 0 10 20 30 40

TIME(SEC)

FLOWMETER DP,: VALVE DP AND STEM FORCE

FOR SECOND VALVE A BLOWDOWN CLOSING STROKE

50

FIGURE 2-9
DISTRIB UT I ON

,. ^ . , .

- Number of Gate Valves In Sample * 404

4....-

63

42500

!2000

Q

1 50 -

100-

50

2500 _

22.50-

2000 _

21750 -f

.. 150 .

-1000

750 -CF500

250 -CF

3~~~~c-.7-7- ;....C - -- --'

(34,000 Lb) (95,000 Lb)

22 %

%

CF - .7854 x DP x D 2

6 % 4 %

IMM~~ . 0M

--50,001- - -

I-100,000 '

Contact -Force (Lb)

00000

-560,-000-- -

- 20;000

0. O 0 2 4 . 6 8 ^ 10-- 12 ;14 :16 18 .24

. . Valve Size (Inches)

VALVE SIZE VS. PRESSURE CHART

COMPARISON OF:RWCUAND HPCI.CONDITIONS TO

GATE VALVE POPULATION BASED ON CONTACT FORCE

FIGURE 2-10

0 22 24
DISTRIBUTION

Number of Gate Valves in Sample - 404

250

200

150

100

50

0 601-1200 1201-2000 2001-3000

+ Linear Stress (Lb/inch) +

C,

C,,

a2500

2250

2000

1750

1500

1250

1000

750

500

250

0

10 12 14

Valve Size (Inches)

VALVE SIZE VS. PRESSURE CHART

COMPARSION OF RWCU AND HPCI CONDITIONS

TO GATE VALVE POPULATION BASED ON LINEAR STRESS

FIGURE 2-11
Section 3

- APPLICABILITY OF TEST VALVES USED IN NRC/INEL TESTS , . i .- ^ . ;

Table 3-1 summarizes construction. configuration, nameplate and history

information regarding each of the valves used in the NRC/INEL tests.

Table 3-2 provides information on the three Limitorque operators used in

the NRC/JNEL tests. This report principally addresses the valves.

In general. available documentation from the NRC/INEL tests does not

describe in detail the configuration of each valve. The inspection

described in Section 4 was effective in obtaining detailed configuration

information for Valves I through 6j(and the disk from Valve B). This

information ii applicible to ValveslA'and B for surfaces'which were not

reworked between Phase I and Phase 2.

.. .- .* .

Existing documentation from therNRC/INEL tests does not describe in

detail the manufacturing/storage/maintenance history of each valve. This

was pursued to the extent possible through the valve manufacturers (and

refurbishers where applicable)'; the information presented in Table 3-i

and discussed below reflects the findings of this process. Each test

valve is: individually described below. Emphasis is placed on the

applicability of the test hardware to 'nuclear power'plant valves.

VALVE A (PHASE 1) AND VALVE I (PHASE 2)

Valve A was used in the Phase I tests Subsequently, the valve was

refurbished'ind reused is Valve 1 Inthe Phase '2 tests. Valve'A isan

Anchor/Dairlig 6-inch flexible 'wdge gate valve with anr ANSI class

pressure rating of 900 lbs.' This valve was specifically fabricated by

Anchor/Dirling In 1988 for use in the INEL Phase I test program. -This

.

The data described in Section 4 were obtained by the NRC-funded, joint

NRC/EPRI posttest hardware inspection. The data from this effort are

part of the available documentation fram the kRC/INEL tests."

v ,' . . '- . , ' . ' . ' 

This Section of the EPRI report points out that the valve manufacturers

whose valves we tested have supplied to the utilities valves with other

designs. Section 3.3.1 of this report addresses this issue. A few

remarks are also provided here.

3-1
valve was fabricated using parts which were in inventory at

Anchor/Darling from onaeof the SNUPPS plants that was canceled in the

late 1970's. The figures and Information in Section 4 and Appendix D of

this report (for Valve 1) show the configuration of this valve. This

valve had machined guide slots in the carbon-steel disk, cast guide rails

in the carbon-steel body, and Stellite 6 hardfacing on the disk and seat

faces. Anchor/Darling indicates that Valve A is similar in design

features to a large population of flexible wedge gate valves they have

manufactured and supplied to nuclear power plants. However, it is

important to point out that Anchor/Darling has also manufactured gate

valves with other design'features.

- A considerable number of flexible wedge gate valves with

integral machined body guide surfaces have been supplied to

nuclear power plants.

- A small population of flexible wedge gate valves with machined,

hardfaced guide slots and/or rails have been supplied to nuclear

power plants.

- A considerable population of double disk (parallel disk) gate

valves have been supplied to nuclear power plants.

In each of the above cases, Anchor/Darling indicates that valve

performance is affected by the differences in design. Accordingly. Valve

A results from the NRC/INEL tests are not considered to be directly

We tested integral machined body guides on Valve 5 (10-inch Powell). The

valve was nonpredictable.

With Valves B and 2 (same 6-inch Velan valve), we tested hardfaced versus

non-hardfaced guide slots. They performed the same.

In the EPRI/Marshall PORV and block valve tests conducted in 1980. an

Anchor/Darling double disc gate valve was tested. The test valves were

basically uninstrumented (go/no-go tests). In the block valve test, the

Anchor/Darling double disc gate valve did not close with the originally

sized operator, requiring a seat design change prior to retest. No data

are available to indicate why the Anchor/Darling valve failed, what stem

thrust was required to close each valve, or how these results compare to

industry calculations.

This statement might lead the reader to infer that the other designs

might perform adequately. In light of the above discussion, that might

not be a good assumption.

3-2

i. I I. I~Is
applicable to valves with these other features.

Anchor/Darling indicates that. at the time Valve A was provided to INEL.

it met all of the configuration and tolerance requirements for that

particular valve design. - Anchor/Darling considers Valve A to be

representative of Anchor/Darilng' valves in service at nuclear power

plants which have this same overallidesign. Unfortunately, detailed

dimensional inforimation on Valve A is nof aivillable. (Valve 1 dimensions

for surfaces not reworked during refurbishment'would be applicable to

Valve A.) Because of limited liiformation. the extent' of the

applicability of data from Valve A to a particular valve (whose detailed

dimensions may be different from Valve A) may be difficult to evaluate.

- . ., . - .. : ',1, tWS, \ .;~ . -

After the Phise I test' prograin VilviA'was refurbished-to b&e used as

Valve I in the Phase 2 test program.-The refurbishment-wasperformed by

Crane Valve' Services>: Unfortunately."this'iefurbishiint wias not

performed in accordanceywith the. Crane nuclear Q/A program, and the

available recordsare minimal. It-.Is.not possible to, tell from the

records, what operations were carried out in the refurbishment. The

purchase order indicates, the following: - ;!

'Inspect Anchor/Darling valve - 6". 900 pound, Valve serial No.

.E-A345-1-L.and refurbish. In addition, manufacture a new stem

nut for an SMB-O Limitorque Motor Operator. Refurbishment will

require'disc and seat repair. -The downstream disc face'and body

seat were previously, damaged in testing." .

The final work invoice indicates that the following additional work was

performed: * . i

- Machined and redrilled actuator mounting plate.

- Machined and spray welded stem.

Some detailed dimensions are available. To restate EPRI's parenthetical

statement, all non-refurbished surfaces of Valve I are Valve A surfaces.

Comparison of detailed dimensional information to other valves is

difficult if not impossible because detailed dimensional information on

the valves installed in nuclear plants is typically not available. More

documented information exists for Valve A than for the typical nuclear

plant valve. . :

A complete discussion of this issue is presented in Section 3.3.2 of this

report. A few remarks are also provided here.

This was required to attach the Phase 11 motor operator.

The valve stem was gouged in Phase I and had to be repaired. . . t .

3-3
- Installed Chesterton brand live loaded packing system.

INEL indicates-that their understanding of the refurbishment was that the

damaged disk and seat face surfaces (downstream surfaces In Phase 1) were

rebuilt and refinished and that the upstream surfaces from Phase I were

not refurbished. The valve was turned around for Phase 2 testing. so

INEL understood that the load-bearing, downstream surfaces of disk and

seat for Phase 2 (i.e. the upstream surfaces from Phase 1) were original.

undamaged surfaces1.

The live loaded packing was installed to test its influence (if any) on

valve performance.

The valve was Installed In the system with flow direction reversed from

Phase I so that the downstream disc surface and valve body seat ring were

original Anchor/Darling surfaces. Valve 1 was disassembled immediately

after the Phase 11 testing to verify that the Crane refurbished surface

was not downstream. As verified by INEL and NRC. the original

Anchor/Darling surface was In the proper downstream orientation.

Based on information from the valve Inspection as discussed In Section

4, Anchor/Darling Indicates that the downstream disk face of Valve 1 does

not meet the configuration requirements for the Anchor/Darling valve

design. Two particular points were noted.

- The Stellite face was very thin. Such a condition can be

detrimental to valve performance because the Stellite may have

high Iron content, which results in poorer friction. hardness

and wear properties. The hardness and iron content measurements

from the inspection confirmed that this Stellite face had

degraded properties. Specifically, the Iron content was about

20X (versus a "normal" value around 5X) and the hardness was 35

Rc (versus an expected value of 40-45). I I

- The Stellite disk face had a sharp edge at the OD.

Anchor/Darling indicates that In their fabrication process this

sharp edge is removed by hand stoning. A sharp edge is

potentially detrimental to valve performance because it

Increases the likelihood of disk/seat damage when the parts come

Into contact under highly loaded conditions. The seat damage

pattern observed In the Inspection confirmed that the disk had

aggressively attacked the seat during the tests.

This surface was manufactured by Anchor/Darling.

The edge configuration of Valve 1 is the same as that delivered by

Anchor/Darling on Valve A.

Anchor/Darling has determined that Valve 1 is not representative of

Anchor/Darling valves and that data from Valve 1 tests are not applicable

The INEL considers the performance of Valve 1 to be representative of

hardware delivered by the manufacturer to the INEL. The valve was

3-4

I 2~~~~
I

Ix

to Anchor/Darling valves in nuclear power plants. The observed

configuratidn of"Valve' 1' cbuld'have been the result of the disk face

being machined down during refurbishment'at Crane.' Such a process could

thin 'the existing Steillite 'laer and remove an existing bevel at the

edge. Unfortunately, available 'do'icimnentation' is not 'sufficient to

evaluate this hypothesis..althou'gh it is plausible.

VALVE B (PHASE 1) AND VALVE 2 (PHASE 2)

Valve B was used-In. the Phase I tests.,. Subsequently, the valve was

refurbished and reused as Valve 2 in the Phase 2'tests. Valve B is a

Velan 6-inch flexible wedge gate valve with an ANSI class pressure rating

of 900 lbs. This valve was fabricated by Velan in 1988 specifically for

use in the INEL Phase I test program. ..The-figures and information in

Section 4 and Appendix 0 of this report show the Valve 2 configuration..

Valve B had machined guide slots in the disk which were hard-faced with

Stellite.6,,and machined..welded-in. carbon-steel guide rails in the

valve body. The disk and-seat faces were-also hard-faced withStellite

6. Velan indicates that-Valve 8 had design features similar to-a

considerable population of gate, valves which, they manufactured and

supplied to nuclear power plants. However. it is important to note that

Velan has also manufactured gate valves with other design features.

A considerable' number' of flexible wedge gate valves with

machined, carbon-steel guide slots have been supplied to nuclear

power plants. (It appears Valve 2 has this design feature, see

below.) Y '

A considerable population of flexible wedge gate valves with a

much different disk design have been supplied to nuclear power

plants.. The other, disk design is much thinner, has longer guide

slots and has the T-heid connection above the disk seating faces

rather than between them; Figure 3-1 shows' a'general comparison

of the two designs. According to Velan, the thin disk design is

used only in valves with ANSI class ratings up to and including

delivered with the understanding that it was representative of

Anchor/Darling hardware delivered to the nuclear industry.

Ve agree with the Velan assessment of Valve B applicability: WVelan

indicates that Valve B had design features similar to a considerable

population of gate valves which they manufactured and supplied to nuclear

power plants."

For the Phase 11 test with Valve 2. the disc was changed to one with

carbon-steel guide slots. A comparison of Valve 2 test results with

Valve B test results shows no difference due to disc guide hardfacing.

Valve 3 (6-inch Valworth) used a thin disc design. The on-the-seat

performance was similar to that of Valves B and 2.

3-5
600 lbs.

In each of the-above cases, it appears that valve performance can be

affected by the differences In design. Accordingly, Valve B results from

the NRC/INEL tests are not considered to be directly applicable to valves

with these other features. Velan indicates that, at the time Valve B was

provided to INEL. it met all of the configuration and tolerance

requirements for that particular valve design. Accordingly. Velan

considers Valve B to be representative of Velan valves in service at

nuclear power plants which have the same overall design. Unfortunately.

detailed dimensional information on Valve B is available only for the

disk. (Valve 2 body dimensions for surfaces not reworked during

refurbishment would be applicable to Valve B.) Because of limited

information, the extent of applicability of data from Valve B to a

particular valve (whose detailed dimensions may be different from Valve

B) may be difficult to evaluate.

Hore information exists for Valve B then for a typical valve installed

in a plant.

After the Phase I test program. Valve B was refurbished to be used as

Valve 2 in the Phase 2 test program. The refurbishment was performed by

the manufacturer. Velan Inc. The Velan refurbishment summary indicates

thefollowing was done.

- The disk was replaced with a new disk without hardfacing on the

guide slots. Otherwise, the disk was of similar design.

- The valve body seat faces were re-lapped.

Based on information from the valve inspection as discussed in Section

4. Velan indicates that Valve 2 is representative of valves in nuclear

power plants which have this same overall design. Data from Valve 2

tests in the NRC/INEL program would not be directly applicable to Velan

valves with other design features (l.e. hardfaced disk guide slots and/or

body guides, or alternate disk: design).

We agree with the Velan assessment of Valve 2 applicability, 'Velan

Indicates that Valve 2 Is representative of valves in nuclear power

plants which have this same overall design." Based on the above

information, we believe the results from Valve B and Valve 2 are

applicable to both hardfaced and nonhardfaced disc guide designs.

3-6

t* : I~~~~
VALVE 3

Valve 3 is a Walworth 6-inch flexible wedge gate valve with a 600-lb ANSI

class pressure rating., This valve was fabricated by.Walworth Valve in

1979 for one of the North Anna canceled units (3 or 4). The figures and

information in Section 4 and Appendix 0 show the Valve 3 configuration.

This valve had carbon-steel, machined guide rails. The guide rails were

fabricated as a single, removable 'U piece which was held in place by

a slot-at the bottom of the body and dowel;pins at the top; *The guide

was free to deflect between the upper And lower supports. The disk and

seat faces were hard-faced with Stellite 6.

Presently. Crane Valves controlsiand services the Valworth line of gate

valves; Crane indicates that the Valve 3 design features are similar to

Valworth flexible wedge gate valves supplied to nuclear power plants.

They also-indicate that this Valworth valve has design features similar

to some Crane valves. X V . ! 

* , ,. -, _ 9 ,. . X. ,*'

After INEL obtained Valve 3. it was shipped to Crane Valve Services for

"refurbishment." This work was not performed in accordance with the

Crane Nuclear QA program, and the available records are minimal. It is

not possible to tell from the records what operations were carried out

in the refurbishment. The "Request for Quotation" states the following:

Refurbish Valworth 6" 600 pound flex. wedge gate valve either

Serial Number 066316.i 066350, or 066507 (identified at a later

date);. Figure 5232. PS.; The valve will;be furnished to CraneALOYCO CC-A) without a motor operator. Refurbishment will

include manufacture of new stem nut and mating new motor

operator. EG&G/INEL will furnish a Limitorque SMB-O motor

operator to C-A for final valve checkout. C-A will furnish all

other parts for refurbishment. CA will disassemble valve and

dimensionally, inspect and record critical dimensions; reassemble

with new gaskets and packing and perform normal checkouts prior

to shipping valve."

We agree with the Crane-Aloyco assessment of Valve 3 applicability:

'Valve 3 design features are similar to Valworth flexible wedge gate

valves supplied to nuclear power plants. They also indicate that this

Valworth valve has design features similar to some'Crane valves."

- ' ' '. . ' I ' - " '' !

3-7
The final purchase order was not available. The work invoice indicates

that the following additional work was performed:

machined and redrilled actuator mounting plate.

No records of dimensional measurements required, by the Request for

Quotation are available. No records of seat leakage or hydrotests are

available.

This was required to adapt the valve yoke for mounting the Phase 11 motor

operator.

The records of dimensional measurements taken by Crane-Aloyco are

considered proprietary. Full dimensional measurements were taken as part

of the NRC/EPRI posttest hardware inspection effort and are contained in

this EPRI report. The ANSI/ASHE B16.41 Qualification tests contain the

hydro and leakage test results.

VALVE 4

Valve 4 is an Anchor/Darling 10-inch flexible wedge gate valve with an

ANSI class pressure rating of 900 lbs. This valve was fabricated by

Anchor/Darling in .1982 for Hope Creek Unit 2. which was subsequently

canceled. The figures and information in Section 4 and Appendix 0 of

this report show the Valve 4 configuration. This valve had machined

guide slots in the carbon-steel disk. cast guide rails in the carbonsteel body. and Stellite hardfacing on the disk and seat faces.

Anchor/Darling indicates that Valve 4 is similar in design features to

a large population of flexible wedge gate valves they have manufactured

and supplied to nuclear power plants. However, it is important to point

out that Anchor/Darling has also manufactured gate valves with other

design features.

- A considerable number of flexible wedge gate valves with

integral machined body guide surfaces have been supplied to

nuclear power plants.

We agree with the Anchor/Darling assessment. 'that Valve 4 is similar in

design features to a large population of flexible wedge gate valves they

have manufactured and supplied to nuclear power plants."

We tested integral machined body guides on Valve 5 (10-inch Powell). The

valve was nonpredictable.

3-8

t '. I1. I A
- A small population of flexible wedge gate valves with machined.

hardfaced guide slots and/or rails have been supplied to nuclear

power plants.

-. A considerable 'population of double'disk (parallel disk) gate

valves have been-supplied to nudlear power plants.,

In each of the above cases, Anchor/Darling Indicates that valve

performance Is affected by the differences In design. Accordingly Valve

4 results. from the NRC/INEL tests are not considered to be directly

applicable to valves with~these otherfeatures..:

$,~~~~~~~~~~~~~~~~~~~~~~~~~~~~. ...

After INEL obtained Valve4.4- it was shipped, to Crane Valve Services for

.'refurbishment'. . Unfortunately.- this work was not performed in

accordance with the Crane nuclear QA program, and the available records

are minimal. It Is not possible to tell from the records what operations

were carried out. in the "refurbishmnent% ..The purchase order'indicates,

the following:. e.

"Refurbish Anchor/Dalinge (A/D) 10". 900 pound flexible wedge

gate valve..Serial No.,. E6162-8-2: furnished without motor.

operator. Refurbisab hment will include manufacture of new stem

nut for an SM48-1 Limitorque motor operator. Refurbishment Is

not expected to include, any new valve parts. In addition,

disassemble the 4valve and dimensionally inspect and record

critical dimensions. reassemble with new gaskets and packing and

perform normal valve checkouts-before shipping the valve. Then

package the valve' and stem nut for shipment to locations

specified at a later date by EG&G."

the ollwing - * , , -

With Valves 8 and 2 (same 6-inch Velan), we tested hardfaced versus

nonhardfaced guide slots. They performed the same.

In the EPRI/Harshall PORV and block valve tests conducted in 1980, an

Anchor/Darling double disc gate valve was tested. The test valves were

basically uninstrumented (go/no-go tests). In the block valve test, the

Anchor/Darling double disc gate valve did not close with the originally

sized operator, requiring a seat design change prior to retest. No data

are available to indicate why the Anchor/Darling valve failed, what stem

thrust was required to close each valve, or how these results compare to

Industry'calculations. .

This statement might lead the reader to' infer that the other designs

might perform adequately. In light of the above discussion, that may be

a poor assumption.

3-9
The final work invoice Indicates that the following additional work was

performed:

- Machined new gasket pull up plugs.

- Machined and redrilled actuator.

No records of dimensional measurements implied in the purchase order are

available. No records of seat leakage or hydrotests are available. INEL

indicates that, at the start of testing, the valve internal parts were

in an as-manufactured condition. I.e. the refurbishment work at Crane did

not affect the internal parts.

Anchor/Darling indicates that, based on inspection results. it appears

Valve 4 met all of the configuration and tolerance requirements for that

particular valve design. Accordingly. Anchor/Darling considers Valve 4

to be representative of Anchor/Darling valves in service which have this

same overall design.

No dimensional records were requested. ANSI/ASNE B16.41 Qualification

tests contain the results of hydro and leakage tests.

We agree with the Anchor/Darling assessment that 'Valve 4 met all of the

configuration and tolerance requirements for that particular valve

design." and that 'Anchor/Darling considers Valve 4 to be representative

of Anchor/Darling valves in service which have this same overall design."

VALVE 5

Valve 5 is a Powell 10-inch flexible wedge gate valve with a 900-lb ANSI

class pressure rating. This valve was fabricated by William Powell Co.

in 1979 for the Marble Hill plant, which was subsequently canceled. The

figures and information in Section 4 and Appendix 0 of this report show

the configuration of this valve. The valve had carbon-steel, machined

guide slots in the disk and carbon-steel, cast, machined guide rails in

the body. Stellite 6 hardfacing was on the disk and seat faces. Powell

indicates that this valve is generally typical of Powell valves in

nuclear service. However, it is important to point out that Powell has

supplied gate valves to nuclear power plants with a variety of design

features Including:

We agree with the assessment that 'Powell indicates that this valve is

generally typical of Powell valves in nuclear service."

3-10

a. 1 . 1

.
male and female body guides

cast-in and welded guides Valves A, 1. 4, and 5 used cast-in guide designs, and Valves B, 2, and,

6.used welded in designs. Data under blowdown loads are available.

hardfaced and non-hardfaced guide surfaces Valves B and 2 tested hardfaced and nonhardfaced disc guide designs.

Results show similar performance for the two designs.

- various tee-slots and tee-head configurations

It appears the features listed.above could affect valve performance

particularly under blowdown conditions.. The data from the NRC/INEL tests

would not be applicable to Powellivalves with different design features

In the above areas. , . .

In addition, Powell indicated that the sharp edge on the seat of. the disk

of the NRC/INEL test valve; identified during theivalve inspection. is

typical of, Powell 0" 900-lb class pressure seal gate valves;, however,

it is not typical of most Powell gate valve designs. fIt appears the

sharp edge had an mnfavorable effect on valve performance under blowdown

conditions.

After INEL obtained-Valve 5,- the, valve was shipped to Powell for

refurbishment. According to Powell. "the valve was disassembled,

inspected, reassembled using new gasket, packing, and yoke arm,,tested,

per API 598 (hydrotest and leakage testing). and painted., The valve was

equipped with a yoke arm designed to accept a Limitorque SMB-1 actuator."

VALVE 6

Valve 6 is a Velan 10-inch flexible wedge gate valve with an ANSI class

pressure rating of 600,lbs. -This valve was fabricated, by Velan Valves

Again, we caution the reader not to infer better performance for other

valve designs.

We agree with the Velan assessment of the applicability of Valve 6, "the

Valve 6 design features are similar to a considerable population of gate

I %; . . . . I .. . -. . .

3-11
In 1989 specifically for the INEL Phase 2 test program. The figures and

information in Section 4 and Appendix D of this report:show the Valve 6

configuration. The valve had machined guide slots in the carbon-steel

disk and machined. welded-in. carbon steel guide rails In the body.

Stellite 6 hardfacing was on the disk and seat faces. Velan indicates

that the Valve 6 design features are similar to a considerable population

of gate valves they have supplied to nuclear power plants. However. it

Is important to note that Velan has also manufactured gate valves with

other design features.

A considerable number of flexible wedge gate valves with

hardfaced guide slots have been supplied to nuclear power

plants.

A considerable population of flexible wedge gate valves with a

much different disk design have been supplied to nuclear power

plants. This disk design Is much thinner, has larger guide

slots and has the T-head connection above the disk seating faces

rather than between them. Figure 3-1 shows a general comparison

of the two designs. According to Velan, the thin disk design is

used only in valves with ANSI class ratings up to 600 lbs.

valves they have supplied to nuclear power plants."

The remarks made on the 6-in Velan apply here.

In each, of the above cases, it appears that valve performance can be

affected by the difference In design. Accordingly, Valve 6 results from

the NRC/INEL tests are not considered to be directly applicable to valves

with these other features. Velan indicates that, at the time Valve 6 was

provided to INEL. it met all of the configuration and tolerance

requirements for that particular valve design. Accordingly, Velan

considers Valve 6 to be representative of Velan valves In service at

nuclear power plants which have this same overall design.

3-12

 11 I. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~.II
Table 3-1

KEY INFORMATION ON INEL TEST VALVES

Item Valve A & I Valve B & 2 Valve 3 Valve 4 Valve 5 Valve 6

Manufacturer Anchor/Darling Velan Valworth Anchor/Darling Powell Velan

Year Manufactured .1988 1988 1979 1982 1979 1989

|I.. Number E-A-345-1-1 F14-70548-02TS (MO) 4SDP-MOV422B E-6162-8-2 19023V.F. B16-2054B-02TS

No. 5232PS Ser. No. 93211

Ser. No. 0-66350 . _

Drawing Number W8722603 P2-70916-SOI A-9781-M-171 93-i4358' C-60999 P2-72916-SOI

Size (in.) 6 6 *; 6 - ; 10 10 10

ANSI-Class (lb) 900 - 900 --- 600 900 600

Seat Diameter, mean/lD 5.40/5.125 5.59/5.18 5.69/5.44 8.70/8.375 -/8.28 8.37/7.88 (in) : _ : 

Disk Base Material A216-WCB A105 SA-217-WC6s SA216-WCB Grade WCB AI5S

Disk Seat Material Stellite 6 Stell1te 6 Stellite 6 Stellite 6 Stellite 6 Stellite 6

Disk Guide Material A216-WCB Stellite'6 (B) SA-217-VC6 SA216-VCB Grade.WCB A105

AI0S (2) : __:

BodyGuide Material A216-WCB A36 SA-217-VC6 SA216-VCB Grade VCB A36

Seat Ring Base Material A515-70 - _ A216-WCB - SA105 _ SA-515-70 ---- - (Not Available) AIDS --

Seat Ring Seat Material Stelifte&6 Stellite 6 Stellite 6 Stellite 6 Stellite 6 Stellite 6

Stroke -I'25 5.75 5 9 ;9.375 8.75

Length (in.) . . - .

Stem .. 1.75 _- 1.25 1.50 -- - 2.00- 2.125 2.50-

Diameter (in.) _ .

Thread Type Stub ACME ACME ACME Stub ACME L. H. ACNE ACME

Threid Pitch (in.) 1/4- ; 1/4 1/4 1/3 1/4 1/3

Thread Lead (in.) 1/4 1/4 1/2-- ... I 1/2 2/3

Torque Arm Yes Yes Mo- . Yes* No Yes

3-13
Table 3-1

KEY INFORMATION ON INEL TEST VALVES

Item Valve A & 1 Valve B & 2 Valve 3 Valve 4 Valve 5 Valve 6

Packing|

#Grafoil rings 3 ** 6 (Not Available) (Not Available) (Not Available) 6

#Braided rings 2 2 2

Year obtained by INEL 1988 1988 - 1989 - 1989 1989 1989

Yr. Refurbished 1989 1989 1989 1989 1989 __

W|here refurbished Crane Valve Services Velan Crane Valve Services Crane Valve Services Powell __

Other nameplateinfo. __ 2200 psi Bldg. Area HV-2 Class I Stem CR13 Made In Canada

38 C 100F Hark No. VGW-60B-2 ASHE Section III B16.34 Forged Steel Body

816.34 Greensburg Plant 2163 psi at 575-F Press 2220 at 100- 1480 psi

Stem S/S 410 Nat'l Bd. No. 1843 Press Rating 38-C 100F

Body Comp. SA105 Des. Press. 1050 psi 8 2250 psi at 100F 816.34

630- Stem S/S 410

WOG 440 9 100- Body Comp AS105

Stem CR13 Dwg. No. 8890-D89

Code 652325706001N

Class 2

1. This was indicated by INEL in the April 18. 1990 Valve Test Review Meeting. See meeting transcript, p. 48.

* Valve 4 did not have a torque arm.

** Valve 1 was live loaded. packing configuration incorrect.

1. This was Indicated by INEL in the April 18, 1990 Valve Test Review

Meeting. See meeting transcript. p. 48.

3-14

A .
Table 3-2

INFORMATION ON LIMITORQUE OPERATORS USED IN

NRC/INEL TESTS -

Operator Type/Size SMB-0-25 SMB-1-60 SMB-2-40

Valves Used with B, 1, 2, 3 4, 5,6 A

Limitorque Order 147441.01 147441.02 360365A

Number

Unit Ratio 34.9 (Valves B,1,2) 82.5 (Valve 4) Not

69.5 (Valve 3) 42.5 (Valve 5) Available

56.6 (Valve 6)

Operator Rated Thrust 24,000 lbs 45,000 lbs 70,000 lbs

Operator Rated Torque 500 ft-lb 850 ft-lb 1800 ft-lb

Spring Pack Part No. 0501-184 0701-212 Not

-__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A v a i l a b l e

Max. Torque Switch 2-1/2, 376 ft-lb 3-1/2, 1012 ft-lb Not

Setting/Output Torque ;_ __ Available

Max. Pullout Torque 314 ft-lb (Valves B,1,2) 1782 ft-lb (Valve 4) Not

625 ft-lb (Valve 3) 918 ft-lb (Valve 5) Available _____________________ _______________________ 1222 ft-lb (Valve 6)

Gear Box Lubricant., Exxon Nebula EP-O Exxon-Nebula EP-O Not

Available

Limit Sw. Gear Box- Beacon 325 Beacon 325 Not -

Lubricant , Available

Limit Switch Type 2-rotor 2-rotor Not .._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ,, _ _, _ _ , ., _ _. _. _ _: _. A v a il a b l e

Motor Speed 1800 rpm : 1800 rpm -3600 rpm

Motor* Voltage 460 V/3 ph/60 Hz 460 V/3 ph/60 Hz 460 V/3 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ !ph / 6 0 H z

Motor Starting Torque 25 ft-lb 60 ft-lb 40 ft-lb

Year Manufactured 1988 1989 1973'

Year Obtained by INEL I 1988 1989 1988

This operator was originally supplied to Darling Valve by Limitorque.

modified for INEL. Detailed information on the modified configuration

be obtained in-timelto include here.

It was

could not
MPR o~ASOITES]

IF 140-49-91

11/1290

a

T-slot

within Disk

VELAN DISK DESIGN TESTED BY INEL

/ 11 II

Short

Guide Length .

Thick Body

OTHER VELAN DISK DESIGN T-slot

above Disk

- Long Guide

Length

Thin Body

COMPARISON OF TWO VELAN DISK DESIGNS

FIGURE 3-1
Section 4

VALVE INSPECTION

The objectives of the inspection of the NRC/INEL'test valves were to

develop infoimation regirding the valve donfiguration and post-test

condition. This information is needed to support the evaluation of HOV

performance in the tests and to help understand the potential

implications of the NRC/INEL'test' results to`valves currently in use in

the nuclear industry.

An industry team performed the valve inspection. the industry team was

directed by EPRI under the auspices of the EPRI HOV Performance

Prediction Program. The Utility Technical Advisory Group (TAG) for this

program provided technical direction for the inspection effort. HPR

Associates was.responsible-for the coordination of the inspection and

preparation ofthe~Anspectlon-plan (Reference 5). The- industry team

representatives (listed in Table 4-1),reviewed the inspection plan and.

participated in the actual valve inspection. Specifically, industry team

members supervised the dimensional measurements on the test valves and

performed individual inspections to assess-the post-test condition of the

valves. Individual. inspection-reports -provided, by-team members are

included as Appendix C. . .

Chemical composition measurements were performed by TN Technologies under

industry team supervision. INEL provided technical support and equipment

for performing valve dimension measurements. INEL efforts in support of

the inspection were directed by R. Steele.

We have no technical comments on this section. However, we feel it

necessary to make a few minor corrections as follows.

The NRC funded 100% of INEL costs to perform the posttest inspection.

This funding constituted important financial support to the inspection

effort. The NRC contribution to the inspection effort also served to

professionally accommodate the requests and needs of the Inspection team.

The NRC/INEL provided more than technical support and equipment. INEL

personnel disassembled and reassembled all valves, provided all handling,

performed most measurements, recorded data, took photographs and video

footage, and provided quality oversight and data verification.

. , -. .. . . ... . . .1 -. . .... I . .. .

All Inspection activities were performed in accordance with the ...- . .. . ' I I I , I I

4-1
inspection plan which included procedures and data sheets. In general,

inspection activities and procedures for performing measurements were

consistent with procedures outlined in the EPRI HOV In Situ Test Guide

(Reference 6). Special tests such as surface roughness, chemical

analysis, blue check, clearance check and range of position tests are

beyond the scope of the In Situ Test Guide and were done in accordance

with procedures developed for this task.

VALVE DESCRIPTIONS

Measurements and inspections performed to document the test valve

configuration showed that although not all possible design features were

included in the six test valves, a wide variety of designs were covered.

A summary of the design features is given in Tables 3-1 and 4-2.

Table 3-1 provides general Information on the valve configuration, while

Table 4-2 focuses on the types of guide and seat designs. Each of the

valves is briefly described below. (Note that Section 3 discusses the

history of each valve and the applicability to nuclear power plant

valves.)

Valve I

Valve 1 is a 6-inch. 900-lb Anchor/Darling flexible wedge gate valve with

a pressure seal bonnet. The "top works' of the valve, including bonnet.

stem, packing, etc., were not available during the inspection. This

valve has a cast steel body including cast guide rails, and has welded-in

seat rings which include Stellite seating surfaces. The disk is a steel

casting with Stellite overlay to form the seating faces. The stem

connects with the disk in a T-slot oriented parallel to the flow axis.

Valve 1 was also used as Valve A for Phase 1 testing. The disk was

refurbished and the valve turned around for Phase 2 testing.

Valve 2

4-2

*1 U~~
I'-

Valve 2 Is a 6-Inch, 900-lb Velan flexible wedge gate valve with a bolted

bonnet._ This valve has a forged steel body. Guide rails are machined

from bar stock and welded to the body. Seat rings are also welded into

the body and seating surfaces are hardfaced with Stellite. The singlepiece disk also has seats that are hardfaced with Stellite. Disk guide

slots are located between the disk faces and are not hardfaced. The stem

connects to the disk in a T-slot which is oriented perpendicular to the

flow direction and is located between the disk faces.

The body of Valve 2 was also used for Phase l testing as Valve B with

another disk.- The disk used for` hase 1 testing was the same design

except it hiad hardfaced guides.

Valve 3 -

Valve i isa 6-inch 600-ib Valworth flexible wedge gate valve with a

pressure s'es bonnet. This valve has i cast steel body. Valve 3 has' a

machined;', removable "U'-shaped guide rail. Welded-in seat rings are

hardfaced with Stellite as are the seats on the single piece disk.

Neither guide rail nor disk guide slot surfaces are hardfaced. Disk

guide slots are recessed between the disk seating faces. The disk

connects to the stem at a T-slot which is located above the disk seating

faces and Is oriented parallel to the flow.

Valve 4

Valve 4 is a 10-inch, 900-lb Anchor/Darling flexible wedge gate valve

with a pressure seal bonnet. Design features of Valve 4 are essentially

the same as Valve 1.

Valve 5

4-3
Valve 5 is a 10-Inch. 900-lb Um. Powell flexible wedge gate valve with

a pressure seal bonnet. This valve has a cast steel body. Guide rails

are cast into the body then machined. Guide rails are not hardfaced.

Seat rings are welded Into the body and are hardfaced with Stellite.

Disk guide slots extend outside of the disk seating faces and are not

hardfaced. The disk seats are hardfaced with Stellite. The stem

connects to the disk at a T-slot which Is located above the seat faces

and Is oriented parallel to the flow direction.

Valve 6

Valve 6 is a 10-inch, 600-lb Velan flexible wedge gate valve. The

Valve 6 design is similar to Valve 2.

MEASUREMENTS OF TEST VALVE CONFIGURATION

Tools and Equipment

Measurements were made with conventional machinists tools such as dial

calipers, micrometers. feeler gages. etc. Special tools and equipment

required for the Inspection included an NDT Instruments NOVA 100-D

ultrasonic thickness gage with DF505 probe, Equotip hardness tester,

Pacific Transducer Corporation Model 316 hardness tester, Federal

Products Corporation Model EAS 2418 surface profilometer with an EGH-1019

general purpose probe, and dental molding compound.

Dimensional Measurements

In general, length measurements on machined surfaces were recorded to the

nearest 0.001". Angle measurements were recorded to the nearest 0.1'.

Generally, length measurements of as-cast surfaces were recorded to the

nearest 0.01". Where the condition of the valve internals did not permit

an accurate measurement typical of the pre-test condition, the dimension

4-4

P I E
was taken to the best possible accuracy. In some cases, due to the

presence ofdamage the measurement was made at a different location.

Explanations were provided In the Remarks section of valve data sheets

for these cases.

The intent of the dimensional measurements was to obtain information on

the configuration of-the valve-inthe pre-test condition.. In selected

casesi (based on the. Judgment of. the team members, performing the

dimensional, measurements), separate dimensional measurements were

obtained for the damaged configuration.

Sets of body, disk and stem measurements were taken on each of the six

valves. Figures 4-1 through 4-9 show simplified generic sketches

Illustrating the general location of various measurements. Because each

valve had a unique configuration,. detailed figures depicting each valve

are provided as Appendix D. These figures show key design features of

the valves and the specificl!ocations at which measurements were taken.

Valve Body Mieairemeets. The valve body dimensions which were measured

and recorded are:

- Upstreaim and downstream flow orifice diameters

- Guide rail thickness

- Body seat to guide rail spacing

- Seat Inside and outside diameters

- Seat to seat spacing

- Radius or bevel of seat rings.

Results are summarized in Table 4-3.

Valve Disk Measurements. The valve disk dimensions which were measured

4-5
and recorded are:

- Disk seat measurements including inside and outside

diameters

- Disk guide slot Inner and outer dimensions and thickness

- Disk wedge angles

- Dimensions necessary to characterize stiffness of disk

-- Hub diameter

-- Disk thickness at critical locations

- Radius or bevel of seats

Results are summarized in Table 4-4.

Stem/Disk Connection Measurements. Dimensions which were measured and

recorded are:

- Depth and width of disk T-slot

- Depth and width of stem T-head

- Stem runout

Results are summarized in Tables 4-5 and 4-6.

Seat. Guide and Stem Surface Characterization

Specific information which was obtained included seat, guide, stem and

stem nut surface roughness. Accessible surfaces were measured with a

surface profflometer. Inaccessible surfaces were described

qualitatively.

Results are summarized in Table 4-7.

Pressure Areas

4-6

TN
i Atp

During the one week inspection period, INEL measured the horizontal

*projected disk surface areas for evaluating the effects of body and

bonnet pressure on stem rejection loads. These data are not included in

this repbrt, INEL' indicates that the 'data will be available when they

have been collated and organized. --

Chemical Composition and Hardness/

Chemical composition of disk seat and body seat ring hardfacing was

determined using a TN Technologles 'Hetallurgist-XR" X-ray fluorescence

analyzer. Due to access limitations, measurements on the body seat rings * .. , .*; ;,.~*'. 

were limited to the 10-inch valves and were made only at the 12 o'clock .. t . -~ Dis n.a .iS. the 12 o'clock, position. Measurements were performed at a numberof locations on seven

valve disk seats. including Dsk "B" from Phase I testing..

The purpose of chemical composition tests: was to determine the iron

o ilte disk and body seat hardfacing. Accuracy of test

.. _, 

-+ . .. ,I : ! ,. L ,. 

.. .. .. 

. .. 

.

equipment was verified through pre-test., post-test and periodic mid-test

measurements on NIST traceable standards. Repeatability of measurements

was verified through periodic repetition of selected measurements.

* -,", .. , 

.

. ... 

. .,:

An Equotip hardness tester was used to measure the hardness of disk seat.

body seat ring and body guide rail surfaces. A Pacific Transducer

Corporation (PTC) hardness tester was used to confirm Equotip

measurements on the disk seats. Due to access limitations the PTC

hardness tester could not be used on' bodyseats.

The measured iron-content and hardness of seat materials are provided in

Table' 4-8. The iron content of seat hardfacing varied from 3% to'30%an'd

-hardness -also varied significantly. The high iron content and low

hardness in some valves indicates that hardfacing application processes

may not have been well controlled resulting in high iron dilution, or

4-7
that excessive seat machining had taken place leaving only a thin

hardfacing layer with high iron dilution.,

Replication

Plastic molds were made using a dental molding compound to show detailed

body and disk seat configuration including edge bevels and face seat

width. Replicas were made at the three. six, nine and twelve o'clock

positions. These replicas are being stored at HPR Associates.

POST-TEST CONDITION ASSESSMENT

Post-test condition assessment was by visual inspection, per the

inspection plan. Results were recorded on the data sheets. All visual

inspections were performed and documented by industry team members.

Manufacturer representatives in attendance reviewed and concurred with

the information recorded on the data sheets. The objectives of the

visual inspection of the INEL test valves were to characterize the

location, extent and appearance of surface damage and plastic

deformation. Where damage was found the condition of potential mating

surfaces was also noted. The condition of many components was documented

by photography. Appendix H contains selected photographs of each valve.

Depth of surface damage was quantitatively estimated and also

characterized by replication with a dental molding compound. A

borescope. 30X illuminated microscope, mirrors and surface profilometer

were also used for the inspection.

Post-test condition assessment visual inspections showed that the

majority of test valves experienced significant wear and damage. Table

4-9 summarizes the results of visual inspections of the valves. Dental

molding compound was used to make plastic replicas of the damage observed

at various locations.' Table 4-10 describes the locations at which

replicas were made to document valve damage. These replicas are being

4-8

I I !
R

stored at HPR Associates. Detailed inspection results are provided as

Appendix E.

On all vialves some'degree of wear was observed on downstream contact

faces of the disk seat ind body seat ring. The weir ranged from slight

burnishing. which is typical of valves which have been in service

(Figure 4-10), to severe gouging and gross metal removal The most

severe wear wasconcentrated along the lower'sides of seat faces near

four o clock and eight o'clock positions (Figure 4-11).

All valves exhibited some guide wear~. However, severe wear occurred on

some valves which involved significant metal galling/removal.. Typically.

this wear was concentrated near the iower, edge of disk guldes"and body

guide rails.. Figure 4-12,shows an example of moderate wear on the guides

and Figure 4-13 sh6ws an example of`severe wear In the guides. Three

valves (Nos. 2. 5 and 6) showed evidence of wear on guide faces parallel

to the flow direction' which aie not normally expected to be load bearing

surfaces. This damage was most severe on Valve No. 6 (Figure 4-14). The

guide rails of two valves (Nos. 3 and'6) were permanently'deformed 'in the'

downstream direction. Deformation of the valve No. 3 guide rail occurred

between top and bottom supports of the removable U-shaped rails, while

deformation of Valve No. 6 occurred below the lowest of three welds

supporting a welded-in guide (Figure'i-15). -

The majority of valves showed no significant wear on the stem or bonnet,

bore. An exception is Valve No. 4 which had wear indications on the stem

where it passed through the bonnet bore and on the bonnet bore

(Figure 4-16). Each of the valves had a separate stem nut. No unusual

stem nut damage or wear was identified on any of the stem nuts.

SUPPLEMENTAL TESTS

4-9
The following supplemental tests were performed to provide special

insight on valve behavior by providing a more clear understanding of the

total effect of clearances on the relative positions of valve components

prior to and during disk seating.

- Blue Check

A blue check was performed on each of the six test valves. On

upstream and downstream disk faces, the overall appearance of

the contact pattern was recorded by sketches and photography.

Mean contact diameter and width of contact were also measured

and recorded. In addition, the position of the contact pattern

relative to inside and outside diameters of the seat was

described..

- Clearance Check

Guide-to-guide rail clearances were verified by direct

measurement using 12 inch long feeler gages with the valve disk

manually placed in the fully closed position.

- Range of Position Test

The highest possible stem position at which disk to body seat

engagement can occur was determined by incrementally lowering

the disk and stem (without packing and bonnet) Into the body.

At predetermined levels the disk and stem were manually tilted

or pushed in both upstream and downstream directions to

establish extreme disk positions. Points and areas of seat-toseat contact (if any) at the limits of disk motion were

Identified at each stem position for each type of loading.

Results of the blue check, clearance check and range of position test are

summarized in Tables 4-11. 4-12 and 4-13, respectively. Figure 4-17

shows the locations at which clearances were measured. Detailed results

of the range of position test, which include seat contact locations as

a function of stem position for disk tilting and disk pushing loads, are

provided as Appendix F.

In general, supplemental evaluations confirmed the results of dimensional

4-10

I
examinations and the post-test condition assessment. The blue checks

showed that the actual seat-to-seat contact areas were generally

consistent with the direct measurements performed on the body seats. It

was noted that these measurements were simpler to perform than the directmeasurements in~the valve body. Therefore, this method is likely to be

more practical for field applications (e.g. In Situ Test Guide).

Photographs of the disk seat'blue patterns are provided in Appendix 6.

: , .- . Is J- ..

The clearance checks revealed that the total lateral guide to guide rail

clearance varied from 0.240 inches to 0.002 inches and that the total

clearance measured parallel to the flow direction ranged from 0.299

inches to0;018 inches.'Generally the most severe seat damage occurred

'for valves with the largest guide clearances in the direction of flow.

The range of position test showed that disk' seat to body seat' ring

contact'could occur it higher stem positions for" vaves with larger guide

clearances. Feeler gage clearance measurements showed smaller clearances

than those determined by comparing the disk and body measurements due to

the presence of:rolled up material on galled surfaces. Accordingly.

clearances obtained by comparison of measurements rather than by the

feeler gage method should be used for. detailed analyses and for

validation of predictive models. . ; 

4-11
Section 5

TEST DATA REVIEW

PHASE 1 TEST DATA

Two 6-inch 900 lb. flexible wedge gate valves were tested in Phase 1.

One qualification test sequence (ANSI/ASKE B16.41) and 11 blowdown test

sequences were performed on Valve A (an Anchor-Darling valve). Valve B

(a Velan valve) was subjected to one qualification test sequence and 5

blowdown test sequences. The blowdown tests were performed at various

temperatures and pressures and included cycling the valves at normal flow

as well as at blowdown flow conditions. The valves were not inspected

following each blowdown test. Results of Phase I testing are presented

in NUREG/CR-5406 (Reference 1).

PHASE 2 TEST DATA

Six flexible wedge gate valves were tested during Phase 2 -- three 6-inch

valves and three 10-inch valves. The two valves used in Phase I of

testing were refurbished and used in Phase 2. The vendor, size, and

pressure class for each valve are listed below.

Valve No. Valve/Vendor Size Pressure Class

I Anchor-Darling 6-inch 900 lb

2 Velan 6inch 900 lb

3 Walworth 6-inch 600 lb

4 Anchor-Barling 10-inch 900 lb

5 Powell 10-inch 900 lb

6 Velan lO-inch 600 lb

5-1

!' I I
Each of the six valves was subjected to a qualification test sequence

(ANSI/ASME 616.41) and a flow interruption test sequence at normal

operating pressure and temperature. In addition, two of the valves

(numbers 2 and 3) underwent additional flow, interruption test sequences

in which the test parameters (temperature, pressure. and fluid density)

were varied. In all flow interruption test sequences, the valves were

cycled at both normal flow And blowdown flow conditions. The valves were

not inspected following-each blowdown-stroke. The valves were only

inspected after all testing was completed (see Section 4). Results of

Phase 2 testing were presented by INEL at a public meeting in April. 1990

(Reference 2). For this effort, data plots from the INEL data report

(Reference 7) were used.

After the Phase I tests we were criticized for not performing valve

inspections between tests and for further testing damaged hardware.

Valve Inspections between tests were considered for the Phase II test

program, but we later decided against them because of cost factors.

Experience had shown us that valve damage could be detected through a

sensitive stem thrust measurement. During the Phase 11 testing, we were

able to detect every occurrence of valve damage.

SUMMARY OF DATA USED IN EVALUATION

Appendix A summarizes-the test piramieirsfand flow conditions for each

valve stroke performed with 'differential pressuie in the tests of both

Phase I and Phase 2. ;

There were'85 strokes with'differential pressure (DP) in the Phase I

tests and 149 in Phase 2. Apparent disk factors could not be calculated

for some strokes because the DP was too small *or the data were

insufficient. Table 5-1 summarizes the strokes analyzed In thisevaluation and explains why some strokes were not analyzed. In general.

there were three types of strokes with' DP. as shown in the following

table. - - -

5-2
Type General Procedure DP Behavior

No Flow Upstream side pressurized and DP rapidly dissipated as downstream

(Open strokes downstream depressurized; valve volume pressurized.

only) opened.

Normal Flow Flow established using pump (Phase 1) DP increased as valve closed and then

(Close and open or orifice (Phase 2); valve stroked dissipated as valve opened. In most

strokes) closed then opened. cases this DP was very small at all

times.

Blowdown Flow established using quick-opening DP increased as valve closed and then

(Close and open device; valve stroked closed and then decreased as valve opened. In all

strokes) partially opened and re-closed. cases this DP was substantial

throughout the stroke.

ANALYSIS APPROACH .

Apparent valve disk factors were calculated using the equation below.

which is derived from the classic form of the valve thrust equation for

gate valves. The word "apparent" Is used because it is assumed that stem

force which is not due to packing load or stem rejection load is due to

friction between the disk and guides/seats.

The INEL response to the EPRI reports discussion of apparent disc factor

Is presented in Section 3.4.2.

ADF - FS t± (P x AS) - Fp

DP x AD

(+) for opening

(-) for closing

Where.

ADF: Apparent valve disk factor

FS: Measured stem force (lbf)

DP: Differential pressure (psi)

As: Cross-sectional area of valve stem (Wn2)

Fp : Stem force required to overcome packing load (lbf)

P : Upstream system pressure (psi)

5-3

3
AD: Disk area (in2

)

F , DP and P are taken from the data plots provided by INEL. Fp was

determined using data from a valve stroke with no pressure, or using data

from a combined opening/closing strokeiat constant pressure. As and AD

are based on valve geometry.> The disk arei is based on the mean contact t

diameter between disk and seatwhich was obtained.from inspection and

measurement of Valves'l thr6ugh 6. For valves A a nd 8, manufacturer . .. r .. A a dimension information was used; The disk and stem areas used for this

analysis'are tabulated below. Also sh6wn are the disk areas used by

INEL. In References 1. 2 and 7, INEL plotted 'predicted" stem force

assuming disk factors of 0.3 and 0.5. and compared these predictions to

measured stem force data. These comparisons imply values of disk factor

for the test valves (e.g... greater than 0.5). As shown below, the actual

disk areas used here are slightly different, from;those- values fused

previously,by.INEL. The areasjused by INEL-are.- In general, slightly

lower (average 8X).. This causes the INEL computed stem-thrusts to be

lower than actual and the implied disk factors:to be higher than actual.

Figure 5-1 shows how the disk areas used in this evaluation and by INEL

were determined. The INEL disk area is based on upstream seat ring bore

.diameter. This evaluation uses a more, precise approach based on

downstream mean contact diameter.

5-4
Valve AS (in2) AD (in2) AD (in2) used by INEL

A 1.767 23.6 20.6

B 2.405 24.4 21.1

1 1.767 21.9 20.6

2 2.405 24.4 21.1

3 1.227 23.9 21.8

4 3.142 58.6 61.0

5 3.547 61.2 61.9

6 4.907 54.7 48.7

Valve apparent disk factors were calculated at four different events

during each stroke as described below. Figure 5-2 shows the four events

on a stem force versus time plot. Note that this plot is not an actual

stem force trace but is intended only to illustrate where and how the

events were identified. In particular, the maximum stem force occurred

well after isolation in many cases.

Events at which data were evaluated are:

1. At zero stem position, as indicated by the "Valve Stem

Position" data plot. INEL reported that, for Phase 2

testing, this position indicator was calibrated before

testing so that it would read zero when the disk

completely covered the flow area. Valve stem position

information is not interpretable In this way for Phase I

testing. Note that the Interpretation of stem position

is subject to hysteresis effects due to the stem/disk

The INEL response to the EPRI report's discussion of valve positions for

analysis is presented in Section 3.4.1 of this report.

The disk areas for Valves 1 and A are different because the valve was turned around for Phase 2 testing. The area for Valve A is based on the

manufacturer drawing and that for Valve 1 is based on measured dimensions.

5-5

I,,j I |
clearance (i.e., for a given stem position, the disk

can be at either of two locations, depending on whether

the stem is pushing or pulling the disk). Therefore,

zero stem position may not always represent the instant

that a true' seal between disk and seat is made.

2. At flow isolation (or unisolation). For closing

strokes, Isolation was generally identified as the point

when downstream static pressure fell to zero. For

opening strokes, isolation (or unisolation) was

identified as the point when downstream pressure

increased above zero. This method did not work for

normal flow tests, where a downstream orifice was used

to control flow and resulted in the downstream pressure

remaining at a high level beyond valve closure. (i.e.

the DP was small). Further, it appears dynamic pressure

(which is measured with a tap facing the flow as opposed

to a flush tap which is used to measure static pressure)

may be a more sensitive indicator of true isolation.

The exact determination of flow isolation should be

studied more carefully in a long-term evaluation of the

test data.

3. At wedging, as identifed from the stem force plots.

For closing strokes, wedging was identified as the

instant just prior to the essentially vertical section

of the stem force plot which corresponds to a rapid

increase in' stem force." For opening strokes, wedging

was identified by the plateau immediately after the

initial "cracking" peak on the stem force plot.

5-6
4. At maximum stem force (excluding cracking peak)

regardless of disk position. This value is the highest

stem force during the stroke. On some stem force plots.

this coincided with one of the three points mentioned

above. On others. there was a maximum stem force which

occurred at a time other than isolation, wedging, or

zero stem position indication.

ANALYSIS RESULTS

Apparent valve disk factors calculated for each stroke with differential

pressure are listed in Appendix B. Results are discussed in Section 6.

5-7

U
Table 5-1

SUMMARY OF VALVE STROKES ANALYZED

FROM PHASE 1 AND PHASE 2

MOV TESTING

Total # Strokes,, Number

Valve # with DP . Analvzed Strokes Not Analvzed

A

B

58

27

38

19

57

20 - normal 'flow-tests*

8 !normal flow tests*

Phase 1 Totals: 85 28

1

2

3

4

5

6

13

52

32

12

17

23

--12

50

29

10

13

17

1

2

3

2

4

6

normal flow tests*

normal flow tests*

stem force plots bad

normal flow tests*

normal flow tests*

normal flow tests*

Phase 2 Totals: 149 131 18

* Differential pressure was too low on

factors to be calculated.

these normal

t I ".

flow tests for disk

always be calculated

Specifically, disk

NOTE: For those tests'analyzed, disk factor could not

at-all--of the desired events during'the stroke.

factor could not be calculated at:

1. Zero valve stem pos'ition'for:7 .strokes because valve stem

position plots-were inaccurate unavailable.. Plots were

considered inaccurate if zero'stem position occurred prior to

cracking or after stem force-leveled off to its "running load'

(on opening strokes).

2. Zero valve item 'position-for 19-notmal''flow strokes because of

low DP., --

3. Zero valve stem position for the 57 Phase I strokes because valve

stem position plots were not interpretable in this manner.

4. Isolation for 19 normal flow tests because of low DP.

5. Isolation for one (1) stroke because isolation could not be

identified.

6. Wedging for three (3) strokes because the disk did not wedge.

See Appendix B for a complete stroke-by-stroke list of calculated

disk factors.

5-6
a

MPR ASSOCIATES

F-140-49-96(A)

t ~11/9/90 ,

Midpoint of

Disk/Seat

Contact

..

Flow

Diameter used in

this Evaluation

to Calculate Disk

Area

Diameter used by

INEL to Calculate

Disk Area

DISK AREAS USED IN THIS EVALUATION

AND BY INEL

FIGURE 5-1
MPR ASSOCIATES

F-140-49-23(8)

11/9/90

Stem Force

Valve Stern

Position

if

0

Downstream

Static Pressure

nime

TIME INSTANTS FOR CALCULATION

OF APPARENT VALVE DISK FACTORS

FOR NRC/INEL PHASE I AND PHASE II'DATA

FIGURE 5-2
Section 6

EVALUATION OF DATA REVIEW AND INSPECTION RESULTS

BLOWDOWN ISOLATION

Table 6-1 summarizes the apparent valve disk factors and test parameters

for selected blowdown closing strokes from Phase 1 and Phase 2. The

first blowdown stroke for each valve is highlighted in bold. Figure 6-1

sunmmrizes the results from the first blowdown strokes. Several

important conclusions should be noted:

1. For Valves A. 4. 5. and 6, all the strokes listed exhibited

anomalous behavior (See 'Behavior Beyond Friction' below).

Therefore. the apparent disk factors listed in the table do not

necessarily reflect true friction since damage mechanisms likely

resulted in higher required stem thrusts. There could be

significant variation In disk factor for valves which have these

damage mechanisms.

Table 6-1 is addressed in Section 3.4.2 of this report. The table

consistently shows too small a value for the stem force required to

isolate flow.

The anomalous behavior identified by EPRI for each valve is discussed

below In view of how we used the test results from each valve.

Valve A -

Valve 4 -

See our discussion of the EPRI reports item 3 below.

This valve was badly damaged during the initial design

basis blowdown test sequence. No additional blowdown

tests were performed with this valve. We did not use

the results of the valve In developing the INEL

correlation.

Valve 5 - The high loadings during the initial design basis

blowdown test sequence resulted in disc tippage and an

Interference between the disc and the seat. Subsequent

testing did not exhibit this behavior, as the material

interface had been removed during the initial design

basis blowdown test. Therefore, subsequent testing

using this valve was used in developing the INEL

correlation.

6-1

I!
Valve 6 - See our discussion of the EPRI repart's item 4 below.

2. As discussed in Section 3, Anchor/Darling indicates Valve I Is

not representative of 6" Anchor/Darling valves; therefore. the

disk factors calculated for Valve I are not considered

applicable to typical Anchor/Darling Valves.

:, - : - 1. - I , ! 1

3. Valve A had nitrogen flow rather than the desired saturated

water flow for the first blowdown closure stroke. The effects

of nitrogen versus water are not known. but this fluid : ., wol not nom n:a .,ii .. .. difference would not nominally hive been expected to affect the

disk cocking/machining behavior observed with this valve. I . .I . .. 1 .1 . . . ,- .. -......................... . . .

Accordingly, the disk factor for Valve A is considered

potentially applicable.

4. As discussed later. it appears Valve 6 was damaged in a hot

cycle, no-flow test prior to the first blowdown stroke.

Specifically, the guide rails were bent downstream. If the

guide rails had not been damaged, it appears similar damage

would likely have occurred In blowdown strokes. Accordingly,

the disk' factor for Valve 6 is considered potentially

applicable..-

Valve A was delivered to the INEL with the understanding that it is

representative of Anchor/Darling valves delivered to the nuclear

industry. The.downstream disc surface on Valve I was the original

valve A unrefurbished surface. See Section 3.3.2 for additional details.

The EPRI report is concerned with the presence of nitrogen during several

of the Phase I tests and its effect on the friction factor between the

disc and the seats.- -e have assessed the Phase I tests and concur that

the seven tests, listed in-Table.2-1 of the EPRI report included nitrogen.

(nitrogen entrainment, not dry nitrogen). However, the eight tests

listed in Table 2-2 of the EPRI report did not. It is also important to

remember that using the JNEL methodology, we saw no difference in the

response of the valve-during testing that had a nitrogen/steam mixture.

compared with the response during testing with a water/steam mixture.

See section 3.4.6 for additional details.

Damage to this.valve consisted of disc and seat damage. guide damage, and

a bent guide. We initially attempted to use measurements from design

basis testing taken when the disc first started to ride on the seats.

hoping to avoid the results of abnormal Interferences between the bent

guide and the disc and the seats. However, upon further assessment of

the response of this valve during design basis blowdown testing, we have

decided not to use any of the results from this valve In developing the

INEL correlation.

6-2
5. For Valves B, 2, and 3. the apparent isolation disk factors for

the first blowdown stroke are 0.35. 0.33. and 0.19.

respectively. These valves did not show anomalous behavior

associated with valve damage. Therefore, it appears that disk

factors for blowdown isolation strokes from this testing are

bounded by a value of 0.35. when anomalous behavior is avoided.

Disc factors for blowdown isolation tests of valves B. 2. and 3 are not

bounded by a value of 0.35. Sections 3.4.1 and 3.4.2 of this report

address the EPRI report's evaluation of apparent disc factors at

Isolation.

BLOWDOWN UNUSUAL BEHAVIOR

Anomalous Behavior on Blowdown Closure Strokes

This behavior occurred on Valves A. 1. 4. 6 and to some extent on Valve

5. This behavior was characterized by jagged thrust traces and. In some

cases (Valves A, 4, and 5). maximum stem thrust prior to wedging

(yielding a transient high apparent disk factor). Figure 6-2 is a plot

of stem force versus time for the first Valve 4 blowdown closing stroke.

The apparent valve disk factor calculated at the force "peak" is 0.58;

the disk factor calculated at wedging is 0.32. This plot also

illustrates the jagged force traces that were observed.

This behavior is attributed to mechanical Interaction of valve internals

beyond simple sliding friction, that is, machining or shaping of

surfaces. The inspection results support this conclusion. Inspection

of Valves I through 6 showed evidence of wear/damage on the guide and

seating surfaces of all valves; however, major damage was observed on

Valves 1. 4, and 6 and, to a lesser extent, on Valve 5. Stem/bonnet bore

damage was also observed on Valve 4. Table 6-2 shows a summary of guide

and seat damage to Valves I through 6; the correlation of major damage

to valves showing anomalous behavior Is evident.

The stem force responses do indeed exhibit jagged traces, and such traces

are indicative of valve damage. Apparent disc factors calculated at the

peak stem force must be used with caution, because the extent of valve

damage and the stem force necessary to move the disc against such damage

must be estimated, while the actual damage and actual stem force vary

considerably from test to test and from valve to valve. Calculating a

disc factor Just prior to wedging may have some qualified use, but the

nonpredictable nature of the valve needs to be emphasized.

The EPRI report has assessed the results of the wear and damage to each

valve tested by the INEL. Identifiable wear and damage to the disc seat.

body seats, disc guide, and body guides of each valve for the Phase 11

and the Valve B disc from Phase I testing are described by EPRI in

Table 6-2. along with an assessment of whether the conditions noted could

have caused anomalous behavior. Generally, the EPRI report concludes

that damage to the disc guide and body guides and the disc seat and body

seats directly affects whether a valve is considered to be predicable or

nonpredictable. Such nonpredictable behavior can result in high stem

forces and, as a result. high apparent disc factors. The results from

tests showing anomalous blowdown behavior are nonetheless valid. GI-87

valves showing such behavior during testing can be expected to show such

behavior under similar conditions should a line break occur in the plant.

6-3

i ! I a
However. the nonpredictability of the results renders them not very

; ! useful in the assessment of valve response In general.

r.~~~~ -

It should be noted that the Inspection was carried out at the conclusion

of the test program after numerous strokes had been performed on each

valve. Because there were no inspections during the test sequence. it , I , I ., ,1 . . I:. ..

is not possible to6precisely.reconstruct the damage scenarios. In all

cases except one (Valve 6) it appears the significant damage occurred

during, the blowdown strokes. This conclusion is based on the strong

correlation of major damage with the anomalous blowdown closure behavior

(Table 6-2). Specifically, a highly loaded closure stroke provides the

best opportunity for the disk guide slot edge and disk seat edge to

machine the mating body guide rail and seat ring surfaces. The exception

for Valve 6 Is discussed more extensively below under the discussioniof * ; A, . . 4. . - .* .

"No-flow Tests" and under the discussion of 'Valve 6".

Pictures of the type of damage referred to in Table 6-2 are given in

Section 4. -

- Figure 4-13 shows major guide damage (Valve 4)

- Figure 4-11 shows major disk seat damage (Valve 4)

- Figure 4-12 shows moderate guide damage (Valve 5)

- Figure 4-10 shows minor disk seat damage (Valve 6)

The EPRI report expresses concern over the lack of inspections between

tests and the possibility that we tested damaged valves. Sections 3.2.2

and 3.3.3 address these issues.

: . 4 . ... I- -. .. . . -

. . .. ..* .. ..

..... I

These figures-show the significant lo6al material deformation which

occurred in some valves in the tests. The damage is characteristic of

very high local bearing stresses, indicating that guide'and seat 'surfaces

For a nonpredictable valve, the highest loads typically occur while the

disc is still riding on the guides. These loads are the result of an

Increasing differential pressure near closure and the increasing disc

6-4
were carrying load in a highly nonuniform manner. The surfaces are most

susceptible to this when the disk is partially through its stroke and the

load is being transferred from the guides to the seat. This is where

transient force maximums were seen in the data, e.g. Figure 6-2.

area being exposed to the flow. There is evidence to suggest that

clearances between the disc and the guides were larger, allowing the disc

to tip excessively. This tippage of the disc concentrated the disc to

guide loads and resulted in localized damage to both the disc and the

guides.

This damage occurs while the disc is riding on the guides. Once the disc

comes in contact with and starts riding on the seats, it straightens

somewhat. This helps to distribute the load over a larger area and also

allows the harder and stronger Stellite-coated surfaces to carry the

load.

Force Increase During Opening Stroke

This behavior occurred on Valves 4. 5, and 6 (Phase 2 10-inch valves)

and, to a very limited extent, on Valves A and B (Phase I 6-inch valves).

This behavior was characterized by a maximum stem force after the flow

path was opened (yielding a transient high apparent disk factor). Figure

6-3 is a plot of stem force versus time for a Valve 5 blowdown

opening/closure stroke. The apparent disk factor at unwedging Is about

0.31. which is consistent with sliding friction. The disk factor at the

stem force peak is about 0.45, which indicates phenomena beyond friction

appear to be occurring. Also, the DP has dropped off at the time of the

force peak, further indicating that phenomena beyond simple sliding

friction are occurring.

We suspect that internal valve damage did not cause the response noted.

If it had, we would expect the highest stem force to occur at the same

time the highest load between the disc and the seat occurs, i.e.,

immediately after unseating. This was not the response noted.

The behavior also occurred to a very limited extent on hot, no-flow

opening tests, which can be attributed to the brief existence of

blowdown-like conditions in the very initial parts of these strokes (see

discussion of "No-flow Tests" below). Two possible causes are postulated

for this behavior: valve damage (analogous to closing strokes as

6-5

a
discussed above), and flow effects.

Valve damage was observed In the inspections and likely contributed to

this behavior. However. damage is not considered to be exclusively

responsible for this behavior because:

- The correlation between observation of the behavior and presence . ! ' '

of significant damage was not as strong as. for the closure

behavior. For example, Valve S showed the most significant

behavior but had much more moderate damage, and Valve 1 showed

among the most severe damage but none of the behavior. Damage

may have been a significant contributor for Valve 6. where the

'behavior changed distinctly to this unusual form between the

first and second nominally identical hot, no-flow opening

strokes (see discussion of 'No-flow Tests" below).

Intuitivelj' daiiage c6nsistingj of 'digging in'd gouging would be

much less likely on opening 'strokes. because the surfaces tend

not to' interact it'aggressive angles. On Valve 6. where a

deformed guide was a major damage'contributor, this-could have

(and likely) occurred on the first hot no-flow opening test;

hence, damage appears to be i significant contributor for Valve

6.--.

Flow effects have been identified by INEL'as being responsible for the

force increase during blowdown opening mid-stroke. 'This explanation Is

plausible because local internal pressure data show a reduced pressure

below the disk' giving rise:to a downward load on the disk from flow

effects. Quantitative evaluation of this explanation has not yet been

presented by INEL. nor his it been evaluated yet In the EPRI NOV

Performance Prediction Program. Quantitative evaluation will require

6-6
detailed examination of pressure data In the valve body and valve

disk/body geometry. Hydraulic modeling to predict pressure distribution

will likely also be required.

The detailed explanation of this behavior Is a question for future study.

Although this behavior can have an Impact on valve performance

predictions, the applicability of this observed behavior to nuclear power

plant valves Is not known; In general. nuclear power plant valves do not

have to open against design basis blowdown opening conditions such as

tested in these NRC/INEL tests. However, some valves need to open in

systems where the flow rate may be significant as the valve opens, and

there could be the potential for this type of behavior. Accordingly, to

the extent this phenomenon is due to flow effects. It would need to be

adequately accounted for In valve opening applications. For most nuclear

power plant valves, which face opening conditions far less severe than

the NRC/INEL blowdown conditions, this effect is not expected to be as

strong as observed in the NRC/INEL tests.

We potentially agree with the EPRI report that most nuclear power plant

valves do not have to open on blowdown flow conditions. PORV block

valves maybe an exception. We have never quoted a safety function for

a valve to initiate blowdown flow. We performed normal flow openings.

no flow openings, and maximum flow openings. Some systems in a nuclear

plant are connected to large vessels where momentary to slightly more

sustained high flows could be anticipated, depending on the downstream

volume. The EPRI report acknowledges this fact.

High Apparent Friction Near Seated Position

This behavior occurred on Valve 2. The behavior was characterized by

significantly higher apparent disk factor (over 0.5) while the disk was

travelling at or near the final wedged (hard-seated) position. The

average apparent disk factor calculated at blowdown isolation for Valve

2 was much lower, about 0.3. The stem force sharply increased after flow

was isolated but before wedging occurred. Figure 6-4 shows a blowdown

isolation stem thrust trace, with the points of isolation and wedging

marked.

Based on our assessment of this test and the results presented on this

figure. the 0.3 apparent disc factor presented In the EPRI report was not

at Isolation. but instead at a point earlier in the stroke, while the

disc was still traveling on the guides. We estimate that another

1.5 seconds of motion occurred before the disc was fully riding on the

seats and flow was actually isolated; an additional second passed before

wedging occurred. We consider the apparent disc factors as presented by

the EPRI report to be typically too low because a value for the stem

force measured while the disc was still riding on the guides was used.

Note also that this was a 100F subcooled test. Appendix C of this

report describes the fluid dependencies of valve response.

6-7

I ! I In
The high disk factor, on Valve 2 was also seen on opening strokes. In

particular, apparent disk factors of over 0.5 were observed when the disk

was sliding from unwedging to unisolation.

The reason for this behavior is not thoroughly understood. The valve

inspection provided some insight._Ftrst, the disk seat face of Valve 2

had a high iron concentration (20% - see Table 4-8) which can contribute

to increased friction. Typical Iron concentrations should be in the

range 5-10%. However, other valves had observed high iron concentrations

and did not show the abnormally high disk factors. Further, iron content

would not reasonably explain the sudden changes in apparent friction as

the disk approached .the wedged position. Accordingly, the high iron

content, although it could be a concern, does not appear to explain the

particular high disk factor forValve 2. .

Next, it was noted that Valve 2 showed a distinct wear pattern on the

body guide rail edges and disk guide slot edges parallel to the flow.

which normally are not load-bearing surfaces. Figure 6-5 shows the

observed wear pattern on one of the guide rail edges. The wear indicates

these surfaces were contacting near the bottom of the stroke. The

contact was enhanced by small lateral disk/gulde clearances in this

directionl(total clearance of 0.050 inches - see Table 4-12) and by a

tendency of the'Valve 2 disk to rotate very slightly (about an' axis along

the pipe) as it first caineinto contact with the seat. These effects

apparently resulted in the disk engaging the guide rail on the surfaces

parallel to flow." Figure 6-6 shows the hypothesized phenomenon.

It appears'that'as the additional surfaces came into contact, additional

friction forces may have been generated resisting valve disk motion.

We have not assessed opening disc factors extensively and have not

assessed opening friction factors per the INEL equation at all. However,

it is Interesting to note that the opening disc factor is very similar

to the closing disc factor just prior to wedging.

While the EPRI report considers the response of Valve 2 to be anomalous,

the method employed by the INEL (see Appendix C) to assess disc to seat

friction factors indicates that the response of Valve 2 was typical of

the response of the other predictable valves.

EPRI has identified disc to valve body wear due to rotation of the disc

as one possible abnormality with this valve. This valve sustained by far

the largest number of strokes. In light of the large number of valve

cycles, we believe that the Identified markings reflect normal wear for

the test conditions the valve was subjected to. The appearance of such

wear on a valve is not surprising. None of the valves have any mechanism

to prohibit the disc from rotating relative to the pipe center line,

other than resistance from the stem and by disc contact with the guides.

We have no reason to suspect that any rotation of the disc in Valve 2 is

more pronounced than in any other valve. In fact, the limited lateral

clearance between the disc and the guide would minimize any rotational

tendencies of the disc and prevent aggressive contact angles from

occurring. In addition, the methodology employed by the INEL to assess

valve response indicates that the behavior of Valve 2 during the testing

6-8
These additional forces would be interpreted as a higher apparent disk

factor. If this explanation is true. it appears Insufficient lateral

disk/guide clearance may have been the root cause of the abnormally high

disk factor. Because this abnormal behavior may be related to design

aspects and to valve-unique clearances. there may be some potential

applicability to nuclear power plant valves. However, the root cause

needs to be verified before the detailed applicability can be evaluated.

In this regard, additional ltesting to reproduce and isolate these

phenomena is warranted.

Unusual Seatinci Behavior

Unusual seating behavior occurred on closing strokes for Valve 6. The

behavior was characterized by a stem force trace which did not have a

sharp "corner" when the disk was hard in the seat; instead, the thrust

gradually increased more sharply toward the end of the stroke before the

disk was hard in the seat. A high apparent disk factor at the point of

wedging was calculated. Figure 6-7 is a plot of stem force versus time

for Valve 6 and illustrates this behavior.

was typical of the other predictable valves tested.

As previously discussed damage to this valve consisted of disc and seat

damage, guide damage, and bent guides. The data was not used in the INEL

correlation.

The valve inspection provided some insight on this behavior.

Specifically, the lower end of the guide rails, which were cantilevered,

were deformed in the direction of flow. Figure 4-15 shows a picture of

the deformed guide rails. The deformation was to such an extent that the

disk was wedging between the downstream seat and guide rails, and was

gradually forcing the guide rails back toward their original position.

Also, the disk guide slot was "digging into" the guide rail on one of the

faces parallel to flow, as evidenced by severe damage. The root cause

of this behavior is considered to be a guide rail design with inadequate

support at the bottom end. Also, insufficient disk/guide lateral

clearance may have contributed. It is believed the guide rail

deformation occurred during initial hot no-flow testing (see discussion

6-9

I
of "Ho-flow Tests" below).

BLODJOWN FRICTION BEHAVIOR

In the discussion below, "disk factor" refers to apparent valve disk

factors calculated as part of this evaluation (see Section 5). Data from

blowdown closure and opening strokes were reviewed to identify portions

of each stroke, if any, where the sliding of the disk on the seat

appeared to be the'dominant load phenomen'on (rather than machining or

shaping of surfaces). This evaluation focused'ohnthe brief time period

between flow Isolation and wedging, and attempted to ensure that the

unusual effects as discussdabove were'excluded. The appearance of the

force plot was used to determine periods of 'apparent sliding friction."

For example, Figure 6-2 shows the first blowdown'closure strokefor Valve

4. The force plateau right after the peak at Isolation is'considir&d to'

be the disk sliding on the seat; the disk-factor'in this'period is 0.32.

Based on evaluating all of-the:blowdown closure and opening strokes in

this manner, average apparent disk factors due to sliding friction for

each valve were determined. Table-6-3 summarizes the average disk

factors for blowdown conditions when sliding of the disk on the seat Is

occurring. -As shown'in this table, the values are between 0.28 and 0.41

for closing strokes,. and are between 0.25 and 0.40 for opening strokes,

with the exception of Valve 2 at 0:47.- If data for wedging of-Valve 2

are considered,- the, average apparent'disk factor Is as high as 0.52:;

however, as mentioned previously, itsappears-additional surfaces were

coming into play during wedging and the apparent disk factor does not

necessarily represent true friction. The unusually high value of 0.47

for opening strokes of Valve 2 (based on the point of isolation) may also

be affected by this, phenomenon. In summary. the blowdown sliding

friction disk factor results suggest the traditional 0.3 disk factor used

in the valve thrust equation may need to be somewhat increased (to about

The apparent disc factor analysis is discussed in Section 3.4.2 of this

report. Averaging these data in this analysis will not improve their

usefulness.

6-10
.0.4) to cover sliding friction under blowdown conditions. The high

Valve 2 results suggest that the unusual behavior in this valve can be

interpreted as apparent sliding friction.

NORMAL FLOW TESTS

No results could be obtained from normal flow tests on Valves A. 5, 4.

5. and 6 because the test configuration and approach resulted in

negligible DP during these strokes (see Section 2). In Phase 1 testing

(Valves A and B) a low-head pump was used for flow. In Phase 2 testing

(Valves 4. 5, and 6). a downstream orifice was used to set the flow, and

downstream pressure remained at a high level while the valve was closed

and re-opened. resulting in very low differential pressures being

developed during the stroke (see Figure 2-3).

The normal flow tests are discussed in Section 3.2.5 of this report. We

found the data from these tests useful.

For Valves 1. 2. and 3. significant differential pressures were developed

(see Figure 2-4), and apparent disk factors could be calculated at the

point of wedging/unwedging for both closing and opening strokes.

Isolation could not be identified from the downstream pressure plots

because of the effect of the downstream orifice as discussed above. and

the differential pressure at zero stem position was so low that disk

factors could not be accurately calculated.

Results for apparent disk factor during wedging/unwedging of these three

valves during normal flow strokes are given below.

Valve

1

Average Apparent

Disk Factor

0.34

Exolanation

2 0.58

Based on wedging of 1 closure stroke.

Based on wedging of 6 closure and 6 opening strokes.

3 0.27 Based on wedging of 4 closure and 4 opening strokes.

6-11

I . .. ..I -I F'~~~i U1
Note the result for Valve 1. is based on only a single stroke. Also, for

Valve 2 It was previously shown that-phenomena beyond friction may be

occurring during wedging so the 0.58 value above is not likely due to

true friction. Nonetheless, It is higher than average wedging disk

factor for.blowdown conditions (0.48 to 0.52). The value for Valve 3

(0.27) is less than the comparable value for blowdown conditions (0.33

to 0.38). The limitations In the present analyses and the apparent lack

of, agreement between these. tests. and others underscores the need to

evaluate the normal flow data In more detail. The unusual behavior of.

the DP during the. stroke. (Figure 2-6) made, these data difficult to.

evaluate using plots. LUntil further evaluationis performed using the

digital data, It appears no disk factor, conclusions can be made from

these tests.

NO-FLOW TESTS, ,

In ."no-flow" tests, the volume downstream .of the test- valve was

depressurized while the upstream side was kept pressurized, and then-the

valve was opened. As discussed in Section 3' a brief period-of flow

actually occurred as the flow path was initially opened up. Particularly.

with the hot-steam "no-flow" tests (10-inch valves), the period of flow

was significant (several seconds).. Accordingly, the-description "noflow" (adopted here from the INEL reports) may be a slight misnomer.

The lack of agreement among the disc factors for the different valves is,

more than anything else, an Indication that the standard industry

equation is deficient.

A no-flow test with a pressurized fluid upstream of the valve will

produce a momentary motion of the fluid when the valve is opened. This

phenomenon will be more pronounced If the fluid Is highly compressible.

The term "no flow" is not an attempt to Ignore this momentary phenomenon.

but rather to distinguish between sustained forced flow and pressure

relief. Note also that during the no-flow tests there was no flow at the

discharge end of the test facility. The no flow tests are discussed In

Section 3.2.6 of this report.

The brief period ofeflow in steam tests of 10-inch valves Involved

considerable DP. across the valve. - It appears these tests simulated

blowdown opening conditions for-the first few seconds of the opening

stroke. Because of this feature, the unusual force increase after flow

6-12
initiated (discussed previously under "Blowdown Unusual Behavior") was

seen to some extent on hot. "no-flow" strokes of IO-inch valves. The

behavior was only observed to a small extent on Valve 4 but to a more

significant extent on Valve 5. Figure 6-8 shows the stem force time

history for the first hot no-flow opening of Valve 5. The force peak

after start of flow can be clearly seen. Other hot no-flow test results

for Valve 5 looked similar.

For Valve 6. the first hot no-flow stroke showed little or no evidence

of the unusual behavior. but the second hot no-flow stroke showed

significant evidence of this behavior. Figure 6-9 shows the stem force

time histories of the first two hot no-flow strokes. These two strokes

had essentially identical conditions In terms of pressure. temperature

and OP history across the valve. Because the unusual stem force was

observed only on the second stroke, it appears flow effects are not

responsible for the stem force increase on this valve. Rather. it

appears valve damage likely initiated on the first hot no-flow test.

which contributed to the subsequent unusual behavior. As discussed in

Section 4 and earlier under "Unusual Seating Behavior". Valve 6 had body

guide rails bent in the direction of flow (see Figure 4-15). It appears

this deformation initiated on the first hot, no-flow test, based on the

appearance of the data. It is noted the bent guide damage mechanism

could readily occur on an opening stroke, and it appears the OP persisted

long enough to allow load to be transferred to the guides on this stroke.

Accordingly, valve damage likely contributed to observed valve behavior

for all valve strokes following the first hot no-flow test (including all

blowdown strokes). The root cause of this damage was a guide rail design

which was inadequately supported at the lower end. It should be noted

that this guide rail may not have permanently deformed If the valve was

installed in a typical nuclear power plant system (non-blowdown) where

pressure is relieved more quickly as the valve opens (see Figure 2-5) or

6-13

.
in a system with a lower temperature where the material yield stress

would have been higher.-'. :

The cold no-flow tests performed on all valves preceding the hot no-flow

tests generally showed a much lower disk factor, which is discussed later

under Effect of Valve Exposure History". -

-. '.1 ,

The hot no-flow tests from all eight test valves were reviewed to define

test periods where it appeared :sliding friction was the dominant

behavior. The force increase after start of flow was excluded from

consideration. Average apparent disk factors are summarized in Table 6-

4. In general. 'a favorable comparison between Table 6-4 (No-flow) and

Table 6-3 (Blowdown) is observed. Figure 6-10 highlights the comparison.

Disk factors for sliding friction are in the range 0.25 to 0.41, except

for' Valve 2: and Valve B to a slight extet. 'As discussed earlier. it

appears unusual phenombna may be inv-olved while Valve 2 is near the seat.

The unusual behavior may add to true disk/seat friction, which would

likely explain the unusiaiiy'high disk facto Non theless. it appears

generally that valve sliding performance obtained from no-flow tests can

be used to predict sliding performance in blowdown tests. For valve

designs/ipplications where behavior beyond friction is avoided it design

basis condi'tions. performance can be adequateiy predicted or extrapolated

from tests at lesser conditlons.'

EFFECT OF VALVE EXPOSURE HISTORY

Figures 6-11 through 6-26 show apparent disk factor for every valve

stroke with OP evaluated in this study. Each plot.shows apparent disk

factor plotted against total stroke number for that valve (where only

strokes with DP are counted). Separate, consecutive plots are provided

for opening and closing strokes on each valve. For each stroke, up to

4 apparent disk factor values are plotted, corresponding to the 4 events

Average and apparent disc factors are discussed elsewhere in this report.

Section 3.4.1 addresses our concern with the EPRI reports definition of

apparent disc factors at isolation, wedging, or maximum. We have also

expressed concern over the choice of a disc area for calculating the disc

factor and Its applicability to the standard Industry disc equation (see

Section 3.4.2).

6-14
during the stroke which were analyzed (see Section 5). Blowdown and

Normal flow strokes are identified by the Indications "B" and "N at the

top of each graph; also, observations of anomalous blowdown closure

behavior and unusual force increases during opening strokes are indicated

by "A" and "U" respectively. Finally, lines have been drawn showing

average apparent disk factors for indicated events. All of the values

shown on Figures 6-11 through 6-26 are tabulated in Appendix B.

The first major observation is that on all 8 valves the initial cold noflow strokes yielded low apparent disk factors (0.1 to 0.2). Upon

initiation of hot no-flow testing. disk factor increased (to above 0.3).

There was also some evidence of disk factor increasing with repeated

strokes at cold temperature (see Valves 6 and A, Figures 6-21 and 6-23).

In cases where cold temperature tests were conducted after hot tests

(Valves A. B and 2). disk factor did not return to the initial low level

but instead remained at the higher level. Figure 6-27 is a plot of disk

factor (based on wedging) versus temperature covering all. strokes of

Valve 2. which Illustrates the irreversible nature of the disk factor

change.

The tendency of the disc factor to remain high when cold testing is

performed after the hot testing has not been assessed by the INEL. An

independent assessment of the these phenomena might confirm these trends.

Ve agree that the mechanisms identified here in the EPRI report could

contribute. If these trends are confirmed, their Impact on our original

conclusions will be minimal.

The cause for this behavior is not know, but several mechanisms have been

postulated. These include:

- Removal of residual machining oil from disk and seat

surfaces

- Removal of an oxide layer on disk and seat surfaces

- Microscopic surface changes on disk and seat surfaces

(normal 'wear")

- Macroscopic surface charges on disk and seat surfaces

(indicating damage).

The INEL data are insufficient to determine the cause. Nonetheless, the

data from these test indicate that valve performance information

6-15

I *i I ! . I 0
I

meaningful to hot conditions can be obtained by tests at cold conditions,

once the valve hisben expsed to hot conditions. Conversely initial

tests at cold conditions may not'give bounding information' on future

valve performance at hot or cold conditions.

LINEAR STRESS'

Section 2 discussed the use of a linear stress parameter to evaluate I , -, , 1

valve application severity. Figures 6-28 through 6-35 are plots of

apparent disk factor versus linear stress (differential pressure times

disk area divided by circumference of disk) for all valves tested. ,,. ,. , i :

Opening and closing strokes are indicated on each plot separately, as are

blowdown and non-blowdown strokes. There appears to be no clear

correlation of strokes overall or for a particular subset of strokes.

It appears that linear stress, by itself, is not necessarily an adequate

valve severity evaluation parameter for separating valves into "lightly

loaded" and `heavily loaded" classes. As discussed in Section 2., it

appears the behavior of DP during mid-stroke plays an important role.

The INEL assessment of the closing tests, as presented in Appendix C.

concluded that a load dependent response does exist. This response was

observed for both the Phase I and the Phase II closure testing. Sections

3.4.2 and 3.4.4 at this report present discussions that might explain why

the EPRI work did not demonstrate a load dependent response.

The linear contact stress model should have a distant relationship to the

normal loading concept employed by the INEL, but more study is needed. , I .L . . ..

DISCUSSION OF INDIVIDUAL VALVES

Although the eight NRC/INEL test-valves were discussed-in the preceding

data evaluations. below is a summary of key performance observations for

each valve along-with Insights from inspections regarding explanations

for the observed behavior. ,.

Valve A and Valve I -

Valve A/i showed a'sliding friction apparent disk factor in the range 0.3

to 0.4 but was susceptible to anomalous behavior on blowdown closurle:

strokes. Blowdown isolation disk factors as high'as 0.75 were observed

on Valve A and as high as 0.86 were observed on Valve 1. The anomalous

6-16
behavior is attributed to the sizable disk-to-guide clearance in the

direction of flow (about 1/4" total clearance). This clearance

apparently allowed the disk to displace and/or tip downstream during

blowdown closures such that the disk attacked the seat aggressively and

led to interaction beyond sliding friction (shaping and machining).

Significant disk and seat damage resulted. The damage appeared to be

exacerbated by a sharp edge on the disk edge of Valve 1. Anchor/Darling

indicates this sharp edge is atypical. Also. the Inspection of Valve 1

noted significant guide damage. The as-cast. fairly rough surfaces of

the guide rails in conjunction with the sizable disk-to-guide clearance

(which allowed tipping to concentrate the guide load over a small area)

apparently contributed to the extent of damage.

The disk of Valve 1 had a Stellite Iron dilution (20%) much higher than It is Inconsistent for the EPRI report to suggest that Iron dilution may

typical, according to the manufacturer. Anchor/Darling. The high iron have affected the performance of Valve 1, when in the following

content may also have exacerbated the behavior for Valve 1. discussion of Valve 8 and Valve 2 results the report states, 'the high

iron content did not appear to contribute detrimentally to valve

behavior.'

The first blowdown stroke of Valve A passed nitrogen (rather than the

desired saturated water) for the final 60% of the stroke. Although

nitrogen is atypical, the potential for the disk to displace and/or tip

and aggressively engage the downstream seat would apparently still have

been present with water flow. Finally, although damage apparently

occurred on the first blowdown stroke of Valve A, several subsequent

blowdown strokes were run. Generally, the measured behavior Improved

with succeeding strokes. The Improvement is attributed to the valve disk

machining a slightly altered (i.e.. "easier") path. This indicates

valves should be able to be designed (or perhaps modified) to be able to

accommodate blowdown conditions adequately.

6-17
Valve B and Valve 2

Valve B/2 is somewhat opposite of Valve A/I. Specifically. Valve B and

Valve 2 performed quite well at isolating blowdown flows (apparent disk

factor 0.3 to 0.4). but showed an undesirable performance feature in that

the apparent disk factor-for wedging and unwedging (for both blowdown and

no-flow conditions) was higher than desired -- about 0.4 to 0.6. The

disk and body seat faces were in very good condition on this valve after

testing, with only very minor wear. The guides, particularly 'on Vailve

2 (not hardfaced) showed significant wear, butrguide wear likely would

not have influenced wedging and unwedging performance because the disk

is normally sliding on the seat during wedging/unwedging. The short disk

guide length probably contributed to the extent of guide wear. The disk

had very tight clearances (total about 0.050") in the flow direction.

which'likely minimized disk displacement and'tilting. and helped ensure

good blowdown isolation performance. However, this valve also had tight

disk/guide clearances dn the lateral direction (perpendicular to flow),

which it appears may have contributed to the high wedginglunwedging disk

factor. The observed wear suggests the disk built up significant loads

laterally against the guide during wedging/unwedging, contributing to

increased:resisting forces. 'The disk Stellite surface had a high iron.

dilution (20X), but the high iron content did not appear to contribute

detrimentally to valve behavior. : ,

Valve 3

Valve 3 showed good performance in blowdown isolation and no-flow tests.

with apparent disk factors near 0.3. Moderate damage was observed on

disk! and guide surfaces, thus showing that damage does not preclude

reasonable performance. This-valve had a flexible, U-shaped, removable.

guide rail which was permanently deformed, apparently during the blowdown

tests. , Hence, it appears significant damage does not preclude reasonable

performance.. The guide deformation., similar to that occurring on an

6-18
overloaded, simply-supported beam. may have helped the valve achieve good

performance by easing the transition from guide to seat. However, it Is

not clear that similar guide deformation will generally result in good

performance. Although not observed on Valve 3. it appears flexible and

potentially plastically defaming guides could have performance hazards

as well. particularly if deflections become excessive.

Valve 4

Valve 4 behaved in a manner similar to Valve 1, L.e. reasonable sliding

fiction performance but susceptibility to anomalous behavior on blowdown

closures. The maximum isolation disk factor (0.49) for Valve 4 was not

as large as Valve 1. The presence of more reasonable disk Stellite iron

dilution and the proper manufacturers beveled edge on Valve 4 may have

contributed to the lower disk factor.

As with Valve A/I, it appears sizable disk/guide clearances (1/4") in the

direction of flow allowed disk displacement and/or tipping during

blowdown closure which allowed the disk to aggressively interact with the

seat. Significant disk/seat damage was observed.

In addition, Valve 4 showed the following other features:

- Major guide damage -- it appears the rough as-cast guide

rail surface contributed to damage.

- Stem/bonnet bore damage -- it appears excessive lateral

disk/guide clearance may have allowed the disk to

migrate laterally (particularly during the part of the

stroke where the guides were damaged), which caused a

stem/bonnet bore interference.

- Body seat iron dilution (-11) somewhat higher than

desired -- high iron content may have contributed to the

extent of seat damage.

6-19

.I 2
Valve5 -5 l - - -

Valve 5 showed good sliding friction-performance_(O.3 to 0.4.apparent . The last seni

disk factor) but appeared to show limited susceptibility to anomalous lateral surfa

behavior during blowdown closure strokes. The sharp edge at the bottom the EPRI repo

: of the disk 4iMd thehigh iron dilution in the disk seat (-30X) forces fob Va

-- contributed:tothe tendency of-the disk to catch onthe se0tand try to ' the use of an

. machine It away,- bt-the relatively-tight-disk/guide-clearances-in the' EPRI analysis

direction of flow and the smooth machirted guide surfaces apparently kept additional we

the adverse behavior from getting excessive. Valve 5 also had relatively shows the on-

, tight disk/guide clearances in the lateral direction and some indications identical. I

; of wear on the lateral surfaces.lHowever. (unlike Valves 2 and 6) there--- - either valve'

were no indications in-the data that this interaction contributed to,

* - - increased stem thrust requirements. - - -- - - -

Valve 6 -. '-- a; - E - i i .

Vilvei6 showed perhaps the most unique behavior during the tests. It:

showed alImited-te-ndenc. to calousibehavior in blowdown isolation

tests, -and-also showed-unusually-high wedging/unwedging disk factors.

It appears the~behavior of-this valve!was dominated by the deformation,

of the unsupported lower ends of the body.guide' rails. . The seating

surfaces were not extensively damaged on this valve and the disk/guide

clearances in the direction of flow-were relatively tight, suggesting

that if the guides had not bent,,good performance may have been achieved.

However, the disk/guide lateral 'clearances (perpendicular to flow) were,

also tight on this valve 'ad there 'were indications of severe damage on

the guide rail surfaces parallel to flow, indicating there may have been

some interference with wedging/unwedging performance even if the guide

rails had not bent. Finally, the disk showed a higher than desired iron

dilution In the Stellite (-26%). -However, the effect of iron content

cannot be separated from the test results.

6-20

tence in this discussion states-that weir Indications -on

ces did not contribute to increased stem thrusts. However,

rt suggests that similar indications caused the higher stem

,lves 2 and 6 The EPRI report's conclusions are based on

i incomplete equation for determining stem force. -Thus, the

tends to attribute any underpredIction by that equation to

ar or other loads

the-seat behavior

The lateral guide

s performance. -

not normally-seen., The INEL correlation

of Valve 2 and Valve 5 to be essentially

wear did not' contribute-significantly to :

i. ;.1

 I. I--- - ...-- . -.. -.... - - I

I

I .

i

A:
Test Conditions .iL---

TABLE 6-1

and Apparent Disk Factors Calculated for . -_ Dt 2r 11 I-. - -{ - --AIO

-________ rndse 5 8IJrssc rr ase bIIU _-

Differential Pressure

Disk Stem Packing (psi) Stem Force (Ibs) Apparent Disk

Area Area Pressure Temp Load Factor I

Teat* Valve (in2) (In2) (psi) (F) Hedium (Ibs)

_solation Wedging Isolation Wedging Isolation Wedging

A-3-5 Anchor-DarLing 23.6 1.767 450 480 Hot Water 633 510 525 9,000 5.500 (A) 0.63 0.33

6-inch

1-1-25 Anchor-Darlting 21.9 1.767 900 525 Hot Uater 1600 870 870 19,500 None (A) 0.86 --

_ _ _ _ _ _ _ _ 6 -inch - _ _ _ I_ _ _ _ _ _ _ _ _ _ _

B-2-5 Velan 6-i nch 24.4 2.405 950 524 Hot Water 1621 1000 1000 12,500 14,400 0.35 0.43

2-1-25 Vetan 6-inch 24.4 2.405 950 525 Hot Water SOO 940 940 10,400 13,400 0.33 0.46

2-2-25 Velan 6-inch 24.4 2.405 1050 545 Steam SOO 1060 1060 9,000 14,200 0.23 0.43

2-3-25 Velan 6-inch 24.4 2.405 750 145 ColdU - 500 770 700 5.200 12,900 0.15 0.56 ________________ ~ ~~ ~~~Water__ _ _ __ _ _ _ _ _ _

2-6A-25 Velan 6-inch 24.4 2.405 530 455 Hot water SOO 500 500 5,300 8,200 0.29 0.53

2-6A1-25 Velan 6-inch 24.4 2.405 590 440 Hot Water 500 580 600 6,000 9,200 0.29 0.50

2-6B-25 Velan 6-inch 24.4 2.405 860 475 Hot Water SOO 830 830 8,800 13,000 0.31 0.52

2-681-25 Velan 6-inch 24.4 2.405 950 475 Hot Water 500 920 960 9,200 14,200 0.29 0.49

2-6C-25 Velan 6-inch 24.4 2.405 1280 530 Hot Water SOO 1260 1280 12,200 16,100 0.28 0.40

3-1-25 Ualuorth 6- 23.9 1.227 840 525 Hot Water 1000 870 870 5,900 8,200 0.19 0.30

inch

3-1A-25 yWalworth 6- .23.9 1.227 910 530 Hot Water 1000 900 900 7.000 9,000 0.23 0.32

inch , _

3-5-25 WaLworth 6- 23.9 1.227 1100 550 Hot Water 1000 1100 1120 9,100 11,500 0.26 0.34

ifnch _ _ _ _ _ _

4-1-25 Anchor-Darling 58.6 3.142 710 485 Steam 1600 700 720 23.800 17.500 (A) 0.49

0.32***

¶0-Inch____

5-1-25 Potell 10-inch 61.2 3.547 590 520 Steam 1375 880 880 28,000 23,900 (A) O." 0.36

5-1A-25 Powell 10-inch 61.2 3.547 1020 485 Steam 1375 1020 1020 26,500 28,000 (A) 0.34 0.37

6-1-25 Velan 10-inch 54.7 4.907 1000 455 Steam 0 1000 1000 28,000 35,000 (A) 0.42 0.55

6-1A-25 Velan 10-inch 54.7 4.907 1200 480 Steam 0 1190 1190 32,000 43,500 (A) 0.40 0.58

6-18-25 Velan 10-inch 54.7 4.907 1010 475 Steam 0 1000 1010 19,000 38,200 (A) 0.26 0.60 * us vA .~~~*. . _ -. _..... .. vaive " - rage FIer nxrUp5J U . .. . -._. lesl ICMuflterJ - IIL IInVe

5* Valve did not wedge. Maximum Value of 1.04.

Maxiiruu Value of 0.58

2U.I; F b indicates tfoat anomalous behavior occurred.

2. First blowdown stroke for each valve is in bold.

.
i

Table 6-2 -

SUMMARY OFWEAR/DAMAGE OBSERVATIONS IN SEATS AND GUTDFS

Valved Anomalous j Summary of Wear/Damage ., ,,-. . Performance ., . -. ?

.1 -n-Blowdown Tests? ~~~~~~isk Seat D A Guide Body Guide Seeau Disk 

Yes . Major, 'Major Major Moderate

,. 2 No Minor, Minor. Moderate Moderate

B (Disk - No Minor. .. . Minor

Only)'4 ' . N 

r 3 - CModerate No.Moderate Moderate Minor'2'

4.- C ~~~~~- S a'_._..,. .._._..._._._

";'i2- 4 w Yes,'} : , Maes.ajor, .'- Major . Major ';

- - Yes' 3'1 - Moderite Moderate ; Moderate Moderatee, Y -' I 1' ' 2

-6 ) Yes -'' Minor ! Minor -"a Major Major'2'

("Definit'on''of wear/damige descriptions is as: follows: --

:Minor-- -light surface scratching, less than 0.003 inch deep in carbon steel and less than

O.OO1"'inch deep in'Stellite.

* .Moderite' -- distinct.'surface scratches and small gouges, up to about 0.20 'inch deep in

carbon steel and~uo to 0.005-inch deep in Stellite.

Major - Deep isurface scratches and distinct gouges or areas of gross metal'lremoval.

'2'Body'guide' rails had permanent deflection in direction of flow.

'3'Valve No. 5 showed low disk factor in spite of anomalous features in stem force traces.

14'Disk B used in Phase I testing only.

6-22
a

Table 6-3

SUMMARY OF AVERAGE SLIDING FRICTION

APPARENT DISK FACTORS UNDER BLOWDOWN CONDITIONS

Valve Description Average Explanation

Apparent Disk

Factor

l ______ _____________________ Open Close

A Anchor/Darling, 6", 0.33 0.41 Based on wedging during 6

900#, Hot Water and openings and 16 closures.

Nitrogen (A only)

Tests

1 0.40 Based on wedging during 1

opening.

B Velan, 6", 900#, 0.38 0.29 Based on isolation during 3

Hot Water, Cold (0.35) (0.41) openings and 7 closures. Value in

Water (2 only) and parentheses is that obtained

Nitrogen (B only) using wedging for same strokes,-

Tests which may not be simple friction.

2 0.47 0.28 Based on isolation during 8

(0.52) (0.48) openings and 16 closures. Value

in parentheses is that obtained

using wedging for same strokes,

which may not be simple friction.

3 Walworth, 6", 600#, 0.38 0.33 Based on wedging during 3

Hot Water Tests openings and 6 closures.

4 Anchor/Darling, 0.34 0.34 Based on wedging during 1 opening

10", 900#, Steam and 2 closures.

Tests

5- Powell, 10", 900#, 0.30 0.36 Based on wedging during 2

Steam Tests openings and 4 closures.

-~ 6 Velan, 10", 600#, 0.25 -- Based on isolation during 3

Steam Tests openings..

*

Apparent disk- factor is determined from measured stem force using the sta

industry equation. See Section 5. This table-covers only apparent.-disk fa

from data where it appears sliding friction was the dominant phenomena.

** This value is unusually high compared to other values and may be attributab

phenomena beyond simple friction.

to

6-23
Table 6-4

SUMMARY OF AVERAGE APPARENT DISK FACTORS'

FOR SLIDING FRICTION CONDITIONS IN NO-FLOW TESTS

Valve Average Disk Explanation

, Factor for

No-Flow ,__ __ _ ___ Opening

A 0.34 Based on unwedging of 11

strokes.

1 0.33 Based on unwedging of 4

strokes.

B 0.44'. Based on unisolation of 5-

,(0.46) strokes (value in parentheses , is based on unwedging).

2 0.54" Based on unisolation of 9

"(0.54) strokes (value in parentheses

is based on unwedging).

3 0.28 Based on unwedging of 8

* ' - strokes.

4 0.30 Based on unwedging of 4

strokes.

5 0.28 Based on unwedging of 4 - strokes.

6: ' 0.32 Based on unisolation of 5

-' - strokes.

* Apparent disk factor is determined from measured stem force using the standard ind

equation. See'Section 5. This table covers only apparent disk factors'from data where

it-appears sliding friction was'the dominant phenomena.

** These values are unusually high compared to other' valves and :may be attribu

to phenomena beyond simple'friction'.

- I

6-24
NITROGEN

MEDIUM: 4 .

VALVE SIZE:

1

- WATER

6-INCHSTEAM O

10-INCH -

1 -VALVE DAMAGED PRIOR

TO FIRST BLOWDOWN

. ..- *-

D

I

S

K

F

A

C

T

0

R

0.8

0.8

0.4

0.2

0

A

... . .. . ... . . . . .. . .. .... .. . _ . .

4 5 6*

_ B- B 2

3

A/D VELAN A/D VELAN WALWORTH A/D PO W LLI

A/D POWELL VELAN

VALVE

APPARENT DISK FACTORS FOR ISOLATION ON

FIRST BLOWDOWN STROKE OF NRC/INEL VALVES

FIGURE 6-1

f I In
0 5 F A - -e1: I D-PT~~* 

3 10

o -20 5 ____ __ b

CO)

o

IL _30 ------- FORCE PEAK

W: BEFORE SEATING

CO -35 : _ _ ...... . .,. . . .:-- . _

-40 DATAFROM | -- ,- i -

. TEST I STEP 251l

0 5 10 - .20 25 30 35

TIME (SECONDS) . . . , - ,

STEM FORCE HISTORY FOR FIRST -

BLOWDOWN CLOSURE OF-VALVE 4

FIGURE 6-2
p

30

20

z

M

0T

a. CL

z

U)

0

C.D

0

l')

0n

10

0

-10

-20

-30

-40

rI

UNWEDGING FORCE. PEAK

s(DPe9d PSI) -- .DP--85PSl- ,

\FLOWSTARTS . (DP=900 PSI) |

I . -%% -- -.- - - - .-, -, -, --7 " - -, , -1 - " I

_ <-- ' OPEN -

DATA FROM

ITEST I ST EP 26J

. . . . I . . I I

L A ~~~~~~~~~~~~~~~~~~ ~~~~~~~

PI 'N - - %OL.%JQLW. I

i 11

I

i

I

I

I

-50

-60

I I

I

i . . . . I . . I

I . . . .

0 5 10 15 20 25

TIME (SECONDS)

STEM FORCE HISTORY FOR BLOWDOWN

OPEN/CLOSURE CYCLE FOR VALVE 5

FIGURE 6-3
0

CO -5~~~~~~~~~~~~

&3 -5 . - - - - - - i'._'. - - - --

z

Z -l

- ISOLATION , -

O - ADF=0.312

0

-25 .... ,, . .. , .

0 5 10 15 20 25

TIME (SECONDS)

-- STEM- FORCE -HISTORYFO

'VALVE--2 B3L'OWDOWN' CLOSURE

FIGURE 6-4
': U

[CRASOCATES

JF-140-49-931 111131,' 0

Flow 1>

No Visile Wear

Perceptibl Wear

(Scuffing and Indentatlonl

hI Two Strips

(Corresponds To Edge

Configuration Ofl Mating

Disk Guide Slot)

__

Distinct Up

(Corresponds to Position

Of Disk Guide Slot Edge

When Disk Is Seated)

Note:

Because of access imitations. It was not possible to make a photograph

of this guide rail wear during the valve Inspection. The INEL videotape

of valve Internals (Reference IO) shows this guide rail wear.

DIAGRAM OF GUIDE RAIL WEAR IN VALVE 2

FIGURE 6-5
IF-H40-45-921

0(

I,

I,

I'

*II

I'

Guide Rails

t AT FLOW SOLATiON

Stem thrust [a Is opposed by disk/seat friction

forces E Disk is sightly rotated relative to

-- uide tails. and contact occus at points E

and m but there are not sinificant reaction

forces. Rotation Is exagerated: actual vaiue Is

less than 10. Mechanism for disk rotation Is not

known. but coutd be sight stem misalgnment.

flow effects, non-uniform frictionr ete.

la

2. APPROACHING HARD SEATWG

Because of disk angular poslilon seat reacts

disk eccentrically at first M Dlsk rotates

clockwise to &Ign with seat EJ Contact force

butds up on guide due to squeezing point -

g reacted by lateral seat friction H

Additional friction at gulide Oneeds to be

overcome by stem thrust

3. HAR .SEATED

Disk motilon is stopped and wedglng force rg

is established. Disk is sprung Into guide at

point l

Guide Rails

HYPOTHESIZED MECHANISM FOR VALVE 2 BEHAVIOR

FIGURE 6-6
0

10

z -0 -______'___

Cl -20

a STEM FORCE

Z STARTS TO

C/) ~~~~~~~~~~~~INCREASE

0 -30

w IFLOW ISOLATION

0 -4 o 4O *. . . .. ... . .... :- -- - e

w HARD SEATING

If- ;(WEDGING)

-50 . -- ___

.DATA FROM; tr

TEST 1 A STEP 25 , , , , . , . i . . . . . . .

-60

0 5 . 10 15 20 25

TIME (SECONDS)

STEM FORCE HISTORY FOR

VALVE 6 BLOWDOWN CLOSURE

FIGURE 6-7
40

30

0

z

0

C] 0

z

cj)

0

t,

a:

0

LL

cj)

20

i 10

0 0

-10

-20

4 'MAXIMUM . AFTER.

FLOW OPENING ,

\ , , . . -. ... .. .....

i~ .. \. -i . , . I

N: _I~ I' * 7.:~~ 7 77

* , : .-, '; ' 'l - '- 4 ' 6 ' -- ' i _ _ _ t _ _ !*

~~~~~~~~~~~~~~~~~~~~~* .. I.

FLOW OPENIN.

(ISOLATION) §

/ :~~~~~~~~~~~J& j j

-30

!_d U0

;.I i . I, -

tI * I I . * .

* ~~~~~~~~~~~~~~~~I

I I I F AT ROM

I ~ K TEST HC STEP15[.

11550 PSI 600 F1

i I .1. . I . . . . * I * . .

-50 - - - - - - - - - - - - - -

..- 0 5 10 -, 15 20 25 ; 30

..TIME (SECONDS)

ISTEM 1 FORCE HISTORY FOR FIRST,:

*VALVE 5 HOT NO-FLOW QPENING

' FIGURE 6-8
30

20

FLOW OPENING

OSOLATION)

SECOND HOT NO-FLOW OPENING

< DATA FROM TEST HC STEP 23

----- (NOTETHE FORCE PEAKAFTER FLOW OPENING) S ~ ~ , ~ ~~~~ 

co0

z

m

0

CL

0

z

cn

0

tl

llJ

0

LL

C)

10

' O

-10

-20

-30

-40

I

I - i 1 -i

FIRST HOT NO-FLOW OPENING !

DATA FROM TEST HC STEP 15

(NOTE THERE IS NO FORCE - ' PEAK AFTER FLOW OPENING)

I_1 - . - .. - --...- t- -- -- .- --

- .. ._ .- ........... _ _ . _. _ ,_ ........... __ . .. _- .................. -

I

-50

-60

... 4..

a NOINALCONITIONS

i ~~1200 PSI 570 F

. . . .. i X . I I . . . . i . . . . I . . . . I . . . . . . . . . . . . . . . . . . . . . . .

0 5 10 15 20 25 30

TIME (SECONDS)

STEM FORCE HISTORY FOR FIRST TWO

VALVE 6 HOT NO-FLOW OPENINGS

FIGURE 6-9
These Unusually High Values May Be

Due To Phenomena Beyond Simple Friction

0.6 i

0.6 r| . ||_ NO-FLOW (OPEN)

0.5 _ BLOWDOWN OPEN

D :-; BLOWDOWN CLOSE

s 0.4 7

K

0.3 A I.

C INS

T0.2

O

R

0.1

0 . A .. 1. B" 2-.3 45 .6

VALVE

*APPARENT DISK FACTORS FOR SLIDING

FRICTION IN, NO-FLOW AND BLOWDOWN STROKES

FIGURE 6-10
I

B - BLOWDOWN - AVERAGE MAXIMUMAND UNWEDGING

D

S

K

F

A

C

T

0

R

1

0.9

0.8

0.7

0.6

0.6

0.4

ZERO STEM POSITION + ISOLATION u WEDGING 0 MAXIMUM

CLD WA~E H I-AJ

I. 3 I i

I I I .1I I I I I I I

0.3 I0.2 F0.1 r

O I . . . . 1

0 1 2 3 4 6 6 7 8 9 10 11 12 13

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #1 OPENING STROKES

FIGURE 6-11

MPR ASSOCIATES

F-140-49-61(B) 11/13/90
B - BLOWDOWN

N - NORMAL FLOW

A - ANOMALOUS BEHAVIOR

i

l-, . 8

1.2

1.1

1

I I

0 ZERO STEM POSITI,

_ + ISOLATION

,..a*WEDGING

D _0 MAXIMUM

S

K;

F

A:

T

0

R

i0.9

0.8

o.7

0.8

0.6

0.4

0.3

0.2

i

i

i., . .-. - I

1.

i II

i

i

I

I

. l

i .- .. I

I i

I ~~~~~~- 

I ~ ~ ~~~~I I

I

I

I

i

I , I , , . I

I

i

i

I

. I . i

i

I

I''

I I

.4

0.1

0 L a L - A.

0. 1 2 3 4 6 6 7 8 .9 10 11 12 13

* - STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #1 CLOSING STROKES

FIGURE 6-12

MPR ASSOCIATES

F-140-49-62(B) 11/13/90
/

B - BLOWDOWN

N - NORMAL FLOW

- AVERAGE MAXIMUM

.'AVERAGE UNWEDGING

1.4

1.2

D

I

S

K

F

A

C

T

0

R

1

0.8

0.6

0.4

0.2

0

0 - 6 10 16 20 26 30 36 40 45 50 55

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #2 OPENING STROKES

FIGURE 6-13

MPR ASSOCIATES

F-140-49-63(B) 11/13/90

~~ iN
B - BLOWDOWN

N - NORMAL FLOW -

... . I

.........

AVERAGE MAXIMUM

AVERAGE ISOLATION

. .

. . .

1.8

1.4

D

I

S;

KF.;

At

C..

T0

O..

R1.2

I

0.8

0.5

0.4

0.2

I0

0 6 10 16 20 26 30 36 40 4

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #2 CLOSING STROKES

FIGURE 6-14

5 66

IMPR ASSOCIATES

F-140-49-64(B) 11/13/90
B - BLOWDOWN

N - NORMAL FLOW

AVERAGE MAXIMUM

UNWEDGING .-AVERAGE, 

1

0.9

0.8

D

S

K

F

A

C

T

0

R

0.7

0.6

0.5

0.4

0.3

0.2

0.1

f 0

0 2 4 6 8 10 12 14

STROKE

16 18

NUMBER

DISK FACTOR VS STROKE NU

VALVE #3 OPENING STROK

FIGURE 6-15

20 22 24 26 28 30

MBER

ES MPR ASSOCIATES

F-140-49-66(B)

11/13/90

i 1 1 Ii:. Ia
B - BLOWDOWN

N - NORMAL FLOW

1.2

t * ~~v

D 0.9

K i0.7

'F 0.6

o 0.6

*. .

:. AVERAGE MAXIMUM

I ...... .. AVERAGE ISOLATION

.I I ~~~~ -

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

-- VALVE #3 CLOSING STROKES . FIGURE 6-16

MPR ASSOCIATES

F-140-49-66(B) 11/13/90
B - BLOWDOWN

U - UNUSUAL BEHAVIOR

I - AVERAGE MAXIMUM

UNWEDGING .AVERAGE 

1

0.9

0.8

D

S

K

F

A

C

T

0

R

0.7

0.6

0.6

0.4

0.3

0.2

0.1

0

0 1 2 3 4 6 6 7 8 9 10 11 12

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #4 OPENING STROKES

FIGURE 6-17

MPR ASSOCIATES

F-140-49-67(A) 10/26/90

A
offf

B - BLOWDOWN

A - ANOMALOUS BEHAVIOR . . .

.. I

/m-N

kE)

1

0.9

0.8

D

I

K..

F.^

A''

C.

T

0

R

0.7

0.6

0.6

0.4

0.3

_ 0 ZERO STEM POSITION

+ ISOLATION

'WEDGING

. 0 MAXIMUM I,

,~ ~ m -- ! l- I -X-

., . I .I. I ; i

, .-.- I '..-A .: I -: ' ' . I

!~ .1 1 - I

I , I . . I .,, 1 .~ ,.i _ _ _ _ _ __ _ _ _ _ _ _jI~

0.2

0.1

0 t

C

_ :

I. 1 2 . . . . . . . . .

. 3 4 -.. 6 ._ - 7 - - 8 9 10 11 12 .

STROKE NUMBER'

DISK FACTOR ~VS STROKE NUMBER . VALVE #4 CLOSING STROKES - II!, i . ! FIGURE 6-18 --- MPR ASSOCIATES F-140-49-58(B)

11113/90
B - BLOWDOWN

U - UNUSUAL BEHAVIOR ® @ ®®

AVERAGE MAXIMUM

......... AVERAGE UNWEDGING

©)

1 | I I I I I' , ! I !

0.9

0.8

D 0.7

S

K 0.8

F 0.6

A

C 0.4

T

0 0.3

R

- ZERO STEM POSITION + ISOLATION WEDGING O MAXIMUM

COLDWATLR 4TW I I.l

- I 4 44' ! -sI _ § 1__ I I I _ _ _ _

.2 ..... ---' .... ...... ....i.......... ...... ....'... ..l..... ...... . -129 1 .. . . 0.2

0.1 I

0

0 1 2 3 4 6 6 7 8 9 10 11 12 13 14 15 16 17

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #5 OPENING STROKES

FIGURE 6-19

MPR ASSOCIATES

F-140-49-69(B) 11/13/90

I ,.I , 11 I
Vq

AVERAGE MAXIMUM

B - BLOWDOWN ' AVERAGE 1SOLATION ..-

A - ANOMALOUS BEHAVIOR I . . .

D

I

..,

A

T

0

R

1

0.9

0.8

0O.7.

0.6

0.4

0.3

o. -ZERO STEM POSITION

+ ISOLATION

Cl*; WEDGING

O MAXIMUM

! ! _u m u

;;I .,

I I I I I I

IO~.: ,e

I

II ,

I

I

i

I

I

,

.38

.35

I . ..

! 1, . I I

I I ,

I

I

I

I

i

I

II . - i

I . I

O

i

(I

_,_ t, 1-* - - - - p -

0.2

- I

'I

I,--.

-I

* I

I... ~~~~~~~~~~~~~~

i I

I I

....... $I,,,,-

O.1 ;I

.1

0

0 1 -- 2 -- 3 4 6 6 7 8 9 10 11 12 13 14 16 16 17

STROKE NUMBER I

DISK FACTOR VS STROKE NUMBER

'-.-VALVE #5 CLOSING STROKES. ,

FIGURE 6-20

MPR ASSOCIATES

F-140-49-70(B) 11/13/90
B - BLOWDOWN

U - UNUSUAL BEHAVIOR

AVERAGE MAXIMUM

AVERAGE UNWEDGING .

U) ()( ) () 1

0.9

I I I Ir I I I I I I I

L O ZERO STEM POSITION + ISOLATION * WEDGING O MAXIMUM

I . u . . . m .m ..

0.8 ID

I

S

K

F

A

C

T

0

R

COLD ER HRPT TIR

0.7

0.6

I

II

i

i

0 'I

0

0.6 _- .50

0.4 i-

.36

0.3 _-

0.2

0.1

0

A

ID

-...+ ......... ",--

i

.I

t I

a

.......... ..... o ...

r. * j LF. wl

i

1 : I' . ! I I ...... i..a..i.......1

i '!i I ii

ID I

1 ,I i

i I

II I . I . .

0 2 4 6 8 10 12 14 16 18 20 22 24

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE #6 OPENING STROKES--

FIGURE 6-21

MPR ASSOCIATES

F-140-49-71(B)

11/13/90

a
/

B - BLOWDOWN

A - ANOMALOUS BEHAVIOR

- ~~ AVERAGE .MAXIMUM . ..

'!-- I....... AVERAGE ISOLATION.

I, . , .

II) A I. @ A A A

I

0.9

0.8

I I *Ii I I I I

0 ZERO STEM POSITION + ISOLATION * WEDGING 0 MAXIMUM

_ ID

I

S . K.

F.

A'-.

C.

T - 0.

Rft

0.7 _

0.6

0.5

0.4

0.3

0.2

0.1I .

- im

I

I.

. . .56

! .36

I

II

I

I

I

I

I

I

II

ml mu

I

i

I

i

I . . 4 .4 -

.... ....... .......

I

+ i

I m......... S +

i -I

l

.........

0

*l

i

; I

n L i i I I I,I I v

, . .

2 4-- 6 8 10 12 14 16 18 20 22 24

STROKE.NUMBER

DISK FACTORNVS STROKE NUMBER.

VALVE #6 CLOSING STROKES MPR ASSOCIATES

FIGURE 6-22 1 11/13/90 (
B - BLOWDOWN AVERAGE MAXIMUM

AVERAGE UNWEDGING .- 

1

0.9

0.8

I I I

+ ISOLATION

* WEDGING

O MAXIMUM

i

IIi

i

I

I

I

D

I

K

F

A

C

T

0

R

- .- . -

0.7

0.8

0.6

0.4

0.3

0.2

0.1

0

HiT WATE I I

A, I.

I

tAl * j|I

2 .1i I

L o i

.38 A I

.33t

i

'I+4+

*1 ..........

Ii -

.-. I

... .. . ... . f .. ... .. .TA*, .....+i......t4..

_ _ I

I I

.......

0 6 10 16 20 26 30 35

STROKE NUMBER

40 45 60 66 60

DISK FACTOR VS STROKE NUMBER

VALVE A OPENING STROKES

FIGURE 6-23

MPR ASSOCIATES

F-140-49-73(B) 11/13/90

. l I a
i

-. AVERAGE MAXIMUM

B - BLOWDOWN

A - ANOMALOUS BEHAVIOR

0.9 _

0.8

D 0.7 7_

K 0.8-

F 0.5

,C 0.4_ ., 8 1*.

o os.!,

0.2 R *i- !-!-K

,.s- O--.4 ... . ..... j

. I -.

- I . I -. .  I

I I I I

ISOLATION

,(M) (M)

-l : ,Ol 6 - 10 16 20 26 30 36 40 46 60 66 60

- STROKE NUMBER ---

DISK FACTOR VS STROKE NUMBER

VALVE A CLOSING STROKES

FIGURE 6-24

MPR ASSOCIATES

F-140-49-74(B) 11/13/90
B - BLOWDOWN - ~ AVERAGE MAXIMUM

AVERAGE UNWEDGING .---- 

1

0.9

0.8

D

S

K

F

A

C

T

0

R

0.7

0.6

0.6

0.4

0.3

0.2

0.1

0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE B OPENING STROKES

FIGURE 6-25

MPR ASSOCIATES

F-140-49-76(B) 11/13190

.II., a
.

B - BLOWDOWN - ~ AVERAGE MAXIMUM

AVERAGE ISOLATION ...-. 

00 9

0

/-M-% rml\

.kFl/ kE 1 I I I I I

I i

i

I .,

D-"

I , " S -_

K

F:

A',

C.,

0..'

0.9

0.8

0.7

r.

0.6

0.6_.

0.4

0.3

0.2

0.1

+

- Em. - urn

ISOLATION

WEDGING

MAXIMUM

i

i

II

i

I

i

i

i

.4

.29 ... ..

i I I

I I

I :

.i i

..... 4

I

i

I

i

I

i

9.

*......

I'

I

I ± .. 

I

I

I

I

i i I l 0

0 2 4 6 8 10 12 14 16 18 20 22 24 28 28

STROKE NUMBER

DISK FACTOR VS STROKE NUMBER

VALVE B CLOSING STROKES

FIGURE 6-26

MPR ASSOCIATES

F-140-49-76 (B) 11/13/90 -
a

.MPR ASSOCIATES

F-140-49-77(A) 11/13/90

0.8

0.6 i

D

S

K

F

A

C

T

0

R

0.4 --

* U

U

U

* U

U

- .------- U

U

m U U U. U

* -.

* U U

mu U U

U U * U

* U

* U U

U

U.

* U U

U - -

U

U

I I I I

0.2 -

0

0 100 200 300 400 500 600

TEMPERATURE (DEGREES F)

DISK FACTOR VS TEMPERATURE

WEDGING OF VALVE #2

FIGURE 6-27
MPR ASSOCIATES

F-140-49-82(A) 11/13/90

. .. 1. -

.,

a

,x

OPEN

CLOSING

-il BLOWDOWN

Z BLOWDOWN

OPEN

1.4 CLOSE I1.2 1 . --- --- - ---- . -.. . - _. _ -

D

I

S

K

1

I

I

I

F 0.8

A

C

T

0 0.6

R

0.4

0.2

! 0

x . U

U

U?

II I I

. . .. ..0 500 1000 ' . 1500,;

LINEAR STRESS (LB/IN) i .... .", . . i: ... .k

2000 2500

DISK FACT-OR VS, LINEAR STRESS

VALVE,# 1 MAXIMUM VALUES

FIGURE 6-28
a

MPR ASSOCIATES

F-140-49-83(A) 11/13/90 ..

1.2

1

D

I

S

K

F

A

C

T

0

R

0.8

0.6

* OPEN 2I BLOWDOWN OPEN

X CLOSING BLOWDOWN CLOSE

x x x

X~~~ _ . .. ---

la]~~~

00~61

El s s i s i 3 * *-~~~'

I _ ~ _ ~~~~_ I......... __ ............._. ..

0.4

0.2

0

0 500 1000 1500

LINEAR STRESS (LB/IN)

2000 2500

DISK FACTOR VS LINEAR STRESS

; VALVE #2 MAXIMUM VALUES

FIGURE 6-29
MPR ASSOCIATES

F-140-49-84(A) 11/13/ 9 0

0.8

. .. I I -

a OPEN .- BLOWDOWN OPEN

X CLOSING - -- BLOWDOWNWCLOSE

0.6 i - - - - - -- ..

D

S

K , - 0 I,. . El

A

C

T

0

R

0.4

of

.

a a

x

x

0.2 I

x .

.

x

I ~ ~ ~~~I I

. . .L i

0o

,- . . . .,, . , 1: I _' ..

500 . ,. A000, _ 1500

LINEAR STRESS (LB/IN)

2000 2500

'DISKK FACTOR -VS' LINEAR -STRESS

VALVE #3 MAXiMUM VALUES

FIGURE 6-30
xm 0

MPR ASSOCIATES

F-140-49-85(A) 11/13/ 90

1.2

1,

* OPEN

X CLOSING

[[i BLOWDOWN OPEN

[Z BLOWDOWN CLOSE I

D

I

S

K

F

A

C

T

0

R

0.8

0.6

0.4

0

a

aU

0.2 --

a

a

0 1 1 1 1

0 500 1000 1500 2000 2500

LINEAR STRESS (LB/IN)

3000 3500

DISK FACTOR VS LINEAR STRESS

VALVE #4 MAXIMUM VALUES

FIGURE 6-31

a

.. . ........ ............. .. . . .. . ...... ....... .
MPR ASSOCIATES

F-140-49-86(A) 1113/90_

0.8 1-

,

8

41x

.OPEN -

CLOSING

[I BLOWDOWN OPEN

09 BLOWDOWN CLOSE I L_ _ 0.6

D

I

Si

K * U

F

A

C

T

0

R

0.4

i~~~~~

0 0

a

0.2

0

aa

I I

0-. -^ ... , ,, -,1000 ,~~~~I .. I i ....wh 2000 .3000 4000

LINEAR STRESS (LB/IN)

DISK FACTOR'.VS -'LINEAR .STRESS

VALVE #5 MAXIMUM VALUES

FIGURE 6-32
IF-140-49-87(A)I

L1 1/1I90

1

OPEN iE BLOWDOWN OPEN

|X CLOSING Z BLOWDOWN CLOSE

0.8

D

I

S

K

F

A

C

T

0

R

0.6

0.4

0.2

0

0 m~

' '9 U

a U

U

- - ~ ~~~~~~

-

0 500 1000 1500 2000 2500 3000

LINEAR STRESS (LB/IN)

DISK FACTOR VS LINEAR STRESS

VALVE #6 MAXIMUM VALUES

FIGURE 6-33
IF.140-49-88(A)I

L 1/13/90 .

1

0.8

OEN E* BLOWDOWN OPEN

X CLOSING - BLOWDOWN CLOSE!

ED

D

Il S

K

F

A

C

T

0

R

0.6

0

0~~~~~~~~~~~~~~7 0

0.4 _

. 129 a 0 J~U

EU 

a

E la]

a

a

0.2 I

I --..  - - - -.- - I , , - - "' , , I - 0

0 X v ' - 500 ; - 1000 x 1500

' LINEAR STRESS (LB/IN)

2000 2500

DISK FACTOR-VS LINEAR STRESS

VALVE A MAXIMUMVA LUES

FIGURE 6-34
Iin

MPR ASSOCIATES

F-140-49-89(A) 11/13/ 90

0.8

|* .OPEN ;E BLOWDOWN OPEN

X CLOSING. Z BLOWDOWN CLOSE

0.6 --

D

S

K

.

.

F

A

C

T

0

R

0.4 0 0

a

l a]

0

0.2

0

-- ~ ~ ~ ~ -0-

a

I~~~ I _ _ L _--

0 500 1000 1500 2000 2500

LINEAR STRESS (LB/IN)

DISK FACTOR VS -LINEAR -STRESS

VALVE B MAXIMUM VALUES

FIGURE 6-35
I

Section 7

RECOMMENDATIONS

DETAILED EVALUATION OFJTEST AND INSPECTION DATA

* , , ' - *; ..i. 8..- :

This evaluation effort had.l1mited scope and schedule. It is recommended

that the NRC/INEL, data be1 further evaluated in areas discussed below.

The objective-of these additional evaluations is to develop an Improved

understanding of some of the areas of. question identified in this study,

and to support use of these-data in the overall EPRI NOV Performance

Prediction Program. These additional evaluations-will contribute- to

developing the detailed NOV performance prediction methodology for use

by utilities, which provides a suitable approach for NOV evaluation when

directly applicable data are not readily available.- It may be practicalto include.- some of these evaluations In selected test/developmentelements of-the EPRI WOV-Performance Prediction Program., Items to'beconsidered for potential further evaluation-are listed below.-

I. Confirmation of values-obtained from plots in-this evaluation

using digital data.-:Use of data plotsdid not support-high

resolution and accuracy in interpreting the data. -Although no

gross errors are suspected. -use of the digital data formalizes,

this process and eliminates inaccuracy from the "plot-reading"

step. - . - - - -

2. Detailed evaluation of "normal flow" strokes using digital data.

As shown in this report, normal flow data were difficult to:

interpret and the limited results obtained appeared somewhat

suspicious. A detailed evaluation of the digital data permits

INEL comments on this section of the EPRI report are not within the scope

of this review.

7-1
higher accuracy in interpreting the data and a more detailed

study of transient changes, in the brief time period where the

disk is arriving at the seat. This effort supports obtaining

improved information out of these tests and eliminating present

unanswered questions.

3. A more detailed evaluation of system flow behavior and flow

effects on valve performance,,using digital data. As discussed

in this report. it -appears test system .configuration and

operation affected the way the valve was loaded by DP. Further,

apparent flow effects on valve performance were seen. At

present, these effects have not been analyzed and quantified.

A more detailed evaluation is needed to support evaluation of

these effects in the NOV performance prediction methodology.

Specifically, It appears these effects should have a less

detrimental effect on valve performance for most power plant

valves than for the NRC/INEL test valves. Additional work is

needed to quantify this expectation.

4. A detailed review of-data quality, using the digital data.

Although not discussed in this report, some instances of

apparent zero shifts were observed in the data. In general.

these were not substantial, but could affect the accuracy of

calculated disk factors.. Additional work is needed to identify

and quantify these areas of.the data, so that final quantitative

values being used in the EPRI NOV Performance Prediction Program

are well-qualified.

5. Evaluation of surface roughness data from the valve inspection

and correlation with valve performance data. This report

summarizes an extensive amount of surface roughness information;

7-2

. ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ * .3
In some cases, it appears valve behavior may have been affected

by surface roughness.. An evaluation of detailed features of the

test data and comparison to observed roughness is useful to

support the NOV performance-predictlon program and to develop

guidelines (which could be Incorporated in valve specifications)

regarding acceptable surface conditions.

- . ,

6. Evaluation of dimensional, data from the valve Inspection.

including development of a disk/guide/seat Interaction model and ... .. . . . . . . . . . .

comparison to test data. This.report shows valve behavior was

apparently strongly affected by the nature of disk/guide/seat

interaction. The substantial dimensional data gathered from the

inspection should be evaluated in light of.an analytical model

Of disk/guide/seat, behavior.. This. effort would support:.

development of a methodology to be able to predict, independentof tests, whether a valve will behave normally or anomalously in

a specific application. Also.. configuration requirements for

valve specifications (e.g.. clearances) would ultimately flow

out of this effort.

7. Evaluation of Iron content measurements and comparison to test

data and other data sources. As discussed in this-report., a

wide variation of-disk and seat Stellite Iron content was

observed in the test valves, and the effect on valve performance

is not understood. A'more systematic look at the INEL data and

other potential data sources could help to improve the

understanding. This is important for guiding friction tests in

the EPRI NOV Performance Prediction Program, and ultimately, for

developing appropriate requirements for valve specifications.

ELEMENTS OF EPRI NOV PERFORMANCE PREDICTION PROGRAM

. - *

7-3
Based on this review of the NRC/INEL data and the valve inspection

activities. several insights were gained which should be considered in

the EPRI NOV Performance Prediction Program. It is noted that the

existing EPRI Program Plan already includes several elements which will

address valve performance issues coming out of. these tests. Additional

items not identified explicitly in the existing plan but which should be

included are listed below.

1. Test hardware (valves and operators) should be extensively

characterized prior to testing. Information should be obtained

and documented according to procedures, and should include

dimensional measurements. photographs, and performance

information such as motor characteristics, spring pack

stiffness, etc. This approach provides the needed information

to properly evaluate the test data and observations.

2. The hardware vendors should be involved with the test program to

provide immediate information on valve set up. performance.

dimensional characteristics, inspection interpretations. etc.

This approach helps avoid wrong interpretations and tangents

which could be detrimental to completing the program in a

focused way.

3. Valves should be internally inspected between strokes to check

for damage. This approach avoids having to guess when damage

occurred after several tests are performed. It appears use of

a borescope/fiberscope through an access nozzle may provide an

acceptable approach.

4. Valves should be tested at conditions generally progressing from

less severe to more severe. This approach allows damage

thresholds to be determined and maximizes the amount of useful

7-4

t' a1
1.

data prior to damage.

5. Flow loops for testing should cover conditions typical of

nuclear power pliant-systems containing applicable HOV's.

Further, the systems should have configurational and operational

flexibility so that ranges of paramet'ers (e.g., 'flow, pressure)

can be covered in the tests. This approach provides maximum

usefulness of'the test program.'

6. The MOV performance prediction methodology should incorporate

insight which has-been gained from the NRC/INEL tests. For

example,

' - '''' Guid'leirainces, guide support and edge configurations

all- appear 

-to affect' the;. potential for' disk

cocking/binding/gouging behavior. These features should

bei"included' in' the methodology to screen out

-,susceptibility to this behavior; ''; -:-; 

-

DP l6adin 'during 'mId strke ! appears to strongiy influence:-potential, disk "-cocking/binding/gouging

behavior. The DP versus stroke characteristics should

be considered in the methodology to screen out

susceptibility to this behavior.

- Disk/seat friction coefficients may be slightly higher than typically assumed values of 0.3. A value of O.4

appears sufficient to cover friction phenomena based on

the NRC/INEL.tests. 

- ' 

, -' 

- ! G U. i , 

.

7. Separate.effects elements for friction testing should plan to

cover effects of. stroke/temperature history and iron content.-

This is particularly important so that justified information is

available on ! how friction may change in an installed

application. Potential effects of machining oil, oxide layers,

topography. changes and damage should be addressed in these

tests. 

- e; -* ; 

'

7-5
S. Separate effects analyses and flow loop tests to cover the flow

effects on valve stem force need to be included. This topic is

only lightly addressed in the existing program plan; information

on the extent to which these effects influence typical power

plant valves is needed.

9. Additional testing of NRC/INEL Valve 2 or special testing.to

reproduce and explain the phenomena causing the Valve 2 unusual

behavior is warranted. This testing should include

investigation of unexpected disk/guide contact and should seek

to identify the root cause of the Valve 2 behavior and explore

potential modifications to alleviate the behavior. -

VALVE DESIGN FEATURES

Several aspects of valve design which are important to achieving good

performance under severe conditions were qualitatively identified by this

effort. In general, these important aspects are consistent with existing

experience and intuition; however, quantitative methods for rigorous

valve design may not in all cases be fully developed. These important

valve design aspects are discussed below in a qualitative way.

Important Hardware Features

1. Disk-to-gulde clearance needs to be kept to a small enough value

so that disk tipping and potential aggressive interaction with

the seat are minimized. Also, tight clearances in the direction

of flow permit a valve design which engages the seat at an

overall lower stem position. thus minimizing potential disk/seat

machining. However, clearances need to be kept large enough so

that the disk does not bind on the guides. - In the NRC/INEL

tests it appears such binding may have occurred in the lateral

direction.

7-6

A' e ; 1 ? "~~~~~~~~
2. Guide slot and guide rail surface finish should be a smooth,

machined finish to promote favorable valve performance. Ascast, unmachined surfaces do not necessarily preclude acceptable

valve operation, but do tend to aggravate damage.

3. Edge configuration of guide slots, disk seats and body seats

should be a rounded or beveled configuration to ensure favorable

sliding performance. Sharp edges appear to; increase the

potential for gouging/machining damage of, surfaces.

4. Body guide rail length needs to be sufficient to ensure the disk

does not tip off the end of the-guide rail. Sufficiently long

guide rails.thus minimize the potential for disk/seat machining

damage. . -;

5. Disk guide slot length needs to belongenough'to minimize disk

tipping on the guides, and also to provide adequate bearing area

to carry the disk load without damaging the materials.

6. Support of body guide rails should be adequate to ensure that

elastic or plastic deformation does not occur which would

inhibit smooth disk/seat interaction. -In particular, it appears

cantilevered guide rail ends can lead to performance

difficulties. Simply iupported guide rails can give adequate

performance as shown in the INEL tests. However, a simply

supported guide rail which is expected to plastically deform

under normal conditions would not likely be a favorable

approach.

7. Guide slots; and 4uide ralls should be hardfaced for improved

performance behavior under blowdown isolation conditions. One

7-7
NRC/INEL test valve had hardfaced disk guides and the

wear/damage was significantly less.

8. Iron content of Stellite hardfacing should be controlled during

valve manufacturing to ensure favorable friction and wear

properties. Iron dilution from the base material into the

Stellite should be minimized by controlling Stellite application

processes and subsequent machining.

Important System'Apolication Parameters

1. DP versus stroke can be an important parameter in evaluating NOV

performance in a specific application and in designing a valve

for the application. Blowdown conditions typically give

significant OP during mid-stroke, which more severely challenges

gate valves.

2. Temperature and/or temoerature/stroke history can be an

Important parameter In evaluating test data from a gate valve

and predicting valve thrust requirements in the future. Valves

in cold applications. in particular. may show disk factor

increases with stroking for a considerable time. Hot conditions

may stabilize disk factor, although complete data are lacking.

3. Flow rate may be an important parameter, particularly for gate

valves which need to open as a design basis condition. High

flow appears to add to the required stem force to open the

valve.

7-8

t I ;1.1 U
Section 8

; ; PERSPECTIVES ON NRC AND INEL CONCLUSIONS

This effort has yielded insight on-existing, documented NRC and INEL

conclusions with regard to these-test-results.- For the purpose of this

effort. NRC conclusions as-documentedlin Information-Notices 89-88 and

90-40 (References 8, and 9) were- examined, and INEL conclusions as

documented in, NUREG/CR-5406 for Phase 1. testing (Reference I)-and the

April 18.- 1990 public presentation for Phase 2.testing (Reference 2) were

examined. . Only conclusions related to NOV performance are addressed;

conclusions-related to In-situ testing, diagnostics- training. etc.,-are.

not included in the scope of this report.

NRC conclusions are-llsted in Table 8-I along; with an explanation of

additional insight yielded by this study. INEL conclusions are given in

Table 8-2. along with an explanation of additional insight yielded by

this study. On both of these two tables, the NRC and INEL conclusions

have been recorded in the table exactly (word-for-word) as they appear

in the appropriate source documents.;. - -

Tables 8-1 and 8-2 shouldbe consulted for the detailed insight on eachf

NRC and INEL conclusion. -Three-overview perspectives are noted:

1. Some of the NRC and INEL conclusions imply applicability of the

test results beyond what is warranted. As an example, some

conclusions. are, based exclusively on observations during

blowdown opening tests.., Generally nuclear power plant valves

are not subjected to these extreme conditions. ..,. -

In this section we have altered the original format of theEPRI report. -

The text has not been changed. Ve list the text of the EPRI reports

Tables 8-1 and 8-2 In the left hand column, starting with the NRC/INEL

conclusion EPRI report Is responding to, followed by the EPRI response.

Our review convnents are.in the parallel right hand column.

I I 1 7 - -- - . .. ,.T

The NRC/lNEL conclusions quoted In the EPRI report are exact quotations.

They:were;worded carefully-in an-attempt to avoid confusion over the

applicability of each conclusion. As we discuss In the remainder of this

section, we believe the applicability of our, conclusions Isiclear and

correct. . - I . '' .

8-I
2. In some cases, the conclusion Implies more than is supported by

the data. For example. the NRC conclusion that "...during the

KWU tests. several blowdowns did not achieve full seating of the

valve" is overstated and misleading. In reality, out of 38

blowdown closure strokes, only two (on a single valve) did not

achieve full seating.

3. Some conclusions imply unduly restrictive approaches to deal

with certain situations. For example, the INEL conclusion.that

"only testing at design basis conditions will provide Insights

on predictable or nonpredictable behavior" excludes legitimate

engineering alternatives.

I.N. 89-88: The test results are generally applicable to any HOV

that must open or close in a high flow, a high

differential pressure, or a low subcooling situation.

The NRC/INEL tests examined specific flexible wedge gate valves under

specific flow conditions. As discussed in this report. there are many

other types of valve designs (including other gate valve designs, globe

valves,.etc.), and many HOV's are exposed to design basis conditions

considerably different than the NRC/INEL test conditions. If a valve in

a nuclear power plant is similar to only one aspect of the NRC/INEL test

conditions (e.g. high differential pressure), this does not mean that the

valve will behave in a manner similar to the INEL test valves.

Accordingly, it appears the test results are potentially applicable only

to similar gate valves under blowdown conditions.

The quoted conclusion Is correct; however it should have also Included

the Phase I testing, where valve B, a predictable, valve failed to fully

seat. It should also be noted that the torque switches on all the valve

operators were set higher than the Industry would have set them prior to

this testing. The idea was to close the valves and determine from the

data the required stem force to close. Without this policy, many more

of. the valves would not have achieved full seating.

Our conclusions reflect the state of the art with regard to KOY testing

and operability. The quoted statement is correct; we know of no method

available today for determining whether a valve is nonpredictable other

than full scale testing. Research Is being performed to understand and

predict this behavior; however, at the present time no 'legitimate

engineering alternative' to design basis testing exists.

This statement from I.N. 89-88 is true. In fact, some of the NRC/INEL

test results are applicable beyond the applications stated In this quote.

One of the findings of the NRC/INEL valve test program was that the

Industry equation for sizing and setting valve operators is Incomplete.

If an equation for predicting valve stem force Is incorrect or

incomplete, legitimate questions arise concerning any application sized

with that equation. The INEL valves were tested over a wide range of

pressures, temperatures, and flow rates. Data curves characterizing

valve performance were developed from the resulting data. The analysis

effort produced a correlation for stem force shows that on-the-seat valve

performance is predictable from low flow to blowdown flow. While It is

true that blowdown conditions apply only to valves that might experience

those conditions, the overall results of the test program are applicable

to many rising stem valves.

8-2

V . ., I

I
I.N. 89-88: Even with the high settings used during the KWU tests.

several blowdowns resulted in closure of the flow area

but did not achieve full seating of the valve.

Based on review of the test data.;only two tests on a single valve were

identified wvhere full seating wasnot'achieved. These two tests were the

two blowdown closure strokes for Valve I (Test 1 steps 25 and 26). Since

it appears that Valve I was likely damaged prior to the second blowdown' ,' t eaon se26

stroke, the failure to seat on step 26 is not totally surprising. Most

importantly, as discussed in this report, Valve 1 'is not typical of

valves produced by this manufacturerdue td some unusuaI featuies in the

test valve. For all other test valves, full seating was obtained.

I.H. 89-88: The valves required stem thrusts well in excess of those.. ' predicted by the' industry design formula in use at the

time-of theirdesigniandzmanufacture. :- ' ; i '

This report examines, to the extent possible, data from all of the ,,,, o. ,,,,, .. .

NRC/INEL test strokes withOP.. It is found that. for a substantial.

portion of the strokes. the-apparent disk factor is less than or

marginally in excess of that assumed by industry design formula.

However, there are selected strokes for some valves, under specific

conditions which showed required stem thrusts considerably in excess of ¢~ ~ ~ . .w ~~hs were ,y if ^ I I A I e' i 

industry formula. These were typically associated with blowdown

conditions, which are not similar to the majority of safety-related MOVs

in nuclear power plants. Accordingly great care is necessary in

applying the NRC/INEL results to industry valves.

The NRC statement quoted is a statement of fact. As stated above, the

NRC statement should have included the Phase I testing, where valve 8

also failed to fully seat. The typicality of the hardware is discussed

in Section 3.3 of this report.

The NRC statement quoted Is a statement of fact. Standard Industry

calculations for full DP closure were performed for each of the valves

prior to testing. The torque switches were set well above the setting

calculated to ensure closure, and the maximum stem forces during closure

were measured. In all cases, the stem force measured during blowdown

i.~~~~~~~~~ . _

clsue was wtaelltuoe inxes of sthatecaculte fc.Standard usin industry

As stated .in Sections 3.4.1-f and 3.4.2 of-this report,f the analysis:

procedures upon which the. EPRIt report bases w this conclusion. are

Incorrect. The. standard industry stem force equation is incomplete, and

with the typical orifice area and typical 0.3 disc factorused to size

the majority ofFlex Wedge gate valves-in the Industry, It often produces-:.

non-conservative results compared to the stem force measurements taken

during the INEL testing. A careful review of the uicensee Event Reports

and NRC bulletins (r E. Bulletin 85-03, for example) shows that plant

experience with valves in pumped flow systems is consistent with this NRC

8-3
conclusion. A number of valves in pumped systems have failed when

subjected to design basis conditions.

I.N. 89-88: The required stem thrust of the valves was not linearly

dependent on the differential pressure across the valve

at the time of closure. This circumstance precludes

determination of the required stem thrust from data that

could be obtained under normal -plant 'operating

conditions. ...

Under blowdown conditions, some of the NRC/INEL test valves exhibited

"anomalous" behavior which was characterized by. gouging/machining of

valve internals rather than sliding friction. It Is agreed that when

this behavior occurs, valve performance may not be linearly dependent on

applied differential pressure. However. when this behavior is avoided

(as is expected to be the case for the vast majority of industry NOV..

e.g.. in pumped systems), performance extrapolation to design basis

conditions is reasonable. The EPRI NOV Performance Prediction Program

includes elements to identify the potential for anomalous behavior in NOV

applications, and will develop data to support extrapolation methods.

I.N. 89-88: The thrust at which torque switch trip occurs was not

constant with respect to the loading history of the

valve. Many within the industry refer to this as the

"rate of loading" phenomenon. However., the testing

indicates that there may be more involved than

variations of the torque switch spring pack's response

time.

Although rate-of-loading effects apparently were present, this area of

data was not examined in detail. The EPRI NOV Performance Prediction

Program has elements to assess "rate-of-loading" phenomena.

I.N. 89-88: The stem factor (i.e.. the ratio of the motor operator's

output torque to the valve's stem thrust) appears to be

With regard to the standard industry equation, this NRC statement Is

true. In our early analyses we made an unsuccessful attempt using the

standard industry equation, to determine disc factor from low pressure

tests and relate that to the blowdown tests. That, attempt failed

because, as explained in Section 3.4.2 and in Appendix C of this report.

the standard industry equation is incomplete. The INEL correlation

includes additional forces acting on the disc, making this kind of

extrapolation possible.

This NRC quote Is a statement of fact. The NOV load sensitive behavior

is real. It has been observed in full-scale design basis tests and

during utility in-plant tests. We have duplicated this phenomenon in the

laboratory using our NOV load simulator. This behavior is still under

Investigation, but early data relate the problem to degradation of stem

nut lubrication during cycling at high stem loads and not to the spring

pack response.

This NRC quote is a statement of fact. As stated above, the NOV load

sensitive behavior is real. Research into this phenomenon is ongoing.

8-4

t. I ! U0
dependent on direction and magnitude of the load being

applied to the stem.

Examination-of stem'factor'results was beyond the scope of this Initial

evaluation. Existing information avallable from INEL or NRC (References

8 and 1) does not~show lnfo'rmation regarding dependence of stem factor

on stem travel direction. Limited information on stem factor ipparently

varying with load magnitude is given in Reference I for the Phase I

tests, but available data'are not sufficient to permit an independent

evaluation; It appears-further study of this'coinclusion has not been

addressed by INEL for the Phase2;,results. The EPRI NOV Performance

Prediction Program includes elements to study and ultimately predict stem

factor, including tests.ofseveral valves and lubricants over-prolonged

per iods. . . .

I.N. 89-88: Several of the valves significantly damaged themselves

during closure. -- '!'.' ,'''--.- .. .' f.,, ' !-;;'*

As discussed in this report, Indications of significant Internal damage

were observed during inspection of the valves. The data and the damage

patterns are- indicative that damage occurred' during the blowdown

closures. Unfortunately, in no cases were the valves inspected after

non-blowdown strokes or after the first blowdown 'stroke. so'the'time of

damage cannot be determined. P

I.N. 90-40: Regardless of fluld'conditlons' (i.e. steam, slightly

subcooled water; or cold water), the tested valves

required more thrust for. opening and closing under

various-differential pressure'ard flow conditions than

would: have been predicted from standard industry

calculations and typical friction.factors. Thus, a

potential exists for'the underestimation' of thrust

requirements for valves in applications, and under fluid

conditions, other than those of the valves involved in

the NRC research.

Daniage to the test hIardware occurred:. INEL has stated numerous times

'that the' damagi was due to`the tremindous loads experienced under

blowddwn conditions.' e have ails6'shown that careful examination of stem

force traces can be used to identify when damage occurred. The lack of

Inspections between tests does not detract from the significance of the

fact that more than half of the valves suffered damage when exposed to

their design basis conditions.

This quote from the NRC Notice is correct. Sections 3.4.1 and 3.4.2

address the EPRI report's analyses of apparent disc factors. The

industry equation is incomplete and did not produce conservative results

for any of the valve strokes referenced even those at loads lower than

blowdown loads. A prudent review of utility LERs establishes a

historical and technical basis for the NRC remark.

8-5
This report examines, to the extent possible, data from all of the

NRC/INEL test strokes with DP. It is found that, for a substantial

portion of the strokes, the apparent disk factor is less than or

marginally in excess of that assumed by industry design formula.

However, there are selected strokes for some valves under specific

conditions which showed high required stem thrust. These were typically

associated with blowdown conditions, which are not similar to the

majority of safety-related MOV3 In nuclear power plants. The technical

basis to apply these data to other valves/flow conditions does not exist.

Most MOVs (e.g., in pumped systems) have design basis conditions where

DP builds up only in the nearly closed position, which is much less

severe than the NRC/INEL blowdown tests. A key element of the EPRI HOV

Performance Prediction Program is to develop appropriate methods and data

to evaluate valves based on design features and flow conditions.

I.N. 90-40: Some of the tested valves sustained considerable

internal damage during the blowdown tests. The

occurrence of internal damage can cause the thrust

required to operate a valve to exceed the thrust

requirements predicted by the valve thrust equation.

Such valves were referred to as "unpredictable" in the

test program and included the 6-inch Anchor/Darling

valve and the 10-inch Anchor/Darling. Powell, and Velan

valves. In some instances, this increase in required

thrust can be considerable and might exceed the

capability of the motor or operator. Thrust

requirements to close unpredictable valves under designbasis loads cannot be accurately determined without

testing the valves. (either -individually or, as

prototypes) under these conditions.

The NRC statement quoted here is correct, and the EPRI report essentially

agrees. The valves were damaged under their design basis loadings. At

this time no one knows the loading at which nonpredictable behavior

begins. Until It is known how high a load a given valve can experience

without damage, there is no justification for the assumption that damage

will occur only at blowdown loads.

As discussed in this report, indications of significant internal damage

were observed during inspection of the valves. The data and damage

patterns are indicative that damage occurred during the blowdown

closures, and valves with major damage correlated to observation of

unpredictable or anomalous behavior in the blowdown tests. The 6-inch

8-6

a
Anchor/Darling, 10-inch Anchor/Darling and 10-inch Velan valves were in

this category'; this report shows that the- 10-inch Powell valve was only

slightly in' this regime. Vith regard to thrust requirements for such

valves, the EPRI NOV Performance Prediction Program includes elements to

identify potential anomalous behavior based on'design features and flow

conditions. Because most MOVs have much less ;severe' design-basis

conditions (e.g. pumped flow) than the' NRC/INEL biowdowi tests, it Is

expected most MOV ipplications'will not be potentially anomalous.

1N. 90-40: ;The' research'proram 'revealed that the testing of a

valve under static or low flow conditions cannot always

be used to accurately predict the behavior of the valve

under design-basis'conditions by extrapolation. For

example, the valves that were damaged during blowdowntests operated normally under-less severe flow tests.

Thust low-flow tests might notidentify a valve that

requires significantly more thrust than predicted by the

valve ;thrust ' equation.,,(I.e.%. a' valve- that: is

unpredictable);, *'- '; ' . . i

This NRC conclusion, which is confirmed by this study, underscores the

fact' that the'label'"unpredictable" 'or "anomalous"- refers to a valve

apolication and-not to simply'a valve. .:'The'normal operation of the

NRC/INEL valves under less severe conditions indicates that most valves

in-nuclear power:plants (which see less-severe conditions)' would be

expected to operate normally.': As-discussedin the item above, the EPRI

MOVYPerformance Prediction-Program Includes elements-to identify valve

applications with potentially-anomalous behavior. " --

I.N. 90-40: - During opening of the:valves,'the maximum required

thrust did not always occur at unseating. Rather, in - . - certain instances, At'occurred much later during' the A '''valve stroke.-- At nuclear plants.-the staff has found.

that torque switches forMOV's are sometimes bypassed

only during the initial portion of the opening stroke on

the assumption that the thrust required to unseat the

valve would be the maximum thrust for the full'stroke.

8-7

The EPRI report'agrees with'this NRC conclusion. Al ftePase I and

1I valves were destgned and installed to Isolated pipe b'reak' flow in the

RWCU or HPCI systems.' The valves that per'forwed n npredficiably did so'

under thieO'i~ sigi'bis'is conditions. 'Other valv'es'pe'rfor~me'd~prdictably

under the sam-e"'cond'itlions. The loading'at which any nonpredictable valve

becomes nnpdictabe has not been dete.mi.ed .

The EPRI report agrees that higher loads sometimes occurred during

opening after unseating Instead of before. This phenomenon is not fully

understood, so the f low or OP at which higher opening forces become

significant Is unknown. Restricting it to blowdown flow opening cases

may not be Justifiable. The INEL has attributed the force Increase to

other effects in addition to Bernoulli effects. The additional force is
Thus. the research results raise a concern that the

torque switches in some NOVs at nuclear plants might not

be bypassed for a sufficient period of time during the

opening stroke. -

produced by the total instantaneous pressure distribution on the valve

internals at any point in the stroke.

On some blowdown opening tests an increase in stem force was observed

after flow Initiated. INEL has attributed the force increase to flow

(Bernoulli) effects. As discussed in this report. NOVs In nuclear power

plants except for PORV block valves do not have blowdown opening

conditions. Under typical opening conditions this effect is expected to

be much less severe. The EPRI NOV Performance Prediction Program will

include elements to identify and quantify additional loads which may

occur in mid-stroke due to flow effects. It is also noted that the

possibility of higher loads occurring after unseating would not

necessitate increasing torque switch bypass period, as long as torque

switch settings are adequate to cover the increased load.

I.N. 90-40: For certain tests. the valve was closed from a partially

open position. This partial stroking of the valve

failed to predict the thrust requirements and to

identify nonpredictable performance that were found

during closure of the valve from a full open position.

For example, during certain blowdown tests, valve damage

began to occur before the valve was half closed. The

accumulated damage over the full stroke influences the

thrust required to close the valve.

This NRC conclusion is speculative in nature; specifically, it neglects

how valve damage Drior to a stroke can also be influencing behavior. In

the partial stroke blowdown closure tests which showed differing behavior

from full-stroke tests, the partial stroke was always conducted after a

full-stroke in which damage was suspected to have occurred. It appears

the damage may have created a "modified" valve condition which behaved

differently from the initial stroke. To confirm this, we compared

partial-stroke results with the subsequent (not prior) full-stroke

blowdown closure. There were no cases where a subsequent full-stroke

It is true that no subsequent full closure test was more severe than a

prior partial closure test. No such test sequence was performed. In all

cases, the first blowdown test was, for all intents and purposes, a full

closure test. The NRC conclusion would have been more accurate if it had

stated that partial stroking "would have failed to predict" thrust

requirements needed for full closure. Nevertheless, the intent of the

NRC conclusion is correct. Valve damage on some nonpredictable valves

began early in the valve stroke, and the accumulated dam"ge over the

entire stroke influenced the thrust required to close the valve. Partial

valve strokes that do not include this early portion of the stroke can

not indicate the influence of early damage on maximum stem thrust. The

EPRI report is correct in the observation that subsequent testing was

less severe than earlier tests. Each time the valve was cycled it

machined itself again to eliminate interferences (the cause of

nonpredictable behavior). For some valves, subsequent cycles showed

predictable-like behavior after this machining.

8-8

I a
L

showed more severe or more nonpredictable behavior than a partial stroke.

In summary. there are no NRC/INEL data which show more severe behavior

in a full-stroke closure than Inma partial stroke6closure for initially

undamaged valvecornditions in both cases.

I.N. 90-40: Table 1 (of I.N. 90-40) provides a summary of the

blowdown tests and the minimum required thrust to close

the tested valves. The table also indicates whether the

valve thrust equation would have bounded the thrust

requirement if valve friction factors of 0.3 or 0.5 had

been used

* The notes to.Table 1 of I.N.90-40,indicate that 5 of 8

test-valves are not bounded by a friction factor of 0.5

and no tests are bounded byia friction factor of 0.3.

The results presented in Table 6-1 of this report show a more complete

evaluation of the information given in Table 1 of NRC I.N. 90-40. There.,

are three important insights:

- Table 1 of I.N. 90-40 gives only the maximum thrust measured

during the stroke; in most cases the thrust to isolate flow was'

considerably less. lnruseof these' results to evaluate blowdown

isolation functions. it appears flow isolation is pertinent.

- 0~ As discussed:'nMthis report. results from Valve 1 are not

considered applicable to Ahchor/Diiing 6inch valves.

- The disk areas used by INEL in the industry equation are

generally less than the values which should be used with the

equation. This gives an Incorrect "appearance' that higher disk

factors are needed.

The information contained in Table 6-1 in the EPRI report is not

accurate. See Sections 3.4.1 and 3.4.2.

...

section 3.4. shows that the EPRI evaluation erred In its identification

Of flow isolation. The data contained In Table 1 of I... 90-40 are

correct'.

As discussed in Section 3.3.2 of this report, the working surface of the

Valve I disc was the Valve A surface that Anchor/Darling delivered to the

INEL with the understanding that the valve was representative of their

hardware'delivered to the nuclear industry.

We have discussed the use of apparent disc factor and mean seat diameter

throughout in this report. The data In Table i of I.N. 90-40 are an

accurate representation of the stem force required to close the valves.

As explained Gn Section 3.4.2 of this report, the standard industry is

'S.A:I. . ,1 . .,a .!.

8-9
inadequate for assessing valve performance. This is true whether either

the orifice area or the mean seat area is used as the disc area term in

the equation. We used the orifice area in our analyses because that is

the term that was originally used to size many of the operators for the

valves. and because it is the least conservative term used by industry.

In summary, this report supports a conclusion that all valves except one

(Valve A) would isolate flow with a disk factor less than 0.5 and that

several cases isolated with disk factors less than O.3; this is quite In

contrast to the NRC conclusion that 5 valves are not bounded by 0.5 and

that no cases are bounded by 0.3.

The EPRI reports' conclusion is incorrect for the reasons stated above.

NUREG/CR-5406 (Phase 1): The typical Industry sizing equation using the

standard variables did not conservatively

estimate the total thrust needed to close the

tested valves; disc factors higher than the

normal 0.3 disc factor (pd) were encountered.

This report examines, to the extent possible, data from all of the

NRC/INEL test strokes with DP. The conclusion that disk factors higher

than 0.3 were encountered is correct. An important finding is that a

large number of strokes. particularly those for which anomalous behavior

did not occur, are bounded by a disk factor only slightly greater than

0.3, L.e. in the 0.3 to 0.4 range.

NUREG/CR-5406 (Phase 1): Temperature also affects the thrust

requirements of these gate valves ...... The

disc factor needs to be increased for both the

opening and closing direction to account for

In Section 3.4.2 we discuss the use of apparent disc factor based on mean

seat diameter. Hean seat diameter was not used to size the majority of

valve operators in the industry. In Section 3.4.1 explain the error in

the EPRI report's selection of the valve position associated with flow

isolation. Data indicate that flow occurred through the valves beyond

the designated isolation position. Comments concerning disc factors

obtained using that analysis are incorrect.

This consent may lead the reader to believe that the difference between

a 0.3 and 0.4 disc factor is small. This is far from true. Valves sized

with a 0.3 disc factor will require one third more thrust if operating

at 0.4. Even with the gross conservatisms often employed, 33X additional

force is difficult to bound (conservatisms must also cover operator

repeatability, stem factor changes. etc.).

This consent on this Phase I conclusion is correct. The stem thrust does

appear to irreversibly increase In the first hot cycle. Our analysis of

the Phase 11 data supports this observation. However, for different

8-10

I . I U
I

the higher loads associated with high

temperature operation.

...... ;. ,,,j... ....

As discussed In this report, the disk factor irreversibly went to a

higher value starting with the first stroke at hot conditions, on every

valve. Subsequent tests, whether at hot or cold conditions, did not

significantly affect disk factor. The explanation of this behavior is

not presently known. Nonetheless, once the valve passed through this.

transition. temperature does not appear to influence thrust requirements. ~~~~~7 ' f;,-. I ; *. * . I.

reasons, temperature effects (degree of subcooling) cannot be completely

ignored. Appendix C discusses thin film lubrication and how it

influences on-the-seat disc friction. Data support a change in frictiod

from lower energy fluids (greater than 70'F subcooled) to high energy

fluids (less than 70F subcooled).

HUREG/CR-5406 (Phase 1): Industry has, also assumed-!that for. valve

opening thrust requirements, the highest. load

would be when.the disc-lifted off the seat.

This was also determined for the valves tested

not to be true. The highest opening loads with

flow occurred at different degrees of opening

for both valves, but in both cases they-were.

well off their respective- seats when the

maximum thrust was measured.l'

On some blowdown opening tests an inre'asetin steimforce was observed

after flow initiated. INEL has attributed the force increase to flow

(Bernoulli) effects. As discussed in thisireport, OMsGin nuclear power

plants except for PORV block valves, do;. not- have blowdown opening

conditions. Under typical opening conditions this effect Is expected to

be much less severe. The EPRI. OV Performance Prediction Program will

include elements to identify ad' quantify"additi6nil loads which may

occur in mid-stroke due to flow effects.-; ; 1 : -

_, , ~ ' ' ,

NUREG/CR-5406 (Phase 1): The thrust sizing equation is not applicable to

valves that sustain damage (such as galling and

plastic deformation of the sliding surfaces) at,

- i design basis loadings. - .. -

The EPRI report agrees with this INEL observation. The blowdown opening

tests are discussed in Section 3.2.4 of this report. The results are

valid for the conditions of the test. If an application exists for high

flow opening, the results should be considered. We have not yet

conducted a complete analysis of the opening tests. However, preliminary

analyses indicate other effects in addition to Bernoulli effects.

-I . .  . '". I- -I I It 1.': I -.  - '_ - "I  I ?

. , . I -, . 1. : . ,, ;

The EPRI report appears to agree with this INEL conclusion.

This conclusion appears to be correct. Since the thrust sizing equation

is based on sliding friction, the equation will not predict the force to ,. ,,. , I ,, .. - -,~" , -. " -, :.,I '., -.

8-11
machine metal. The EPRI NOV Performance Prediction Program includes

elements to identify valve design features and improvements which ensure

minimal damage and predictable performfance at design basis loadings.

NUREG/CR-5406 (Phase 1):The design basis hot water blowdown testing has

shown that. given enough thrust. typical gate

valves will close against the. high flow

resulting from a line break. Proper operator

sizing depends on correct Identification of the

values for the sizing equation. Evidence

exists that values used in the past may not be

conservative for all valve applications.

especially at design basis loadings The

following items need. to be considered during

sizing of gate valve operators:

1. Gate valve guide design and clearances

can have a significant effect on the

operator stem thrust requirements at

design basis fluid loadings.

The EPRI report is correct--our subcooling conclusions from Phase I do

disagree with the conclusions from Phase 11. The Phase I data were

evaluated using the industry equation. and the observations regarding

subcooling were unexpected. To further investigate this observation, the

Phase 11 instrumentation was designed to better evaluate the subcooling

influence. In our efforts to correlate the Phase I and 11 data, we found

that the Industry equation could not be used. Appendix C shows the more

complete INEL correlation. Using our method, the Phase I and II data

analyses support one another and produce identical conclusions. The

scatter of the data analyzed according to the INEL correlation shows two

distinct patterns separating at approximately 70F subcooling.

2. The degree of subcooling at the valve

inlet can greatly Influence valve

closure forces. Valve operator force

requirements increase as inlet fluid

conditions approach .. saturation

temperatures.

3. Industry trends toward using 100%

system pressure for all pressure terms

in. the sizing calculation are

Justified for high-flow applications.

This effort examined the data and valve inspection results and identified

valve design items (in Section 7) which are important for valve

performance. Clearances and fluid conditions (Items I and 2 of INEL

conclusion) are important parameters. We note the INEL conclusion on

subcooling here disagrees with their conclusion from Phase 2 results (see

below); this discrepancy has not been resolved. Overall, it is not clear

if subcoolina is the proper fluid condition parameter on which to base

comparisons.

8-12

' 1 I I I I a
NUREG/CR-5406 (Phase 1): Tests have shown that some form of valve type testing outside the plant might be necessary to

establish specific valve design thrust

requirements and ,verify that a given valve - design exhibits linear characteristics' when -* , -; !subjected.to design loads.

Type testing may be one acceptable approach. However., the data and

Inspection results suggest it should be possible.to determine if

predictable behavior will be achieved in a given valve application based

on valve design features and fluid conditions. The EPRI HOV Performance

Prediction Program includes elements to develop methods and data to ~~* * * , *. . .......,,,E determine if a valve application will have predictable behavior. . ost

HOVs have conditions much less severe than the NRC/JNEL tests and are not

expected to be as susceptible to anomalous behavior.

Our conclusion that some form of type testing might be required to

determine predictable behavior is correct. At the present time we know

of no way other than testing to determine predictable/nonpredictabli

behavior.

. ,.. . , ,. 

NUREG/CR-5406 (Phase 1): For the valves" that. have -a linear thrust

response, valve, opening tests' (with ;a- full

pressure drop;and'no flow) at normal'operating

temperatures performed with valve diagnostic

test equipment can provide:insights' for the

valve disc-factor and therefore degradation In

valve performance for both opening and closing.

Based on the results in this report, this conclusion is correct.,

However, it appears that tests-do not necessarily have to be at normal

operating temperature, as long as the valve has been previously stroked

at normal operating temperature.

NUREG/CR-5406 (Phase 1): Contrary to common belief, the- ratio of

operator torque to stem thrust [stem factor

(ji )] is not a constant but changes with valve

loldiig. '

This INEL conclusion; isi based on Phase I data.. Unfortunately.

insufficient data from the Phase I tests is available to allow the

conclusion to be independently evaluated.. INEL has not addressed'this

We consider our original statement to have been speculative. When we

complete the in-depth analysis of the Phase i1 opening data, we will be , I. ! ' ' t' C

able to respond to this comment more thoroughly.

,, , h, -gly ,.*

This INEL statement was based on Phase I data. Since that time this

conclusion has been substantiated by the Phase 11 data, utility testing,

and our special effects testing on the INEL MOV load simulator. The

Phase I data were sufficient for our analysis of the stem factor. ., . Jo , ' .' .

8-13
conclusion In their Phase 2 results. The EPRI NOV Performance Prediction

Program includes elements to study and ultimately predict stem factor.

NUREG/CR-5406 (Phase 1): Improper operator lock ring installation

following test or maintenance can invalidate

in-situ test results and render the valve

unable to perform its design function.

We mentioned this in the first place only because we found that care

needed to be taken when Installing the lock ring.

Although addressing this conclusion was beyond the scope of this effort.

it seems reasonable that proper maintenance/re-assembly are required to

achieve proper function.

April 18. 1990 Presentation (Phases I and 2):

NRC Gate Valve Tests have shown that there are

two classes of valves:

- Those that respond predictably during

operation under load. albeit with a

higher than expected disc friction.

- Those that respond unpredictably. sustaining internal mechanical damage

during operation under load.

Based on the work described in this report, it appears behavior should

be classified by valve application (i.e. valve design L fluid

conditions) and not simply by valve. The evaluation of the NRC/INEL

tests described in this report shows that some valves under specific flow

conditions will show anomalous (unpredictable) behavior; these same

valves under other flow conditions do not. Accordingly, fluid conditions

(not lust valve design configuration) are Important to determining the

class of behavior. Further. based on the work described in this report.

it appears most of the valve strokes with predictable behavior did not

have friction significantly higher than expected. Generally, a disk

factor in the range 0.3 to 0.4 was observed when the behavior was

predictable.

The EPRI report argues that predictability/nonpredictability is more a

matter of valve application. The valves used in Phase I and 11 were

purchased with the G6-87 application as the design basis. It was under

these design basis conditions that we observed the two kinds of response.

The April 1990 presentation addressed G6-87 concerns. (See Figure 1 of

this report.) However, it is not known at what loading a valve first

experiences damage. We believe our statement Is accurate.

The remainder of the comment deals with apparent disc factor; we respond

to that issue elsewhere In this report.

8-14

i I

I .I N
April 18. 1990 Presentation (Phases I and 2):

All of the valves required more force to open

and close at line break flow than would have

been predicted by the standardindustry thrust

equation using the normal 0.3 constant

coefficient, of friction, regardless of fluid

conditions., ..

As discussedeairlier. opening tests it' line break conditions generally

do not match design basis conditions of nuclear power plant valves. For

valve closing tests, if flowi'solation is used as a functional'oriteria'.

and the correct disk areas are used in the equations, the INEL conclusion

is not true. Several blowdown'isolations were bounded by 0.3 and only

one valve (A) exceeded 0.5. (Valve 1 has been excluded as inapplicable.)

April 18. 1990 Presetatitlon (Phases I and 2): - . ':.-,There were some subtle differences In response'

I, ,, ,during ,the parametric studies; ,these,

differences indicate that there'may be a better - i?- ~equation, to!'predict actual thrust." 'Such 'in- * , , , . , -equation would be more, important to PWRs than

BWRs.'

This effort-did not explore subtle differences in the parameter studle.'

However, it is noted this conclusion refers to parametric studies at line

break conditions. This report shows line break conditions are not highly.

prevalent in PWRs; hence, the importance towP1WRs is not understood.

-- ~ ~ ~ ~ ~ ~ ~ .~ ~ ~ ~ ~ ~ ~ .

April 18. 1990 Presentation (Phases I and 2): - ' We believe the nonpredictable behavior is a

function of the: following valve. design.

deficiencies: . : -'

1) Internal disc-body' guide clearances

that allow the disc to tip downstream

under differential pressure loading,

We discuss the applicability of the opening tests and apparent friction

factor calculations elsewhere in this report. (See Sections 3.2.4 and

3.4.2 for example.) The INEL conclusion is accurate.

I . I ~,; ;.1* I

The INEL statement is correct. Refer to Appendix C of this report for

an explanation of how the parametric studies support a better stem force

correlation. The correlation distinguishes between valve performance at

low versus high subcooling. Thus, the correlation applies to both BWRs

and PWRs, but the differences in subcooling might be more important to

PMRs, where sane valves are required to operate under steam conditions

while others are required to operate at high subcooling (100F). The

difference is significant; a valve assessed with the INEL correlation,

seating with a friction factor at 0.4 at low subcooling (less than about

707F subcooling). would seat with a friction factor of about 0.5 at high

subcool ing.

The EPRI report agrees with our statement regarding design deficiencies

leading to nonpredictable behavior.

8-15
resulting in one or a combination of

the following:

A. The disc tips far enough to

engage the seat at an

aggressive angle. machining

the conical seat off as it

closes;

B. The disc tips far enough to

reduce the load bearing guide

surface, resulting in

localized deformations.

2) Disc-to-body guide surface finishes

are excessively rough, resulting in

high friction and rapid surface

degradation.

This report identified key valve design parameters in Section 8. Among

them are clearances and guide surface finish, so these INEL points appear

correct. It is important to note there may be other Influences such as

disk and seat edge configuration. Stellite iron content, fluid

conditions, etc. The EPRI HOV Performance Prediction Program includes

elements to develop methods and data to predict the potential for

anomalous behavior in valve applications.

April 18, 1990 Presentation (Phases 1 and 2):

The valves that exhibited predictable thrust at

a higher than expected, friction value also

showed signs of damage from the loadings,

although less than the valves with

nonpredictable thrusts.

The EPRI report agrees with this INEL statement. The reference to

friction not higher than expected is based on the EPRI report's apparent

disc factor calculations. We take issue with those calculations (see

Sections 3.4.1 and 3.4.2 of this report).

The data review and Inspection results described in this report show that

valve aamage was much less severe in the cases where anomalous behavior

was not observed. This INEL conclusion appears correct; it also applies

to the numerous predictable cases where the friction was not

significantly higher than expected.

8-16

a
April 18. 1990 Presentation (Phases 1 and 2):

*Post-test inspection of valve internals - Indicated 'that these valves, operating at

design basis loadings, are very near to their

guide surface physical fragility limits.

The' results described 'in this report Indicate the guide And seat

materials were challenged locally, beyond their normal load bearing

capability. *Howeve'r there was no-evidence that any one of the valves

was 'near a gross failure; 'Accordingly ; use' of 'the word "fragility"

(implying near-a breakagellimit) is strongly questioned.

April 18. 1990 Presentation-(Phases l and 2):

Nothing in the low flow or differential

pressure opening tests would provide any

evidence of how the valve would behave under - ..,design ba s loadings.

'The INEL tests showed behavior of some valves was different in normal

flow or no-flow tests than under blowdown conditions. The work described

in this report shows that'for:valves not:-showing- anomalous behavior

apparent disk factors between no-flow and blowdown tests show reasonably

good agreement. (See INEL conclusion 7 above.) Accordingly, this INEL

conclusion (i.e. "nothing") is not correct for all valves. The EPRI NOV

Performance Prediction Program includes elements to identify valve

applications with potenthially anomalous behavior.

April 18, 1990Presentation (Phaies 1 and 2): m. -. Until valve design guide tolerances and surface

finishes have been, improved for valves that

must operate under full flow loadings, only

testing at design basis conditions will provide

insights on predictable or. nonpredictable

behavior.

The data review and inspection results described in this report show that

there were unique-features associated with each valve which could be

The INEL statement clearly-addresses surface'fragility, not structured

fragility. The nonhardfaced surfaces showed heavy bearing pressure and

metal smearing. The next step is galling, which would put the valve in

the nonpredictable category.

One cannot tell from the tests mentioned if the valve would behave in a

nonpredictable manner. The conclusion is correct for the valves tested

and for the specific tests.

The April 1990 presentation addressed G1-87 valves. The INEL remark is

restricted to full flow applications as stated. At this time no methods

exist, other than full scale testing, to determine

predictable/nonpredictable behavior.

8-17
qualitatively related to the observed valve behavior. Although detailed

methods are not yet developed. quantitative prediction of the potential

for anomalous behavior In a given valve application appears feasible.

The prediction methods need to account for fluid conditions and valve

design features. Host HOVs have much less severe conditions

(e.g., pumped flow) than the.NRC/INEL tests and are not expected to be

as susceptible to anomalous behavior. The EPRI NOV Performance

Prediction Program includes elements to develop methods and appropriate

data to predict the potential for anomalous behavior in valve

applications. Accordingly, this INEL conclusion does not recognize other

approaches to dealing with this issue.

April 18. 1990 Presentation (Phases I and 2):

Industry in general has assumed that for valves

that must open under potentially high flow

loads, unseating is the highest load. The

highest loading was unseating with all of the

6-inch valves. but not with the 10-inch valves.

We agree that this conclusion, the result Phase 11 analysis and reanalysis of Phase I data, disagrees with the original Phase I conclusion.

The INEL conclusion stated here is correct. The blowdown opening issue

is discussed in Section 3.2.4 of this report.

It is noted that this conclusion disagrees with the third INEL conclusion

given above which indicated that the highest load was after unseating on

two 6-inch valves.

On some blowdown opening tests an Increase in stem force was observed

after flow initiated. INEL has attributed the force increase to flow

(Bernoulli) effects. As discussed in this report, HOVs in nuclear power

plants except for PORV block valves do not have blowdown opening

conditions. Under typical opening conditions this effect is expected to

be much less severe. The EPRI NOV Performance Prediction Program will

include elements to identify and quantify additional loads which may

occur in mid-stroke due to flow effects.

April 18, 1990 Presentation (Phases I and 2):

Valves that must open, and valves that could be - mispositloned and have to open, should be

tested at the temperature at which they will be

required to operate.

The comment on this Phase I conclusion is correct. However for different

reasons, temperature effects (degree of subcooling) are important. See

8-18 Appendix C for temperature effects on thin film lubrication and how it

influences friction.

i, 1

U
The evaluation results presented in this report indicate that increased

temperature strokes in the NRC/INEL gave rise to an irreversible increase

in disk factor. Disk factor was not sensitive to temperature changes

after this occurred. Although the mechanism and explanation for this

behavior is not understood, the NRC/INEL data do not support the INEL

conclusion. It appears that. for elevated temperature applications.

useful information can be obtained from cold tests after the valve has

been exposed to hot conditions.

April 18. 1990 Presentation (Phases 1 and 2):

The difference in required thrust between hot

and cold testing must be accounted for when

determining the required thrust for valves that

must open.

The INEL potentially agrees. See above.

As discussed above, the NRC/INEL data show that differences are small

after the valves have been exposed to design basis temperature.

April 18. 1990 Presentation (Phases 1 and 2):

The results also show that 0.3 disc friction

factor is not conservative for valve opening

under low flow conditions.

The EPRI report's apparent disc factor calculations and flow Isolation

positions are Incorrect. These Issues are addressed in full in Sections

3.4.1 and 3.4.2 of this report. Our comment is correct.

As discussed in this report, a disk factor of 0.1 to 0.4 was observed

during low-flow opening tests for most INEL test valves. This result is

generally consistent with Industry practice.

April 18. 1990 Presentation (Phases I and 2):

Many torque switches are bypassed for

unseating, so in those cases motor capacity not

opening torque switch setting. Is the concern.

Motor capacities should be verified.

This INEL remark was made to alert the utilities that when raising torque

switch settings or bypassing them, motor capacities should be verified.

We made this observation in the April 1990 meeting because of the number

of motors that burn out in the plants every year.

Examining this conclusion in detail is beyond the scope of this effort. ; --. . . I -

It appears reasonable that when;the motor capacity is limiting, this

capacity should be verified to exceed thrust requirements.

8-19
April 18. 1990 Presentation (Phases I and 2):

Our low flow and differential pressure test

results provide some evidence that even in the

less demanding service. a 0.3 disc friction

factor is not conservative.

See discussion of apparent disc factor calculations and flow isolation

positions discussed in Section 3.4.1 and 3.4.2 of this report.

See discussion of disk factor above.

8-20

i . I U
APPENDIX B

Sections 1, 2, and 3 of NUREG/CR-5558, 'Generic Issue 87:

Flexible Wedge Gate Valve Test Program, Phase 11

Results and Analysis," January 1991.

B-1
GENERIC ISSUE.87,

FLEXIBLE WEDGE GATE VALVE TEST PROGRAM,

PHASEII RESULTS AND ANALYSIS

:1. INTRODUCTION

The-Idaho' National Engineering Laboratory could resultn common cause failure of other

(INEL), under the sponsorship of the US. Nuclear components necessary to mitigate -the' accident.

Regulatory Commission (NRC), is performing'-' The ,test program also provides information

research" to resolve specific generic issues and - applicable to the implementation of Generic Letter

develop', and improve- industry -mechanical",, (GL) 89-10, wSafety-Related Motor Operated Valve

equipment qualification and operating and , ' bsting'and Surveillance for 'all -light water

maintenance consensus standards. This overall reacor (LWR) safety-related motor-operated

research effort includes a program that tested the ' - valves (MOVs) and 'selected position-changeable

: operability (opening and closing) of six full-scale i MOVs in

-motor-operated -gate- valves typical of the '' systems

containment isolation valves installed in boiling The analyses performed to date on the measured

water reactor (BWR) reactor, water cleanup, -data -during obtained the GI-87 Valve Test

(RWCU) process lines and high-pressure coolant ,' Program"'and the conclusions derived from the

injection (HPCI) turbine steam supply lines. The - analyses ire discussed in this report. -A complete

valves were qualified and parametrically tested analysis of the data'required by the program

above, at, and below the pressures, temperatures, objectives will follow in a later report. We are

and flow conditions of a worst-case downstream issuing this report now because the findings to date

pipe break in the RWCU and HPCI turbine supply -- contain information that may be beneficial to the

lines outside of containment. -One of the RWCU ' industry when. responding to current regulatory

valves also was tested with steam to provide - recommendations. Additionally, the 'Phase II

'insights :for the reactor core isolation cooling - testing did Not answer all'of the test"objectives

(RCIC) turbine steam supply line isolation valves. because we could not locate a dc motor in time for

' ---: 4-^- . -. L,, '-e -the,. test program. That work -and the open

The purpose of the test program was to provide questions regarding stem factor and rate of loading

technical input for the NRC effort regarding - will be , performed on the INEL valve load

Generic Issue (GI-87, *Failure of the HPCI Steam simulator.

z.c wlarour zsozauon.- n-wi also appues to we

RCIC and RWCU isolation valves. All three of

the GI-87 BWR process lines communicate with

the primary system, pass through containment, and

normally have open containment isolation valves.

The concern with these containment isolation`-

valves is whether they will close in the event of a

pipe break outside of containment. A high energy

steam or water release" in''the auxilllay building

.a. Work supported by the U.S Nucleiar Regulatory

"-Commission, Division of -Engineing Office of;

Nuclear Regulatory, Research, under US..

Department of Energy Contract No. DE-AC67.

761D01570.

For those individuals or organizations who wish

to do their own analysis of the data, the measured

data are available fom the NRC Public Document

Room. The Phase I programis reported in BER

,Reactor Water Ceanup Sysitem Flxcbli Wedge Gate

Isolation Valve Quahficadon arid fz Eneg Flow

Inranupdon Test' [EG-&G Idabo; Inc. (EG& G

Idaho), 1989] (NUlREG/CR-5406). The Phase II

*- st Program actual measured data are reported in

-C ~Iwse-87 Feaible Wedge Gate Valve Test

rogram Phase t Daa Reporr, '(EG&G Idaho,

1990). The -Phase II data are also available in

- International Business, Machines 'Corporation

(IBM) personal computer (PC)-compatible format.

There is also a video tape documenting the post

B-2
.

test disassembly and inspection of the test valves.

Both -the video and the magnetic data can be

obtained through the INEL Technology Transfer

Office at (208) 5266042.

1.1 Background

1wo sets of experiments have been conducted

for the1GI-87 research program. In Phase 1, two

full-scale RWCU valves typical of those in

operating plants were tested with high energy

water. The results of the Phasie I program, as

previously stated, were reported in

NUREG/CR-5406.- These results challenged the

validity of many gate valve design rules. The

two-valve sample was small and one valve

sustained damage as a. result: of the high flow

loading. Because of this, some experts in the

industry did not accept the results as having

general applicability. -In the Phase II program, the

NRC increased the valve sample size to six valves

representative of those installed in both the HPCI

and RWCU Systems.

Phase 11 test program objectives were

reevaluated and modified to include'the lessons

learned in 'Phase I and'to include tests on the

RWCU valves that would be applicable to RCIC

valves. The resulting objectives were as follows:

' Determine the valve stein force required to

close typical RWJCU,' RCIC, and HPCI -system isolation valves'at typical operating

conditions and under blowdown conditions

* Compare valve closing loads to opening

loads at various system conditions

* Evaluate valve closure; force components,

such as disc friction, packing' drag, stem

rejection load, and fluid dynamic effects

*Measure theeffects of temperaturepressure,

and valve design on valve closing and

opening loads

'a Evaluate the terms and variables in the

present standard valve and motor-operator

sizing equations

* Provide detailed information to assist in the

NRC effort regarding 01-87

- Correlate the data to develop a methodology

for in-situ motor-operated valve testing,

supporting the implementation of GL 89-10.

The results of the testing may also contribute to

specific guidelines being developed to improve

valve qualification and in-plant test standards such

as American National Standards Institute

(ANSI)/Anerican Society of Mechanical Engineers

(ASME) standards B16&41 (1983), OM-8, and

OM-10.

Surveys of utility Installations performed before

the Phase I program determined that in the BWR

systems of interest, the flexwedge gate valve with a

Limitorquea motor operator was the predominant

configuration. lb avoid duplication, we reviewed

previous applicable industry test programs. The

review included the Electrical Power Research

Institute (EPRI) power-operated relief valvelblock

valve testing at Duke Power in 1980, the Central

Electric Generating Board (CEGB), United

Kingdom,' gate valve testing performed at

Kraftwerk Union (KWU), Federal Republic of

Germany and the KWU- testing 'performed for

their own plant designs. The EPRI and CEGB

'work were go-no-go tests; however, the results

showed that' both flexwedge' gate valves and

parallel disc designs did have problems. The KWU

work on their own gate valve designs resulted in

many gate valves being replaced with globe valves.

Where they could not replace the gates, they

developed a structurally stiff design with rather

close internal clearances.' The U.S. has valves with

close and large clearances, but none of our designs

are as structurally stiff as the KWU designs. The

KWU testing indicated that we might expect

trouble based on their findings.

a. Mention of. specific products and/or

manufacturers In this document implies neither

endorsement or preference nor disapproval by the

U6S. Government, any of its agencies, or EG&G

Idaho, Inc ,'of the use of a specific product for any

purpose.

B-3

. . . ... . .. . . .. .. . . .
The previous test programs did not answer our

G1.87 questions, however. It must be noted here

that after reviewing all of our test results, the most

flexible U.S. design performed better than our

moderately stiff designs. Therefore, a valve may

perform correctly without being stifL The valve

design needs to be tested with the worst-case

tolerances-to ensure operability.

The NRC Office of Inspection and Enforcement

(IE) Bulletin 85.03, "Motor Operated Valve

Common Mode Failures During Plant Transients

Due to Improper Switch Settings, and GL 89-10,

require the utilities'to develop and Implement a

program to ensure that the switch settings on

selected safety-rclated MOVs are set and

maintained correctly to accommodate the

maximum differential pressure expected on these

valves during both normal and abnormal events

within the design basis. The GI-87 valves arc a

subset of this larger class of safety-related valves. -

Industry has helped to meet these criteria by.

developing new MOV diagnostic test equipment.

and methods for in-situ valve testing. Prior to the

GI-87 Valve Test Program, the motor-operator

control switches settings were based primarily on

standard industry practices and analysis. Very little

design basis testing had been conducted in or'

outside of the plants. Utilities typically verified

the analytically-determined MOV output torque or

stem force through valve seating or baclkseating

loads with little or no valve hydraulic loading. The

GI-87 Phase I test results cast some doubts on this

industry practice, primarily on whether the true

-design basis load can be determined analytically.

1.2 Motor-Operator Sizing

The gate valve is a high recovery positive shutoff

valve and is typically used in systems where

minimal pressure drop is desired when the valve is

open. The design Is ideally suited for isolation

purposes and usually Is not used for throttling

flow. When the disc is in the seat, the upstream

pressure load on the disc assists in sealing. This

feature is less important in the flexwedge'than in

the parallel disc gate.

There are a number of calculations made to

determine the correct operator size for a given

valve application. The term sizing means that the

output -power available from, a given motor

operator is determined by its size. Typically, the

larger the operator the higher the allowable

output. Thble 1 lists the typical maximum output

in torque and stem force for the various SMB

Model Urmitorque operators. This table should

only be used to -understand what sizing means.

Requalification of motor operators and other

limitations on valve hardware can affect the use of

a specific operator size.

The four'mnost important calculations that are

made in sizing a. motor operator for a specific

valve application are (a) total stem force necessary

to operate the valve at its design basis load, (b) the

operator torque necessary to produce that force,

(c) the operator gear ratio (including the stem nut

thread necessary to produce the needed valve

stroke time)-and (d) the size and speed of the

electric motor necessary to produce the needed

operator torque for that gear ratio. To be

conservative, other calculations are made, such as

degraded voltage concerns, which do not need to

be explained for a basic understanding of

motor-operator sizing. Two of these calculations,

the gear ratio and the electric mot6r sizing, appear

to be well understood and the results are

repeatable 'in application. The required stem force

and the operator torque to produce that force

appear to be the areas. that have not been

conservatively predicted -in the past for some

classes of valves.

Figure 1, a cutaway 'drawing 'of a typical

motor-operated gate valve, shows the components

Important to this discussion. The necessary forces

currently defined by industry to close the valve and

Isolate flow must overcome the resistance imposed

by three loads: (a) the disc frictional drag load

caused by the differential pressure across the disc

as the valve closes, (b) the stem rejection load

caused by static pressure on the stem, and (c) the

packing drag load. Industry has developed a set of

equations for use in sizing motor operators. The

first equation In this set predicts the total stem

force, as detailed below. Each manufacturer

modifies the variables in the equation slightly-,

however, In the long run the application of the

equation is the same.

B-4
-

Table L. Limitorque operator nuclear ratings

Model-Size

SMB-O0O

Ratio'

Rante

12.5- 30.6

33-5-100.0

102.0-136.0

Rated

Torque

(ft-lb)

90

90

90

Rated

Stem force

(lb)

8,000

Maximum

Threaded

Stem Diameter

(in.)

1375

SMB-00

SMM0

SMB-I

9.7- 22.0

23.0-109.0

114.0-183.9

11.8- 26.1

26.4- 96.2

102.6450.8

158-3-247.0

116. 25.7

27.2- 8&4

92.4-171.6

191.7-234.0

10.6- 25.6

26.2- 82.5

84.8150.0

153.0-212.5

250

250

190

500

500

500

340

850

850

780

625

1800

1800

1250

950

14,000

24,000

45,000

70,000

1.75

2.375

2.875

SMB-2 3.5

A.

a. Unit overall gear ratio.

B-5
.. ,;-,. t ....J| >_ - Seat ring

val. 0vel e [ * .~~stem

Seat ring

Disc~~~~~~~~Ds - Disc . . - ~~~~~~~~~~~A - A - -....................... .

Figure L Typical motor-operated valve showing components important to calculating stem force. -Two of

,the test valves were modified by installing a load cell in the valve ster.-

., tes .v 5...:a re MO -m. *---*;

B-6
*

Ft = OdAdAP + ASP + Fp

where

Ft - total stem

force

(1) operators depends on a stem factor calculation

given by

T - OsF, (2)

where

Ad = disc factor

Ad =disc area

AP = differential

pressure

dynamic

component

T =operator torque

A = stem factor

Fg = total stem force [from Equation (1)].

As = stem cross-section area

P - stem pressure

Fp = packing drag load

(a constant).

static

component

For wedge-type gate valves, the disc factor (ad)

normally used by the industry in Equation (1) is

0.3. Note that in this equation the stem rejection

load can be either positive or negative,

dependingon whether the valve is closing or

opening. This is because the stem rejection load

is always in a direction out of the valve body, this

load resists valve clos'ure and assists in opening the

valve. - The packing load' is typically constant and

depends on the packing design, the gland nut

torque, and the direction of operation.

The equation is divided into two components,

which will be referred to in the analysis found later

in this report. The components are (a) the

dynamic component, which includes the disc load

due to differential pressure, and (b) the static

component, which is the sum of the stem rejection

and. packing drag loads. The pressure values

(P and AP) used in the force equation are supplied

to the valve manufacturer by each individual utility.

Determining the motor-operator torque necessary

to produce that force is complicated by the fact

that motor operators control output torque, not

stem force. Thus, In determining the necessary

output torque one must consider the conversion of

operator torque to stem force. The torque-to-stem

force relationship normally used in sizing motor

* The stem factor used in Equation (2) is a

function of stem diameter, thread pitch and lead,

and the coefficient of friction between the operator

stem nut and the valve stem. As in Equation (1),

the only variable that cannot be measured in the

stem factor equation is the coefficient of friction.

Normally, it is assumed that only damage and

lubrication of the stem/stem nut threads can

significantly alter the stem coefficient of friction.

Limitorque personnel, in their diagnostic work,

have measured coefficients of friction from 0.10 to

0.20 In actual operation. Losses internal to the

motor operator, up to the capacity of the electric

motor, will typically be accounted for by the torque

springhwitch position. Losses in the stem factor

will not be accounted for by the motor operator.

The problem with the conversion of torque.

to-stem force (stem factor) is not in conservatively

bounding it in the sizing calculation. It is that the

stem factor appears to change with stem load.

This will complicate utility efforts to comply with

regulatory recommendations to develop and

implement a program that will ensure that

safety-related motor-operator torque switch

settings (the switch that regulates the

motor-operator output torque) are chosen, set, and

maintained correctly to accommodate the

maximum differential pressure load expected on

the valves during both normal and abnormal events

within the design basis. Additionally, MOV

torque-to-force relationships can vary with age and

maintenance Torque springs age, changing the

torque switch setting in comparison to output

torque. The stem factor can change for two

B-7
primary reasons: (a) lubrication quality at the valve

stem-to-motor-operator stem nut interface, and (b)

degradation of the threads of either component

The stem factor can also improve with wear

between the stem and stem nut threads.

The INEL believes the biggest iotor-operator.

sizing problem today'is verifying the capability of

the operators, in .'the plants *This problem is

".~ 1-compounded for gate valves arid. to some degree

for ail rising stem motor-operated valves according

'to NRC G1-87 valve test' results. This indicates

that the variables used by industry in the past for

determining -'valve opening and disc force

[Equation (1)] at high flow were not conservative,

and that the stem factor may vary with load,

making it very difficult . for the utility to

diagnostically determine operator capability in

place without design basis -testing. This is not

always possible In a plant. -

Motor-operator sizing topics that apply to both

GI-87 and GL 89-10 will be discussed in more

detail in later sections of this report.

V.

I . i .

. ...

. .. . ' 

B-8
2. APPROACH TO TESTING,

Six full-scale, representative nuclear valve

assemblies were 'tested under various normal

operations and design basis pipe break conditions

for the RWCU, HPCt and RCIC systems. Table

2 lists the test valves and motor operators used in

both Phase I and II test programs.

As shown in Table 2, the two valves used in

Phase I were reused in Phase IL Phase I Valve A

was refurbished and became Valve 1 in Phase IL

The valve's internal manufacturing tolerances

allowed the disc to tip downstream during the

Phase I testing, causing damage to the disc guide

surfaces. Gate valves are bidirectional; therefore,

the valve was turned around for Phase II, reversing

flow through the valve to see how the internal

manufacturing tolerance stackup in the other

direction affected valve performance. Valve B

from Phase I was returned to its manufacturer for

a valve disc replacement and became Valve 2 in

Phase IL The valve disc or gate in Phase I was

equipped with hardfaced disc guides, representative

of valve assemblies built after 1970. For Phase I,

the hardfaced guide disc was replaced with a

normal material disc guide, representative of those

valves made before 1970. With the exception of

Valve B in Phase I, all other valves in both phases

had normal carbon steel disc guide surfaces

representative of the largest majority of the

installed gate valves. All valves in both phases had

hardfaced sealing surfaces on both the body and

the discs. Valves 3, 4, and S were new valves

obtained through canceled nuclear plant surplus.

These three valves and the two valves used in

Phase I were returned either to their manufacturer

or to a nuclear valve service center for

refurbishment and/or inspection prior to their use

in Phase II testing. Valve 6 was manufactured new

for the Phase II Program. Prior to Phase HI

testing, each valve body was assembled with

instrumented spool pieces and instrument taps as

shown in Figure 2.

Table 2 also identifies the 460-Vac, 3-phase,

60-Hz Limitorque electric motor operators used on

the valve assemblies. For Phase II, the same

SMB-O0-25 was used on all three 6-in. valve

assemblies, and the same SMB-1-60 was used on

the three 10-in. valve assemblies. The

motor-operator stem nuts and helical reduction

gears were changed to accommodate the valve stem

thread pitch and lead and to establish, as close to

as possible, a 30-s stroke time for all six valves.

For valve stem force measurements, two of the

valves were Instrumented with direct stem-mounted

load cells, as shown in Figure L The other valves

used a set of four load cells mounted between the

valve yoke and motor operator. During final

checkout of the motor operators, Limitorque ran

a special torque spring deflection versus operator

output torque calibration on their dynamometer.

By using a linearvariable displacement transformer

(LVDT) and the Limitorque torque spring

deflection versus operator output torque

relationships, we were able to monitor apparent

motor-operator torque on-line during the test

program. Figure 3 shows the general location of

the valve response instrumentation used during the

Phase II test program.

The Phase II test program was performed in the

late summer and early fall of 1989 at the KWU

facilities near Frankfurt, West Germany. Two test

loops were used. Figure 4 shows the loop used for

the 6-in. valve tests; Figure 5 shows the loop used

for the 10-in. valve tests. Both test loops used a

22-MW oil-fired boiler for heating and test media

propellant The 6-in. valve test stand also had the

capability of being charged with gaseous nitrogen

for cold water high flow testing. Both test stands

were equipped with bypass lines around the loop

blowdown device. These lines were used to

establish normal fow through the valves for

normal-service functional testing. Maximum flow

was established on the 6-in. valve test loop through

a rupture disc and on the 10-in. valve loop through

quick opening valves.

The data collection objectives for Phase II testing

were driven by the lessons leamed from the Phase

I program, where the performance of the valves

under higher loadings was unlike previous industry

claims for valve performance. Valve thermal

hydraulic inlet conditions appeared to influence

these performance problems (i.e., the

measurements made during the Phase I program

B-9
Table 2. Valve and operator information

Test Hardware

I' ' I Valve Manufacturer and Valve Identification

Valve Desienation

Phase I Phase !'

Anchor/Darline

Velan'

Walworth

Anchor/Darling

Wn. Powell

Velan

A_

, ` .

1'

. - - ' 2

Size

6-Ei

6-in.

Class mm

. - I .o

I . .

3 6-i

10-

'.'- S '. 10-

10-

",6 '- -- .10-

'Size

UL.

in. ~

In. "

IL

900 lb

900 lb

600 lb

900 lb

900 lb

600 lb

Flexwedge Gate

U

a

Ua

a

a

Motor-Operator Manufacturer : Valve Used

Limitorque

Llmitorque '

Limitorque '

- SMB-1-60

SMB-2-40

1, 2,3 and B

/I

.I. 

4, 5, and 6

A

a. Valves A and B from Phase I were refurbished for Phase II as Valves 1 and 2.

were not sufficient to allow a thorough analysis of

specific thermal hydraulic influences). The Phase,

II measurements, instruments, and data-collection

tools were optimized as thoroughly as practical to

characterize the test valves' and motor-operators',

performance it the various test conditions. 'Inpuis '

to these measurement and ditacollectionschemes

included suggestions from experts at the INEL,

from the NRC staff at planning meetings, and from

industry experts at several review meetings.

To quantify the test loop thermal hydraulic

conditions and valve response, an averageof 70

channels of information were measured and

recorded on a high-speed tape recorder.-The tape

recorder was an integral part of the INEL data

acquisition system (DAS). The DAS transducer

excitation voltage was measured at the transducer

and the'system adjusted the internal voltage to

account for line losses. The outputs from the

transducers were then measured by the DAS and

committed to the tape.

The DAS was also configured to make

incremental calculations of the stem force

throughout the closing and opening cycles using

the measured values for the parameters in

Equation (1) (differential pressure, disc area, etc.)

and a constant disc factor, either the common 03

or a more conservative 0.5. We performed our

calculations in this manner to see how well the

-equation modeled the actual stem forces during the

entire cycle. A comparison of the calculated forces

to the measured forces shows where the deviations

B-10
Terrperalure Temperature

Dynamic pressure Static pressure Dynamic pressure

and temperature 0.3060'

Flow

Rotaled 90 for clarity

Figfire 2. Valve assembly showings Insiruinenied spool piccs.

A, ' w~~~~~~~~~~~
0

t

Legend

] > < Accelerometer (Irlaxial measurements)

_ _~-4-~- Strain guages

] @2 P8 Pressure (static)

pi__ Pressure (dynamic)

[] Temperature ;. .

I~AP

E|J> -.Valve posilion j

2i Valve current -. .

W3 Valve voltage

- j E :- Torque spring deflection

W Stem force load cells

EJ Motor speed

H Measurements In pipe diameter

'-

L] @f El

ligre t3. Phaisc 11 valvc assembly and local piping insirumcntalion.

0-3056
Waler lank Inlermedlale

lank

Normal flow line

From

HP

boiler

< } T X v22 m3 18- and

1O~~~~~~~~~~~~~~~in. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 2-n

w. \ / 1 lO-ln. l _ 1 1 1 R~~~~~~~~~~~~~~~~~~~~uplure disc piping

X / P8 piping [i Pd P~~~~~~~d Pd [Pd|Ps iT

Design pressure: 160 bar (2321 psi) Condensalion

pool

0-3042

Figure 4. SimpiliicId KWU 6-In. valvv lest loop showing conflguralion, lcngths, and piping sizes.

b . I
Lo

Water lank f - I

W

.LI .06

Condensation

pool . .

Design pressure: 116 bar (1682 psl)

0-3041

lgtureS. 5. Simpliflcd KWU lo.in. valvc test loop showing configuration, Icngths, and pipc sizes.
V

start to take place and allows us to look at the

fluid conditions and other parameters .anddetermine if infuences other than the terms in

Equation (1) affect the stem forces during valve

operation.

At various times during the test programs,

parallel diagnosticmeasurements were made by

Bechtel-KWU Alliance, General Physics, Liberty

Technology, Limitorque, Movats, Westinghouse,

and Wyle? Laboratories. This allowed the

diagnostic vendors to compare measured loadings,

similar to those that might be developed during

in-plant testing, to design basis loadings, which

typically cannot be developed in the plant

B-15
3. TESTING

-Six qualification; tests -and seventeen flow ANSIASME B16.41). The details of this step

'Interruption tests were performed. Seven of the ' are provided below.

flow interruption tests were design basis tests; the -

other ten were parametric studies. The parametric Exceptions to this basic procedure are as follows:

studies were an attempt to understand the effects -, -

of pressure, temperature,'and fluid properties on , Because of operator limitations at the very

valve performance. The fluid conditions and valve high torque switch settings used, some of the

operating 'responses ''provided information under-voltage tests recommended by the

- concerning valve and motor-operator perforiance standard in hot and cold cycling were not

at various valve loadings. ' performed.

{The two lists below summarize the qualification ' The torque switch settings in some cases were

and -flow interruption test procedures for each - 'increased after hot cycling to ensure valve

: valve: The basic test'procedure'for each valve closure. (Our objective was to close the valve

-through the design basis flow Interruption test was. and determine -from the measurement how

nearly the same, with a' few exceptions (listed much stem force was actually required to

later). isolate flow and seat the valve. In one case

(Valve 1),we underestimated the closing force;

The following list is an overview of the test ' we obtained flow isolation but did not fully

procedure performed In accordance with the test seat the valve.)

plan for each valve'through the design basis flow

interruption test, which was always performed first - The- flow interruption test .consisted of the

on each' valve assembly -- following numbered steps.' The numbers reference

the headers of the, Phase 1I plots used in this

* The valve was installed in the test loop report-

* The motor operator was installed and limit * Bring the test loop and valve up to NOP/NOT

control switches were set (Step 7)

* Instrumentation was installed . C16se the valve at NOP/NOT without flow

(Step 13)

* The torque switch was set

* Depressurize the downstream side of the valve

* A baseline opening and closing test without (Step 15)

pressure was performed

. Open the valve against NOP/NOT upstream

. Cold leakage test (Annex A of ANS/ASME pressure (with the downstream valves closed)

B16.41) (Step 17)

* Cold cyclic test (Annex B of ANSIIASME * Establish normal flow through the test valve by

B16.41) opening the valve in the normal flow line (see

Figures 4 and 5)

* Hot cyclic test (Annex C of ANSI/ASME

B16.41) * Close and reopen the test valve at normal

system flow (Step 18)

* Flow interruption test at the normal operating

pressure and temperature (NOP/NOT) for the * Close the valve in the normal flow line

valve's representative system (Annex G of

B-16.
in

* Establish line break flow through the test

valve and close the test valve (Step 25)

* Reopen the test valve 30% open and reclose

at maximum flow (Step 26)

* Depressurize the test loop and open and close

the test valve while still at temperature

without system pressure-(Step 30).

Following the flow interruption tests, we reviewed

the quick look plots, which served two purposes:

* To determine if the valve had been damaged

during the tCSL- .Valve stem force plots are

very good indicators of valves sustaining

damage during the high flow tests (see

Figure 6).

* To determine if the thermal hydraulic

conditions at the valve Inlet met the test

objectives.

If the valve was damaged by the loading (as

determined from a review of the stem force plot),

we stopped testing and installed the next valve. If

the valve was not severely damaged and the

thermal hydraulic conditions were met, we then

subjected the valve to parametric studies (varying

the pressure and/or temperature). If the thermal

hydraulic conditions were not met, we repeated the

test.

Table 3 provides the test matrix for the flow

interruption test sequences performed on each

valve. The temperatures and pressures listed for

each sequence include the target pressures and

temperatures for a nearly closed valve. Facility

capability limitations necessitated that some tests

be started with a slightly higher pressure than the

target pressure. In some cases, the valve was

started from less than 100% open in the maximum

flow closures so that the target pressure would be

achieved as closely as possible when the valve was

nearly closed.

Table 4 provides the maximum working pressures

for the valve classes tested in this program and the

test pressures for the leakage and cyclic tests. Test

pressures were not always maximums for the valve

class because of facility limitations; however, they

did bound the qualification pressure for the

intended service.

B-17
5000 v ctI v ,vI | ;> t I, t tJ ! t *tJ, JJ - IJ, LJ t dJ I ' I UE I I

0

-5000.

n -10000 _ ,,< ~~~~~~~Final seating 3 -10000

-15000

U-350000: Fo slto

E

* a -25000

co Possible dave(amage

-30000 9

-40000 ~~~~~~~~~Flow isolation',-,

-45000

0 5 10 15 - 20 25 .30.

Time (s) S2

F p * , o Ind damage.

FIigure 6. Valve stem roroc hislory rrom Phase il tstsing shnows nonlinear pcrrormance or thc valvc, indlicating vaivc dlamage.

35

II KGD-0490-02 ;

,, I
it

Table 3. Flow interruption test target temperatures and pressures

Valve Test

No- No.

Target

Pressure

(gsie)

Actual

Pressure

_(piz)

Target

Temperature

( F)

Actual

Temperature

(- F Media

6-in. Valve Tests

1 1

2

2

2

2

2

2

1

2

3

6A

6B

6C

1000

1000

1000

1000

600

1000

1400

1000

1200

1400

900

950

1040

750

600

1000

1300

920

1100

1300

530

530

545

<100

300

430

480

530

550

580

520

520

550

<100

450

470

520

520

550

570

Hot water

Hot water

Steam

Cold water

Hot water

Hot water

Hot water

Hot water

Hot water

Hot water

3

3

3

1

7

10-in. Valve Tests

4 1

5

S

1A

lB

1000

1000

1400

1000

1400

1200

750

800

1040

990

1400

1100

545

545

590

545

590

570

510

520

550

580

590

550

Steam

Steam

Steam

Steam

Steam

Steam

6

6

6

IA

lB

1C.

B-19
Table 4. Valve qualification test pressures

Maximum ANSI working pressure by

pressure class for these alloys

Valve No. Class

1. Z 4,5 900 lb

900 lb

Temperature

, (F)

<100

600

<100

600

Maximum Working

Pressure

(psie)

2250

1815

1500

1210

3, 6 600 lb

600 lb

Cold Leakage Test Annex A

Valve No.

Temperature

(OF)

Test Pressure

(Rpsi)

1

2

3

4

5

6

<100

<100

<100

<100

<100

<100

2200

2200

1500

2200

2200

1500

Cold Cyclic Test Annex B

Valve No.

1

2

3

4

5

6

Temperature

(OF)

Test Pressure

(psi)

<100

<100

<100

<100

<100

<100

* 1650

1650

1200

1600

1600

1200

Not Cvclic Test Annex C

Valve No.

Temperature

(O F

Test Pressure

(Rsize

1

2

3

4

5

6

600

600

550

610

610

550

1650

1650

1200

1600

1600

1200

B-20
APPENDIX C

J. C. Watkins, R. Steele, K. G. DeWall

"NRC Test Results and Operations Experience Provide Insights

for a New Gate Valve Stem Force Correlation'

Nineteenth Water Reactor Safety Information Meeting

October 1991

C-1
NRC TEST RESULTS AND OPERATIONS EXPERIENCE

PROVIDE INSIGHTS FOR A

'NEW GATE VALVE STEM FORCE CORRELATION'

'J. C. Watkins, R. Steele, K.'G. DeWall - .: . , ., , . . ............................... ,. .

-'' -Idaho National:Enginee'ring' Laboratory -

: ,EG&G:Idaho, Inc.

;. :.*Idaho . ' Falls,.;Idaho :83415 -

-. --. . .: -ABSTRACT..-

- ' . -- The "Idaho National Engineering Laboratory (INEL) is 'performing

motor-operated valve '(MOV) -reseav*h' in nsupport of- the U.S. Nuclear

-Regulatory Commission's (NRC's):'efforts'regarding'Generic Issue 87,

'.Failure ofzHPCI'[High-Pressure Coolant :Injection] Steam Line'Without

.' Isolation," and: Generic - Letter.!89-10 (GL-89-l0), -"Safety-Related

*-Motor-Operated Valve'Testing.and Surveillance." i-This paper.presents . the results of testing'to assess-valve and "motor operator.performance

under varying pressure and fluid conditions.-"This effort included'an

examination of the methods used by the industry to predict the'

required stem force of.a valve, and'researchto provide guidelines for

the extrapolation of in situ test results to designrbasis conditions.

This research has identified several inconsistencies with the

existing industry gate valve stem force equation and has challenged the overly simplistic assumptions inherent in -its, use. IThis paper

discusses the development of the INEL correlation to bound the stem

force necessary to close flexwedge gate valves whose operational

characteristics have been shown to be predictable. The authors also

present a method whereby the results of testing such valves at low

differential pressure can be used to bound valve response at

conditions up to their design basis.

~~~~~-* : - ; * -* -. .jf;H

* ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ,, ~ ~ ~ ~ * ~ ~ ~ ~ ~ ~~i X,. . ;* , '. ' '.' - _: -I - ..

; '- a. :Work-supported bylthe U.S.' Nuclear Regulatory Commission Office 'of Nuclear

Regulatory Re'search',--Division -of Engineering' and 'Division 'oft Safety Issues

Ad . s Resolution, iunder'DOEE Contract1No; TDE-AC07-761D01570; G.`H. Weidenhamer and

' . O.O.'Rothberg, Technical; Monitors.

r C-2
INTRODUCTION

Flexwedge gate'valves 'were tested in'two U.S. Nuclear Regulatory Commission

(NRC) test programs and reported in NUREG/CR-5406 (DeWall and Steele, 1989) and

NUREG/CR-5558 (Steele et al., 1990). Both reports were published in support of

Generic Issue 87. After the latter report was published, we developed a

technique to (a) bound the stem force -of a five-degree flexwedge gate valve

closing against medium to high' flow conditions and (b) validate a low

differential pressure closure-test and then bound the stem force of a flexwedge

gate valve closing against design basis conditions.

In the two test programs mentioned above, six valves with a total of seven

different internal designs were tested. The valves were subjected to a broad

range of fluid conditions and flow rates, from normal system flows to design

basis line break flows. Two of the valves, including the valve that was tested

with two discs, performed in a manner we have called predictable. A predictable

valve is one that does-not exhibit evidence of internal damage during testing.

In such valves, the-highest stem forces occur when the disc is riding on the

valve body seats Just-before wedging. Conversely, an unpredictable valve

exhibits evidence of internal valve damage duringtesting, characterized by an

erratic, sawtooth; shaped stem force response. In these valves, the highest stem

force requirements typically occur while the disc is riding on the guides rather

than just before wedging.

The test results were-initially evaluated with the standard industry gate

valve stem force equation. Although some of the manufacturers modify the

variables in this equation slightly, the application of the equation is basically

the same.

Ft =PdA/p ± AP + F0 (1)

where -

ft - stem force

Pd - disc factor

Ad - disc area

AP - differential pressure across the valve

A, - area of the stem

P- - pressure upstream of the valve

Fp - packing drag force.

For wedge-type gate valves, the industry has normally used a disc factor of

0.3, although they sometimes specify a more conservative disc factor of 0.5. The

disc factor acts in conjunction with the disc area and-the differential' pressure,

and the three multiplied together represents the largest component in the stem

force equation. -However, the disc, area term is-not used:uniformly throughout the

industry. This term is based on the orifice diameter by some manufacturers, on

the mean seat diameter by others, or even on the orifice diameter times one or

C-3
more factors to artificially enlarge the area on which the differential pressure

acts.- We used a disc area based on the orifice diameter when we evaluated the

standard industry stem force equation''be'caus' it represents the least

conservative use of the term by industry. This results in a lower-estimate of

required stem force.

Comparisons of the industry equation, Equation (1), with selected test

resultslare shown in Figure 1.-' This figure presents the results of the same

valve isolating a break at a common upstream pressure of approximately 1000 psig,

but with the fluid at various degrees of subcooling. The subcooling ranges from

none (steam) to approximately 4000F (cold water) with intermediate values of 100 F

and 100 0F. The recorded stem force is'shown as a solid line; the'dashed lines

show two calculations of the stem force history'using the industry-equation and

real time test data with standard industry disc factors of 0.3 and 0.5. This

figure shows that at flow isolation, each test required more force to close the

valve than wouldsbe estimated using the standard industry disc factor of 0.3.

In fact, for the tests shown on this figure, the more conservative industry disc

factor of 0.5 range's'from acceptable (th'e ,steam test) to marginally acceptable

(the 10OF subcooled fluid 'test) to unacceptable (the 1000F and the 4000 F

subcooled fluid tests).: Note that although the results'ofthe industry equation

are presented over the entire closure cycle, the equation represents a bounding

estimate of the maximum stem;force. As such, only the-,estimated stem force at

the final horizontal line, just before wedging, is applicable. 'The-results are

presented for'the'entire closure'-to aid'in ngtrends-in the recorded

stem force, not to assess the equation throughout the closure cycle.' Note also

that although the same valve 'and operator'were-usedifor each test, the closure

durations are different.- "Due to facility limitations,'someiof the tests were

initiated with the valve partially closed.

It is :also' interesting 'to-note that, the 'shape 'o'f the recorded stem force

from flow 'initiation to flow -isolation 'varies depending on the, degree of

subcooling of the'fluid. In tests with greater subcooling, the stem force during

the initial portion of the closure is lower.'' In fact, during the test with cold

water, the stem force trace was initially positive (i.e., the valve was self

closing during this 'portion of the'closure). However, just prior to wedging, the

required stem force'is generally higher in tests with greater subcooling of the

fluid so that closure against cold water requires more force than closure against

steam. ; : ; .

ASSESSMENT OF-THEDISC-FACTOR ; ''

*As we studied the~test results and'anialyzed'the industry equation', it became

increasingly evident that the disc factor used in-the' equation 'was not well

understood. It appeared `that'-the disc factor depended on': parameters not

currently being accounted for, such as the'subcooling of the7fluid. Thus, we

examined the equation in more-detifl, and specifically the disc-factor term as

currently defined. To perform this evaluation, we used both"the'baseline and

applicable parametric testing'to..determine what influence pressure and fluid

properties, such as subcooling',;had on the required stem force;of'a'valve.

. . . . . . . *4-

;-C'4
20000 ,20000

C-n

I'

=10000

-o

a)

o 0

0

IL.

2.0000

4-

U)

-20000

-30000

20000

-10000

.0

o

U.

U)

-20000

-30000

0 6 10 15 20

Time (s)

26 30 35

10000

.0

0 I o 0

0

U.

Eloooo

_. r".

(a

-20000

-30000

20000

_10000

.0

0 0

0

UE10000

4-

U)

.20000

-30000

- Valve 2, 1000 psi. <10b0F (Cold Water) _---- CActual 'M - 0.31

--- * - -Calculatld lA - 0.5-

1111II IIcull lmi - 0.6I lu lp -

0 5 to 15 20

Time (s)

25 30 35

I

0 5 1o 15 20

Time (a)

25 30 36 0 5 10 15 20

Time (s)

25 30 35

MS291 RS-0491-04

Figure 1. Comparison of the standard industry gate valve stem force equation with selected test results.

U
If all of the-parametric.studies-could have resulted in just one parameter

being varied, then the tests could have been compared to each other to determine

the effect of that one parameter (e.g., fluid properties). That was not the

case, however;. It was impossible to. provide such precise temperature and

pressure control at the valve. This,'.along with other facility limitations, such

as the total system supply volume; resulted in tests that cannot -be compared to

one another-without some-type of normalization.

We normalized the test results.using Equation (1) by solving for the disc

factor. This was possible because the stem force,: the system pressure, and the

valve differential pressurethroughout the closure cycle were known. The results

of a typical comparison are shown^ini-Figure 2.' The plot is read from right to

left as the valve closes.- As time increases,"the-disc factor increases in the

negative convention (indicating valve: closure)- and' is plotted against stem

position. The zero stem position represents that point in the:valve closure

where-the-horizontal-visual area is blocked so that you'could not see down the

pipe. ~ Remember, however,-that although the visual area' is blocked;' fluid can

still-flow under'the disc and through the valve'.-- At this point' the disc area

term in Equation (1) becomes constant.- The.differential pressurerterm is also

near its maximum during this portion of the valve closure. From the'zero stem

position to the minus 10% stem position, the stem travel involves seating and

finally wedging. There are noaterms in the'industry equation to represent the

increased resistance before wedging. The figure also indicates that the disc

factor is influenced by fluid properties, steam being the best performer with the

lowest disc factor and cold water'the worst with the highest disc factor. -'This

fluid properties effect is evident not only at the zero stem 'position, but from

the minus 5% to the minus 10% stem position, when the disc is riding on the seats

just before wedging. This effect is contrary to what was expected; one would

expect water to be a better lubricant than steam.

Our next effort was to determine if the disc factor was dependent on

pressure. Figure 3 shows a comparison'for using three parametric tests where the

fluid properties 'remained constant but; the pressure was varied.- Although the

disc factor-did not exhibit a significant pressure dependency at the zero stem

position, it'did from the minus 5% to the minus 10% stem position when the disc

was riding on the seats Just' before wedging. The figure also indicates that the

disc factor was lowest during---the 1400-psig test and highest during the 600 psig

test.. This, too, is contrary'to what was expected; one would expect a lightly

loaded disc to have a thicker lubrication film and thus a lower coefficient of

friction than a heavily loaded disc. ' -

Figure 4 depicts the effect of pressure in the opening direction, further

highlighting inconsistencies with Equation (1). This-plot is read':from left to

right as the valve opens. Although the disc factor (a positive value because the

valve' is opening) did -not- exhibit as pressure dependency at ~the, zero stem

position, it didfrom-'the minus 5% to the minus 10% stem position." 'This trend

is similar to what was observed in the closing direction. The figure also

reaffirms our!previous'observations that-the disc factor is lower' during a highpressure test and higher during a low-pressure test. The opening disc factor is

also observed to be higher. than theclosing disc factor at its peak, non-wedging

....- - ;. . - .

C-6
a

o0.0

-0.1

-0.2

0

co

C,-

a'

VI

-0.3

-0.4

-0.5

-0.6

-n 7 _.,

-15 -10 -6 0 5 10

Stem position (% of travel)

15 20

MS29t RS-0491-06

Figure 2.

subcooling

Disc factor for Gate Valve 2 closing on line

at 1000 psig.

break flow, effect of

0.0

-0.1

-0.2 L0

C3

co

U,J

-0.3

-0.4

-0.5 - l

* I 8~ ~ 0 ~~~~~~~0 P 31 -10~~~~000 Psig

.B 1''l- x ~~~~~~~~~1400 psig

-0.7 1

-15 -10 -5 0 5 10 1s 20

Stem position (% of travel) M5291 RS-04O1-0S.

Figure 3. Disc factor for Gate Valve 2 closing on line break flow, effect of

pressure at 100F subcooling.

C-7
I , I I. 4 . 1 i*4 .. '

1.0

0.9

0.8

0.7

.o

- '0.5 Ct,

0.5

o 0.4

- - 0.3

0.2

0.1

0.0

-1

_ . .

- a j. , .: , a *. s g **'.Ie ....

Effect of pressure at .100°F sbcooling , . . ; ,, , :. -.4 : . . .

Opening . . : ' .;

: -'4 2 I a , , , ; L h f i

. I

- .601

.1001

- 140(

0 psig . I. _:

PSig , " . :

) psig, -

. . . . I . . . .

15 -10 -6 0 5 10 15 20

.- Stem position (% of travel) : MS291 RS-0491-10

4 , , .¶ '. , 4 .! ,. - - .' .

-Figure 4.' Disc factor for;Gate''Valve'2'opening'on''1ine break flow,' effect of

pressure at100F subcooling.'

* * ; ~~~~~~~~~~~* - 1 .: 4 ? ..... ,.

., tW [ .i-;,;, 4
The previously unaccounted influence of fluid subcooling and pressure on the

disc factor is very evident. This influence is also contrary to what one might

expect in terms of the effectiveness of a lubricant. However, what was expected

is based on a lubrication that separates the load bearing surfaces with a

relatively thick film of lubricant to minimize metal-to-metal contact. This type

of lubrication is known as thick film lubrication. In the event the load bearing

surfaces are not separated by a film of lubrication, metal-to-metal contact can

occur. This condition is known as thin film lubrication. The deficiencies of

this type of lubrication are aggravated by surface areas that are too small to

carry the maximum load, a load that exceeds the maximum expected or design basis

load, or a decrease in the velocity between the moving surfaces.

When metal-to-metal contact exists, any condition that increases the ability

of the lubricant to penetrate the bearing region will decrease the friction

between the two -surfaces. For instance,' the higher the differential pressure

across a bearing region, the, more likely a given lubricant will be forced into

this region and thus lower the friction between the surfaces. Likewise, a

lubricant in a vapor state is more likely than the same lubricant in a liquid

state to penetrate the bearing region and thus lower the friction between the

surfaces. Other researchers have noticed these same phenomenon; however, they

attribute this sensitivity to changes in the temperature of the fluid and metal.

We are still investigating this phenomenon, and we hope to provide more

conclusive results in the future.

From the results discussed above and from similar results for the other

valves evaluated, it is apparent that Equation (1) is incomplete and does not

totally identify and predict the increasing stem force once the disc is past the

horizontal visual isolation or zero position. In addition, the fluid subcooling

and pressure dependencies of the disc factor are inconsistent with past

assumptions inherent' in the application of the industry equation. Thus, we

concluded that the equation does not consider parameters that have an important

effect on the observed responses of the valves..

FLOW PHENOMENA THROUGH A VALVE

In response to the unexpected test results, we directed our efforts toward

investigating the flow phenomena through a flexwedge gate valve and the effect

that pressures throughout the Yalve had on the resultant stem force. Figure 5

shows a cross section of ,a typical flexwedge gate valve and identifies those

areas on the disc and stem where the various pressure, forces can act. This

figure also indicates where we drilled three pressure measurement ports into each

of the valve bodies prior to the Phase II testing to assist in this internal

pressure distribution study. Figure 6 shows a typical pressure distribution

observed during our testing. The pressure in both the bonnet region of the valve

and under the disc are lower than the upstream pressure during most of the valve

closure cycle. This reduction in pressure is due to the Bernoulli effect, the

result of fluid accelerating through a valve in response to a reduction in the

flow area. This phenomenon is dependent on the pressure and subcooling of the

fluid and on the magnitude of the reduction in flow- area through the valve.

Thus, the Bernoulli effect will be system and fluid dependent. The bonnet area

also shows a lower pressure because of the split in the disc and because of the

C-9
Statc

pressure

Flow ,,

-:. : - - pressure M291 ,u.0491.07

- I- i - , . , , , I; * . I- i

Figure 5. Gate valve disc cross section showing pressure forces.

* C-10
U)

0.

.U)

U1)

a.

1,000

900

800

700

600

500

400-1

_

Upstream pressure .., J.

Bonnet oressure ...----- 

I I I I

0

Under disc pressure

0 .0 .50 10 ..... 20 4. 

- - - - - - -

0 10 -20 30 40 so

Stem position (% of travel)

Gate valve internal pressure distribution.

60 70 80

MM2 "44"t11

Figure 6.

C-ll
gap-between the disc and the valve body seats; these structural features provide

a path such that the pressure in the bonnet region can more closely follow the

pressure in the region under the disc.

However, from the minus 3% to the minus 10%. stem position during this test,

the pressures converge. During this portion of the valve stroke, flow has been

isolated and the disc is riding on the valve body seats; however, wedging of the

disc has not yet begun. It is also during this portion of the valve stroke that

.predictable valves exhibit the largest stem force. Thus, we concentrated our

efforts on this segment of the valve closure cycle. Wedging forces were not

considered because these forces are not. the result of fluid dynamic *and

frictional effects, but instead. depend on the force capabilities of a given

operator and on the structural stiffness characteristics of a specific disc and

valve body.

DEVELOPMENT OF THE INEL CORRELATION

Our first effort was to develop a relatively detailed free body diagram of

the disc while it is moving-in the closing direction, after the flow has been

isolated but before wedging. This was done with the hope of better understanding

the pressure and area terms that effect the stem force. Figure 7 presents the

results of this effort and identifies all the nonsymmetrical forces acting on the

disc. Note that according to thejfree body diagram, the forces acting on the

disc ultimately react through the valve-body seats, which are at a slight angle

(for a flexwedge gate valve)-'relative "to the horizontal and vertical valve

coordinate system. To account for this slight seat angle so that the forces are

expressed in values consistent with the definition of'a traditional friction

factor, we found it necessary to transform the horizontal and vertical forces

into a coordinate'system that is normal and tangent to the valve body seating

surfaces.

Following this logic, we theorized the existenceo'f1two horizontal forces

acting on the disc. The first horizontal, force (Fop) is due to the upstream

pressure (Pa) acting on that area of the disc .defined by the mean diameter of

the downstream seating.surface. The downstream seating surface presents a

circular profile in the horizontal planet The mean seat diameter was selected

because it best approximates that area of the disc in contact with the crown of

the downstream seating surface over which the various pressure forces act. Fw

is defined as

Resisting this force (Fun) is a horizontal force (Fd.0 ,) due to the downstream

pressure (Pdown) also acting on that area of the disc defined by the mean

diameter of the downstream seating surface. Fd.- is defined as

C-12
MU

i Fstem

V M291- re-0491*12

Figure 7.

wedging.

Gate valve disc cross section showing unbalanced forces just before

C-13
F~~~ =pd~~~~~~flL7D.¶] ~~~~~~~~(3)

[4]

These two forces -represent the-.only:horizontal forces acting on ;the. disc and

provide a far more realistic estimate -of the horizontal force component than the .-'.orifice area term which is-oftentused -in the:Andustry.equation. -.The net

horizontal force component (H) can be expressed as

H = F,, - fd.. (4)

Likewise, the free body diagram indicates that there are actually five

vertical forces acting on the disc. The first vertical force is due to the

operator and represents the net stem force delivered to the valve.

-Forum ='stem load ' - ' ' (5)

The second is due to the resistance of the packing while the valve is closing.

The effect of the disc and stem weights is also included in this term.

F,.*n = -packing drag - discand steim weight - ,; - (6)

-d ag d.c . . . (6),.. 

-The third represents'the stem rejection force, the result of the pressure under - the'disc (P -once the'fl whasi'beini is'olated) tryingntogexpel the stem.

F. . = P .7D . (7) 44

The fourth force is due to the pressure in the bonnet region of the valve (Pm

once the flow has been isolated) acting on the area of the disc defined by the

mean diameter of the seat cast in the vertical direction. This area term is the

result of the slight angle of the seat in a flexwedge type gate valve. (nominally

a five-degree angle) and results in an elliptical area-over'which thempressure

acts. The major diameter is equal toethe mean diametere oflthe seat; the minor

diameter is equal to the mean diameter of the seat times the~tangent of the angle

the seat makes with the vertical axis of the valve.

. ,; , .. ., . t; Q ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i i -;^r

iC-14
F =0 an tan' (8)

Resisting Ft 'Is a:fifth force due to the downstream'pressure (Pd.,)' acting on

the area of the disc defined byf the mean diameter of the seat cast in the

vertical direction. This-force is also the result of the slight angle of the

seat.

Fbonw. Pd.. tana (9)

The net vertical force component (V) during valve closure can thus be expressed

as

V Fg-,-,, Fo;-, - F Fb.. (10)

The net horizontal and vertical forces can now be.recast into the plane

defined by the valve body seat and normalized to' remove the effect of valve size.

Figure 8 shows these two forces and their resolution into forces normal and

tangent to. the seats. Note that the two normal. forces' resulting from this

transformation act' in the same direction, whereas the two tangent or sliding

forces oppose each-other.' These can be expressed as follows for the normalized

normal force (F,) and the normalized sliding force (F.), respectively

F = H cosa + V sina

no.2. ~~~~~~~~~~~~~~

H sina - V cosa F,,

(12)

The analysis described above allows us to better characterize the normal and

sliding forces acting on a flexwedge gate valve disc just before wedging. Our

next effort was to determine if the Phase I and Phase II flexwedge gate valve

test data supported a relationship between these forces. We extracted from our

data base the test results of all predictable valves during the closure cycle

when the disc was riding on the seats. We did not include the results of any

C-15
t ;

. .f

I . KIdaf * . i~~~~404 VQIVV VVILILoI~I I1

* Surface sildinga Normal comp(

Surface normal load. Sldnco oet

- . . '~~~~Sliding component

Net, vlVe .

horizontal load.. . *. '*' Normal component

Val v' .d ;sc/seat a': -

interface'surface

aCdU

)nent

A291 re-0491-08

' .. .: , ; . * . -

.Figure 8. '-'Resolution of.horizontal and vertical gate valve disc forces into

surface normal, and sliding forces. '-

I . - -

I " *" -

' 

1. . - . I

C-16
U

testing if severe internal damage was evident. However, if the valve exhibited

evidence of internal damage while the disc was riding on the guides but showed

no evidence of such behavior while the disc was riding on the valve body seats,

we included the results.

The Phase II data extraction included testing with three valves representing

two valve sizes (6-in. and 10-in.). Design basis flow isolation tests and normal

operating flow isolation tests were used; upstream pressures ranged from 600 psig

to 1400 psig, and fluid conditions ranged from steam to 4000F subcooled water.

However, the results of tests when the differential pressure was less than 20%

of the upstream pressure or when both the, differential pressure and the stem

force were increasing very rapidly while the disc was riding on the valve seat

were not included. This is because the magnitude and trends of the resulting

forces are obscured by relatively low loadings on the valve disc (which affect

the transition from thick film lubrication to thin film lubrication), and by

rapid changes in both the stem force and the differential pressure. This

extraction yielded data from 30'tests.

The Phase I data extraction included testing with two valves representing

a single valve size (6-in.). By way of comparison, these valves were nearly the

same as Valves 1 and 2 in the Phase II testing. Only design basis flow isolation

tests were used from .the Phase I testing. Upstream pressures ranged from

400 psig to 1400 psig, and fluid conditions ranged from 10OF subcooled to 1400 F

subcooled water.- This extraction yielded data from 12 tests.

The results of both data extractions were used in the force balance

developed as described above and presented in Figures 9 and 10. The results

reveal two linear relationships between the normal force on a seat (Fj) and the

tangent or sliding force (F.) necessary to. induce motion. One is representative

of a fluid subcooling of less than 700F, while the other is representative of a

fluid subcooling of 70°F or greater. The two dashed lines on either side of the

solid line represent'the limits of the observed data scatter. The tight grouping

of the data scatter lends confidence that not only can we bound the force

requirements of a flexwedge gate valve, but we can also devise a method where the

results of low differential pressure flexwedge gate valve testing can be verified

and then the design basis conditions used to bound the maximum stem force. Note

also that the dashed lines do not extend below a normalized normal force of

400 lbu/in2. Due to the limited low pressure and low differential pressure data

available and the postulated friction mechanism, the applicability of the INEL

correlation is' currently limited'to normalized normal forces of 400 lbJin2 and

above. We are continuing to extend the applicability'of the INEL correlation.

THE INEL CORRELATION

We can now rearrange the previously developed force balance and solve for

the stem force based on a linear relationship between the normalized normal and

sliding forces. Using Figures 9 and 10, the slope of the solid line (the

friction factor between the disc 'and the seat) can be used to relate the

normalized normal force (Fj) to the normalized sliding force (F.) as

C-17
0

-,, -100 . JN

8' -200

3 -300 0

-j

= -400

C,'

la -500

a)

.N

X -600

E

; 0 

Z; -700

-800

I . - 200 40O0 ' 600 800; 1,000 1,200.

--;Normalized Normal Load (lb1 Min2)

1,400 - 1,600

,4 I, .I.. 1 . I .. .

s .ASS kod-101-22

Figure 9. Normalized surface sliding force versus normalized surface normal

force for gate valves closing against less than 70*F subcooled fluid.

0

ew

C

C.O

10

-o

*0

a)

N

01 z

-100

-200

-300

-400

-500

-600

-700

-800

0 200 400 600

Normalized

800 1,000 1,200

Normal Load (Ibf/in2)

1,400 1,600

LM455 kow-1091-3b

Figure 10. Normalized surface sliding force versus normalized surface normal

force for gate valves closing against 70*F or greater subcooled fluid.

:C-18
W

F. O-f Fe, C (13)

where

f - friction factor, the slope of the line that relates the normal

force to the sliding force and is equal to

0.400 if the fluid is less than 700F subcooled

0.500 if-the fluid is 700F or greater subcooled

C - offset bounding term reflecting the scatter in the observed data

and is equal to

0 for no offset bounding

50 lb,/in2 to bound the data provided a normalized normal force

of 400 lb,/in 2 or greater exists according to Equation (11) (shown

as.the dashed lines in Figures 9 and 10).

Substituting the -horizontal and vertical components of the normal force

(Equation (11)] and the horizontal and vertical components of the sliding force

[Equation (12)] into the above relationship yields

H (f cosa + sina) t C | (14)

(cosa - f sina)

Now,Isubstituting the horizontal and vertical force components [Equations (4)

and (10)] into Equation (14), limiting the final result to a bounding estimate

of the stem force, and rearranging yields

02

where

Fh =F.. - Fd (16)

C-19
Fv =Fpkjv + F., - fto + FS a^; (17)

61 = f cosa + sina . (18)

:; 2'=Cosa - f sina . .. (19)

f = friction factor and is equal to'

0.400 if the fluid is less than 700F subcooled

0.500 if. the fluid is 700F.or greater subcooled.

:, ' t ' . : . . . .- .

-- Thus, Equation (15) c'an b~e used to bound the maximum stem force requirements

of a flexwedge gate valve closing against medium to high 'flows whose operational

characteristics have been demonstrated to be predictable at design basis

pressures and temperatures. 'This method will also provide the basis"by which the

results of in .situ'tests conducted-on'predictable valves at less than'design

basis conditions' ca'nbe:verified. 'Then-the design'basis conditions can be used

to bound the maximum-stem force.",-'Note !that the correlation applies only to

flexwedge gate valve closure against medium to high flows, flows that will result

in a normalized normal force of 400 lb/in2 or greater according to

Equation (11).

USE-OF THE INEL CORRELATION

To use the INEL correlation to bound the closing stem force requirements of

a flexwedge gate valve, Fthe- analyst must first determine, if operational

characteristics of the valve are considered to be predictable. If the valve is

predictable, the following information can be used to bound the stem force:

* The mean diameter of the-valve body seat (the average of the inside

diameter and .the-.outside diameter of-the valve body seats'measured

in the plane perpendicular to the stem)

* The angle the valve body seat makes with the vertical or stem axis

* The outside diameter of the stem

* An estimate of the maximum packing drag expected less the effects of

the weight of the disc and stem

* The maximum upstream pressure that would exist after flow isolation

but prior to wedging, typically the design basis pressure

. C-20
* The maximum differential pressure that would exist after flow

isolation but prior to wedging, typically, the design' basis

differential pressure

* The subcooling of the fluid at design basis conditions, either less

than 700F subcooled or 700F or greater subcooled.

With this information, the net horizontal force (Fh) can be estimated with

Equation (16) and Equations (2) and (3). The net vertical force (Fv) can then

be estimated with Equation (17) and Equations (6) through (9). The angle between

the seat and the vertical or stem axis can then be used with Equations (18)

and (19) to estimate terms associated with transforming the horizontal forces

into forces on the disc and seat, and finally into a vertical force. Thus, all

the terms in Equation (15) can be determined, and the maximum stem force

necessary to isolate flow at the specified pressure and differential pressure can

be estimated.

By way of example,. the actual upstream pressure and differential pressure

recorded after flow isolation but prior to wedging during one of the tests will

be used, and the maximum stem force requirements of the valve using the INEL

correlation will be estimated. The result will then be compared with the actual

stem force recorded during the-test.

The results.from Valve 2, Test 3, Step 25 wil.l,-be used for this comparison.

Since this was a cold water, test (400 0F subcooled fluid), ..the 700F or greater

subcooled friction factor will be used in the INEL correlation. Pertinent valve

information and the pressure and differential pressure recorded just before

wedging are

Stem diameter 1.750 inches

Orifice diameter 5.187 inches

Seat inside diameter 5.192 inches

Seat outside diameter 5.945 inches

* Packing drag 200 lbf

Upstream pressure just before wedging 746 psig

Differential pressure Just before 753 psid

wedging

C-21
This information can be used with the INEL correlation as follows:,

D (seat ID + seat OD) = (5.192 +'5.945); 5.569

2 2

A,,.,-.nD, ,(5-569?2 24.354 - -

4 2 = '4 .2 ,~ :2rr405 ;, .

-'' A,"m *4 " ( 145° .io-;

r,

:.I,- F 5

8F,

.. 1. Fb82

=Up Pw A~'= (746)(24.354) '18,168

'Pd. Acme =-(746 - 753)(24.354)'= -170 '

=Pa A,,. tana = (746) (24.354) tanS = 1590

-P,., An,, tano= '(746 --753)(24.354) tanS = -15

-'P, A,,, -'(746)(2.405) - 1794;

oF,, - _Fai , 18,168 - (-170) = 18,338

Pp-.+F - F'+ F .a3"200 +1794-1590

a f cosa + sini = 0.500 cbos'5 ' sinS = 0.585

= cosa - f sina * cosS - 0.500 sinS = 0.953

+ (-15) = 389

F, ;= F.+ ie Fh + 50 A 389 + (0.585)(18,338) + (50)(24.354) = 12924 -" : Lt Ve g -1: ; ^ 0.953 o2 

During th'is -test,' the peak 'stem 'force recorded'just before wedging was

12,787 -bf. Thus-, the 'INEL'correlation-bounds the actual recorded'stem force.

'Similar comparisons' using the industry equation'do' not consistently bo6und the

observed stem force with-either a 0.3 or ai0.5 dis& factor and uslng'either the

orifice area''or'theimean seat'area.E'

LOW DIFFERENTIAL PRESSURE 'TEST VERIFICATION

Utilities have numerous flexwedge gate valves in systems throughout a

nuclear power plant; many of thes'e v'alves must function in various design basis

events. The capability of these valves to operate at design basis conditions

usually cannot' be verified with 'in ssitu testing, `especially for v*a'lves where

_L.de'sign 'basis conditio include nt -higon pressures 'and"medium to-high flows.

Usually, only low flow and low'differential'pr'essure conditions can-be developed

near valve closure. Where the utility can demonstrate that 'their medium to high

-flow valve-designs exhibit predictable-behavior at -design basis ''conditions,

'--thro* --type''tes'tinj'or -othr !means; -ini'situ'' testing 'at low flows and

differential pressures can be used in conjunction-withi'the-INEL correlation to

verify that the valve being tested is representative of the valves tested by the

INEL. If so, the INEL correlation can then be used to bound the stem force

requirements of the candidate flexwedge gate valve at design basis conditions.

This is accomplished as follows:

tC-22
a

- Step 1: A differential pressure test is performed. The results of the

testingare then used to estimate-the normalized normal and

sliding- forces for the valve-according-'to:Equations (11)

and (12). If the upstream pressure and differential pressure

while the disc is riding on the seats results in a normalized

normal force of not less than-400 lbf/in 2 and if the resulting

forces fall within the upper and lower bounds expected for

valves of this design (see''Figures 9 and 10), the valve is

considered to be representative of thev'4alves tested by the

INEL. If the resulting forces do not fall within the expected

band, the results of our testing are not representative of the

valve being tested and the INEL correlation may not be

applicable.

Step 2: If the results of Step 1 fall within the expected band, actual

design basis conditions can be used in the INEL correlation to

bound the stem force'requirement of the valve being tested.

This maximum stem force estimate-is then used, along with the

other necessary motor operator sizing calculations, to verify

'the'size of the operatoreand~the setting of the torque switch

to ensure that sufficient stem force is available to operate

the valve at design basis conditions.

CONCLUSIONS

The indu'stry'sy Jtraiditi'6nal gate valve sizing equation is incomplete

regardless of the disc area term or the-disc factor used. This is because more

terms are included in the disc factor than the sliding friction term.

- A new correlation was developed based on the results of two full-scale

flexwedge. gate valve qualification and flow interruption test programs; This

correlation has been; shown.to consistently bound the stem force- requirements of

a flex'wedge gate~valve whose operational, characteristics have been. shown to be

predictable. This correlation also allows a flexwedge gate valve to be verified

based on the results of a low differential pressure test. If so verified, the

results of the INEL correlation are shown to. be applicable at design basis

conditions.

REFERENCES

DeWall, K. G'., and R. Steele, Jr., 1989, BWR Reactor'Water Cleanuo System

Flexible Wedoe Gate Isolation Valve Oualification and High Energy Flow

Interruotlon Test, NUREG/CR-5406, EGG-2569.

Steele, R., Jr., K.: G. DeWall, and J. C. Watkins, 1990, Generic Issue 87

Flexible Wedqe Gate Valve Test Program. Phase II Results and Analysis,

NUREG/CR-5558, EGG-2600.

C-23
NOTICE

This report was prepared as an account of work sponsored by an agency of the

United States Government. Neither the United States Government nor any agency

thereof, or any of their employees, makes 'any warranty, expressed or implied, or

assumes any legal liability or responsibility for any third party's use, or the

results of such use, of any information, apparatus, product, or process disclosed

in this report, or represents that its use by such third party would not infringe

privately owned rights. The views expressed in this report are not necessarily

those of the U.S. Nuclear Regulatory Commission.

C-24
APPENDIX D

INDUSTRY GATE VALVE SIZING SHEETS

D-1
LIMITOROUE MOTOR OPERATOR CALCULATIONS

P.O.No.or PROJ.:F2-72916-S

CUSTOMER NAME: 'E.G. t G.

VELAN NO.: ' VALVE DESCRIPT.t 10 "

;- rS -'I

IDAHO

ITEM(S); ;

-9C0# PS ;,GATE * FORGED

-REF.0: VELA

7054P DWG:No'.:

8890.6092'

LINE PRESS.: 1000 PSIg DIFF.PRESS.: 1000 PSI' 8 TEMP. 550 F .

ORIF. DIA.: 7.S75 in THREAD : THREAD

STEM DIA.: 2.500 in FACTOR: - ,.01962-' PITCH:'-' 0.3333 in'

MOTOR DES.RPM.: 1300 ', STEM SPEED: 10.00 in/minTHREAD -

PULL OUT EFFEC.: 0.49 APPL.FACT.: 1-.00 LEAD: '0.3333 in *V

REDUCED VOLTAGE: 0.80 MOT.STALL- - - LIFT: - .44 in

STALL EFFECIEN.: 0.50 TORQUE: 42.00 ftlb - -

H/W RATIO: 25.30 UNIT EFF.: 0.30 , FREQU.i 60 HZ

MOT.TORQUE: 40 4tlb CURR.SUPPL.: .460'VOLT TYPE: AC

STEM THRUST: FHYDR.- ORIF.DiA.'2 x-PI/4,xDIFF.PRESS.-x SEAT FACT;= *14612 lb

PISTON EFFECT-STEMDIA.'2-x PI/4 x-LINEPRESS.i- 4909 lb

PACK.FRICT.LOAD= - e- 8482 lb

TOTAL STEM THRUST * - 28003 lb

STEM TORQUE < STEM THRUST x STEM THREAD FACT.= - - '549 4tlb

THEOR. O/A OR UNIT RATIO ,-MOTOR DESIGN R.P.M. x THREAD LEAD/STETISPEEDT'w 47.01

ACTUAL' O/A OR UNIT RATIO:- tMOTOR DESIGN R.P~M. x-THREAD'LEAD/STEM'SPEEDA W 56.64'

MOTOR CALC. TOROUE'- 'STEM TORW E /(PULLOUTEFF x APPL.FACT. x O/A RATIO) ' 24.25 ftlb

MOTOR CALC. TORQUE e fEDUCED VOLTPGE ' - - -s - ; 37.90 ft lb

-N.B. IF DC SUPPLY, DO NOT SQ. % V.

STALLED TORQUE 2`110% VOLT.- MOT. STALL TORQUE x ST; EFF; V. x O/A RATIO a - 1645 ftlb

-STALL THRUST STALL TORQUE 'STEM THREAD FACTOR - -- ' ' - 83824 lb

MAX. ALL. ACTUATOR STALL THRUST = -- -112500 lb

H/W PULL. 2 x STEM TORQUE /(HWRATIO x UNITEFF.-.x HWDIA.~xADD.GEAR x EFF.) 145 lb

MAX.TORQUE SWITCH SETTINGe 'RED.VOLT.=MOT.TORQUE x PlO EFF. x APP.FACT. x 752.15 4tlb

MAX.VW/N TORQUE - MAX.'VALVE TORQUE /,(H/W RATIO x UNITEFF.) - ' -'72.40 ftlb

:OPERATING TIME n (60 x LIFT) /'STEM SPEED = - ' ' 50.60 sec'

SMB - I ,- E - ACTUATOR , . 40:f tb MOTOR MOTOR'MAX.THRUST= 45000 lb'

MAX. STEM TORQUE 850 ftib' .ADDITIONAL GEAR -- no MAX.STEM DIA.--' 2.750 in

H/W RATIO r '. 25.3 :1 .<ADD.G/RATIO- 1.00 :1: 'Q/A RATIO RANGE 42.5-8.40'

CURRENT SUPPLY:: '460 VOLT ,:STD.H/WHEEL: -'>12 4n. in MUST OPERAT RED.V '0.80

TYPE: AC/3/60 HZ ''bOVERSIZED H/WHEEL : no

BEVEL GEAR ACTUATOR DIRECTLY, MOUNTED ONTOVALVE:v, no ' MAX.ALLOW.THRUSTI '- -Ib

ACTUATOR MODEL: RATI~i hMAX.STEM: MAX.ALL0W.TORQUE: -' tb

REV. 0 REV.1 REV.2 REV.3

COMPILED BY'

APPROVED BYt

IND.REV. BYs , ''
U

LIMITROU£ MOTOR OPERATOR CALcULATIONS

P.O.No.or PROJ.oP2-72916-S

CUSTOMER NAME: E.G. & G. IDAHO

VELAN NO.: ITEM(S):

VALVE DESCRIPT.s 10 " 9004 PS

5MP - I REF.: . -

VELAN

7054P DWC No.:

SATE FORGED 8890.092

LINE PRESS.: 1000 PSIg DIFF.PRESS.: 1000 PSI e TEMP. 550 F

ORIF. DIA.: 7.375 in THREAD THREAD

STEM DIA.: 2.500, in FACTOR: 0.024S2 PITCH- O.3233 in

MOTOR DES.RPM.: t800 STEM SPEED: 12.27 in/m'inTHREAD

PULL OUT EFFEC.: 0.40 APPL.FACT.: 1.00 LEAD: 0.6667 in :

REDUCED VOLTAGE: 0.80 MOT.STALL- LIFT: 8.44 in

STALL EFFECIEN.: 0.V0 TORQUE: 48.00 fttb

H/W RATIO: 25.30 UNIT EFF.: 0.30 FREGU.s 60 HZ

MOT.TOROUE: 40 ftlb CURR.SUFPL.: 460 VOLT TYPE: AC

STEM THRUST: FHYDR.= ORIF.DIA.^2 x P1/4 x DIFF.PRESS. x SEAT FACT.= 14612 lb

PISTON EFFECT= STEnDIA.'2 x PI/4 x LINEPRESS.= 4909 lb

PACK.FRICT.LOAD 8482 lb

TOTAL STEM THRUST = 28003 lb

TORQUE = STEM THRUST x STEM THREAD FACT.* 679 ftlb

Ti._.;. O/A OR UNIT RATIO v MOTOR DESIGN R.P.M. x THREAD LEAD/STEM SPEEDT = 94.02

ACTUAL O/A OR UNIT RATIO =.MOTOR DESIGN R.P.M. x THREAD LEAD/STEM SPEEDA = 92.40

MOTOR CALC. TORQUE,= STEM TORQUE /(PULLOUTEFF x APPL.FACT. x O/A RATIO) = 13.37 ftlb

MOTOR CALC. TORQUE e REDUCED VOLTAGE - ' 23,70 ftlb

N.B. IF DC SUPPLY, 00 NOT SQ. % V.

STALLED TORQUE e 110. VOLT.z MOT. STALL TORQUE x ST. EFF. % x O/A RATIO * 2683 ftlb

STALL THRUST a STALL TORQUE / STEM THREAD FACTOR 110666 lb

MAX. ALL., ACTUATOR STALL THRUST * 112500 lb

H/W PULL= 2 x STEM TORQUE /(HWRATIO x UNITEFF. x HWDIA.x ADDGEAR x EFF.) 179 lb

MAX.TORQUE SWITCH SETTING e RED.VOLT.=MOT.TORQUE x P/O EFF. x APP.FACT. x 1504.31 ftlb

MAX. H/W TORQUE = MAX. VALVE TORQUE / (H/W RATIO x UNITEFF.) - 39.46 ftlb

OPERATING TIME (60 x LIFT) / STEM SPEED * 41.28 sec

SMB.- 1 E - ACTUATOR - 40 ftib MOTOR MOTOR MAX.THRUST= 45000 lb

MAX. STEM TORQUE e50 ftlb ADDITIONAL GEAR : no MAX.STEM DIA.= 2.750 in

H/W RATIO - 25.3:sl PADD.6/RATIO= 1.00 s O/A RATIO RANGE 42.5-88.40

CURRENT SUPPLY: -460 VOLT STD.H/WHEEL: 12 in MUST OPERAT RED.V O.SO

TYPE: AC/3/60 HZ OVERSIZED H/WHEEL : no

BEVEL GEAR ACTUATOR DIRECTLY MOUNTED ONTO VALVEi no MAX.ALLOW.THRUST: lb

ACTUATOR MODEL: RATIO: MAX.STEfM: MAX.ALLOW.TORQUE: ftlb

REV. 0 REV.1 REV.2 REV.3

COMPILED BY:

APPROVED BYs

IND.REV. BY:

D-3
MOTOR Or:?MA7C' :07O:

|?. O. vo0. c-7. nro_-,-CT:_ E . G .,":.

VC..~-: C N . X; : 1Xe

\\as~~ sau -E1 6 go s. G> _

-

- ;D-:C. NO. :

o.:- . . D -.-. : * 5-18 a8 A.-m.o-k: 21.14"

S =-.' -A A. 1.75 gR_%;, 2.404

7--?rSS: 16;0 _ tS:

t? 16io ?S' 6 .-- t~~~~~~8

.,7: 1/4 ?' 11 .-!. os 77 . 7/ /8

I

i~~~~u,~~d _- sz5,- 20.A. : x = : ~;.....21.14 x ; 1650 C) 03

LM;S ?.Z:SS. x S.^ 16i0 >:2.404 . t~~~~~acki'-. 74c.' colC Load

SS -^V *0;>' S-ERZET. x SS-- :FAC7. 1 °558 x0Q1391q

OJ/, 07 1=-.; _ , 71 . M370N, _e G . '. 1 700 -

si SP= ----- 12.157

4-.--&D L:-MD 1-/ 4

..

1 0643

3967

1 0:>;8

77? 1

-4

34. 96

ImooO.0- CA' C. oiqvs --

Ie1-.I- . ,-0?t0

I...' 0._.. X AZ-?. 7-AC7. ;;0/ '.=

272

0. 4 = 0. 9 x 34. 56 21.61 , l

,X70- 'r CZC. T0R0UE e .-=DUC=- Vo_-.TAC_ - C

IST; :3 C .q_; Z h VI. ST A-1 L T OR~u x ST._. T r . : 0/A. R..,0

II 1XDG-G m 29.6 x0.55 x 34.96 . 1.21

!--v-- x ~2 r. STM TJO-,0jZ Z_ 2 2'f2

~~~-il'4 FA7*10; x^ .. ai X>_:- 7 / v3- 21.1 x, 0.3 7: I

=689 -'v

a 86 e

~~~~~~~~1,.0T. TO.Q -t bNQ:l0. ,Q-x ?lO _ Al-?. FAC70R x O/A .w-

|(C-= *'O:-.G_) 2 -- 0.4 x0 ,9 * x34;96 3t;5 t

c ?W A7 0O x Po

= 21 J X 0.3 ~'° '

!°^--.T!.7'NG I.M. = (60 o_% * s S?Z-D 29 smconn. (APPROX.)

I

|SM3 0~0 '^ p mom0?. *.t 7.''J. mU'r: -24,000 ..... n

9.a 7.QV-r S. OO.L:X 0/1. 0 r.'.1 7...................... U);C- r 26.4 -150.8

|-/'¢ r; 0 21.1 :1 ADD C:X __ n .v,. Se,{- ZI.:' 2 318

_ _ 1 0 7RzV. J1 2 3 i S 6

' I nE CC._._v J _

D-4
APPENDIX E

PHASE I AND 11 INSTRUMENTATION DIAGRAMS AND ACCURACIES

E-1
PHASE I

. -I

, 11

. -1%

'. . .- - I

. .-  r

FIGURE 1. SYSTEM. .- .

S . A

SCHEMATIC

E-3
PHASE I

TABLE I I

INSTRUMENTATION REQUIEMENTS

P I

P3

PI

*17

.1.

T 4

ST

'3

El

7

51*

TS9

TS

System Water Pressure

Valve Upstream Pressure

Valve Downstream Pressure

Discharge Section Pressure

Flow rate

Test Valve

System Temperature

Test Valve Water Temoerature

Test Valve Temperature

Water Heater Temperature

Load Cell Temperature

Valve Stroke - LVDT/Potentiometer

Actuator Current

Actuator Current

Actualor Current

Actuator Voltage

Actuator Voltage

Aclderat1c

Actuator Force

Open Limit Switch

Clsed Limit Switch

Closed Torque Switch

ctr Speed

0-2500 psig

0-250o psig

0-2500 psig

0-2500 psig

0-500 in. wMater

0-2500 psid

0iOO0°r

0-60007

0-oiGOOF

0--600 0F

0-6 inches

0-15 amps

0*-15 amos

0-15 ames

0-480 VAC

0-480 VAC

0-1000 G's

0-40,G00 lbs.

on/oif

tih

on/:0 R

0-o50 RPM^,

E-4
PHASE I

iNxS j nUMENTAT^ICNI T ,E _._rPMENT e:___7,

.:.Tr. 04/20/is

- T:NICIAN: j. XlE!HY

"waS mr:a~:*0;

QCUSIMERI E.J. & ,,

.cr.Z ,;EA: :.'n;V inc

M{E -?TIFICA7= MI| 

.:. 'NS NLST .. .... .=A~iCAME? X . $ WIAL I ;YLE I !'-5ic: pr~wa./ :U. *,,2S;~

i .DATAEcm. - U.^

FF.-r CwD NYTIMICS

t 3IXTR il Tc-XTRUNIS

3 P6l SUPPLY - TEKTRONII

9 05CIIlOSCPE TEXTMhNI

:0 i6 CMMITI0MER VISHAY

11 Si CONDITIO.NER Vl.SAY 7

:2) S5 CoN.Nl~io.^E V S-4 I

i4 i; r D2s. l,,

5 3Cn. SUPPLY V IiSRY

t., -tF :i;4,ES -MUC=/

A w.1MA :Hi;RE - czliCO

:? 4sPP -i~;GE EDED-VC0

i._ S ::2n . _LV01. 

:S ;PL i.AnEE MDMaCC

20 ;tPL CA;Gz E liCD

;M PL AS2EE-_, 20FiMt

22 011WL GiARM ; :4DEVCO.

23 O.MPL CARGEE -- cllC0

2, PWR SUJPPLY V=DX

25 AMP ;i4Lv0 .SENELL :

E5' AX!PL GALYOC .. wemuL

n2 APLt Gi;LYO iOEWE

29 FILME BP iWCXLAM

;° SC.Lgo'nAi4 C' M

30 2EORD WAE :_BML5H~lEL

_V RE;ORD TAPE BESLWL .

i2 0EWE RES 1E

33 AC BRUEL I KJAER

3; NcE i- - :t SIJAER

Zs ACCQ :Rl.EL I Kt.;lEU

AM BRM Ias vina

AC=E L3 !ie X9JAERI

Ua rz S§REIQ S iJAE

.-a01 !413l2 .42.17 0.0.4IH-1MIH *:

;5'03A B054-101 101195 CIO=C . ;ES

212 iZ603341 IO0!S; ^r_!C.(H^Z ,%

-,C^ e Mao: iv's, s

2110 * 07/293i 4l4-;-SJC-t-'Ga .z.s 2! am^:' sme az U 

V255 F.4 93 3 0. -0.5.is.

27s2! ..XO9 .:0;2!!X. ~ _.'2!3 ii63 =37 1 -(iZ.r

?21723 V9s.7 300;5i9 I-IOKZ , - S. % F

Z?2191 3R41 000471 I'-!OKH4Z . -5$F

.4UlA hB41 j * - 34°3 IWVC- --. SRa

Ior'N5 1618 - , -0945t' DC TO S .XNZ If

T6i;SO HIC4371 ! 0.1M :dC TO r ;(!l ;

Ti~h50 1001 - *- 096%1 DC TO S Aii -- :

SM-)l !2 9607 .- '0414 EC-.O.O kF1 ~ ;L,

.iR30OO 1.1012 !0l'567 . .0".tH 2% 4010 ft100 011199 CXr>M4l _!$L2

4010- - i OtI43il* .!DBBV ,!:l

t'S-2DI -_-00748 .. . 100748 1-!0.4 t2H . . :

436i '1104940 !Ola! SK ;RSVtE ;i M

43ei It 1104945 WimsO -'9M rzx/5 X

5F4j 10949 i,- 101767 '-yGXVlrGX -%

6;ai* ::4942 -!OI1si9 at~osV/M;z-A L'_

4Uu ' 1104837 -!11 I; St25V/ntGVX,' r

4B 11431 l 1.016 I t O ui Ofi; XS/G;

ovotfaa %;-'^5ca

.,4 .: ^. -t

I'!4;lB I : C/t

04/05/i& 09/2_Oi 3

Ic/:'/e7 ;Cz6o2eM

lW02.1J2a :5/.i !2 

1*021133 0.-C!

o4/tL_,Jl3 IciS#S

0 /02;is 3 0;o. 5 /sa

04/0c130 09/cS/89

04/02/88 Oaq/22/sa~

trtiO4/68 :W/c46/as

/i04. '3 09Cr6/ ^3/S8

04104t/58 7iH

04/04/81 8 /1S

04/04/as ,7-V0::ss

0)-/t233/87 0/911/8d

04/06;28 *.77/05188

04/0;/ct8 0,1oTic6

05/06il!9 07.7?J.1/6

-.410618 07O-/0S168 la .

HIS I'S TO CERTIFY THAT THEC hABM IttMSThUEIZ WmCAE I I~39T .'; xr_-O-. _.nN~'wtxit;in5;?_>'gf.Y,

.npsAS At TO 7Er NATIM:AL BRJEAU CFf :AWAUS c

, x - NTATIN "'61 .116, ".el

.1 P=P RE.I *;;A /?x~z,,* 14 vt 'Sy 

-E-5
PHASE II

m

I -.*- 2 4D

I~~~~~I

.. P

l~~~~~~~~

El E~~~~l

El a

F V

FIgure 5. Valb

>+ LaLgond

Acceleromrners (Itlaxial measurements)

___--*-*-- Strain gauges.

PieSsmel (5static)

El Pressure (dynamic)

W Temperature

[EAP

E] Valve position

2@ Valve current

lWi Valve voltage

E]i Torque spring (delliecion

W Slain force (strain gages)

W Motor speed

iS Mass flow

Si Measuremenis In pipe diameter EiIIE L.

IEl

ie and piping instrumentation.

., I ! I A
Wm

1. ! I .", : I ' :

.I !- - - , .; I !; ! ' .'

PHASE II

Waler lank

!4 .. , I

. From

lip '. '

bo~lcr.

- Inlemodlailo

, lank ',

.. f.I .. I

i

, ;   , -; 1, 

22 m3 In. and.

Design pressure: 160 bar (2321 psi) Condetisltion

pool

Figure 3.

Legend Is

Simplified diagram of KWU 6-In. valve test loop, showing configuration, lengths, and piping sizes. shown in.-Figure 5.
PHASE II

Waler lank

'I

Condensallol

pool

Design pressure: 116 bar (1682 psi)

II

figure 4. Simplified diagram of KWU 10-en. valve test loop, showing configuration, lengths, and pipe sizes.

Legend is shown in Figure 5.

! - 1~~~~~~~~~~~~~~~~~~~~~~~~~~
PHASE II INSTRUMENTATION ACCURACY

Chan.

ID Measurement Description

Full

Scale Accuracy Error. Units , ________ -------- -------- -------- -----

Comnents

CHAN 0 Bonnet Fluid Temperature

CHAN 1 Shadow Fluid Temperature

CHAN 2 Under Disc Fluid Temperature

CHAN 3 Upstream 4D Fluid Temperature

CHAN 4 Upstream 2D Fluid Temperature

CHAN 5 Downstream 20 Fluid Temperature

CHAN 6 Downstream 40 Fluid Temperature

CHAN 7 Valve Body Surface Temperature

CHAH1S Thermocouple Reference Temperature

CHAH16 Motor Current. I1

CHAN17 Motor Current. 12

CHANI8 Rotor Current. 13

CHAN19 Motor Voltage. L1-L2

CHANZO Motor Voltage. 12-13

__,

20 0.14%

20 0.09%

20 0.12%

575 0.09%

575 0.10%

10 deg F

10 deg F

10 deg F

10 deg F

10 deg F

10 deg F

--10 deg F

10 deg F

10 deg F

Steady State (Transient - Ref. Only)

Steady State (Transient - Ref. Only)

Steady Stite (Transient - Ref. Only)

Steady State (Transient - Ref. Only)

Steady State (Transient - Ref. Only)

Steady State (Transient - Ref. Only)

Steady State (Transient - Ref. Only)

Steady State (Transient - Ref. Only)

0.03 Amp

0.02 Amp

0.02 Amp

0.52 Volt

0.58 Volt

CHAN21 XWU Accumulator Static Pressure

CHAN22 KWU Upstream Dynamic Pressure

CHAN23 KWU Upstream Static Pressure

CHAN24 KWU Flowmeter Static Pressure

CHAN25 KWU Flowmeter DP A

CHAN26 KWU Flowmeter OP B

_- Psia

-- Psid _- Psia

_- Psia

-- Paid -- Psid

Reference Only (less than 2%)

Reference Only (less than 2%)

Reference Only (less than 2%)

Reference Only (less than 2%)

Reference Only (less than 2%)

Reference Only (less than 2%)

CHAN27 Rotor Speed 1000 0.11% 1.10 Hz Converted to RPM (Valve Specific)

CHAN28 KVU Downstream Dynamic Pressure

CHAN29 KWU Downstream Static Pressure

-- -- -- Psid Reference Only (less than 2%)

-- -- -- Psla Reference Only (less than 2%)

CHAN30 Limit Switches

CHAN31 Closed Torque Switch

CHAR32 Stem Force

CHAN33 Bonnet Static Pressure

CHAN34 Shadow Static Pressure

CHAH3S Under Disc Static Pressure

CHAN36 Upstream 4D Static Pressure

CHAX37 Upstream 2D Static Pressure

CHAN38 Downstream 20 Static Pressure

CHAX39 Downstream 40 Static Pressure

CHAN40 Upstream 40 Dynamic Pressure

CHAN41 Upstream 2D Dynamic Pressure

CHAN42 Downstream 20 Dynamic Pressure

CHAN43 Downstream 40 Dynamic Pressure

CHAN44 40 Valve Differential Pressure

CHAH45 2D Valve Differential Pressure

40000 0.40% 160 Lbs

3000

2000

2000

2000

2000

2000

2000

1000

1000

2000

2000

2000

2000

0.50%

0.50%

0.50%

0.50%

0.50%

0.50%

0.50%

0.50%

0.50%

0.50%

0.50%

0. 50%

0.50%

15 Psla

10 Psil

10 Psia

10 Psia

10 Psi&

10 Psia

10 Psia

5 Psid

5 Psid

10 Psid

10 Psid

10 Psid

* 10 Psid

CHANS2 KWU Accumulator Temperature

CHANS3 KWU Upstream Fluid Temperature

CHANS4 KYU Flowmeter Fluid Temperature

CHANS5 KWU Downstream Fluid Temperature

deg

deg

deg

deg

F

F

F

F

Reference Only (less than 3 deg K)

Reference Only (less than 3 deg K)

Reference Only (less than 3 deg K)

Reference Only (less than 3 deg K)

/

.. E-9
-tI I.

PHASE II INSTRUMENTATION ACCURACY

Chan.

ID Measurement Description

'CHANS6 Stem Force. General Physics

CHAN64 Valve Stem Position

CHAN65 Spring Pack Oeinlec~t10n

CHAN69 Valve Body Acceleration, X

CHAN70 Valve Body Acceleration,. Y

CHAN7I Valve Body Acceleration.' Z

CHAN72 Motor Operator Acceleration, X

CHAN73 Motor Operator Acceleration, Y

CHAN74 Motor Operator Acceleration. Z

Full

Scale Accuracy Error Units

Validated Against CHAN32 Lbs

5 0.32X 0.02 Inch

0.75 O.SOX 0.004 Inch

Comments

(Refer to Manufacturer for Actual)

-- -- -- g~~

-- -- -- g~~

-- -- -- g

-- -- -- g~~

-- -- -- g~~

Reference Only

Reference Only

Reference Only

Reference Only

Reference Only

Reference Only

N-1

E-10 */. i;'

d, .