NUREG/CR-5515

ETEC 88-01

Light Water Reactor

Pressure Isolation Valve

Performance Testing

Prepared by H. H. Neely, N. M. Jeanmougn, J. J. Corugedo

Energy Technology Engineering Testing

Prepared for

U.S. Nuclear Regulatory Commission

I

---. dM1MMMMww=
.

AVAILABIUTY NOTICE

Avalability of Reference Materials Cited in NRC Publications

Most documents cited In NRC publications will be available from one of the following sources:

1. The NRC Pubic Document Room. 2120 L Street. NW. Lower Level, Washington. DC 20555

2. The Superintendent of Documents. U.S. Government Printing Office. P.O. Box 37082. Washington,

DC 20013-7082

3. The National Technical Information Service. Springfield, VA 22161

Although the Isting that follows represents the majority of documents cited In NRC publikatlons, It Is not

Intended to be exhaustive.

Referenced documents available for Inspection and copying for a fee from the NRC Public Document Room

Include NRC correspondence and Internal NRC memoranda: NRC Office of Inspection and Enforcement

bufletins, circulars, Information notices, Inspection and Investigation notices; Ucensee Event Reports; vendor reports and correspondence; Commission papers: and applicant and licensee documents and correspondence.

The following documents In the NUREG series are available for purchase from the GPO Sales Program:

formal NRC staff and contractor reports. NRC-sponsored conference proceedings, and NRC booklets and

brochures. Also avallable are Regulatory Guides, NRC regulations In the Code of Federal Regulations, and

Nuclear Regulatory Commission Issuances.

Documents available from the National Technical Information Service Include NUREG series reports and

technical reports prepared by other federal agencies and reports prepared by the Atomic Energy Commisslon, forerunner agency to the Nuclear Regulatory Comnmisslon.

Documents available from public and special technical libraries include. all open literature Items, such as

books, Journal and periodical articles, and transactions. Federal Register notices, federal and state legislatlon. and congressional reports can usually be obtained from these libraries.

Documents such as theses, dissertations, foreign reports and translations. and non-NRC conference proceedings are available for purchase from the organization sponsoring the pubilcation cited.

Single copies of NRC draft reports are available free, to the extent of supply, upon written request to the

Office of Information Resources Management, Distribution Section, U.S. Nuclear Regulatory Conmrission,

Washington, DC 20555.

Copies of Industry codes and standards used hI a substantive manner In the NRC regulatory process are

maintained at the NRC LUbrary. 7920 Norfolk Avenue, Bethesda, Maryland, and are available there for reference use by the public. Codes and standards are usually copyrighted and may be purchased from the

originating organization or. If they are American National Standards, from the American National Standards

Institute, 1430 Broadway, New York, NY 10018.

DISCLAIMER 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 thereo, or any of their employees, makes any warranty,

expresed or Implied, or assumes any legal liability of 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,
NUREG/CR-5515

ETEC 88-01

RM

- - - - -- - - -- - -- - - - - - - -

Light Water Reactor

Pressure Isolation Valve

Performance Testing

Manuscript Completed: May 1990

Date Published: July 1990

Prepared by

H. H. Neely, N. M. Jeanmougin, J. J. Corugedo

Energy Technology Engineering Center

P. 0. Box 1449

Canoga Park, CA 91304

Prepared for

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

NRC FIN B3050
Abstract

The Light Water Reactor Valve Performance Testing Program was initiated by

the NRC to evaluate leakage as an indication of valve condition, provide

input to Section XI of the ASME Code, evaluate emission monitoring for

condition and degradation and in-service inspection techniques.. Six

typical check and gate valves were purchased for testing at typical plant:

conditions (550F at 2250 psig) for an assumed number of cycles for a

40-year plant lifetime. Tests revealed that there were variances between

the test results and the present statement of. the Code; however, the

testing was not conclusive. The lifecycle tests showed that high tech

acoustic emission can be utilized to trend small-leaks, that-specific motor

signature measurement on gate valves can trend and indicate potential

failure, and that in-service inspection techniques for check valves was

shown to be both feasible and an excellent preventive maintenance indicator.

Lifecycle testing performed here did not cause large valve leakage typical

of some plant operation. Other testing is required to fully understand the

implication of these results and the required-program to fully implement

them.

iii
TABLE OF CONTENTS

EXECUTIVE SUMMARY . . . ......... . . . . . . . . . . ..... ix

1.0 INTRODUCTION . . . ................

1.1 Background . . . . . . . . . . . . . . . . 1.2 Objectives .. .............. 1.3 Technical Approach . . . . . . . . . . . .

2.0 TEST DESCRIPTION . . . . . . . . . . . . . . . . .

2.1 Test Valves . . . . . . . . . . . . . . . . 2.2 Test Program Logic and Description . . . . 2.3 Leak Rate Test Matrices . . . . . . . . . .

I

1

2

2

7

7

12

17

3.0 TEST RESULTS . . ... . . . . . . . . . . . . .

3.1 Leakage as an Indicator of Valve Condition . . . . .

3.2 ASME Correlation.. . . . . . ..

3.3 Acoustic Emission Monitoringn

3.4 Gate Valve Motor Signature Monitoring . . . . . . . . . . . . 3.5 Check Valve Visual In-Service Inspection (ISI)

4.0 CONCLUSIONS AND REFERENCES ..................... 4.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .

19

19

21

23

24

25

27

27

APPENDICES

A TEST FACILITIES AND INSTRUMENTATION . . . . A.1 Large Leak Test Rig . . . . . . . . . A.1.2 Instrumentation . . . . . . . . . ..

B TEST DATA

B.1 Check Valve Leak Rate Tests . . . . .

B.2 Gate Valve Leak Rate Tests . . . . .

B.3 Gate Valve Motor Signature Testing . B.4 Acoustic Emission Monitoring . . . .

. . . . .

. . . . .

. . . . .

29

29

30

37

44

47

58

TABLES

1. Description of Westinghouse 4-in. Gate Valve

SBD-OO Motor Operator . . . . . . . . . . .

with Limitorque . . . . . a . . . 6 . .

2. Description of-the Westinghouse 10-in. Gate Valve with

Limitorque SBD-3 Motor Operator . . . . . . . . . . . . . .

3. Description of W-K-M 4-IN Gate Valve with Limitorque SB-OOS

Motor Operator . . . . . . . . . . . . . . . . . . . .

4. Typical Leak Test Matrix . . . . . . . . . . .. 5. Loosened Internals Leak Test Matrix . . . . . . . . . 6. Test Facility Design Parameters . . . . . . . . . . . . . .

7. Computer Valve Sequencing for Check Valves . . . . . . . . .

9

. . . . 10

11

14

16

29

31

v
TABLES

8; Computer Valve Sequencing for Gate Valves . . . . . . . . . . . . . 31

9. Instrumentation - Loosened Internals. . . . . . . . . . . ... . . . . 35

10. Post Life Cycling Motor Signature Tests . . . . . . . . . . . . . . . 49

11. Motor Signature Tests 4-inch Westinghouse Gate Valve . . . . . . . . 50

12. 4-in W Motor Signature Tests . . . . . . . . . . . . . . . . . . . . 53

FIGURES

1. Four-Inch Check Valve Internals . . . . . . . . . . . . . . . . . 60

2. Test Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

3. Check Valves--Leak Rate Versus Life Cycling . . . . . . . . . . . . 62

4. Gate Valves--Leak Rate Versus Life Cycling . . . . . . . . . . . . . 62

5. Four-Inch Check Valve Leak Rate Versus Differential Pressure . . . . 63

6. Six-Inch Check Valve Leak Rate Versus Differential Pressure . . . . 63

7. Twelve-Inch Check Valve Leak Rate Versus Differential Pressure . . . 64

8. Four-Inch Westinghouse Gate Valve Leak Rate Versus

Differential Pressure . ... .. . .. . .64 .. 9. Four-Inch W-K-M Gate Valve Leak Rate Versus Differential Pressure . 65

10. Ten-Inch Westinghouse Gate Valve Leak Rate Versus

Differential Pressure . . 65

11. Four-Inch Check Valve Leak Rate Versus Temperature. . . 66

12. Gate Valves Leak Rate Versus Temperature . . . . . . . . . . . . . . 66

13. Four-Inch Westinghouse Gate Valve Leak Rate Versus Density . . . . . 67

14. Acoustic Emission High Sensitivity and Standard Leak Measurements -- Four-Inch Gate Valve Post Life Cycles . . . . . . . . . . . . . . . 67

15. Standard Acoustic Emission Trace -- Four Inch Gage . . . . . . . . . 68

16. Fourier Analysis of Acoustic Data -- Baseline . . . . . . . . . . . 68

17. Fourier Analysis of Acoustic Data Internals Loosened (2 turns) . . . 69

18. Fourier Analysis of Acoustic Data Internals Loosened (4 turns) . . . 69

19. Fourier Analysis of Acoustic Data Comparison of Results . . . . . . 70

20. LLTR Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

21. Check Valve Installed In LLTR . . ... . . . . . . . . . . . . . . . 72

22. LLTR Control Room . . . .72

23. LLTR Data Acquisition System ...... . ..... . 73

24. Three-Element Strain Gage to Measure Stem Force . . . . 73

25. Open Position Bifurcated Fiber Optic Device . . . . . . . . . . . . 74

26. Close Position Bifurcated Optic Device . . . . . . . . . . . . . . . 74

27. Characteristics of Various Fiber Optic Devices . . . . . . . . . . . 75

28. Four-Inch Check Valve Flow Test Setup . . . . . . . . . . . . . . . 75

29. Four-Inch Check Valve Stud After Life-Cycling . . . . . . . . . . . 76

30. Four-Inch Check Valve Bonnet After Life-Cycling . . . . . . . . . . 76

31. Flowrate Versus Time -- Internals As-Received . . . . . . . . . . . 77

32. Narrow Band Acoustic Signal Internals As-Received . . . . . . . . . 77

33. ETEC 10 kHz Acoustic Signal Internals As-Received . . . . . . . . . 78

34. Flowrate Versus Time Loose Internals (2 turns) . . . . . . . . . . . 78

vi
FIGURES

35. Narrow Band Acoustic Signal Loose Internals (2 turns) . . . . .. . 79

36. ETEC 20 kHz Acoustic Signal Loose Internals (2?turns) .' . . . 79

37. Flowrate Versus Time Loose Internals (4'turns). . . .'.'. .'. . . . . 80

38. Narrow Band Acoustic Signal Loose Internals (4 turns) . . . . . 80

39. ETEC 20 kHz Acoustic Signal Loose Internails (4 turns) . . . . .. 81

40. Four-Inch Check Valve Videoprobe Inspection v. .. . .' . .: . . . . 81

41. Four-Inch Check Valve In-Service Inspection--Clapper Stud Assembly . 82

42. Four-Inch Check Valve In-Service Inspection--Clapper Pin Area . . . 82

43. Six-Inch Check Valve Internals . . . . . . . . ..... . . . . . . . . 83

44. Six-Inch Check Valve In-Service Inspection'-- Clapper Stud . . . . 83

45. Six-Inch Valve In-Service Inspection Clapper Pin Area . . . . . 84

46. Twelve-Inch Check Valve Internls . . . .. . ... . . . . 84

47. Ten-Inch Gate Valve With Motor Signature Instrumentation .85

48. Motor Signature Test Four Motor Current Versus Tlime . . . . . . . 85

49. Motor Signature Test Four 'Stem Force Versus 'Time. 86

50. Motor Signature Test four Rotation of'Torque Switch"Versus Time . 86

51. Motor Signature Test Four Valve Stem Velocity'Versus Time .'. .'.. 87

52. Motor Signature Test Four Motor Vibration Versus Time . . .. . . . 87

53. Motor Signature Test Three Stem Force Versus Time' . ... .'. . . . 88

54. Motor Signature Test Three'Rotation of Torque Switch VersusjTime .. 88

55. Motor Signature Test Three Stem Velocity Versus Time . . ... . . . 89

56. Four-Inch Gate Valve -- Motor Current Versus Packing

Torque, Valve Opening & Closing . . . ... . . . . 89

57. W Four-Inch Gate Valve'-- Closing Force Versus Packing

Torque, Various Pressures .. 90

58. Ten-Inch Gate Valve -- Rotation of Torque Switch of '300%.

Packing Torque . . . . . .. . .. . ... 90

59. Four-Inch Gate Valve -- Motor Current Versus Closing Force,

Various Pressures .. . . ';.. . ..;. . . . . . . . . . . 91

60. Ten-Inch Gate Valve Motor Current for Initial Dry'Cycles . . . . . 91

61. Ten-Inch Gate Valve Stem Force for Initi'al Dry Cycles . . . . . 92

62. Ten-Inch Gate Valve -- Motor Vibration for Iitial Cycles " . . . 92

63. Ten-Inch Gate Valve Motor Current for Initial 24 Wet Cycles . .. ' 93

64. Ten-Inch Gate Valve Fiber Optic Close Position for'!

Initial 24 Wet Cycles ... . . . .I . . . . 93

65. Ten-Inch Gate Valve Stem Force for'Initial 24 Wet'Cycles . . .'. . 94

66. Ten-Inch Gate Valve Rotation ofCTdrque Switch for

Initial 24 Wet Cycles . . . . '; . . .. ... . . . . . . . 94

67. Ten-Inch Gate Valve -- 'IncreasingMotor'Temperature and

Valve Stem Temperature During Wet Cycling . . .95

68. Ten-Inch Gate Valve Motor Current for 150 24 Wet-Cycles: ... . . . . 95

69. Ten-Inch Gate Valve Stem"Force for'150 24 Wet Cycles .. . . . . . 96

70. Ten-Inch Gate Valve Fiber Optic Close Po'sition for 150 Wet Cycles 96

71. Ten-Inch Gate Valve Stem'lrorce'During 13 of A150 Wet Cycles . . . . 97

72. Ten-Inch Gate Valve-Motor Current Du~iig 13fof! 150 Wet-Cycles . . 97

73. Ten-Inch Gate Valve Vibration During 13 of 150 Wbt Cycl'es . . . 98

vii
FIGURES

Page

74. Ten-Inch Gate Valve Opening & Closing Motor Current

Versus Packing Torque ...................... . 99

75. Ten-Inch Gate Valve Motor Current after Cycles, at 400F . . . . . . . 99

76. Ten-Inch Gate Valve Stem Force for Cycles at 400F . . . . . . . . . 99

77. Ten-Inch Gate Valve Fiber Optic Close Position for Cycles at 400F 99

78. Ten-Inch Gate Valve Rotation of Torque Switch for Cycles at 400F 100

79. Ten-Inch Gate Valve Stem Force at 400F and 300% Packing Torque . . . 101

80. Ten-Inch Gate Valve Closing Stem Force Versus Packing Torque . . . . 101

81. Acoustic Emission Sensors Installed on Bonnet of Check Valve . . . . 102

82. Acoustic Emission Sensors Installed Upstream on Pipe . . . . . . . . 102

viii
EXECUTIVE SUMMARY

The NRC requires nuclear power plant owners to periodically verify

pressure barriers in systems adjacent to the Reactor Coolant System. This is

usually accomplished through leak testing of two valves at each interface.

These in-service tests are intended to demonstrate the pressure retaining

capability of the valves, and to identify leakage caused by valve degradation

before it reaches hazardous levels.

It was found that the extrapolation of leakage data from previous

reduced pressure tests is potentially in error. Accordingly, recommendations

were made for revisions to existing leak acceptance criteria and for

performance of actual confirmatory valve leak test rates. With this in mind,

the objectives of this program were to:

1) Validate the theoretical work performed to upgrade leakage

criteria,

2) Evaluate the effectiveness of valve leakage as an indication of

valve degradation, and

3) Examine other valve parameters and their effects on valve

operability.

Test articles used for this program included:

* Three Swing Check Valves

* 4-inch disk

* 6-inch disk

* 12-inch disk

* Three Gate Valves

* 4-inch double disk

* 4-inch flexible wedge

* 10-inch flexible wedge.

The test program consisted of:

1) Life-cycle aging at typical temperatures and pressures to assess

leak degradation,

2) Acoustic emission evaluations and motor signature monitoring to

assess leakage and degradation, and

3) Loosened internals testing to correlate degradation with typical

valve failures.

ix
Test results indicated the following:

Validation of Theoretical Work

* ASME Code correlations were-not, acceptable for predicting leak

rates,. In-general, they underestimated flow. rates.

Indication of Valve- Degradation

* Visual ISI (e.g., video probe) is effective for establishing

check valve internal conditions.

* .VWalve seating surfaces were not damaged from wear as a result

of repented cycling.

.- Standard acoustic emission systems could not be used reliably

for predicting.leak rates less than 0.3 gpm; however,

high-sensitivity AE systems were successfully used.

Parameters Effecting Valve Operability

* Neither leak rate testing or acoustic monitoring is effective

for indicating check valve loosened internals and impending

failure.

* Leak rate testing is anmeffective method for determining the.

immediate status of the pressure barrier.

''* Motor signature monitoring was useful for indicating operator

malfunctions-'-a major cause of MOV failure.

Although the results of the testing did not substantiate ASME Code

correlations, the cause for deviation was never established. Therefore, the

validity of Code correlations could not be confirmed. The tests demonstrated

that the current methodologies and equipment employed in this program could

not adequately measure or predict imminent valve failure. Further.

investigations are needed to fully understand the degradation mechanisms so

that new, successful techniques can be developed. The test program was

performed during the period from FY85 to late 1987.

x
1.0 INTRODUCTION

1.1 Background

Nuclear power plants typically determine isolation valve'intersystem integrity by monitoring leak rates. To examine the.validity of this

practice, the Nuclear Regulatory Commission (NRC):sponsored a-survey of nine

utilities to examine their leak rate testing methods 'and to find how'such

tests were used to infer the extent of valve degradation. The.results,

documented' in Reference 1, indicated that current utility practice is to leak

test at reduced differential pressures and-extrapolate to nominal operating conditions using a correlation given in Section XI of'the 'ASMECode. This

correlation is theoretically correct for turbulent flow if.temperature

effects are ignored, however, analysis of the survey data.indicated'that the

correlation is potentially in error for laminar leakage flow across valve

seating 'surfaces. Accordingly, a test program was recommended to validate

the analytical work performed and to evaluate the l.eak test methods.

In November of 1983, NRC requested proposals for a Valve Performance Test Program to "validate the theoretical 'work.performed during the

survey of the nine utilities, to-evaluate the effectiveness of-valve leakage

as an indicator of valve degradation, and'to examine other valve parameters and their effects on valve operability." The Energy Technology Engineering

Center (ETEC) was awarded the Valve Performance.Test Program in'fiscal year

1984. Check valve performance testing started. in April 1985, followed by

gate valve testing which terminated in August 1987.'

The Valve Performance Test Program incorporates leak rate testing

of valves typical of those used for pressure isolation of.the primary coolant

system in a light water reactor plant. Pressure isolation valves (PIVs)

isolate the high pressure primary reactor coolant system from connected lower

pressure systems. Commercial nuclear power plants are required to periodically leak test PIns'in'accordance with Section XI of the ASME Boiler &

Pressure-Vessel Code. 'The acceptable leak-rate across the PIVs-is defined in

the technical specifications for each'plant 'and,.therefore, the acceptable

PIV leak rate can vary among'plants. However,.in'general the`NRC allows a

leakage rate of one-half gpm (0.052 lb/sec at 2250'psi-and'550F)'per inch of

nominal valve diameter, but no more than five gpm (0.52 lb/sec at 2250 psia

and 550F) on any valve.

Leakage through the PIVs is monitored and limited'for three safety

reasons. First, leak rates are monitored'to determine'whether the pressure barrier exists, that is whether the valve is fully seated. Second, leak rate

monitoring is used to detect imminent failureof the valves'.ability to serve

as a pressure barrier. And third, the overall leak rate from the high

pressure system to the low pressure system must not'exceed the low pressure

system's pressure relief and radiological.processing capabilities. Therefore, the leak rate monitoring is intended to identify leakage caused by

valve degradation before ittreaches a hazardous level.:,

.K
1.2 ObJectives

The objectives of the Valve Performance Test Program were modified

during the course of the program as the initial test results were evaluated

and the program redirected to address these results. Specifically, the scope

of objective 4 was enlarged to encompass evaluation of acoustic emission

monitoring as a means of detecting loose check valve internals and objective

5 was added. The ultimate objectives were defined as:

1. Evaluate the use of valve leakage as an indicator of valve

condition.

2. Provide the technical basis for NRC recommendations regarding

the ASME Code Section XI method for correlating leak rates at

test and operating pressure differentials.

3. Evaluate the use of motor signature monitoring as a measure of

gate valve operability.

4. Evaluate the use of acoustic emission monitoring for quantifying valve leakage and as an indicator of valve condition.

5. Evaluate the use of visual in-service inspection techniques to

detect check valve degradation.

1.3 Technical Approach

1.3.1 Valve Degradation

A key element of this program is the method by which seat leakage

paths that are representative of those developed by power plant PIVs are

created in the test valves. ETEC's extensive experience with large valves

and consultation with valve suppliers and nuclear utilities led to the Valve

Performance Program test plan which is based upon life cycling of new valves.

Although artificial wear aging of valves does not fully reproduce actual

plant aging, the life cycling approach does impose a plant valve operational

history on the test valves which simulates some of the wear that an average

PIV undergoes during its life.

PIVs typically have hard faced metal to metal seat and disk mating

surfaces. The liak rate for new valves of this type is usually limited to 10

cc/Hr (4.4 x 10 gpm at 550F and 2250 psig) per inch of nominal pipe size.

At the other extreme, seat leakage rates of 1 to 5 gpm for 4-inch to 12-inch

gate and swing check valves are indicative of valve damage resulting from

wear, maintenance, careless handling, entrapment of construction debris,

defective manufacturing and occasionally from unusual piping reaction loads

distorting the valve. Leakage this great would indicate the valve is already

degraded to the point where it must soon be repaired or removed from service.

Leak rates between these two ranges indicate the sealing surfaces

of a valve are being deteriorated. The leak rates in this range are moni2
tored to determine the rate of deterioration and to predict when maintenance

will be required.

A survey of nine nuclear power plants was made to identify how many

cycles a PIV would see in an average plant application. Ten dry cycles (in

air) and 200 wet cycles at plant operating conditions were determined to be

reasonable.

The check valves were dry cycled by pushing the disk open with

pressurized nitrogen. The check valve wet cycles were made by opening an

upstream valve which allowed pressurized water to push the disk open rapidly.

The valve closed as the pressure across the valve equalized. There was no

period of stable or unstable, such as a disk fluttering, flow through the

valve. The percent open obtained by cycling the valve by these methods could

not be accurately determined.

The gate valves were cycled from their fully closed position to

100% open and returned to the fully closed position by the valves' motor

operators. For the wet cycles, one side of the gate valves was pressurized

to 2250 psig while the other side was held at 50 psig prior to valve opening.

The pressure rapidly equalized once the valves began to open. As with the

check valves, there was no sustained flow through the valves. During the dry

cycles, the gate valves were in air atmosphere at ambient pressure.

1.3.2 Leak Rate Testing & Code Correlation

To gain information on the effectiveness of valve leakage as an indicator of valve degradation (objective 1), a series of leak tests were

conducted. The leak rate data also were used to evaluate the Section XI

correlation for extrapolating leak rates at test conditions to leak rates at

nominal plant operating conditions (objective 2). The leak rates were

measured prior to the start of the test program, following the completion of

the'dry cycles, after the first 50 wet cycles, and following completion of

the wet cycling. The leak tests were conducted at a variety of temperature

and pressure conditions ranging from normal plant operating pressure,

2250 psig, down to pressures less than those typically used during power

plant in-service testing, 150 psig. Temperatures ranged from typical operating temperatures, 550F, to ambient.

1.3.3 Motor Signatures

In addition to reported PIY intersystem failures (i.e. excessive

leak rate), other failure modes also are common. Recent events in the Light

Water Reactor (LWR) community illustrate the importance of valve motor

operator and valve internal integrity. Reference 2 presents the operating

experience with valves in LWR safety systems. Among the findings were the

following:

There was strong evidence that valve operating characteristics change with time as a result of maintenance

activity.

3
The selection of equipment, such *as motor operators and

valves, and settings did not appear to address variations in such-operational characteristics as increases in

differential pressure or temperature,, or variations in

process conditions.

The motor-operator signature portion of the Valve Performance

Program addresses these two issues. A common valve maintenance activity is

the adjustment of the packing nut torque. Plant operators frequently increase the torque to prevent or'stop leakage through the packing. Increased

packing tightness can increase the friction during valve stem movement and

thereby increase the operator torque requirement. It was recommended in

Reference 2 that motor signature tracing techniques be developed which would

indicate changes in operability characteristics and predict the remaining

margin to failure.

To address objective 3, evaluating the use of motor signature monitoring as a measure of gate valve operability, the actuators' performance

parameters were measured during the life cycles. Upon completion of these

tests, the packing gland nuts were set at 50%, 200%, and 300% of the torque

specified by the valve manufacturer. At each torque level, additional cycles

were made while the valve position, stem force, velocity, motor vibration,

motor temperature, motor current, torque shaft rotation, and valve limit

switches were monitored. The valves were cycled at various differential

pressure conditions and temperatures. There was no sustained flow through

the valves either before or after the valve cycling so that only wear due to

the stroking itself was reproduced.

1.3.4 Acoustic Emission

Both the check and the gate valves were used to address objective

4, evaluate the use of-acoustic emission (AE) techniques for quantifying

valve leakage and as an indicator of valve condition. AE data were recorded

during the leak rate testing of both the gate and the check valves. For the

check valves, the AE techniques also were employed to determine whether AE

was a reliable means of detecting loosened internals. Four different AE

monitoring systems were installed during the check valve testing. The

systems were supplied by ETEC, Argonne National Laboratory (ANL), Oak Ridge

National Laboratory (ORNL), and the Naval Ship Research & Development Center.

Four systems were used because this program was a unique opportunity to

obtain AE test data which could be used in a number of NRC programs at

minimal costs. The data were given to each of the AE equipment suppliers for

their analysis and incorporation into their NRC-funded work. In response to

the check valve results, an additional narrow-band AE system was procured by

ETEC and installed prior to gate valve testing.

Check valve disk separation from the clapper is a potentially

serious mode of failure which leaves the valve inoperable with its disk, and

other parts such as nuts and washers, free to move through the piping system.

It has been identified as a major cause of check valve failure. Per

4
reference 3, disk separation accounted for 16.5% of the.Licensee Event

Reports (LERs) associated with valve failure, including the.failyre of five

check valves at San Onofre Unit 1 which led toa .lpossof power andwater

hammer event in November of 1985. Disk separation can result because of the

stud impacting the valve body during cycling or improper valve assembly

causes the nut which secures the valve disk to the clapper to become loose,

see Figure 1. During the Valve Performance Program, the disk assembly nuts,

which hold the disk to'the clapper arm, of each of the three check'valves

were loosened, described in detail in Appendix.B. The 12-inch. valve'had a`

second nut, the clevis assembly nut, which suspends the"clapper assembly.

This nut also was'loosened during testing of the 12-inch check valve. Leak':

rate measurements were made with the valve internals loosened to determine

the suitability of leakage measurements as'a means of detecting this impending 'check valve.failure mode (objective 1).' AE traces were, recorded during

loosened internals cycles, as well as during'the leak rate tests to.evaluate.

whether the loosened internals could be detected with typical AE instrumentation.

1.3.5 Visual Inspection

The fifth objective was identified after the initial-check valve.

life cycling and loosened internals testing were completed. Visual inspection using a rigid borescope and a videoprobe were evaluated is-methods of.

detecting check valve degradation, particularly loosened internals and disk

stud damage. A hole was drilled in the valves' bonnet to provide access for

the borescope and videoprobe.

5
2.0 TEST DESCRIPTION

The individual tests which comprise the Valve Performance Program

were formulated to satisfy the program objectives. Since the program was

stretched out over two years, information from previous tests could be

digested and subsequent testing modified to satisfy the program objectives.

This section discusses the test articles; describes each of the

tests; and discusses the development and logic of the test matrices. The

test results are presented in Appendix B.

2.1 Test Valves

The procurement of the six test valves was a major early effort.

The preferred approach was to obtain new valves. The use of new valves which

had no prior service history eliminated uncertainty about the types of wear

or degradation mechanisms to which the valves were exposed. Numerous utilities or their representatives as well as valve manufacturer's were contacted

to obtain the test valves. The test valves, described in the following

paragraphs, were obtained from cancelled LWR plants.

It was more difficult to locate gate valves of the correct size

which were typical of PIVs currently used by nuclear power plants. A number

of gate valves were available from the cancelled Washington Public Power

Service plants, but these gate valves were of a parallel double disk design

which was infrequently installed in early LWRs, although they were often

included in newer LWRs.

Eventually two flexible wedge disk gate valves, a 4-inch and a

10-inch, were located and procured. The flexible disk type of gate valve is

widely installed in LWRs.

To compare a flexible disk and a parallel double disk gate valve of

the same nominal size in terms of valve degradation versus wear, a four-inch

parallel double disk gate valve also was procured.

All six of the test valves were purchased from utilities who had

obtained them from nuclear units which were cancelled subsequent to valve

fabrication or from unit-s which had surplus valves. The majority of the

valves are ASME Section III, Class 1 valves although one is a Class 2 valve.

Class 2 valves are of the same design as the Class 1 valves and thus are

equally representative of LWR PIYs. However, Class 2 valves do not have the

same quality assurance/verification documentation as Class 1 valves. The

test article descriptions are as follows:

1. 4-inch, 1512 lb, swing check valve, buttweld ends, 316 stainless steel body, Stellite hard facing on the seating surfaces,

ASME Section III, Class 1, manufactured by the Nuclear Valve

Division, Borg-Warner Corporation.

7
2. 6-inch, 1500 lb, swing check valve, buttweld ends, 304 stainless steel body, Stellite hard facing on the seating surfaces,

ASME Section 1II, Class 2, manufactured by Atwood & Morrill

Company.

3. 12-inch, 1512 lb, swing check valve, buttweld ends, 316 stainless steel body, Stellite hard facing on the seating surfaces,

ASME Section III,.Class 1, manufactured by the Nuclear Valve

Division, Borg-Warner Corporation.

4. 4-inch, 1600 lb, gate valve, buttweld ends, 316 stainless steel

body, double disk-parallel seat, hardfaced seating surfaces,

electric motor operated (Limitorque), ASME Section III, Class

1, manufactured by ACF Industries, W-K-M Valve Division, Model

M-I-OPG POW-R-SEAL.

5. 4-inch, 1525 lb, gate valve, buttweld ends, 316 stainless steel

body, flexible wedge disk, Stellite hard facing on the seating

surfaces, electric motor operated (Limitorque). ASME Section

III, Class 1, manufactured by Westinghouse (W-EMD).

6. 10-inch, 1525 lb, gate valve, buttweld ends, 316 stainless

steel body, flexible wedge disk, Stellite hard facing on the

seating surfaces', electric motor operated (Limitorque). ASME

Section III, Class 1, manufactured by Westinghouse (W-EMD).

All valves were unused and stored, packaged, and shipped in accordance with ANSI/ASME N45.2.2 requirements. Although some of the utilities

did not have complete operating/maintenance documentation, all drawings,

manuals, and quality records available to the utilities for each valve were

included as part of the valve order. The Limitorque operators, supplied with

the valves, are described in Tables 1 through 3. The characteristics of the

valve and operator are given for analytical calculations of the Motor Operated Valve (MOV) operability.

8
Table 1. Description of Westinghouse

with'Limitorque SBD-00 *Motor

4-in.. Gate:Vilve

Operator

Pressure class:

Design pressure:

Pressure rating:

Differential pressure:

Order number:

Serial number:

1525 ' 2500 psig @065DF

3600 psig ,0AOF

850 close, 2750 open

3A5101E

288202, :

Stem thrust: ' Stem diameter:

Stem threads:

Motor torque: I

Motor speed:

Motor horsepower:

10900 lb.

1.25'inch''

L-1/3 P41/3 . .

15 ft-lb starting,

3400 rpm - :I

1.5hp ' '

3 ft-lb running

Power requirements:

Motor current:

Insulation class:

Duty cycle:' I

Packing material:

3'phase, 60 Hz

3 1/2 A (460 v)

B

15 min

John Crane 187 I1

Recommended packing gland

bolt torque:

Gear teeth:

Overall gear ratio:

27 to'33 'ft-lb -

Motor pinion 40T,'

Worm shaft gear 2ST

Work'gear 45T .

28.2 to l'

*Operator has double compensating spring which does not allow this stem to

float in either direction of travel.

9
Table 2. Description of the Westinghouse 10-in. Gate Valve with

Limitorque SBD-3 *Motor Operator

Pressure class:

Design pressure:

Pressure rating:

Differential pressure (max):

Order number:

Serial number:

Stem diameter:

Motor torque:

Motor speed:

Motor horsepower:

Power requirements:

Motor current:

Insulation class:

Duty cycle:

Packing material:

Recommended packing gland

bolt torque:

1525 lb

2500 psi @ 650F

3812 psi @ 10OF

2700 psid

3A2956F

262957

2.5 inch

150 ft-lb start, 30 t-lb run

3365RPM

19.2 hp

3 Phase 60 Hz

460V, 25.7a

B

15 min.

John Crane 187 I

95 to 105 ft-lb.

*Operator has double compensating spring which does not allow the stem to

float in either direction of travel.

10
Table 3. Description of W-K-M 4-IN Gate Valve with Limitorque SB-OOS

Motor Operator

Pressure class:

Design pressure:

Pressure rating:

Order number:

Serial number:

Model:

Stem diameter:

Motor torque:

Motor speed:

Motor horsepower:

Power requirements:

Motor current:

Insulation class:

Duty cycle:

Packing material:

Internal

Recommended packing gland

bolt torque:

1600

2500 psig @ 650F

3480 psi

3B0671A

259239

M-1 OPG Pow-R-Seal

1.5 inch

1.5 ft-lb start, run 3 ft-lb

3400 RPM

1.33 hp

460.VAC, 3 phase, 60 Hz

3.5 amps running, 26 amps starting

RH

15 min.

1625GF Ext. Rings, Grafiol Gin

30 ft-lb

11
2.2 Test Program Logic and Description

The test logic for a typical valve is shown in Figure 2 for both

check and gate valves. The overall approach for both types of PIVs is

similar. The only difference is that loosened internals tests are applicable only to the check valves and motor signature tests were applicable only

for gate valves. A description of each test is given below; the test numbers

correspond with those shown in Figure 2.

The basic program of life cycling consisted of (a) establishing the

leak rates for the valves in an as-received condition at test conditions

ranging from normal LWR plant operating conditions down to less than normal

inspection test conditions and (b) repeating this series of leak tests after

three periods of valve cycling. This program was geared to provide data for

correlating the leakage versus differential pressure and temperature to

evaluate the ASME Code correlation and to evaluate valve degradation over a

typical plant service life via artificial accelerated wear aging.

1. Pre-Test InsDection and Installation - Following receipt of the

valves, each was visually inspected. The smaller valves,

four-in. and six-inch, were leak tested with nitrogen to verify

their integrity before installation. The larger valves,

ten-inch and twelve-inch, were not leak tested due to the

excessive expense of the leak test for large valves as balanced

against the low probability that the valves would be unacceptable for installation.

2. Baseline Leak Tests - Following installation, the baseline leak

tests were conducted to verify the start-of-life condition of

the test valves. Table 4 is a typical test matrix, at selected

test conditions specified for each valve. The resulting data

was compared to the post-cycle leak rate tests, at the same

temperature and differential pressure conditions, to provide a

measure of the relationship between valve degradation and leak

rate. If extremely low leak rates or no leak rate were

measured during the lower temperature leak test, the elevated

temperature tests were deleted.

Temperature, pressure and leak rate were measured during each

test. Leakage flow was measured by collection/displacement in

a downstream vessel.

Acoustic emission (AE) monitoring was conducted during leak

rate testing to evaluate whether AE is an effective means of

quantitatively measuring leak rates. Four AE systems were

installed on the check valves. The systems were supplied by

ETEC, Argonne National Lab (ANL), Oak Ridge National Lab

(ORNL), and the Naval Ship Research & Development Center. The

Naval Ship Research & Development Center system was a portable

manually operated system and therefore was used less frequently than the other systems. The ETEC, ANL, and ORNL

12
systems each had a transducer installed on the yalve and

another transducer installed on the valve inl'et'pipe.;'

3. Dry Cvclinm. n D 10 - The valves were stroked 1O times ip a

dry, gas environment to simulate valve operation during vendor

checkout, plant construction and start-up. The check valves

were dry cycled by pushing the disk open with pressurized

nitrogen. The motor operators were used to dry stroke the gate

valves.

4. Leak Tests - This series of leak tests duplicated the baseline

leak tests. If significant leak rates were observed, leak

tests at various higher temperatures were conducted. Theobjective of varying the leak rate test temperature was to

determine whether the temperature dependent variables such as

density or viscosity should be included. in the ASME Code

correlation. A typical test matrix is given in Table 4.;-

5. Wet Cycling. n - 50 - The test valves were wet stroked 50 times

in borated water. For the gate valves, full reactor coolant

system pressure was applied to the high pressure side of the

valve with 50 psig on the low pressure side. Stroking was done

with the motor operator. The gate valve'was stroked from a

fully closed position (0% open) to a fully open position (100%

open) and returned to the fully closed position.-

To cycle the check valves, fluid pressure was applied to the

valve on the upstream side forcing the valve open. The check

valves closed as the pressure .across the valve equalized. The

percent open obtained by stroking the check valves with this

method could not be accurately measured.. There was no sustained flow across either the gate or check.valves.

This test was modified for the six-inch and twe1ve-inch check

valves. The six-inch valve was-wet cycled 85 times.' The

twelve inch valve was wet cycled 20 tipes. In addition, test

7, wet cycling n - 150, and test 8 leak tests, were deleted for

these two valves. The cycling of the six-inch and twelve-inch

check valves was abbreviated so that the loosened internals

portion of the program could be expanded to include these two

valves without cost impact. The change to the test plan was

made based on (1) the results of the four-inch check valve

testing which indicated that completion of the planned wet

cycles would have nominal impact .on the valve leak rate and (2)

the belief that it would be important to examine the leak rate

response of different check valve designs to the loosened

internals testing. It was decided that the program objectives

would be better met by expanding the loosened internals portion

of the test program and abbreviating the check valve life cycle

testing.

13
Table 4. Typical Leak Test Matrix

Test Inlet Outlet Differential

ID. Temperature Pressure Pressure Pressure

No. (F) (psig) (psig) (psid)

1. 250 50 0 50

2. 250 150 0 150

3. 250 250 0 250

4. 250 350 0 350

5. 250 700 0 700

6. 250 1100 0 1100

7. 250 2250 0 2250

8. 350 2250 2200 50

9. 350 2250 1550 700

10. 350 2250 1150 1100

11. 550 2250 2200 50

12. 550 2250 1550 700

13. 550 2250 1150 1100

6. Leak Tests - This series of

described in test 4.

leak tests were similar to those

7. Wet Cycling. n - 150 - The test valves were stroked an additional 150 times in the manner described previously in Test 5.

The 150 cycles represents the completion of a typical PIV

service life. It should be noted that some PIVs are stroked

significantly more than 150 times during their service life.

As previously discussed, this test and test 8 were deleted for

the 6-inch and 12-inch check valves.

8. Leak Tests - This series of leak tests was similar to that

described in test 4.

9. Post Test Examination - Following the sequences of cycling and

leak rate testing, the check valves were examined in place for

any damage to the seating surfaces and the valve internals,

particularly the disk stud nut attachment. All flaws or

changes were characterized and documented.

10. Loosened Internals Test - This test applied only to the check

valves. Per the original program plan, only one check valve

was to undergo loosened internals testing. However, as the

program progressed, the test plan was modified in response to

14
the life cycle test results and incidents in the LWR community

to include all three check valves.

The first phase of loosened internals testing was conducted and

involved all three check valves. The loosened internals

testing consisted of breaking the weld between the nut and the

stud on the back of the valve disk, Figure 1. The nut was

loosened a specified number of rotations and locked in place

with a backing nut. The valve then was cycled five times and

the leak tests as specified in Table 5 were conducted. The

leak tests were to determine whether leak tests were effective

for identifying loosened check valve internals. The process of

cycling and leak testing was repeated twice. The goal of the

additional cycles and leak tests was to determine whether a

check valve with loosened internals seated in a reproducible

manner.

The sequence of tests described above was done for two different loosened conditions for each check valve.

Prior to starting the loosened internals testing, it was recognized that check valves used as PIVs are often self-centering

and therefore the valve's leak rate may not significantly

increase even with the integrity of the valve internals compromised. Therefore, the acoustic emission equipment was

monitored during the valve cycling as well as during the leak

.tests. The AE equipment supplied by ETEC was readjusted to

monitor the signal frequencies which occur during valve

cycling. This enabled evaluation of the feasibility of using a

technique, other than valve leak rate monitoring, to detect

valve degradation.

11. Loosened Internals. Phase 2 - During the Valve Performance Test

Program, the decision was made to conduct additional'testing

with check valve loosened'internals to determine whether AE or

visual in-service inspection techniques were effective in

identifying loosened internals. The four-inch check valve was

installed in the Hydraulic Test Facility (HTF), a low-teq-perature, low-pressure, flowing water loop. AE traces were made

with the valve internals in the as-reteived condition at a

range of flow velocities from 3 to 15 ft/sec. The valve

internals then were loosened and the flow tests repeated. The

objective was to evaluate whether the AE could "hear" the

loosened internals with water flowing through the valve. The

flow tests were of short duration, a few minutes, therefore the

objective of the test did not include imposing any additional

wear mechanisms on the check valves. Instead, the test focused

on trying to determine whether the artificially induced

loosened internals condition could be identified with AE

monitoring.

15
Table 5. Loosened Internals Leak Test Matrix

Test Inlet Outlet Differential

ID. Temperature Pressure Pressure Pressure

No. (F) (psig) (psig) (psid)

1. 250 200 50 150

2. 250 300 50 250

3. 250 400 50 350

4. 250 750 50 700

5. 250 1150 50 1100

6. 250 2250 50 2200

The second portion of this task was to examine visual in-service inspection techniques. A rigid borescope and a flexible

video probe were obtained. The four-inch valve was inspected

while it was installed in the HTF; a small hole was machined

into the bonnet to accommodate the probe. The six-inch check

valve was not installed in the HTF for the in-service examination, therefore a wooden plate with a small hole was substituted for the bonnet. This approach allowed the in-service

inspection to be conducted to develop the inspection procedure

without altering the actual bonnet.

12. Motor Actuator Signature Tests - These tests were conducted on

two of.the gate valves; the 4-inch and 10-inch flexible wedge

disk valves.

As part of their work on nuclear power plant aging, ORNL made a

study of motor-operated valve failures. This study showed that

the primary reported failure mode, a failure of the valve to

change position, was caused by problems with the motor operator. The motor actuator signature tests were designed to

identify methods of surveillance effective in detecting significant aging and deterioration of valve operability prior to

loss of safety function. The following parameters, which form

the valve's motor actuator signature, were monitored for this

purpose.

Valve position,

Stem force,

Velocity,

Motor vibration,

Motor temperature,

Motor current,

Torque shaft rotation,

Position,(both standard switches and fiber optic)

16
Torque (limit switches)

Acoustic emission

Prior to the life cycling, the packing nuts were adjusted per

manufacturer's specifications. The motor signature was

recorded throughout the life cycling to identify any significant changes in the signature or the packing leak tightness due

to normal wear. After the life cycling was completed, the

gland nuts were adjusted to 50%, 200%, and 300%-of the manufacturer's recommended torque. The packing torque was varied

because plant operators often tighten the packing torque to

prevent or stop leakage through the valve stem. After the

torque was adjusted, the valves were cycled at 250F, 400F, and

550F. Again, the motor signature was evaluated for indications

of reduced valve operability while the valves were examined for

leakage through the stem packing.

13. Removal and Final Exam - After all tests were completed on a

given valve, the valve was removed from the facility and

examined for degradation or damage.

2.3 Leak Rate Test Matrices

During the life cycling and the phase 1 loosened internals tests,

valve leak tests were conducted at the pressure and temperature conditions

shown in Tables 4 and 5. These matrices generated data for a number of

independent variables; pressure drop across the valve, temperature, downstream pressure (which determines the phase of the fluid leaking through the

valve at a given temperature), and the number of wet or dry valve aging

cycles.

The pressure and temperature variations were specified for evaluation of the ASME Code correlation given below. Sufficient variation in

differential pressures and temperatures were specified to cover the desired

range of operating-to-test conditions.

Pt

where Lo - leak rate at operating conditions

Lt ' leak rate at test conditions

Po - differential pressure at operating conditions

Pt - differential pressure at test conditions

The leak tests were interspersed in the life cycle and loosened

internals program to determine the relationship between valve degradation and

leak rate. The check valve loosened internals matrix was formulated to

determine whether the correlation between leak rate and differential pressure

was the same for valves with loosened internals as it was-for valves without

their internals compromised.

17
The leak rate test matrices also were designed to minimize the test costs without sacrificing the Valve Performance Test Program objectives. Therefore, as with the other Valve Performance Program elements, these matrices were continually evaluated and tests which would not yield useful data were eliminated. For instance, if there was no measurable leak rate or

an extremely low leak rate during the 250F tests, the leak tests at higher temperature were eliminated since experience had shown that the variation of extremely small leaks with temperature was minimal.

The tests in the matrices specified at isothermal conditions provide a direct correlation of leakage versus AP. The tests at elevated

temperatures are conducted at the same AP as the lower temperature tests to obtain data on the effect on temperature on measured leak.

18
3.0 TEST RESULTS

The test data, discussed in Appendix B and References 4 and 5,

were analyzed to address the objectives of the Valve Performance Program.

The results are discussed in this Section as they relate to each of the five

Valve Performance Program objectives.

3.1 Leakage as an Indicator of Valve Condition

For the check valves, leak rate as an indicator of valve condition

was investigated for three types of valve degradation, valve wear due to

cycling, erosion, and loosening of certain internals. For the gate valves,

wear due to cycling was the only degradation mechanism examined.

Figures 3 and 4 are plots of valve leak rate versus the number of

combined wet and dry cycles for the check valves. As Figures 3 and 4 show,

leak rate does tend to increase as a function of normal wear caused by valve

cycling for both gate and check valves. However, the leak rates measured at

the end of the life cycling program were all well within the generally

allowable leak rate of 0.5 gallons (0.052 lb/sec) per nominal inch of valve

diameter (at 2250 psia and 550F).

The check valve test results indicate that erosion of the seating

surfaces, caused by the presence of flashing conditions across the valve,

does not cause rapid degradation of the sealing surfaces. However, the

check valve leak rate generally did increase somewhat during flashing tests.

It is important to note that the results obtained during the Valve

Performance Program show that dry cycling of valves is not an important area

of concern, since limited dry cycling of gate and check valves had little

effect on the seating surfaces. In fact, dry cycling of the check valves

resulted in decreased leak rates. During the initial research that was done

to develop the Valve Performance Program test plan, a number of valve - manufacturers were contacted. Without exception, these manufacturers were

very concerned about dry cycling of valves and felt that dry cycling would

cause severe degradation of the seating surfaces.

There is concern that check valve failure can be caused by the

internal components working loose and becoming incapable of performing their

design function. These types of failure occurred at San Onofre, Unit 1, a

water hammer event which contributed to the loss of power that occurred on

November 21, 1985. At San Onofre, see Reference 3, deformation of the stud

was observed in two check valves. The clapper had separated from the hinge

arm in both these check valves.

During the life-cycling of check valves for the Valve Performance

Program, only the four-inch check valve suffered significant damage to the

clapper assembly or the valve body. The 4-inch check valve is believed to

have suffered more damage than the 6-inch and 12-inch check valves because

it was cycled more often than the latter two valves and because the cycling

method, described in Section 2, caused the 4-inch valve to open more fully

19
and with more force than the 6-inch or 12-inch valves. As previously

discussed, life cycling of the 6-inch and 12-inch check valves was abbreviated in order to expand the loosened internals portion of the Valve

Performance Program. Despite damage to the clapper assembly, separation of

the clapper and the hinge arm did not occur during life cycling of the

four-inch check valve in the Valve Performance Program.

The results of the Valve Performance Program loosened internals

test indicate that the current utility practice of leak testing of PIVs is

ineffective in detecting some types of loosened internals in check valves.

Specifically, leak rate tests did not indicate that the clevis assembly nut

or the clapper stud nut were loosened. In no case did leak rate exceed

permissible levels. See Appendix B for details.

At San Onofre, three other check valves were found in which the

nut which locks the clapper into place hadworked loose. The clappers of

these valves were found to be caught inside the seat ring. During the Valve

Performance Program, none of the three check valves were damaged in this

way. In fact, due to the stud deformation, the nut could not be removed

from the four-inch check valve without cutting the stud. The design of all

three check valves specified a seal weld between the nut and the stud which

probably prevented the nut from working loose.

Only one check valve failure, a failure of the four-inch check

valve to close, occurred during the Valve Performance Program. The failure

occurred before the valve was-disassembled for loosened internals testing.

The leak rate monitoring did not indicate that this valve was going to fail

to close. That is the leak rates were very low during all leak rate tests,

less than 0.01 lb/sec (0.10 gpm at 550F and 2250 psia), prior to the failure

of the valve to close. If this occurred in a LWR, the operators would not

have warning that valve maintenance was required in advance of the valve

failure. However, it is important to note that leak rate testing did

identify that the failure had occurred.

Leak rate testing was useful in verifying the condition of the

check valves following valve maintenance. After the four-inch check valve

clapper assembly was replaced following the loosening of the valve internals, the post-assembly leak rate test identified that the valve assembly

was incorrect. The valve did not fail to close due to the loosening of the

internals, but because of reassembling the valve, an out-dated procedures

was used. This resulted in the clapper getting hung up on the valve seat.

When a revised assembly procedure was obtained and followed, the valve

seated without excessive leak rate, even though the internals were still

loose. Post-maintenance leak tests appear to be a valuable tool for plant

applications.

The leak rate during the program often varied following a single

valve stroke or cleaning of the valve seating surfaces. This indicates that

impurities trapped on the seating surfaces are responsible for some variation in the measured leak rate. Data reported by LWR plants, Reference 2,

verify this observation.

20
3.2 ASME Correlation'

The correlationgiven in Section Xl of the AS4E Boiler and Pressure

Vessel Code is used by commercial nuclear poweIr'plantsjto extrapolate valve

leak rates measured at low differential pressures.to leak rates at larger

differential pressures. The correlation was developed to allow utilities to

conduct the required valve leak rate tests at low differential pressures

during plant shutdowns rather than requiring them to match the differential

pressure conditions which exist during notinmal' lant operation:. The correlation is based on the square root ratio of the differential pressure during

operation (iP0) to the differential pressure during leakrate testing (ePt)

as shown below. The correlation does notiinclude temperature.'affected parameters such as viscosity or density. L is he leak rate at operating

conditions, Lt is the leak rate measured at test conditions.

L- LI ASP ' o Lt 

V APt

To evaluate the accuracy of this correlation,' the check and gate

valve leak rates were measured over a'range of differential pressures. Leak

rate measurements also were made at various'temperatures to determine whether

fluid temperature affects the correlation.. The effects.of the various

parameters on this correlation are discussed separately in the following

paragraphs.

3.2.1 Pressure Effects

Because the leak rates measured during this test program were

typically very low, in the'range of 10'4 to 10t lb/se&, it may be difficult

to extrapolate the results of these'tests-toiMeanii1iful leak' rates in' the

range of one to five gpm. The'higher leak rates are of special interest to

plants because leak rates in this range tndicate that %ialve i-epair is, or

will soon be, required.

However, the results obtained illustrate the mp rtance of applying

an adequate differential pressure across the fa ce of 'swing check yalves

during leak rate testing. Seating force for swing chTeckivaV.es is'supplied

by the differential pressure across the valve face.' If the'applied

differential pressure is too low, the valve may nnot seat pr perly"and overly

conservative results wouldibe obtaihed.. Ini generail`,th data show that the

leak rate measured at low differential pressurees"egceeds the'leak rate'

measured at higher differential pressures.' It can be implied that Ohen the

leak rate increases with increasing pressures, 'a true leak path exists and

that the valve's leak rate should be closely monitored so that valve

maintenance occurs before the leak rate exceeds acceptable limits.

21
For the gate valves, a different pattern of leak rate versus

differential pressure emerged at the lower differential pressures. The

highest leak rates typically occurred with the highest differential pressures.

These results emphasize the fact that differential pressure can

have two opposing effects on leak rate. It provides seating force which

tends to decrease leak rate. At the same time, increased differential

pressure provides a larger driving force for leakage flow which tends to

increase the leak rate. For the check valves, differential pressure is the

primary seating force, therefore, at low differential pressures insufficient

seating force was the dominant effect resulting in higher leak rates.

Whereas for wedge type gate valves, differential pressure is a secondary

seating force. The primary seating force is provided by the motor operator.

Therefore, the second factor was dominant and increasing the differential

pressure increased leak rates.

Figures 5 to 10 are log-log plots of the leak rate versus the differential pressure for the check and gate valves. The ASME Code correlation predicts that all the points on a log-log graph would be fitted by a

straight line with a slope of 0.5. If the leakage flow is laminar, then the

points would be fitted by a straight line with a slope of 1.0. However, as

shown on the figures, the slope of the straight line fitted to the data for

the six test valves varied from 0.13 for the 12-inch check valve to 2.7 for

the 4-inch W-K-M valve. For the check valves, data points at low differential pressures, less than 350 psig, were eliminated if the leak rate was

abnormally high. As previously discussed, abnormally high leak rates at low

differential pressures indicates that the check valve seating force is not

large enough to seal the valve properly. The code correlation would not

apply under these circumstances. Therefore, the data indicates that a

correlation can not be proposed for leak rates in the range of those

measured during the Valve Performance Program, 0 lb/sec to 3 x 10 2 lb/sec

(0.27 gpm at 550F and 2250 psig). For higher leak rates, and thus larger

leak paths, the ASME Code correlation might be more accurate. An LWR would

be most concerned with leak rates in the range of one to five gpm as leak

rates of these magnitudes would require valve repair.

3.2.2 Temperature Effects

There was a general pattern of decreasing leak rate with increasing temperature, see Figures 11 and 12. The sharp drop in the leak

rate of the 4-in. check valve at 350F, see Figure 11, indicates that the

leak rate may be due partially to impurities trapped on the seating surface

which may have been swept off during the cycling between the measurements

made at 250F and the 350F test. (No elevated temperature leak rate tests

were conducted on the 6-inch or 12-inch check valves because the leak rates

across these valve seats were consistently very low. As previously

discussed, if extremely low leak rates were measured, the elevated temperature tests were deleted.)

22
The general trend of decreasing leak rate with increasing temperature would be theoretically expected for turbulent flow. However, the

magnitude of the variation in leak rate versus temperature was greater than

expected. The leak rate at constant differential pressure theoretically

should vary as a square root function of the ratio of the densities. A

log-log plot of leak rate versus density was made for the four-inch Westinghouse valve, see Figure 13. As this figure shows, the measured leak rates

decreased more than would be predicted by this function as the slope is much

greater than 0.50. The general trend of decreasing leak rate with increasing temperature did not hold for all of the test valves. The four-inch W-K-M

valve leak rate increased with temperature. This general trend would be

expected for laminar flow. But again, the magnitude of the change is greater

than expected.

In terms of the existing code correlation, ignoring temperature

effects is conservative. That is, if the correlation is corrected for

temperature, then the predicted leak rate would be less.

3.3 Acoustic Emission Monitoring

Acoustic emission monitoring by the standard acoustic emission

devices originally used in this program was shown not to be viable instrumentation to measure the leak rates produced by life cycling of the valves.

The ETEC high sensitivity AE equipment was shown to measure water leak rates

from 0.001 lb/sec (0.01 gpm at 550F and 2250 psia). Indication was that much

more testing would be required to generate certifiable AE instrumentation for

plant utilization. See Appendix A.1.2.

3.3.1 Leak Rate Monitoring

The leak rates measured during the check valve testing were very

small, less than 3 x 10'3 lb/sec (0.03 gpmat 550F and 2250 psia). These

small leak.rates are below the range of reliable measurement for acoustic

emission systems. Therefore, the data could not be used to evaluate acoustic

emission monitoring as method for quantitative leak rate measurement.

The acoustic emission data was shared with ANL, ORNL, and the Naval

Ship Research & Development Center. In addition, a representative from Leak

Dynamics Company visited ETEC during the long term flashing program and

monitored the acoustic emission traces of the four-inch check valve. Leak

Dynamics is under contract to the NRC. These organizations will make

independent evaluations of the data for the NRC programs in which they

participate.

As with the check valves, a number of different acoustic emission

systems were used to monitor the gate valve leak rate tests. In addition to

the ANL, ETEC, ORNL, and Naval Ship Research & Development Center devices,

ETEC fabricated and installed a new high sensitivity narrow-band system which

monitored frequencies of 180 + 30 kHz. The additional AE system was

conceived by ETEC in response to the low leak rates that resulted from

life-cycling of the check valves. ETEC believes that the new system has the

potential of installed, i.e., 10-4 lb/sec region. As shown in Figures 14 and

15, the ETEC narrow-band system was the only system which showed promise for

23
measuring the low leak rates obtained during the Valve Performance Program.

The AE data was analyzed as a function of frequency versus amplitude.

3.3.2 Check Valve Loosened Internals Monitoring

The original purpose of the acoustic emission systems was to

evaluate the effectiveness of acoustic emission techniques for detecting,

quantifying, and examining trends in valve leakage. However, during the

course of the program, one of the AE systems was adjusted to obtain acoustic

traces of valve cycling during the loosened internals testing. The objective was to evaluate whether loosened internals could be detected with

acoustic emission monitoring during valve cycling. Since the ETEC and ORNL

systems were very similar, the ETEC transducers were chosen to be readjusted

to monitor the acoustic frequencies produced during valve cycling.

The ability of acoustic emission monitoring to detect loosened

check valve internals could not be clearly judged based on the cycling tests

conducted at LLTR. There were indications that the loosened valve clapper

produced a different AE trace, however, the noise from the valve opening and

closing dominated the AE trace. Since this potential failure mode has proven

to be important in operating LWRs, and since leak rate tests do not seem to

identify this condition, a new phase of loosened internals testing was

developed. These tests were conducted at the Hydraulic Test Facility (HTF).

The tests conducted at the HTF consisted of flowing water through

the test valve at velocities from 3 to 15 ft/sec for each of three valve

internal conditions: (1) the valve clapper nut tightened to specifications,

(2) the valve clapper nut loosened two turns, and (3) the valve clapper nut

loosened an additional four turns. The purpose was to determine if the

acoustic sensors could detect the loosened internals during typical flow

velocities.

Fourier analysis of the data was performed and is shown in Figures

16 through 18. This was accomplished to determine whether the data would

show a particular frequency level that indicated loosened check valve

internals. Figure 19 is a comparison of the results. This analysis confirms

that AE monitoring does not produce a detectable pattern that identified

loosened internals for this testing.

3.4 Gate Valve Motor Signature Monitoring

The motor signature of the Westinghouse flexible disc 4-inch and

10-inch gate valves were monitored with the packing torque set at values less

than and exceeding the manufacturer's recommended torque. The fluid pressure

also was varied during the testing.

24
The motor signature monitoring showed that closing current and

dynamic stem force are both functions of packing torque. In addition,'

closing current is also a funct4on of fluid pressure. The results show that

the valve operational characteristics are dependent upon maintenance

activities, such as tightness of the packing gland nuts to prevent leakage

through the packing, and the system. conditions at the time of valve operation, such as the fluid pressure and flow'. The dependence of closing current

on system conditions verifies LWR plant experience which shows'that MOVs that

operate acceptably during ISI are not necessarily functional at emergency

system conditions.

The ValVe Performance Program tests indicate that motor signature

instrumentation can be used in LWRs to monitor valve performance and to

assist in periodic readjustment of the valve to ensure operability under

normal plant operating conditions as well as emergency conditions. These

motor signature tests identified motor operator instrumentation to ascertain

performance that is relatively easy to install and maintain that will give.

practical information for plant operation.

3.5 Check Valve Visual In-Service Inspection (ISI)

A rigid borescope and a flexible videoprobe were used to evaluate

whether visual ISI could identify loosened and deformed check valve internals. The four-inch check valve was inspected while installed in the HTF for

AE testing. The six-inch check valve bench tested to develop the ISI

procedure. The 12-inch check valve wasnot included in these tests. The

results for the four-inch and six-inch valve were conclusive and the same.

Refer to Appendix B for additional details.

The rigid borescope proved to be an adequate tool for ISI when

video recording of the inspection was not necessary as it was adequate to

detect the loose internals. However the flexible probe was preferred because

it could access more area, and was articulatable in four directions, and had

video viewing and recording.

A video tape of the four-inch and six-inch ISI with the flexible

videoprobe demonstrated that the check valves internals can be clearly

inspected, and that a loosened nut, bent stud, bolt, or clapper seating could

be readily seen with the flexible probe. In some instances, even portions of

the upstream side of the check valve clapper'assembly (with the clapper in

the closed position) can be inspected. The visual ISI methodology developed

in the Valve Performance Program can be adapted to facility PIVs. However,

this requires that an access port on the order of 3/4-inch diameter be

drilled into the bonnet to access to the valve internals. Although this

method would accomplish the objectives of an ISI, other problems, such as

breaking the primary pressure boundary, must be resolved before such methods

would be acceptable for plant use.

Sk 25
4.0 CONCLUSIONS AND REFERENCES

4.1 Conclusions

1. Life-cycling and long term flashing of the fluid in the check

valves and life-cycling of the gate valves did not cause severe

degradation of the valve seating surfaces during this test

program. However, plant conditions must be more severe to

include flow effects and additional aging mechanisms to cause

seating surface degradation as reported,

2. During the Valve Performance Program tests, leak rate testing

did not identify whether the integrity of a check valve clapper

or clevis assembly had been compromised, even when the clapper

restraining nut was almost detached from the stud.

3. Acoustic emission monitoring did not identify when the

integrity of a check valve clapper assembly had been compromised either during valve life-cycling or when the valve was

subjected to varying flow rates at operating pressure and

ambient temperature with no upstream flow restrictions.

4. Based on these check valve performance tests, leak rate

monitoring was not effective in predicting impending failure of

the four-inch check valve to close. However, the leak rate

tests did detect the failure after it had occurred, therefore,

post-maintenance leak tests appear to be a valuable tool for

plant applications.

5. Life-cycling of the check valves can damage the clapper

assembly. Although this type of damage did not result in a

valve failure during the Valve Performance Program tests, the

damage to the clapper stud on the four-inch check valve

indicates that clapper assembly degradation could occur during

abnormal plant operation. A possible scenario could include

failure of the clapper stud.

6. Based on these leak performance tests, no conclusion could be

drawn concerning the ASME Code correlation for extrapolating

leak rates based on the results of the Valve Performance Test

Program. The ASME Code correlation was not accurate for very

low leak rates obtained during the Valve Performance Program

(less than 0.3 gpm at 550F and 2250 psig). Nor did the

correlation always give conservative results at these low leak

rates, i.e. predict higher than actual leak rates at higher

differential pressure which was not the case here.

Although the results of this test program do not agree with the

ASME Code correlation, the aging methods used during this

program did not cause sufficient wear/degradation of the valve

sealing surfaces to simulate long term plant leakage which

could be a combination of wear and/or crud on the seats.

27
Therefore, data to validate, or invalidate, the Code

correlation for leak rates greater than 0.5 gpm are unavailable

and from the present program conclusions about the existing

correlation can not be made.

7. There was no discernable pattern between leak rate and temperature.

8. For the low leak rates measured during the Valve Performance

Program, most of the acoustic emission systems tested were not

effective in quantitatively measuring the leak rate. However,

the high sensitivity, narrow-band-width system did show promise

for this application.

9. The motor signature monitoring showed that closing current is a

function of fluid pressure and packing torque and that dynamic

stem force differential also is a function of packing torque.

These results verify that the valve operational characteristics

are dependent upon maintenance activities and that motor

signature instrumentation can be used in LWRs to assist in

periodic readjustment of the valve to ensure operability. The

motor signature tests identified motor/operator instrumentation

that is relatively easy to install and maintain which would

give practical information for plant operator.

10. Visual in-service inspection is a highly effective method of

detecting loosened check valve internals and degradation.

However, this method of inspection requires penetration of the

primary system pressure boundary by drilling a port in the

valve bonnet. The acceptance of this method would require

additional effort to obtain ASME Code approval.

References

1. EGG-NTAP-6175, "In-Service Leak Testing of Primary Pressure

Isolation Valves," R. A. Livingston, February 1983

2. "A Synopsis of Selected Investigations of MOV Events," E. J.

Brown, American Nuclear Society 1985 Annual Meeting

3. NUREG-1190, "Loss of Power and Water Hammer Event at San

Onofre, Unit 1, on November 21, 1985," U.S. Nuclear Regulatory

Commission, January 1986

4. "Valve Performance Testing - Check Valve Results," N. M. Jeanmougin, Transactions of the Fourteenth Water Reactor Safety

Information Meeting, U.S. Nuclear Regulatory Commission,

October 1986

5. "Light Water Reactor Pressure Isolation Valve Performance," J.

J. Corugedo, N. M Jeanmougin, H. H. Neely, Transactions of the

Fifteenth Water Reactor Safety Information Meeting, U.S.

Nuclear Regulatory Commission, October 1987

28
APPENDIX A: TEST FACILITIES AND INSTRUMENTATION

The Valve Performance Test Program was conducted at two ETEC

facilities, the Large Leak Test Rig (LLTR) and the Hydraulic Test Facility

(HTF). The majority of the check valve testing, the basic in-service

inspection (ISI) required for check valve inspection, and all of the gate

valve tests were conducted at the LLTR. Phase 2 of the check valve loosened

internals tests and ISI prototype testing were conducted at the HTF.

A.1 Large Leak Test Rig

The LLTR was selected for the bulk of the Valve Performance Test

Program because of its high pressure water, steam and nitrogen supplies. The

modified LLTR for the VPP is shown schematically in Figure 20. The schematic

shown is for gate valve testing. For check valve testing the piping was

modified to allow for flapper pressurization from the back side. It contains

high pressure water storage vessels suitably sized and designed (Table 6) to

permit all necessary water test operations. Extensive instrumentation are

located on the piping and tanks.

The high-pressure nitrogen supply, valves, pipe/valve preheaters

and heater controls were existing. Thus the only facility preparation was

the relocation of some piping and valves that tied the test articles into the

facility. Points of connection of the test article to existing piping were

downstream of valves PCV-218 and V-204B, Figure 20. The test installation

was located at grade level immediately inside the LLTR high bay door, and the

piping was routed down to the existing high pressure water tanks in the LLTR

vault. This arrangement facilitated test article handling and installation.

A view of the three check valves installed in the LLTR is shown in

Figure 21.

The LLTR digital data acquisition system (DDAS) was capable of

acquiring data at up to 250 samples per second. In addition, analog data

could be analyzed at 0.1 m sec or digitized at 10,000 samples per second.

Existing automated features for synchronizing tests were used for the Valve

Performance Program so that the valve cycling often were run on off-shifts

with minimal facility surveillance.

The LLTR control room and DAS are shown in Figures 22 and 23. The

test facility design parameters that were used are listed in Table 6.

Table 6. Test Facility Design Parameters

Design Code ANSI B31.1

Water Pressure 2250 psig

Water Quality Grade B

System Water Supply 75 ft3

Plant Water Supply 7,000 gal

Heat-up and Cool-down Rates 5OF/hr

Nitrogen Supply Pressure 3100 psig

29
A.1.1 System Operation

Cycling of the test valves was by computer control using algorithms developed explicitly for life cycle valve tests as required for the

Valve Performance Program. Shown in Figure 20 is the gate valve installation; the check valves were installed to open when pressurizing from V240B. The pressure drop across the valves for cycling was created by

venting the downstream side of the test valve prior to test. For check

valve cycling, the system was vented down from V-240B, in order to bang the

valve open. Test pressures were achieved by pressurizing the water tanks

with nitrogen through valve V-217D. The water supply tanks TI, T2, and T3

were valved in parallel for these tests. For wet cycling, the tanks,

piping, and test valves were heated to test conditions using existing

electrical trace heaters. For leak testing the check valves, the water

supply to pressurize the clapper, was from V-244B; while the leak rate

measurement instrumentation was moved to the other side. For the elevated

temperature leakage tests, the supply tanks were maintained at cycling

temperature and only the valves and the valve inlet piping were heated to

the leak test temperature. This minimized the test preparation time.

The cycling sequence algorithms for the computer are given in

Tables 7 and 8 for check and gate valves, respectively. The center valve

test position is described. The sequence for the other two positions were

identical but had different valve numbers. The valve cycling software

certified the supply water level (DP-502), the supply system temperature,

various tank and line thermocouples, system pressure (P-554), proper valve

positions (V-240B) and the test article.

The program was designed to cycle the test valve every two

minutes. During a cycling, V-204B opened first; then, the test article was

opened after the cavity was filled. Post cycle, V-4D was opened to vent the

system after V-240A had been closed; then, V-218 was opened to supply a

purge gas at 150 psig. The purge gas was shut off then the V-4D valve was

closed to prepare for the next cycle.

A.1.2 Instrumentation

The control and data acquisition instrumentation used for the

Valve Performance Test Program were calibrated by the ETEC Instruments and

Standards Laboratory. This lab maintains primary and secondary standards

traceable to the National Bureau of Standards for all instrument calibration. Rigorous procedures referred to as Measurement System Calibration

Procedures were developed and implemented in accordance with ETEC policies

to produce data of certifiable accuracy for each measurement system as it

was installed in the test facility.

Three parallel systems were used to cover the complete range of

interest for leak rate. For ultra-low leak rates (less than 0.1 gpm)

leakage was measured by volumetric displacement versus time in a specially

designed vessel. This is the standard method used extensively at ETEC in

valve bench tests. A low range (0.1 to 1 gpm) and a higher range (1 to

5 gpm) turbine flow meter were installed to measure larger leak rates, F-242

and F-243 respectively, Figure 20. By dividing the measurement range among

three instruments a high accuracy measurement was assured.

30
Table 7. Computer Valve Sequencing for Check Valves

Cycle

Open Close

Valve Start (sec) (sec) End

V-217D 0 C

V-204 A&B 0 0

V-240A-241A or 204H C 8 16 C

V-240B-241B or 204J C 11 30 C

V-4D . C 19. 310 C

V-218* C 25 280 C

*Backed

Legend:

by 200 psig nitrogen

0-Open, C-Closed

Table 8. Computer Valve Sequencing for Gate Valves

Cycle*

Start Open Close End

Valve (verify) (sec) (sec) Program

V-217D 0 C

V-204 ANB 0 C

V-204H, V-240A, V-241A 0 0

Test Article C 2 27 C

V-4D C 65 120 0

V-218** C 75. 100 C

*At 50 sec. into.the cycle-stem position, stem force test article

temperature and water supply was certified and printed out prior

to the next cycle.

**Backed by 200.psig nitrogen.

Legend: O-Open, C-Closed

31
Both the check and the gate valves were used to address one of the

program objectives to evaluate the use of acoustic emission (AE) techniques

for quantifying valve leakage and as an indicator of valve condition. AE

data were recorded during the leak rate testing of both the gate and the

check valves. For the check valves, the AE techniques also were employed to

determine whether AE was a reliable means of detecting loosened internals.

Four different AE monitoring systems were installed during the check valve

testing. The systems were supplied by ETEC, Argonne National Laboratory

(ANL), Oak Ridge National Laboratory (ORNL), and the Naval Ship Research &

Development Center. Four systems were used because this program was a unique

opportunity to obtain AE test data which could be used in a number of NRC

programs at minimal costs. In response to the low leak rates of the check

valves and no effective AE measurement, an additional narrow-band AE system

was conceived and procured by ETEC from Rockwell International and installed

prior to gate valve testing.

The ETEC, ANL and ORNL systems each had a transducer installed on

the valve and another transducer installed on the valve inlet pipe. The AE

sensors were mounted on a waveguide, one-eighth inch diameter, that was

capacitance-discharge welded to the valve, for maximum coupling. A soft

cable connected the transducer to a locally mounted automatic gain control

(AGC) amplifier. The output of the AGC amplifier provided an analog signal

which was wired to the Digital Data Acquisition System (DDAS). This has been

a standard technique for transducer mounting to the Liquid Metal Reactor

(LMR) Development Steam Generator shells for leak detection measurement.

The ORNL device monitored at frequencies of 3.0 kHz to 8.5 kHz, the

ANL system at much higher frequencies of 100 kHz to 450 kHz, and the ETEC

system monitored at 0.4 kHz to 20 kHz. For gate valve testing, ETEC

installed another AE system which monitored over a narrow band of 180 + 30

kHz. The two ETEC sensor systems were also used for phase It of the check

valve loosened internals-testings as well as gate valve testing.

Temperature and pressure measurements of the valve inlet conditions were used for the water density computations. All temperature

measurements were calibrated to an accuracy within +1OF to 600F and all

pressure data was certified to +2% of full scale.

A minicomputer based DDAS was used for acquiring and recording data

for on-line data reduction and display. The basic software was existing and

required only minor modification to accommodate the Valve Performance

Program. The on-line data reduction was used for rapid assessment of test

results to verify that the test objectives were being met.

Valve stem position was measured by an linear variable displacement transducer (LVDT) directly from the stem through the top of the

Limitorque operator.. 'Tftrtem velocity was a direct calculation from

position data versus elapsed time. The LVDT system was calibrated to assure

accuracy.

The stem force was measured from three three-element strain gages

at 120 degrees on the stem and angled at 45 degrees. One of the gages

32
mounted on the 10-inch valve is shown in Figure 24. The circumferential and

longitudinal elements in each gage were measured in a bridge circuit that

provided for temperature compensation. This configuration also increased the

sensitivity by 1.3 since the elongation and the compression were both

measured. The valve stem loading was based on the stem diameter and average

material properties correlated to strain. There was no actual calibration of

the force. The stem temperature was measured and used as an indication of

gage sensitivity and gage bonding integrity. The stem force from e~ach gage

was available to ascertain bending moments, but typically, the average of the

three gages were used in the MOV performance tests.

The motor current was measured by a current transformer on one leg

of the 440 VAC line feeding the motor. This transformer was changed depending on the valve being tested to increase the sensitivity. The total system,

transformer to the computer, was calibrated prior to test.

The Limitorque operator is controlled by a mechanical torque switch

from the gear drive. An electronic indicator was' attached to the torque

shaft for measurement of its rotation in degrees as a function of torque in

the system; it was system calibrated in degrees. During the opening cycle

the torque switch was overridden during the first 30% of travel. This was

done here to simulate plant operation such that the torque switch cannot

terminate opening in an emergency situation if the gate wedge has been forced

in and/or stuck for a long period of time. In that case the motor is allowed

to drive to its limit.

The position limit switches are mechanical. The torque and closed

limit switches were set to activate at 30% of closed.

Fiber optic open and close position sensors were installed on the

10-inch Westinghouse valve during the life cycling of the 4-inch gate valve.

The basis for this instrumentation and tests were to 1) perform prototypic

testing of fiber optic systems and 2) to perform life cycling and motor

signature testing with state-of-the-art instrumentation for LWRs as well as

other nuclear plants. The open limit detector used an EOTec Model ETR-105 - TTL level detector with a bifurcated fiber optic cable and probe, see Figure

25. The close limit detector, Figure 26, used an EOTec model ETR-103S analog

module with a bifurcated fiber optic cable and probe. These two devices were

selected as typical reflective devices for the open and close positions,

respectively.

The open position reflective device was used as a make unit,

switch, indicating that the shaft guide had passed the position. An analog

reflective instrument was selected for the close position to obtain measurements of the seating position of the gate plug as a function of cycling and

stem force. The characteristics for this close position device are shown in

Figure 27 where the analog device could measure about 125 mil with good

sensitivity.

Initially a microbending approach was used for the closed position

to provide high sensitivity because we thought that the seating position

variation with cycling and stem force would be small. But, during the first

test sequence, the microbending mechanism was crushed and was replaced with

33
the reflective analog device. The analog reflective device provided a larger

seat position measurement range, but not with the same accuracy.

A.2 Hydraulic Test Facility (HTF)

The Borg-Warner four-inch check valve was installed in the HTF to

evaluate acoustic leak rate monitoring and in-service inspection techniques

of valve condition. Figure 28 shows how the check valve was installed in the

water loop.

The HTF is a closed demineralized water circulation loop with

remotely operated centrifugal pumps and flow control valves that direct and

vary the flow through designated test areas. A deaeration tank connected to

the pump suction header removes entrained gases from the water and acts as a

surge tank for the circulation system. Heat input to the water from

operation of the system pumps is removed by air-cooled heat exchangers.

Circulating water was provided to the

the facility pump P-i, rated at 750 gpm and 900

flowed from the pump discharge through the test

meter, a flow control valve and returned to the

four-inch check valve from

ft of head (390 psig). Water

article, a turbine flow

pump suction manifold.

A computer-operated DDAS recorded the flow, temperature and

acoustic emissions data on disc for on-line processing and on tape for

off-line processing. An analog tape recorder was used for recording the

acoustic emission signals for Fourier analysis of the data.

The in-service inspection procedure was performed using two types

of probes. One type was a rigid borescope with 90 or 30 viewing, standard to

most utilities. The second one was a commercially available, Welch Allyn

Video Probe 2000, flexible videoprobe capable of being articulated in four

directions. The six-inch check valve was bench examined to develop the

in-service inspection methodology.

A.2.1 System Operation

Testing of four-inch check valve was accomplished by manually

setting the pump speed and a throttling valve was utilized for test flow

adjustments. Data was taken throughout the throttling process. The flow was

held constant at even increments between 3 and 15 ft/sec.

A.2.2 Instrumentation

All instrumentation measurements were calibrated by written

procedures using standards traceable to the National Bureau of Standards on a

calibration schedule commensurate with the characteristics of the measurement system. These calibrations included the measurement transducer, all

signal conditioning equipment, and the measurement recording system.

End-to-end system calibrations in the field were utilized to the maximum

extent possible to ensure that the off-site individual component calibration

were compatible and consistent, and to verify that the accuracy of the

reported data was within acceptable limits. Table 9 shows a list of

instrumentation used during these tests.

34
Table 9. Instrumentation - Loosened Internals

ID Range Nomenclature

AE-HSV 180 ± 30 kHz Valve High Freq. Sensor - Acoustic

AE-HSP 180 + 30 kHz Line High Freq. Sensor - Acoustic

AE-HTFV 20 kHz Valve - accelerometer (acoustic)

AE-HTFP 20 kHz Line - accelerometer (acoustic)

AE-HSC Calculated Delta - High Freq. (Valve - Line)

AE-HTFC Calculated Delta - High Freq. (Valve - Line)

FT-110 50 - 500 gpm Water Flow

TE-107-1 40-200F Water temperature

)

35
APPENDIX B: TEST DATA

B.1 Check Valve Leak Rate Tests

B.1.1 Four-Inch Check Valve

B.1.1.1 Life-Cycle Tests

The four-inch check valve was subjected to 10 dry cycles, 50 wet

cycles, and 150 additional wet cycles (at 250F and 2250 psid). Leak tests

at various temperature and pressure conditions were conducted with the valve

in the as-received condition and following each period of valve cycling.

The baseline leak tests showed very small leak rates, approximately 4 x 10'5 lb/sec (3.8 x' 10-4 gpm) at 250F and 2250 psia. Following the

dry cycles the valve exhibited no measurable leak rate, perhaps indicating

that the seating surfaces had "worn in." After the first 50 wet cycles the

valve leak rate was again in 'the measurable region, but was still very low,

on the order of 1 x10'5 lb/sec (1 x 10' gpm) at 250F and 2250 psia. The

next 150 wet cycles had minimal impact on measured leak rate, marginally

increasing the average leak rate to 2 x 10'5 lb/sec (1.9 x 10'4 gpm) at 250F

and 2250 psia.

As discussed further in Section 3.2, at these very low leak rates,

less than 1 x 10'4 lb/sec (1.0 x 10'3 gpm) at 550F and 2250 psia, there was

no meaningful correlation between leak rate and either differential pressure

or temperature. The only discernible effect of differential pressure was

seen at low differential pressures, less than 350 psid where the leak rate

was highest,.indicating that seating (sealing) is somewhat dependant upon

pressure actuation forces.

The seating force for a swing check valve is provided by the

pressure difference across the valve-; therefore, a minimum differential

pressure is required for proper seating.

The life cycle testing of the four-inch check valve indicated that

wear due to dry and wet cycling does not cause significant damage to check

valve seating surfaces. Although this was an interesting result, it was

decided that the test program objectives could be better met by investigating the effect of other check valve degradation mechanisms. Therefore

ETEC recommended, .and.the NRC approved, a decision to modify'the plan for

check valve testing.

A long-term flashing test was developed to evaluate the effect of

erosion on check valve leak rates. ETEC set-up the long term flashing

program so that it required only periodic operator attendance. This

approach-allowed exploration of the erosion mechanism with little impact on

program cost and schedule.

-Several utilities were contacted and they indicated that some PIVs

are installed in locations where the pressure and temperature conditions

would result in flashing across the valve for extended periods of time.

Average-conditions for these valves was determined to be approximately 550F

37
and 1500 psid. Therefore, the check valve test conditions were set at 550F

and 1500 psi water on the high pressure side of the check valves while the

low pressure side was at atmospheric pressure. These conditions resulted in

flashing of the pressurized water as it flowed through any leakage paths to

the low pressure side of the valves.

The leak rate across the four-inch check valve at the end of the

flashing test had increased only slightly to approximately 1 x 10-4 lb/sec

(1.0 x 10-3 gpm) at 550F and 2250 psia. A power loss was experienced at the

facility during this time which resulted in a loss of pressure differential

across the valves. After the pressure differential was re-established, the

leak rate across the four-inch valve was noted to have suddenly increased,

to approximately 1 x 10- 3 lb/sec (0.01 gpm) at 550F and 2250 psia. Although this leak rate was two orders of magnitude greater than the previously measured leak rates, it was still much lower than the two gpm (0.21

lb/sec) at 2250 psia and 550F currently allowed for most four-inch PIVs.

Because the leak rate increased suddenly after the loss of differential

pressure, and decreased following subsequent cycling of the valve, the leak

rate variations probably were due to impurities which were temporarily

lodged between the seating surfaces rather than any permanent damage to the

seating surfaces.

B.1.1.2 Loosened Internals Test--Phase 1

Following the completion of life cycling and then the long term

flashing test completed, loosened internals testing of the four-inch check

valve was initiated.

The four-inch check valve was wet cycled 10 times prior to

loosened internals testing to obtain baseline acoustic emissions traces.

When leak rate tests were attempted, a differential pressure could not be

established across the valve indicating that the valve clapper was not

seating. A borescope was used for in-situ inspection of the valve internals.

The inspection was made from a port welded into the line just

downstream of the valve weld which was some distance from the clapper and in

the center of the pipe which was not at optimum location. Therefore, the

immediate cause of failure of the clapper to seat could not be positively

identified. However, the inspections made here propagated to an excellent

inspection methodology discussed later in this report. It will be shown

that the methodology developed here could have easily allowed a rapid-positive ISI inspection showing the valve clapper hung up.

It is important to note that the standard leak rate inspection of

PIVs would identify malfunctions of this type once a failure occurred which

is one of the primary objectives of leak rate monitoring. However, the leak

rate monitoring did not indicate impending valve failure therefore, if this

had occurred in a LWR, there would have been no indication that the valve

required, or would soon require, maintenance.

Since, the next scheduled activity was the removal of the bonnet

to loosen the clapper assembly'stud, the valve was disassembled for further

38
examination. Problems were encountered during disassembly. The bonnet nuts

had galled to the studs and some of the studs broke while they were being

removed. New bolts were fabricated. In addition, the valve bonnet had

galled to the valve body despite the anti-seizure lubricant that was applied

during valve manufacture. Special tools, including a spanner wrench, had to

be fabricated to remove the bonnet. Similar tools were fabricated to remove

the twelve-inch check valve bonnet. The valve disassembly was videotaped

which prooved to be a handy training guide for the remaining valves.

The valve body, bonnet and clapper assembly were examined with the

clapper assembly removed. The clapper stud was deformed by impact with the

valve bonnet during cycling, see Figure 29. The four-inch check valve had

been subjected to over two hundred cycles during the life cycle phase of

testing. The valve bonnet was damaged at the point of contact with the

stud, see Figure 30.

Although the stud was damaged mainly on the outside of the nut, it

was all deformed to some extent below the nut and prior to the clapper. It

was not clear that this was the problem of not seating, i.e. the clapper

hung up in the valve seat. However, considering the problem listed below

where the clapper assembly was installed too low, the deformation (and

considering that it never rotated) would have allowed it to be in a proper

direction to hang up. Also, after the long term flashing tests and considering that they were run at temperature with borated water, the mechanism

probably had crude on it not allowing it to operate freely. This phenomenon

did not happen again, and therefore the failure to seat is attributed to or

a combination of the above.

For the loosened internals tests, the deformed stud was replaced,

and the nut backed off two full turns, approximately 0.16 inches (Figure 1).

The maintenance manual for the four-inch check valve was not available

(although valve purchase order included all valve documentation, the utility

from which the valve was purchased did not have, or had not retained,

complete operational/maintenance information for the valve). Therefore, the

manufacturer was contacted to obtain the proper procedure for reassembly of

the valve. A manufacturer's representative verbally described the procedure. However, after reassembly a pressure differential could not be

established across the valve, indicating that the valve was not seating. A

borescope and an X-ray examination were made. The borescope inspection

'backed by X-ray" showed that the clapper was too low and was hung up on the

seat. The manufacturer was contacted and visited the facility. It was

discovered that the manufacturer had revised the reassembly procedure. The

bonnet was removed and the clapper assembly readjusted allowing the valve to

seat properly.

This experience emphasizes the importance of having up-to-date

maintenance procedures for the particular piece of equipment.

Following valve reassembly, leak rate measurements were made. The

leak rate was measured at 250F and at a range of differential pressures from

150 psi to 2,200 psi. The leak rate varied from 1.4 x 10'4 lb/sec (1.3 x

10-3 gpm) at low differential pressures to 7 x 10 lb/sec (6.7 x 10'4 gpm)

at higher differential pressures. The average was approximately

39
1.2 x 10-4 lb/sec (1.1 x 10 3 gpm). This rate was roughly the same as the leak rate measured after completion of the long-term flashing test, and was

well within the range of acceptable PIV leak rates. The valve then was

cycled five times and the leak rate measurements were repeated. The average leak rate from the second set of leak rates was equal to that of the first, 1.2 x 10.4 lb/sec (1.1 x 10-3 gpm).

The purpose of the sequence of leak tests and cycling was twofold: first, to determine if the valve reseated in a reproducible manner, as determined by leak rate, with its internals loosened; secondly, to obtain AE

traces of the valve cycle to evaluate whether the degraded condition of the

valves could be identified using AE data. The results of the leak rate

tests indicated that the valve did seat in a reproducible manner. The AE

data is discussed in Section 5.

The clapper assembly nut then was backed off an additional four rotations. This resulted in a free length of 0.5 inches between the front

of the nut and the back of the clapper. The sequence of leak tests, five

wet cycles, leak tests, five wet cycles, and leak tests was repeated. The

leak rate was consistently very low during all the leak tests, 2.0 x iO 4

lb/sec (1.9 x 10-3 gpm) at 550F and 2250 psia before cycling,

1.0 X 10'4 lb/sec (1.0 x 10 gpm) at 550F and 2250 psia after five cycles, and 2.6 x 10 lb/sec (2.5 x 10'3 gpm at 550F and 2250 psia) after ten

cycles. The leak rate with the internals loosened was not significantly different from the leak rate with the internals in the as-received condi- tion, therefore, leak rate does not appear to be a good diagnostic technique for loosened check valve internals.

B.1.1.3 Loosened Internals Test--Phase 2

This task was the second portion of the Loosened Internals Test

Phase performed at the HTF. The objective of this portion of testing was to examine how well loosened and deformed valve internals could be observed

using visual in-service inspection techniques. The AE tests conducted at

the HTF consisted of flowing water through the test valves at velocities

from 3 to 15 ft/sec for each of three internal conditions: (1) the valve internals tightened to specifications, (2) the valve clapper nut loosened

two turns, and (3) the valve clapper nut loosened an additional four turns.

The purpose was to determine if the acoustic sensors could detect the

loosened internals during typical flow velocities.

Figures 31 through 39 show the data obtained at various velocities

for each setting of the valve internals. Comparison of these figures demonstrates how the acoustic emission monitoring equipment was not capable of detecting the loosened internals. No useful pattern of AE noise level

versus check valve condition can be observed.

For ISI, access to the four-inch valve internals was obtained by drilling and tapping a 1/2 inch NPT through the bonnet. A four inch pipe extension and cap were added to prevent leakage during testing and simulate

an access port on an insulated valve.

40
Two videoprobes were used during the in-service inspection: one

rigid and one flexible. The rigid probe, standard to most utilities, is

available at 30, 60,and 90 degree angles.

The flexible probe is a Videoprobe 2000 from Welch Allyn and it is

capable of recording the complete inspection on VHS tape. It has the

capability to freeze a particular frame. Insert titles to identify the

inspection being performed and instant print of the stopped frame. The

flexible probes come in different sizes; the one used for this inspection

was 0.375 inch in diameter and twenty feet long.

Figure 40 shows the inspection of the four-inch check valve with

the Welch Allyn flexible videoprobe. Figures 41 and 42 show the inside of

the four-inch check valve as seen through the flexible videoprobe.

A video tape (VHS) was made of the flexible videoprobe inspection

of the valve. As with all test data, the tape has been placed in storage at

ETEC for two years. A copy of the tape has been issued to NRC as a portion

of the test results. The tape demonstrates that a boroscope is a very

effective tool in ISI for determining the condition of the check valve

internals.

B.1.2 Six-Inch Check Valve

B.1.2.1 Life Cycle Tests

The results of the life-cycling of the six-inch check valve were

very similar to those obtained with, the four-inch check valve. The baseline

leak rates were very low, approximately 8 x 10'5 lb/sec (7.6 x 10-4 gpm) at

550F and 2250 psia and there was no measurable leak rate following the dry

cycles.

The 6-inch and 12-inch check valves were subjected to long-term

flashing concurrently with the four-inch check valve. At that time the

six-inch check had been dry cycled but had not been wet cycled. Its leak

rate before the flashing test was not measurable. At the end of the

long-term flashing test, the leak rate had increased slightly to an average

of 4.4 x 10-4 lb/sec (4.2 x 10 3 gpm) at 550F and 2250 psia. The minor

increase in leak rate indicated that the ability of the six-inch check valve

to function as a pressure barrier was not impaired by erosion damage to its

seating surfaces.

The leak rate also was measured at intervals during the long-term

flashing test. It varied but was always small. Changes in the leak rate

often occurred after the valves were cycled; probably due to particulate

matter either being swept off or deposited on the seating surfaces during

the cycling.

When wet cycling of the six-inch valve was initiated, a water

hammer problem was encountered and the cycling was interrupted after ten

cycles had been completed. The facility was modified by adding a standpipe

to the inlet line to subdue the water hammer problem. The six-inch check

then was subjected to seventy five additional wet cycles (eighty five total

41
wet cycles). Leak tests conducted after the cycling indicated that the

seating surfaces had suffered only minor damage during the life cycling, the

average leak rate was 1.9 x 10-3 lb/sec (1.8 x 10-2 gpm) at 550F and 2250

psia.

B.1.2.2 Loosened Internals Testing--Phase I

After completion of the wet cycling program, the valve was disassembled for loosened internals testing and the clapper assembly and valve

body were examined after completion of the wet cycling program. Although

the six-inch check valve leak rates after life cycling and the long term

flashing were well within the allowable leak rate for PIYs, they were higher

than the leak rates across either the 4-inch or 12-inch check valves.

Examination of the valve seating surfaces did not show any damage to account

for the higher leak rates. Differences in valve design may account for the

higher leak rates.

Unlike the four-inch valve, the six-inch check valve did not

sustain damage to the clapper assembly, bonnet or valve body during the

cycling. However, the four-inch check valve was cycled more than the

six-inch check valve, approximately two hundred cycles versus one hundred

cycles, respectively, which may explain the difference in stud deformation.

An alternative explanation might be that the check valve wet cycling method,

described in Section 2, did not result in the six-inch valve reaching the

full open position.

The internals of the six-inch valve, shown in Figure 43, were

loosened by grinding off the bolt to clevis assembly weld and loosening the

bolt 0.27 inches. After the internals were compromised the valve was cycled

five times, leak tests were conducted, the valve was cycled five additional

times and the leak tests were repeated. The average leak rate after the

first set of cycles was almost the same as the leak rates measured before

the loosened internals test, 1.5 x i0 3 lb/sec (1.4 x 10.2 gpm) at 550F and

2250 psia. After the second set of cycles, the leak rate decreased by an

order of magnitude to 1.9 x 10-' lb/sec (1.8 x 10-3 gpm) at 550F and

2250 psia.

The decrease may indicate some inconsistency in seating of the

six-inch check valve with loosened internals or may be due to particulate

matter dislodging from the seat thereby producing a better seal.

The six-inch valve internals were loosened a second time with the

bolt being loosened a total of 0.5 inches. After five wet cycles, the leak

rate was 1.9 x 10-' lb/sec (1.8 x 10- gpm) at 550F and 2250 psia, the same

as before the additional loosening. Following five additional cycles, the

average leak rate was measured as 1.1 X 10-3 lb/sec (1.0 x 10-2 gpm) at 550F

and 2250 psia. Thus the inconsistency in leak rate was repeated. The valve

was apparently reseating differently after being cycled. However, the leak

rates were so small that it would be impractical to expect utilities to

detect similar variations.

42
B.-1.2.3 Loosened Internals Testing--Phase 2

Unlike the fourinch check valve, the tsix-inch Atwood-Morrill

check valve was not installed in the HTF for AE monitoring for the second

phase of loosened internals testing, since there was no funding for flow

tests--only ISI setup. A wooden bonnet was fabricated and an in-service

inspection (ISI) port was drilled through the wooden bonnet. This avoided

altering the actual bonnet. ISI was conducted on the six-inch valve to

develop an inspection procedure and to demonstrate ISI with a check valve

that is of a different design than the four-inch Borg-Warner check valve.

The rigid borescope and the flexible videoprobe described previously in Appendix B.1.1.3 for the ISI of the four-inch check valve also

were used for ISI of the six-inch check valve. Figures 44 and 45 show the

inside of the six-inch check valve as seen through the flexible videoprobe.

A video tape (VHS) was made of the Welch-Allyn videoprobe inspection of the valve. As with all test data, the tape has been placed in

storage at ETEC for two years. A copy of the tape has been issued to NRC as

a portion of the test results. During this testing it-was demonstrated that

a boroscope is a good tool to use in determining the condition of a valve

during ISI.

B.1.3 Twelve-Inch Check Valve

B.1.3.1 Life Cycle Tests

The twelve-inch check valve was subjected to the long-term

flashing conditions and then wet cycled twenty times at 250F and 2,250 psid,

the number of cycles which could be made with one full load of supply water.

The life cycling of-the twelve-inch valve was abbreviated because life

cycling did not significantly damage the seating surfaces of the four-inch

and six-inch check valves. As previously discussed, loosened internals

testing was done instead of the complete life cycling program.

As for the smaller diameter check valves, the twelve-inch valve

baseline leak rate was very small, the average was 4.0 x 10.6 lb/sec

(3.8 x 10' gpm) at 550F and 2250 psia. The erosion produced by flashing

across the valve resulted in a small increase in leak rate to an average

leak rate of 7.7 x 10'4 lb/sec (7.3 x 10' gpm) at'550F and 2250 psia.

Likewise, the wet cycling had minimal impaction leak rate as the average

leak rate actually decreased slightly to 3.6 x 10'4 lb/sec (3.4 x l0'3 gpm)

at 550F and 2250 psia. But as later examination would show, neither the

cycling nor flashing caused significant damage to the twelve-inch check

valve seating surfaces.

B.1.3.2 Loosened Internals Tests--Phase I

The valve was disassembled for loosened internals testing and the

clapper assembly, valve body, and seating surfaces were, examined. No

significant damage was found. The seating surfaces were cleaned before

reassembly.

43
The twelve-inch valve is similar in design to the four-inch check

valve. However, there are two nuts in the twelve-inch valve clapper

assembly, the stud nut which holds the disk to the clapper arm and the

clevis assembly nut which supports the entire clapper assembly, as shown in

Figure 46. For the first loosened internals test, the stud nut on the back

of the clapper assembly was loosened. The weld between the nut and the stud

was cut and the nut was loosened 1.12 inches. If the nut were loosened more

than 1.12 inches, the clapper arm would completely slide off the ball

bushing. This would probably cause the clapper arm to hang up on the outer

edge of the bushing preventing the blapper from seating. By loosening the

nut 1.12 inches, the test program evaluated whether the valve could seatwith

the integrity of its internal assembly compromised, rather than illustrating

that it was possible to loosen the internals to a degree that would ensure

that the clapper did not seat. The ability of leak rate testing to identify

impending valve failure also was examined.

The valve was cycled six times and the leak rate was measured.

The leak rate was lower than it was prior to the loosening, 7 x 10-6 lb/sec

(6.7 x 10-5 gpm) at 550F and 2250 psia versus 3.6 x 10-4 lb/sec (3.4 x 10 3

gpm) at 550F and 2250 psia. Cleaning of the seating surfaces was probably

the cause for the decreased leak rate. After five additional cycles, the

measured leak rate was somewhat larger, 1.2 x 10- lb/sec (1.1 X 10-4 gpm) at

550F and 2250 psia.

For the second part of the loosened internals testing, the stud

nut on the back of the clapper was tightened to its manufacturer's recommended torque. The clevis assembly nut was loosened 2 rotations (0.15

inches) allowing the clapper assembly to rotate freely. In order to loosen

the clevis assembly, it was necessary to cut two welds: one between the bolt

and the clevis; and the second between the clevis and the bonnet. After the

valve was cycled five times, the average measured leak rate was 4.5 x 10-4

lb/sec (4.3 x 10-3 gpm) at 550F and 2250 psia. The leak rate following an

additional five cycles-was 3.8 x 10-5 lb/sec (3.6 x 10-4 gpm) at 550F and

2250 psia. Although these results show some inconsistency in leak rate

following cycling, the leak rates are consistently low, well within allowable PIV limits. It would be difficult to accurately measure leak rates of

this magnitude in operating plants.

B.1.3.3 Loosened Internals Testing--Phase 2

The program scope and funding allowed for conducting the phase 2

loosened internals tests on two of the three check valves. The 12-inch

check valve was not used for these tests because it was fabricated by the

same supplier, to the same basic design, as the 4-inch check valve. It was

decided that more information could be obtained by using check valves with

different basic designs.

B.2 Gate Valve Leak Rate Tests

The life cycle tests of the gate valves were very similar to the

check valves. The valves were (1) leak tested in their as-received condition to obtain baseline leak rates, (2) they were dry cycled 10 times and

leak tested to determine the degradation which could result for vendor and

44
plant check-out, and (3) they were wet cycled 50 times and then an additional 150 times with leak tests after each set of cycles to evaluate leak

rate versus valve wear.

The leak tests were conducted at a range of differential pressures

ranging from 150 psid to 2200 psid. The baseline leak tests and the leak

tests after the first set of wet cycles were conducted at 250F. The tests

conducted after the dry cycles and after the last set of wet cycles were

conducted at 250F and then some were repeated at approximately 400F and 550F

if a significant leak rate was measurediat,250F. The leak tests were

conducted at a range of differential pressures to provide data for evaluation of the ASME Code correlation. The leak tests were repeated at higher

temperatures to determine if temperature had any effect on the leak rate

correlation.

B.2.1 Four-Inch Parallel Disk Gate Valve

Prior to initiating the life cycling of the W-K-M four-inch

parallel disk gate valve, the packing gland nut torque was set to 30 ft-lb

per manufacturer's recommendation. The limit and torque switches were set.

The four-inch parallel disk gate valve had no measurable leak rate

during the baseline tests. Following the 10 dry cycles, there was still no

measurable leak rate.

After the first 50 wet cycles, the leak rate was still extremely

low. The average was 2.2 x 10 4 lb/sec (2.1 x 10'3 gpm) at 250F and 2250

psia but no leak rate was measured at the lower differential pressures. The

first time a leak rate was measured was at a differential pressure of

approximately 1160 psi.

After the final set of 150 wet cycles, the leak rate had significangly increased. At approximately 250F, the average leak rate was 1.4 x

10 lb/sec (1.3 x 10 .2 gpm) at 2250 psia. Since the leak rate was relatively high compared to previously measured leak rates, additional leak rate

tests were conducted at approximately 400k and 500F. At 400F the average

leak rate was 1.0 x 10' lb/sec (9.5 x 10. gpm) at 2250 psia and at 500F the

average was 2.6 x 10 lb/sec (2.5 x 10.2 gpm) at 2250 psia. For these

tests, the leak rate again was highest at the higher differential pressures.

A small amount of leakage through the packing was observed after

the 150 wet cycles. This type of leakage is common in PIVs and a usual

maintenance procedure is to tighten down the packing gland nuts. During the

motor signature tests conducted on the 4-inch and 10-inch flexible disk gate

valves, the packing gland nuts were adjusted to various torque settings to

evaluate the effect of this common maintenance activity on MOV operability.

45
B.2.2 Four-Inch Flexible Disk Gate Valve

Before the start of the life cycle tests of the ]i flexible disk

gate valve, the packing gland nuts were torqued to 30 lb-ft and the valve

switches were set. The valve also was instrumented with the motor signature

monitoring instrumentation, detailed description in Appendix A. The

baseline motor signature was recorded and used for comparison with the

signatures recorded during the motor signature portion of the testing.

The baseline leak rate at 250F for the four-inch flexible disk

gate valve was very small, averaging 7.8 x 10'5 lb/sec (7.4 x 10 4 gpm) at

550F and 2250 psia. The average leak rate at 250F after ten dry cycles was

virtually unchanged 7.7 x 10- lb/sec (7.3 x 10- gpm) at 550F and 2250 psia.

The leak rate showed no dependency on pressure. Since the leak rate after

the dry cycles was very low, leak tests were not conducted at higher

temperatures.

After the first 50 wet cycles, the average leak rate had increased

somewhat to 1 x 10-4 lb/sec (9.5 x 10-4 gpm) at 250F add 2250 psia. Again,

the leak rate did not vary significantly with differential pressure.

Following completion of the additional 150 wet cycles, the leak

rate had increased an order of magnitude to an average of 1.5 x 10-3 lb/sec

(1.4 x 10.2 gpm) at 250F and 2250 psia at 250F. However at higher

temperatures the measured leak rate was lower; 4.5 x 10-4 lb/sec (4.3 x 10-3

gpm) at 400F and 2250 psia and 4.1 x 10-4 lb/sec (3.9 x 10'3 gpm) at 550F and

2250 psia. Theoretically, the mass leak rate should decrease with the

temperature for turbulent flow based on the square root ratio of the density

at the higher temperature divided by the density at the lower temperature.

For laminar flow, mass leak rate is proportional to density over the cube

root of viscosity; therefore, leakage should increase slightly with temperature. In either case, between 250F and 55OF the leak rate should not

decrease by an order of magnitude.

For all leak tests, the downstream pressure was held above the

saturation pressure; this prevented flashing of the water across the valve.

If flashing had occurred across the leak path, a large drop in the mass leak

rate would be expected as the water flashed into water vapor. No leakage

through the packing was observed during the life cycle program.

B.2.3 W Ten-Inch Flexible Disk Gate Valve

With the packing gland torque set at 100 ft-lb., the valve

switches were set and the motor signature instrumentation described in

Appendix A was installed. Check out was then completed. Baseline leak rate

tests were conducted with the average leak rate being only 4 x 10-6 lb/sec

(3.8 x 10-5 gpm) at 250F and 2250 psia. After the 10 dry cycles, the leak

rate at 250F had increased to 2.8 x 1O 4 lb/sec (2.7 x 10-3 gpm) at 2250

psia. As opposed to most of the other gate valve leak tests, the leak rate

was higher at the lower differential pressures by an approximate factor of

three. However when additional tests were conducted at approximately 350F,

no leak rate was measured. After the first 50 wet cycles the average

measured leak rate was only 1.4 x 10-5 lb/sec (1.3 x 10-4 gpm) at 250F and

46
2250 psia. These-results indicate that perhaps the valve was not completely sealed (seated in) during the first series of tests after the dry cycles.

However, the leak rates always were extremely low.. It would be very

difficult, and not vital, for plants to measure leak rates in this low range

because these lowileak rates do not significantly impair the ability of the

valve to act as a pressure barrier.

After the next 150 wet cycles, the leak rate substantially

-increased to 1.3 x 102 1b/sec (0.12 gpm) at 250F and 2250 psia. The leak

rate was higher at higher differential pressures. At approximately 360F,

the average leak rate was 1.1 x 10.2 lb/sec (0.10 gpm) it.2250 psia. At

approximately 550F, the average leak rate was 7.4 x 10. lb/sec (0.07 gpm)

at 550F and 2250 psia. The trend seen with the four-inch flexible disk was

repeated; the leak rate significantly increased following the last 150 wet

cycles, the leak rate increased with differential pressure, and decreased

with temperature.

B.3 Gate Valve Motor Signature Testing

The motor signature tests were performed to study the basic

operating characteristics of LWR NOVs and instrumentation required to allow

-MOV operational characteristics. The tests simulated LWR plant conditions,

such as temperature and fluid, to provide sensor sensitivity and

applicability to determine operational readiness of the MOVs. .The

parameters selected to trend monitor will identify suitable pilkat instrumentation that can easily be monitored to assure continuing Oatesq Valve

operability. Today, there are many instances where valves cahni certified

operational by the-ASME Code, i.e., stroke and leak rate, but these certifications do not assure operability. The motor signature tests mayidentify problem areas and indicators to detect impending MOV malfunction.

Motor signature monitoring was performed during and after the life

cycle aging tests. The parameters monitored are given ih Section 2.211 and

shown in Figures 20 and 47. Only the 4-inch and 10-inch Westinghouse gate

valves were fully instrumented for motor signature testing. The 4-inch

;.W-.K-M valve was instrumented for stem position, velocity, torque-switchshaft rotation, limit switches, and motor current (see AppendixA.1.2).

During the life cycle aging tests, data was plotted to trend the

MOV operating parameters. The post life cycle testing MOV signature tests

are given in Table 10; these tests were run from zero to the worst case differential pressure across the seat, 2200 psi. With no differential pressure

across the valve seat, the effects of hydraulic loading on the stem could be

ascertained. In the case of the 4-inch W valve, a special set of MOV

signature tests were run prior to the life cycle aging tests-and are given

in Table 11. They were run at various temperatures and differential

pressures from 0 to 2250 psi and various packing bolt torque values to test

the MOV for opening force characteristics.

47
The data taken during these tests was typically recorded at 3 per

second on disc and at 1 per second on tape. Predominantly, the test data

was plotted on-line from the disc and the tape was only used for general

back up. This allowed the test results to be viewed for validity prior to

proceeding.

For all of the cycle testing, as well as the motor signature

testing, the torque switch was overridden during the first 30% of travel.

This was done in these tests to represent similar plant operations. In a

safety system hypothesis is that the plant would prefer the motor to be the

limiting factor rather than other equipment for the valve to open in an

emergency situation.

B.3.1 Preliminary Motor Signature Test on the 4-Inch Westinghouse

The first set of motor signature testing was performed on the

4-inch flexible wedge disc gate. The tests and characteristics are given in

Table 11. Tests 4, 8 and 13 were used as reference tests in that they were

randomly interjected as a standard and also is typical plant operating

conditions for PIY's.

The first eight tests were ran in the as-received condition and

had a torque setting of only 15 ft/lb on the packing gland bolts after test

8 had been run. The factory specified torque was 30 ft/lb. However, for

test 9 the torque was checked and increased to 30 ft/lb, 100%. Tests 10

through 12, as required, were run at overtorque conditions. The data

plotted were motor current, average stem force, torque switch rotation, stem

velocity, calculated position and motor vibration. A reference test'(4, 8-.:

and 13) was interjected during the test as a comparison to base conditions.

In tests 13 through 16 the torque was backed off to 30 ft/lb but the data

indicated that the loading of the packing was still excessive. This problem

will be discussed later in detail.

. . .~~~~~~~~~~~~~~~~~~~~~~~~.

48
Table 10., Post Life Cycling Motor Signature Tests

Packing Upstream Downstream

:Bolt Fluid, Fluid No.

Torque Pressure Pressure of Temperature - -'Test ,(X) (psi) (psi) Cycles (*F)

1. -50 2250 0 5 250'

2.' 200 2250 0 5 250

3. '300 2250 0 5 250

4. 50 2250 0 5 400

5. 200 2250 0 5 400

6. 300 ' 2250 .0 5 400

7.- -50 , 2250 0 5 550

8. 200 2250 0 5 550

9., ' 300 2250 0 5 550

Other tests were run as required

Figures 48 through 52 are the data from Test 4 that was run at

SSOF and 2250 psig fluid pressure which is a reference test and is typical

of the data characteristics'investigated for MOV operating characteristics.

This test was run then with 2250 psid fluid pressure across the seat at the

start of the cycle sequence..

Figure 48 is the current as measured in one of the 440 VACilegs of

the 1.9 hp motor operator. The cycling was about once every 10 seconds and

run in a manual mode. The close to open current is shown to be about 3 A

while the open to close current is about 4 A. These data were taken at

about'300 msec, therefore, some of the faster transient data at the leading

edge of the close to open cycle is missing in some cases.

On the first part of the opening cycle of the gate valve the gate

was pulled out of seating surfaces after being wedged in by the operator,

Figure 51 and 52. It was shown that during the opening operation the disc

loads then pops out in a few milliseconds to level off for the remainder of

opening as a function of the dynamic forces. In the open to close cycles

the current is higher and a transient pulse (motor start) is noted in some

cases. The higher running current during closure was due to the hydraulic

forces exertedson'the stem by the water pressure. These transients are

related to the motor starting and to excessive stem force being allowed by

the torque'switch in some cases, (see Figure 50).

49
Table 11. Motor Signature Tests 4-inch Westinghouse Gate Valve

Initial Pressure; Packing

Internal Fluid Drop Fluid Bolt No.

Pressure (psid) Temp. Torque of

Test (psig) (close to open) ('F) (ft-lb) Cycles

1 0 0 250 15 3

2 2250 850 300 15 3

3 0 (ambient) 0 550 15 4.5

41 2250 0 550 15 4.5

5 2250 400 & 0 550 15 6

6 2250 800 & 0 550 15 4

7 1100 0 550 15 4

81 2250 0 550 15 4

92 2250 0 550 302 4

10 2250 0 550 60 3

11 2250 0 550 90 2.5

12 2250 0 550 75 2.5

131 2250 0 550 303 4-5

14 0 (ambient) 0 550 303 4

15 2250 800 & 0 550 302 5.5

16 2250 400 & 0 550 302 5

'Reference tests

2Retorqued to specification

3Questionable; see text for details

50
Figure 49 shows the average stem force on the W-4-inch valve for a

fluid pressure of 2200 psid. Just prior to cycling, the downstream pressure

was 50 psig; however, upon opening, the cavity filled very fast and exerted

a compression force (pressure assist) on the stem in the direction of

opening. Pulling the gate from its ways, which is shown as a spike on the

leading edge of the open cycle and was as high as 4,000 lbs in some cases,

which is additive to the dynamic opening force. The opening force on the

stem is the packing friction minus the dynamic hydraulic force, which was

very near the open zero value of -3500 lb in this case. Upon closing, the

dynamic stem force is the packing friction plus the hydraulic force, since

in these tests the fluid was not blown down prior to closing. In Test 4

the dynamic force (during travel) was about 2,000 lb. while the total force

on seating was about 10,900 lb. averaged over the four cycles. The data

from Test 5 indicated about this same seating load.

Test 3, shown in Figures 53 to 55, was similar to Test 4 (550F)

but the fluid pressure was reduced to 0 psig. Test 3 data, in comparison

with Test 4, Figure 49, should eliminate the hydraulic stem forces and leave

only the packing coefficient on stem force. The full average stem seating

force was about 16,200 lb. for Test 3, or about 5,300 lbs. higher than for

Test 4. However, the actual dynamic driving force was only 800 lbs.

Considering this and the dynamic force at higher pressures, the differential

is 1200 lbs. which does not sum to the 5,300 lb. differential between the

two tests. This anomaly is attributed to the mechanical torquerswitch which

governs the Limitorque force on the stem and allpws for greater seating with

no internal pressure. Therefore, the seating force is a function of

internal pressure and in this case, greater by 5,300 lb with zero internal

pressure.

The dynamic torque switch rotation at 2250 psig was 5.8 to 7.2

degrees as compared to 1.9 degrees at ambient pressure, Figures 50 and 54,

respectively. However, the total rotation upon seating was about the same

at 15 degrees. Looking at the difference in the dynamic torque value one

might expect that the seating force should be increasing with increased stem

velocity. This is shown not to be the fact since the closing velocity is

about the same in both cases, Figures 51 and 55, Test 4 and 3 respectively.

The velocity seems to be governed solely by the motor and its gear reduction. The sudden Jump of the gate out of the seat due to wedging, is

clearly indicated at the leading edge of the opening cycle (positive). The

motor current was a constant 3.5 A while the motor vibration did not change

from Test 4.

MOY signature tests were run at the operating conditions of 550F

and 2250 psig fluid pressure during all cycling sequences; the motor

current versus packing bolt torque data are presented in Figure 56. The

first segment of the signature tests was run with a packing bolt torque of

15 ft.-lb. which is 50% of specification; therefore, the packing bolt torque

was increased to 100, 200, 250 and 300% of specification. Three cycles were

typically run for each test. Indications are that the motor power was

terminated early on the last cycle of the 250% and 300%.

The dynamic closing force of the MOV signature tests at 2250, 1100

and 0 psid are plotted in Figure 57. These data indicate about the same

51
trend as the motor current, Figure 56, for different packing bolt torques.

These data show a very good correlation for current to packing torque and

condition. The current could prove to be a viable in-plant parameter to

trend and ascertain MOV operability.

The Figure 58 triangle data (dynamic closing force) and the three

high current data points at 100% packing torque were taken after the 300%

packing bolt torque test. The high data was attributed to residual loading

from the packing even though the bolts had been backed off. The packing

used in both Westinghouse valves is John Crane 187I a graphite impregnated

braided asbestos with a fine braid of Inconel wire. It was shown that this

type of packing does not have resilience adequate to recover, at least, in

the short time utilized here. From these data it is not clear that the

packing would release slowly or not at all if the valve packing was overtorqued and then released since in this set of tests it was cycled to break

it loose. In the plant case, the packing could seize to the stem after long

periods of time at high temperature and not allow appropriate operation at

the next required actuation although the inconel braid in the packing is

supposed to obviate this problem area.

Realizing that the motor current should be a function of MOV

degradation, that is, increased packing load, etc., the closing motor

current versus the dynamic closing force was plotted for this set of tests

and is shown in Figure 59. The dynamic closing force is defined as the

difference from the open valve to the dynamic loading just prior to seating.

The odd point in these data is the 0 delta P at about 3000 lb. That data

point was taken after the valve stem hung up during a 300% packing test and

therefore had not released at the time the next set of cycles and measurement were run.

The operator motor current as a function of the dynamic stem force

was shown to be a linear increasing function of all the cycle tests performed in this set of tests. The data taken after the 300% packing bolt

torquings, where the packing friction was excessive, fit the general data

trend. Therefore, motor current seems to respond the same as the stem force

to give informative information on operability.

The data shows a direct relationship between the two parameters.

These data are indication that MOV motor current could be used in the plant

as an indicator to assess packing problems and operability.

B.3.2 4-In. W Motor Signature Tests - Second Set

After the first set of motor signature tests was performed on the

4-in. W gate valve, the testing was terminated until the next fiscal year.

At that time, the life cycle tests were performed for valve degradation,

then the second set of motor signature tests was run per Table 10. Therefore, after the first set of tests, the packing was left torqued and the

system dry.

The data obtained during these tests are given in Table 12 and

include life cycle testing. The data from the test sequence was very

52
scattered due to packing friction problems; therefore, data listed in the

table are the motor current, differential stem force, and vibration.

The currents and differential stem loads ranged from 3.5 to 5.7

amps and 2,700 to 12,200 lbs, respectively. The larger stem loading due to

the excessive packing friction was such that the torque switch would

terminate closure prior to total gate travel. The vibration of the motor is

included as an indication of excessive motor work. Results indicate that

the valve packing can become over packed during a long period of time and,

even if the bolt packing torque was backed off, the stem to packing frictions may still exhibit loading that is excessive for-operation.

Table 12. 4-in W Motor Signature Tests

Current Differential Motor

(amps) Load Vibration

Test Open Close (lb x 103) (G's) Comments

Dry cycle 3.8 4 N.O. 6 0 psig

Life cycle 3.5 4 2.1 - 3.5 4.5

550F:

15 ft-lb 3.5 4.0 2.8 4 -6

60 ft-lb 4.8 5.0 5.9 5 - 6

90 ft-lb 5.5 5.7 10 - 12.2 5 - 6 Hung up

250F:

15 ft-lb 4.5 5.1* - 4.5 8.3 6.98* 4 - 6 No closure

60 ft-lb 4.6 5.0 .7.9 5.5

450F:

90 ft-lb - - - - Would not cycle

15 ft-lb 4.1 4.5 5.7 4.8

60 ft-lb 4.2 5.1 7.6 -

90 ft-lb 4.2 5.7 >12.2 4 - 6 No full closure

75 ft-lb 4.1 5 10 4 - 5.7 0 psig

75 ft-lb 4.2 5.7 10 4.5 - 6 No full closure

30 ft-lb 3.5 4.2 4.5 3.9

*Current high due to excess friction.

53

N,
B. 3.3 10-Inch W Motor Signature Testin,

The Westinghouse 10-in. flex-wedge disc gate valve was instrumented much the same as the 4-in. to perform motor signature testing, Figure

47 and Section A.1.2. The differences were that the current transformer and

LVDT were changed to maximize the measurements. Fiber optics, Section

A.1.2, was also added to ascertain seating characteristics in the life

cycling and specific motor signature testing. The life cycling test results

of various sections of the life cycling program are discussed in this

section. Then, the motor signature test results, as required by Table 10,

ate included which required tests at various bolt packing torque and

temperature at typical plant operating conditions. All of the life cycling

and motor signature tests were performed with the same gate valve computer

algorithm, Table 8. Typically, all of the tests were run at 250F and 200

psid across the gate at valve actuation, except the first ten dry cycle

tests that were run with zero differential pressure at 650 and 250F.

Plots from the dry cycle test for motor current and average stem

force versus time are shown in Figures 60 and 61 for zero differential

pressure. Shown are cycles four through ten run at 250F. The data plotted

for these tests was at one per second. The opening and closing currents

were very near the same and averaged 28.8 amps. Figure 61 shows the average

stem force during this segment of the test; these data indicate a dynamic

differential stem force of from 5.8 to 8.8 x 103 lbs during the dry cycling.

However, the dynamic differential stem force was increasing as the number of

cycles increased indicating the dry packing giving a problem. This dynamic

differential stem force data at zero differential pressure is directly

related to the packing forces.

During this set of cycles the current did not change appreciably,

but the motor vibration, Figure 62, increased in about the same manner as

the differential stem force. This is a clear indication of the gate wedging

into the seat. A typical unwedging characteristic is shown at the leading

edge of the opening cycle, at about 5 min., and the total vibration during

opening. The remaining unwedging pulses were not recorded due to the data

frequency used here.

The next set of life cycles were in a group of 50 all run at

typical operating conditions of 250F to result in flashing during the

opening. These cycles were run with 2250 psid across the seat just prior to

opening, then closure with 2250 psi fluid pressure on the stem/gate assembly.

Valve operator data of the initial 24 wet cycles for motor

current, fiber optics close and valve stem loading, are shown in Figures 63,

64, and 65, respectively. The motor current, Figure 63, was fairly

consistent during the first and last of this data. The average opening

current during the first half was averaged at about 27 amps and 24 for the

last. The closing current was about 40 amps and 37 to 38 amps,

respectively. The first portion of the data shows large leading edge spikes

(-120 amps) that represent the gate being pulled from the seat. The fiber

optics data, Figure 64, shows a decreasing trend and also a lessening of the

54
envelope. This is assumed to indicate the gate seating in a lower portion

of the seat assembly.

The stem forces are directly related to the motor current in that,

when the gate is being wedged into the seat appreciably; the gate will tend

to hang up on removal causing a high motor current pulse. However, if the

packing friction coefficient increased during cycling, since the cycle is'

terminated on the torque switch, the opening and closing currents would also

change proportionately. Also, a packing friction increase would-cause the,

actual seating to be decreased by the same additional force required for the-~

extra packing drag. Thus, when the packing forces are released, both the - opening and closing motor currents should decrease. Therefore, assuming the

above argument, the gate should not be wedged as hard into the seat. This

is shown to be the case in the second half of Figures 63, 64, and 65, and

also in Figure 66 which is the rotation of the torque switch during the same

test time. This data indicates that the gate, seat, and packing are being ;

worn in initially. The torque switch rotation in Figure 66 indicates that

for greater stem forces, as shown in Figure 65, the rotation is less and

does show an inverse trend. But, it should be remembered that this is a

mechanical device and may have some initial settling. This subject will be

discussed at greater length later in this section.

After the 50 wet cycle leak rate measurements were made, the

facility was reloaded with water and the temperature stabilized for the 15-lOI

wet cycle test. The cycling tests were run in the typical manner. Figure

67 shows the valve stem and motor temperature (top and bottom curves

respectively) increase as a function of cycling. The test valve cycling - temperature was 250F and the valve stem temperature was measured to give an

indication of the strain gage bonding integrity as well as an indication of

the temperature of the operator, and, to some extent, the fiber optics

signal conditioners. The temperature started out at 80F then increased to

about 185F near the end of the cycling program. Considering the valve body

temperature and that the stem was cycling, this was about the limit ex-,,

pected.

The motor temperature is also shown in Figure 67 and depicts the

motor temperature increase during the cycle test. The maximum temperature

was about 135F. This temperature increase is at least partially due to the

fact that this motor has a 15 minute duty cycle, but considering the

specifications, it is still in the operating range.

Figures 68, 69, and 70 show the motor current, average stem force,

and fiber optic closed data during a major portion of the 150 wet cycle

tests. The data indicates the trend of the parameters as a function of each

other and as cycling progressed. These data, plotted over a long period of'

time shows a general trend, but does not have appreciable definition. Areas

of interest will be expanded for discussion later in the text. The areas of

no cycling depicts those areas where required facility parameters were not

met for the computer program, therefore the computer waited until all the

parameters were met prior to the next cycle.

The motor current data starts with current pulses in the 120 amp

range for the opening cycle and closing current of about 35 amps. But, the

55
data through the cycling is not constant and shows the opening pulse and the

closing current running in cycles, which indicates that there was a change

probably due to the packing friction.

Figure 68 shows the valve stem force as a function of cycling.

The data are fairly constant for the closing force except in the region of

about 130 and 200 minutes where there are sudden slips in the closing load.

These same variations are shown in the fiber optic data, Figure 70. An

important region of the stem force data is in the initial portion of the

opening when the gate is pulled from the seat; the indication is a negative

force. The darkened negative pulses are the regions where the gate was

forced into the seat which is identical and typically to the high motor

current region. The closed fiber optic data, Figure 70, indicates some

trend of general decrease but the closed position decreases from -5100 Mv to

a -5400 Mv through the cycle program. This is an indication that the gate

was seating at a lower position as it was worn in.

The region of 200 minutes was expanded for a more detailed

investigation of the step in fiber optics and stem loading. Valve stem

loading in that region, Figure 71, is shown at 15 minutes with about six

cycles before and after it closed. The stress decreased by about 20,000 psi

then recovered by about >10,000 psi, much the same trend as the fiber optic

data. However, the open stem force is less negative in that region, but

does not show the step function. The temperature, torque switch rotation

and motor vibration do not indicate any abnormalities in this region. The

explanation for this data shift and the one at about 120 minutes remain

unexplained except that it could have been a shift in the torque switch

operation.

When looking at the motor current data in the 190 minute region,

Figure 68, there is one of the general increases and then a diminishment by

200 minutes. The motor current and vibration in this region were expanded,

Figures 72 and 73, to look at the general current excursion and the step

function. None of these data show indication of a step function at 200

minutes. These data are good general data for cycling. The first two

cycles show the large current spikes of up to 140 amps on valve opening with

a typical open running current of about 25 amps. The open to close current

dropped from 40 plus amps down to about 36 amps in the dip region. From

this low level there was a general increase in both the open and close

current starting at about 240 minutes Figure 72 data. These expanded data

indicate that the opening pulse current averaged about 75 amps as compared

to 40 amps in the general plot, Figure 68; these expanded data are at a

higher frequency and therefore have greater sensitivity. The motor vibration is fairly constant through this region of cycling, indicating no

sensitivity to the step function phenomenon.

In summary,-The life cycling data indicates that the wedge tends

to settle-in to some extent during cycling and that the closed fiber optic

data tend to verify this. The current indicated a tendency to cycle, e.g.,

increase then drop back to normal. This resulted in exceptionally large

opening pulses of the order of 120 amps. This was attributed to sticking

friction of the gate to the seat. The total increased cycling load was

attributed to packing friction. The standard position indication was not

56
able to detect the trend and minor changes in seating as did the analog

fiber optic device which gave indication proportional to the stem loading

and wedging of the gate into the seat.

The motor signature testing, Table 10, was performed after the

life cycling tests and leak checks were completed. This set of tests was

run only to ascertain characteristics of the motor operator, Table 2, for

non-typical stem packing torques wtth an internal fluid pressure of 2250

psig.

The motor signature tests were run at 250F, 400F, and 550F. The

250F tests were run for ten cycles for each torque setting to ascertain if

extended cycling was required. The remaining tests were run at the required

five cycles for each torque setting. The cycles were typically run in two

minute intervals and the various torque setting cycles are grouped in the

figures.

The operator motor current for the motor signature tests is

summarized in Figure 74 where the motor current is plotted against a percent

of the required packing torque. The specified packing bolt torque was 100

ft-lb. for this valve. The data plotted for 100% was all at 250F and taken

during the life cycle testing. No cycles were run at 100% in this motor

signature phase. Typically, the motor current increased as the temperature

increased except in the 300%-400F test where the current increased to about

51 amps when the excess packing friction stopped the cycle.

Effectively, the close to open stroke running current was fairly

constant at about 25.7 amps for the 250F tests and increased slightly with

temperature. The only anomaly was in the 0 psid test which was run dry and

at the first of life cycling. It showed open and closed currents of 30.5

and 31.8 respectively; the low opening current is directly proportional to

the internal fluid pressure. However, each was higher than the other

minimum currents because the internal pressure, i.e., driving force, was

removed and it was the first dry cycle. This wearing-in characteristic was

shown to continue into the first 50 wet cycle tests, Figure 74, which showed

the initial closing and opening currents at about 42 and 30 amps, respectively, prior to decreasing after some number of cycles.

The closing current during these tests tended to be around 41

amps. The trend was to increase slightly with the temperature of the tests,

except in the 400F-300% case at 51.5 amps. There was some indication that

the packing tests at 50% could have been effectively over-torqued, (indication was that the packing did not release even though the packing bolt

torque was released), from the previous tests, even the 100%. The set ran

at 250F for ten cycles and did show some settling and decrease in current in

the first portion of the cycles and, therefore, may be a little high.

In the case of the motor signature tests at 400F, there was no

indication in the general data that there was a packing friction problem.

The motor current, stem force, closed fiber optic, and torque switch are

shown in Figures 75 through 78. The three data segments are of the 50, 200,

and 300% packing torque. The irregular spacing in the cycling is due to

57
facility parameters being out of specification, therefore the computer holds

until the parameter specification is met.

The motor current starts off in a reasonable range in the 50%

packing tests while the fiber optics show that it was not seating as well

during the cycling. The stem forces agree with the seating characteristics

while there was some decrease in the mechanical torque switch setting which,

to some extent, which could have been contributed to the low current and

stem loading. However, during the 200% test, the open and close pulse

currents increase appreciably and are in agreement with the gate seating

while the stem loading stayed about the same. Then, during the last test at

300% the pulse currents are not as high but close running current increase

to about 52 amps. During this time, the stem force and close fiber optics

indicate the gate not seating to some extent while the torque switch shows

some increase and indicates excess stem load during gate travel. This is an

indication that these parameters trend the actual operating characteristics

quite well.

The dynamic differential stem force versus the packing bolt torque

is summarized in Figure 79. The data of the 100% packing bolt torque was

taken during the cycle tests. These differential stem force data are shown

to increase with the number of cycles. Of course when referencing (Figure

69) the long term cycling data, it is appreciated that we used discretion in

selecting these data, the data plotted was selected prior to the creation of

Figure 69 and only included as a general indicator. The cycling data are

shown to increase with temperature and packing bolt torque in a fairly

linear fashion. These data indicate that at the higher temperatures, one

could expect greater differential stem forces which should be proportional

to the motor current, of which these data are (see Figure 80).

B.4 Acoustic Emission Monitoring

Four acoustic emission measurement systems were installed on both

the check and gate valves for leak rate monitoring. The systems were

supplied by ETEC, ANL, ORNL, and the Naval Ship Research & Development

Center. For the gate valve testing, a fifth acoustic emission system was

developed and installed by ETEC. This device was to hopefully allow the

measurement of water leakage through the valve seats at lower levels than

the other systems. The Naval Ship Research & Development Center equipment

is portable equipment which must be manually operated, therefore it was not

used as extensively as the other equipment. The ANL, ETEC, and ORNL sensors

were read automatically by the facility DAS. Each of the systems had a

transducer installed on the valve and on the valve inlet pipe, Figures 81

and 82, respectively.

The acoustic emission measurement with the various systems was to

ascertain 1) a level of detection and, 2) the ability to correlate AE to

leak rate. Unfortunately, the leak rates obtained in the valves as a

function of life cycling was only in the low 0.01 lb/sec (0.10 gpm at 550F

and 2250 psia) region.

Addressing the AE leak rate measurement problem, ETEC had the high

sensitivity acoustic emission (HSAE) equipment built for the last series of

58
life cycle testing. This equipment consists of narrow band 180 Hz transducers that use a pinger for setup calibration which enhanced the sensitivity. To reduce background system noise, the pinger was located an

appreciable distance on the line away from the line transducer in order to

calibrate the system plant noise transducer on the line and the valve

transducer.

The HSAE device was the only device that gave effective information during these tests. The data from a series of leak tests are presented

in Figure 14. Plotted is the calculated leak rate and acoustic emission as

a function of test time. The initial leak rate measurement was, at 2100 and

1100 psid, 0.0025 and 0.0017 lb/sec (0.02 gpm). The acoustic emission is

shown to increase as a function of leak rate. The lower AE measurement was

at a leak rate of 0.0005 lb/sec (0.005 gpm). The leak rate data show

positive and negative pulses around a center value. The pulses occurred at

times when the differential pressure tubes filled and then blown down in

order to continue leak rate measurements for an extended time.

During some of the leak rate tests, the acoustic emission spectrum

was recorded on analog tape to survey for frequency content and amplitude

that could be attributed to a water leak across the valve seat. It was

recorded at 60-inches per second and when digitized for plotting results in

10,000 points per second. These data indicate that, at least, below 0.01

lb/sec (0.10 gpm) at 550F and 2250 psia, there was no discernable frequency

or amplitude signature that could be attributed to leak rate of the standard

transducers. The HSAE data was not recorded on the analog tape and, therefore, was not analyzed for frequency signature.

Acoustic emission is a good non-intrusive method to measure valve

degradation, however, there is a sensitivity problem to trend the leak rate

by AE. One would like to measure in a low leak rate region and increase

into; a region where maintenance is required. The ETEC HSAE device would

allow this measurement down to at least the .001 lb/sec (0.01 gpm) leakage

region. However, this device requires additional testing prior to certification for LWR utilization.

59
NRC-88-01

Page 60

12/08/89

Figure 1. Four-Inch Check Valve Internals
NRC-88-01

Page 61

12/08/89

II

'.V I. ,

. I

.. .- 11 - -,

111,

i

r II

.I - I . , .

Figure 2. Test Logic
NRC-88-01

Page 62

12/08/89

Leak Wa (lO bjbsoc)

a0

w 1 s

* elf WM at w

Figure 3. Check Valves--Leak Rate

Versus Life Cycling

1a

I a 15 a

* t CP1U% ft & an

Figure 4. Gate Valves--Leak Rate

Versus Life Cycling
NRC-88-01

Page 63

12/08/89

_U lux Oad IE.3

IE-4

I

5- %

IL: I:

I- . .

II- ,- /

I I I I I 11111 I I " III I I I I I I oil I I

I I I

I

1-5

14-6

2 5

g0

WFEFUMA OMM3 Psi

5

£3

I 1

El

Figure 5. Four-Inch Check Valve Leak Rate

Versus Differential Pressure

ftM 1O bluE _ _ _ _ _ _ _ _ _ _ _ _ _ _

2-2 , I~~~ II

5

I

W-a

I I I I fi ll I I I I I II I 4 I I I1 II I- I I I II 11 11-

2 a a I I I I a. Ye Y1X 92

ovnm=A wESmI pisi

In 114

Figure 6. Six-Inch Check Valve Leak Rate

Versus Differential Pressure
NRC-88-01

Page 64

12/08/89

_ WEa ME Oblu

X-z

IE-3

If-A

;

2

_ 11111 I F 111111 I I 11111 I 111111,

IN 2 5 2 5 2 2 5 MA Ed

DIFfW"Dt MpESiE toi

Figure 7. Twelve-Inch Check Valve Leak Rate

Versus Differential Pressure

I' .

5 ,.,,,,,,..ll1s

iE-3

El

2 5

in 2 S 2~'

w ~ e i n E J s

5 I 5

SE if'

Figure 8. Four-Inch Westinghouse Gate Valve

Leak Rate Versus Differential Pressure
NRC-88-01

Page 65

12/08/89

_,g UKm bAevd

IE-Z

IN-,

l

£4

I

f4-

I

fSX 5 2 5 2 5 2 1

IEO ftE SF2 S3 E4

Figure 9. Four-Inch W-K-M Gate Valve

Leak Rate Versus Differential Pressure

I I 111511 I I 11111 I II 111111 I I I uuil

X~~~~~~~ /

fEI

l

I

f-2

2

IE-3

I

I

I 5 - 2

I0 IEI tEA

uh L K 21 E s i3

5 2 5

SE4

Figure 10. Ten-Inch Westinghouse Gate Valve

Leak Rate Versus Differential Pressure
NRC-88-01

Page 66

12/08/89

I

I

HM

5

I .~ ~ ~ ~ ~

.. . ..... ....I . . . . . ' . I . . . . . . I . . . . . . I . . . . .

aH

19-

1t0 20 30 C)

7DUAIUE 1 n

Figure 11. Four-Inch Check Valve

Leak Rate Versus Temperature

La1 PtA cbM/atJ

12-I -

I

2-2

I

IE-3

3

~~~~~~~~~~~~~~~~I 0,

I......I.. ......... I......I......I.....

3

12-5

3

12-I - -. ...- . .. .. . .. .. . .. .. . .. .. . .. .. . .. .. .

a too 200 30W

WMAN 112

M 5oo

Figure 12. Gate Valves

Leak Rate Versus Temperature
NRC-88-01

Page 67

12/08/89

I

f

UW

-I9

i

pa

I

I

Figure 14.

Elapsed Time (min)

Four-Inch Westinghouse Gate Valve

Leak Rate Versus Density

£42

I

I

SE-3

I I I ! I I I I I -. t £1II11II1

I

'.4

ff0 I 8 4 3 1 7 8 I~E

£ 1 1 1 / ci b l f

U 3 A4 6 1 I 1

E2

Figure 13. Acoustic Emission High Sensitivity

and Standard Leak Measurements -- Four-Inch Gate Valve Post Life Cycles
NRC-88-01

Page 68

12/08/89

a 20 40 60 80 100 120

Elapsed Time (min)

Figure 15. Standard Acoustic Emission Trace -- Four Inch Gate

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

83 GPM (velocity = 3 ftlsec) 172 GPM (velocity = 6 ftlsec)

344 GPM (velocity = 12 fWsec) 430 GPM (velocity = 15 ftlsec)

Figure 16. Fourier Analysis of Acoustic Data -- Baseline
NRC-88-01

Page 69

12/08/89

e. ;.! ~. -4 . kS. sN~

, i f ., X,, .... :~~~~-f !

:; ' ; | ' t V +'

A.s. ... .. . 

258 GPMf, (velcit 9, ft/e a)'"

_ T u -- --- - - - A_.s - r

83 GPM (velocity = 3 ft/sec) 172 GPM (velocity - 6 ftWmec)

344 GPM (velocity = 12 ft/Sec) 430 GPM (velocity = 15 ft/sec)

Figure 17. Fourier Analysis of Acoustic Data

Internals Loosened (2 turns)

au a --- - - I r. -- I "' - _ a _- -

83 GPM (velocity = 3 ft/sec) 172 GPM (velocity = 6 ft/sec) 258 GPM (velocity = 9 ft/sec)

344 GPM (velocity = 12 ft/sec) 430 GPM (velocity = 15 ft/sec)

Figure 18. Fourier Analysis of Acoustic Data

Internals Loosened (4 turns)
NRC-88-01

Page 70

12/08/89

U ~ : .

IUAnPM 14* vricri1 344GPM (12 FT/SEC)

172 GPM (6 FT/SEC)

.4Sx X AamtYwI72GPM (6 FT/SEC)

Figure 19. Fourier Analysis of Acoustic Data

Comparison of Results
NRC-88-01

Page 71 -- 12/08/89

Figure 20. LLTR Schematic
NRC-88-01

Page 72

12/08/89

11 , " ,I J&-1 -, - -117

-- 4", , - A , - 4 - A  _t ',

im

Figure 21. Check Valve Installed In LLTR

Figure 22. LLTR Control Room
NRC-88-01

Page 73

12/08/89

Figure 23. LLTR Data Acquisition System

Figure 24. Three-Element Strain Gage to

Measure Stem Force
NRC-88-01

Page 74

12/08/89

Figure 25. Open Position Bifurcated

Fiber Optic Device

Figure 26. Close Position Bifurcated Optic Device
NRC-88-01

Page 75

12/08/89

CTparacterlstlc

Fiber Optics 0.0

0.6

i F 1~~~~~~~~~~~0.4

0.2L

Transmission i

0 25 50 75 100 125 150

Distance (mils)

Reflectr 0e

Distance (mlis)

Optical

Fl r 1~~~~~~~~~~~~~~~~.0

0.8:

0o.

Dotctore Raftect[Ir 06\

U lcmrbe nding\

0 25 8 10t 12

Distance (miss)

Figure 27. Characteristics of Various Fiber Optic Devices

4-n 9-W Check Valve

Figure 28. Four-Inch Check Valve Flow Test Setup
NRC-88-01

Page 76

12/08/89

'4t

i -f" ,I

* c52iiS A 'P

_iii~i iV r +* fr 'L ' !I

__ ~~~~~~~~~~'I

Stud Afeife Cyclin

Figure -2

Figure 29.

Four-Inch Chc Va

Four-Inch Check Valve

Figure 30. Four-Inch Check Valve Bonnet After Life-Cycling
NRC-88-01

Page 77

12/08/89

G ELAPSED TIM19 IM!NU'ESI

Figure 31. Flowrate Versus Time

Internals As-Received

-2FT/SEC ---- IF/$!C- -- 9 Fu5 sC --- 2FIK-1S FTISECEn @ -- : 7--7-- -

CsT. - S

A K* i 4" I_ _ _ _ _ _ _ _ _ i _ I

W -~~~~~~~~

-0 i

a. i

Li - i _ _ _ _ _ _ I__ ~ ~ I__ _ I__ 

z -

I

i -i( .&Nwjj . I

i i I

a I II

a _ _ _ _ _ I _ _ _ _ _ _ _ _ _ _ _ _ I _ _ _ _ _ _ I _ _ _ _ _ _ I _ _ _ _ _ _

, I I I I

ELAP'SED T:ME (IHNUTES)

I;

Figure 32. Narrow Band Acoustic Signal

Internals As-Received
NRC-88-01

Page 78

12/08/89

To

FT/SEC -

sI Iii - 'Ill" hi' I - I k'J I lULl liIII' l.a 'p 0! I I II! I-,, I

CI

C.,

C

A~~~i i!j _

C Or

Figure

a a a , ELRPSE3 TOIE (F-NUTES)

33. ETEC 10 kHz Acoustic Signal

Internals As-Received

12

-IC~~~~~~~E

2 6 5 I lo

ELAPSEO TIME IiENJ-ESI

Figure 34. Flowrate Versus Time Loose

Internals (2 turns)

12
NRC-88-01

Page 79

12/08/89

1- Fl/SEC -f-4 FTISEG- -- FTISEC--12 FT/SEG-C--15 FT/SEC---

ccI 2

2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1

ELP'SED TIME IMINUTESI

Figure 35. Narrow Band Acoustic Signal

Loose Internals (2 turns)

ELRPSEO TIME IMINUTES)

Figure 36. ETEC 20 kHz Acoustic Signal

Loose Internals (2 turns)
NRC-88-01

Page 80

12/08/89

0 ..,__ 

- -_ _ ___ -

1

i. i

i i 1.

t

I I

7I Q I 

I ~~~~~~(9 FT/SC

z

* (6F/SEC1 I

i I I -

(FfISC)

I *I a I Z 3 is 5

ELAPSED ?T1ME flV[NUTES6 7 e I

Figure 37. Flowrate Versus Time

Loose Internals (4 turns)

I S

ELAPSED TIME (MINUTES)

Figure 38. Narrow Band Acoustic Signal

Loose Internals (4 turns)
NRC-88-01

Page 81

12/08/89

f

I

ELAPSED TIME 94INUTES)

Figure 39. ETEC 20 kHz Acoustic Signal

Loose Internals (4 turns)

Figure 40. Four-Inch Check Valve

Videoprobe Inspection
NRC-88-01

Page 82

12/08/89

Figure 41. Four-Inch Check Valve In-Service

Inspection--Clapper Stud Assembly

Figure 42. Four-Inch Check Valve In-Service

Inspection--Clapper Pin Area
{ ArI w

NRC-88-01

Page 83

12/08/89

Figure 43. Six-Inch Check Valve Internals

Figure 44. Six-Inch Check Valve In-Service

Inspection -- Clapper Stud
NRC-88-01

Page 84

12/08/89

Figure 45. Six-Inch Valve In-Service

Inspection Clapper Pin Area

-CLEVIS ASSEMBLY BOLT

Figure 46. Twelve-Inch Check Valve Internals
NRC-88-01

Page 85

12/08/89

OTOR VIBRATION

-tfr _ UMOTOR CURRENT

FIBER . -RCSSETT 3 R 

OPTIC ,r_ STAAIN GAGES

SWMITCHS L. STEVA TEMPERATURE

C~~ ~~~ -

ACPOtSTTC 2 ? .n

OEVIC,_.

t ~~~ ,5, ~LEAKPbATE UEAUREt ENT

Figure 47. Ten-Inch Gate Valve With

Motor Signature Instrumentation

if

a

a

C

I.-

a

ra

2C

.. . . , . . . ... ...

... ..... .... ...................... ....... . ... ............... 1 ..... .........................

4e ao soo eo b

ELRPSEO TIME (SECONDS)

Figure 48. Motor Signature Test Four

Motor Current Versus Time

0
NRC-88-01

Page 86

12/08/89

, 1 ........................................................... .... ................... ..................... .......................

_e,4v4 ~ ~~ ~ ~ ... ~ ..... ~~ ~....... ......................... 

1. II. .. ' ..-. . _ . _ _

0o as 40 80 80Ia 2

r' RPSEL' raft (S CONOS

Figure 49. Motor Signature Test Four

Stem Force Versus Time

...- ................ ...... -- ........... -...: ................. ....

I

ELAPSED TIME ISECONDS3

Figure 50. Motor Signature Test Four Rotation

of Torque Switch Versus Time
NRC-88-01

Page 87

12/08/89

Cl K]''''''''--. - . - . .,- .................................

. l...................................................................... ... ............... ... ....... . . .. ..... .............................

........... . ....... ...............

190' .. .... . .... .. . ... .. ....... .. .... ... . ... ......

ELAPSED TIME fSECOND51

Figure 51. Motor Signature Test Four

Valve Stem Velocity Versus Time

ELAPSEO rIlWE (SECONDSI

Figure 52. Motor Signature Test Four

Motor Vibration Versus Time
NRC-88-01

Page 88

12/08/89

Figure 53. Motor Signature Test

Three Stem Force Versus Time

ELRPSED TIME (SECONDSI

Figure 54. Motor Signature Test Three

Rotation of Torque Switch Versus Time
NRC-88-01

Page 89

12/08/89

.1

4'0 r~b e ELRIPSED TI1E (SECONDS1

Figure 55. Motor Signature Test Three

Stem Velocity Versus Time

'p

a3 0

a

0

03

4

I

I a

A

3 A A A a

a

ft

- 2250 psid * 1 - 0psids 2

Open to close stroke

A Close to open stroke I

I I I I U l

0 60 100

Figure 56

Motor

Torque,

200 300

Packing Bolt Torque (%).

s0 100

* Four-Inch Gate Valve -- Current Versus Packing

Valve Opening & Closing
NRC-88-01

Page 90

12/08/89

10

I-'------0 P31d - xa

01i

2

2250 paid - I

0

0

a

A

0

0 a

8

a

a

0

I I I I I. I .I II

0 50 100 200 300 50 100

Packing Bolt Torque (%)

Figure-57. . Four-Inch' Gate ValVe -i

Closing Force Versus Packing

Torque, Various Pressures

A

m

la

Q..

t:

!----

I

I

I

I i -1 ---- i I

I 11

-i- -

I - -i

I

i

i

- i

I I

-.- L.- ------- --i

i i I

II i .- -1 --------AI- -

I ! ---- -- ;

I - .-I- -.- - . J, -

i I - i

I I I I

U S6 60

ELRP5EO TIME IMINUTESI

Figure 58.

Torque

Ten-Inch Gite Valve -- Rotation of

Switch at 300% Packing Torque
NRC-88-01

Page 91

12/08/89

.0

0

00 0

is 4

C~lAPI

o 1. . . . .

*yftamc ClNg rame IX 1' t)

Figure 59. Four-Inch Gate Valve -- Motor Current

Versus Closing Force, Various Pressures

i

hJ

a

w

C

.i.

I

i

I

I -

- Ii

t

I

f

1 7

I

I

I- __ -

I

I

I

,.. .... ... . . . - | I *1 *

a Ii a I ' mb 1i

ELRPSES TINE ININUTESI

Figure-60. Ten-Inch Gate Valve Motor

Current for Initial Dry Cycles

I'm Si
NRC-88-01

Page 92

12/08/89

z

0

.g

V

-o

s0 _~~~~~~~~~~~~~~. . . . ..... .. . .... ...

0 .......~~~..... ....... ........ .... .... ........ .... .... ........ .... ..... ... ,.... ..... ........ .... ..................

C*. .... ............... .... ........... .... ......... ...... .... ... .. ....... .... .. ...... _.. .... .................

MCI,

U..

LI

8. ... ........ ... -..... ... .......... .... .... ........ .... .... ... -..... .... ........... ... ........ .................. '

cc

x .. ........ ... .... .... ....... ........

0 2

ELAPSED TIME ININUTESI

Figure 61. Ten-Inch Gate Valve Stem

Force for Initial Dry Cycles

16

_-

'oo

0

(np.

IG

a

N

I

... ... . ........................... .................. ...............................................................................

........' .. .. . .. . .. . .... ..... '. . . . . . . .. .. . . . . . . . . . . . . .... . . ..... . . . . ~~~~~~~~~~~~~~~........... . , .. .. . .. ._.. ............. ...

~~~~~~~~~~.... ................... .................. .................. ................, , '.'

....... ..... ... .. '.......... . .......... '... .......... ..........-''' •I.tL1Lll

_. - - : -- : - .- . . ; . . :- .

.0

ELAPSED TIME ININUTESI

Figure 62. Ten-Inch Gate Valve -- Motor

Vibration for Initial Cycles

is
NRC-88-01

Page 93

12/08/89

EL~~~~~~~~LPSSTtEtlNlS

CE

idt

Figure,63. Ten-Inch.Gate Valve,Motor,-

Current':for Initial .24 Wet -Cycles

C3

10W

..

o s b0 e ;5 2; 2s 30 Si * U 50

Figure 64. Ten-Inch Gate Valve

Fiber Optic Close Position for Initial 24 Wet Cycles
NRC-88-01

Page 94

12/08/89

.

I

ELnPSro f imrIMINUIESI

Figure 65. Ten-Inch Gate Valve Stem

Force for Initial 24 Wet Cycles

i

a

Figure 66. Ten-Inch Gate Valve

Rotation of Torque Switch for Initial 24 Wet Cycles
NRC-88-01

Page 95

12/08/89

I....

Moor Twv----?

,; X ~~~~~~~~~t,/ i----~~~~~~~~~~~~~~~~---I

S. so ala lOo too to 2 00vie so 3o 

ELAPSED TIME (MINUTESI

Figure 67. Ten-Inch Gate Valve -- Increasing Motor

Temperature and Valve Stem Temperature During Wet Cycling

. . : :..

'q .9 asS1 "

ELAPSED TIME ININUTESI

Figure 68. Ten-Inch Gate Valve Motor

Current for 150 24 Wet Cycles
NRC-88-01

Page 96

12/08/89

*

i

f10

r.

Zn

1111111 11111111

I

I I ... I 1,F

10b1m

I N I I II

I ..I...

I ""

.

I

Io

'ea se % OO 1S O 2 00

ELAPSEO rIME 4MINUTESO

Figure 69. Ten-Inch Gate Valve Stem

Force for 150 24 Wet Cycles

i

II

i

I

--AI

I

4

ELAPSEO TIME [MINUTES)

Figure 70. Ten-Inch Gate Valve

Fiber Optic Close Position for 150 Wet Cycles
I

NRC-88-01

Page 97

12/08/89

E

a

a

ELAPSED TIME (MINUTES)

Figure 71. Ten-Inch Gate Valve

Stem Force During 13 of 150 Wet Cycles.

e

S

9:

Ior

Figure 72'. Ten-Inch Gate Valve

Motor Current During 13 of 150 Wet Cycles
NRC-88-01

Page 98

12/08/89

2

- o

> c

Figure 73. Ten-Inch Gate Valve

Vibration During 13 of 150 Wet Cycles

50

40

j

I

30

0

0 a

a o o~~~~ 8 03 0

a

AIAA

A A

0 50 100 200 o 0 

I I i I I

20

10*

0 50 l0t notW

Packing Boll Torque (%)

Figure 74. Ten-Inch Gate Valve

Opening & Closing Motor Current

Versus Packing Torque
NRC-88-01

Page 99

12/08/89

I

I

Figure 75. Ten-Inch Gate Valve Motor

Current after Cycles at 400F

!-I

I

I

I I~~~s

I

I

i - I

I

II -

i

i

i

t

i

I

I

-&--. - . .. j.. -

i i t i

I I

i I

70 - so

fl

-r

20

-

is; -~ so lem

ELAPSEO TIME IMINUTESI

Figure 76. Ten-Inch Gate Valve Stem

.Force for Cycles at 400F
NRC-88-01

Page 100

12/08/89

Figure 77. Ten-Inch Gate Valve

Fiber Optic Close Position for Cycles at 400F

;

11 m

I

l

s; 20 30 so so0 0o s Wo so

ELAPSED TIME (MINUTES)

Figure 78. Ten-Inch Gate Valve

Rotation of Torque Switch for Cycles at 400F
NRC-88-01

Page 101

12/08/89

I o

70

60

0

a

40 a

20

Elapsed Tlime (min)

Figure 79. Ten-Inch Gate Valve

Stem Force at 400F and 300% Packing Torque

35

A

30 5 C0

n~~~~~ Io 25.O 50I5F^

20 -

0

S c ~~~2 ~ 0 ~

E 0 0 10 O

Pacing Soll Torque 0s1

Figure 80. Ten-Inch Gate Valve

Closing Stem Force'Versus Packing Torque
NRC-88-01

Page 102

12/08/89

- , - I . - - , 

Figure 81. Acoustic Emission Sensors

Installed on Bonnet of Check Valve

;. -I-" , . - , rr ,

Figure 82. Acoustic Emission Sensors

Installed Upstream on Pipe
INRC FORM 335 U.NUCLEAR REGULATORYCOMMISSION I. REPORTNUMBEAwpwdby rTOCedV. Ae. ifay.

34211C3202, BIBLIOGRAPHIC DATA SHEET NUREGC R-5515

3201,3202 ~~~~~~~~~~~ETEC 88-01

SEE INSTRUCTIONS ON THE REVERSE.

2. TITLE AND SUBTITLE 3. LEAVE BLANK

Light Water Reactor Pressure Isolation Valve

Performance Testing 4. DATE REPORT COMPLETED

MONTH YEAR

I AUTHORISI May 1990

H. H. Neely, N. M. Jeanmougin, and J. J. Corugedo 6. DATE REPORT ISSUED

MONTH YEAR

July 1990 7. PERFORMING ORGANIZATION NAME AND MAILING ADDRESS tifeuM" AP Ced1) S. PROJECTITASKIWORK UNIT NUMBER

Energy Technology Engineering Center 9. FIN OR GRANT NUMBER

P.O. Box 1449

Canoga Park, CA 91304

FIN B3050 10. SPONSORING ORGANIZATION NAME AND MAILING ADDRESS ce Cod) II&. TYPE OF REPORT

Division of Engineering Research

Office of Nuclear Regulatory Research b. PERIODCOVERED If/ftftive dowN

U.S. Nuclear Regulatory Commission

Washington, D.C. 20555 12. SUPPLEMENTARY NOTES

1.. ....... .L I 

--

1@... "A I hi I 1_- a

The Light Water Reactor Valve Performance Testing Program was initiated by the NRC

to evaluate leakage as an indication of valve condition, provide input to Section XI

of the ASME Code, evaluate motor signature testing to measure valve operability,

evaluate acoustic emission monitoring for condition and degradation and in-service

inspection techniques. Six typical check and gate valves were purchased for testing

at typical plant conditions (550 F at 2250 psig) for an assumed number of cycles for

a 40-year plant lifetime. Tests revealed that there were variances between the test

results and the present statement of the Code; however, the testing was not conclusive.

The lifecycle tests showed that high tech acoustic emission can be utilized to trend

small leaks, that specific motor signature measurement on gate valves can trend 'and

indicate potential failure, and that in-service inspection techniques for check valves

was shown to be both feasible and an excellent preventive maintenance indicator.

Lifecycle testing performance here did not cause large valve leakage typical of some

plant operation. Other testing is required to fully understand the implication of

these results and the required program to fully implement them.

1C DOCUMENT ANALYSIS-,. KEYWORDS/DESCRIPTORS 1. AVAILABILITY

Valve Performance Tests STATEMENT

Valve Leakage and Valve Condition

Acoustic Emission and Valve Degradation Unlimited

SI SECURITY CLASSI ICATION

b. IDENTIFIERSIOPEN.ENDED TERMS nrhclassi

Valves Valve Leakage ThA. "pan)

Check Valves Valve Degradation Unclassified

Gate Valves Acoustic Emission 17. NUMBER OF PAGES

S. PRICE
UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON..D.C. 20555

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $300

POTG PFEES PAID

UUSNRC

1