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UNITED STATES PARTMENT OF )MMERCE

JBLICATION

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NBS TECHNICAL NOTE 624

U.S.

ARTMENT

OF

DMMERCE

National

<W {

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i

An Evaluation of Several Cryogenic

Turbine Flowmeters
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac

Radiation2—Nuclear Radiation 2—Applied Radiation 2—Quantum Electronics3 —

Electromagnetics3 —Time and Frequency3—Laboratory Astrophysics3—Cryogenics3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice, and services to Government agencies

upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

bodies. The Institute consists of a Center for Building Technology and the following

divisions and offices: Engineering Standards Services—Weights and Measures—Invention and Innovation—Product Evaluation Technology—Electronic Technology—Technical

Analysis—Measurement Engineering—Fire Technology—Housing Technology4 —Federal Building Technology4 —Building Standards and Codes Services4—

Building Environment4—Structures, Materials and Life Safety4 —Technical

Evaluation and Application4. THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition,

and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

Publications—Library—Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted ; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Researrh.

•i Located at Boulder, Colorado 80302.

4 Part of the Center for Building Technology.
NOV 1 5 TO

An Evaluation of Several Cryogenic

Turbine Flowmeters

00

J. A. Brennan

R. W. Stokes

D. B. Mann

C. H. Kneebone

Cryogenics Division

Institute for Basic Standards

National Bureau of Standards

Boulder, Colorado 80302

-fcL

Co- sponsored by

The Compressed Gas Association

500 Fifth Avenue

New York, New York 10036

.<< ">,

w

U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary

NATIONAL BUREAU OF STANDARDS, Lawrence M. Kushner, Acting Director

Issued October 1972
National Bureau of Standards Technical Note 624

Nat Bur. Stand. (U.S.), Tech. Note 624, 90 pages (Oct 1972)

CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

(Order by SD Catalog No. C13. 46:624).
PREFACE

The comments in this report, the use of descriptive phrases, or the actual

performance of the meters do not in any way constitute endorsement either expressed or implied by the National Bureau of Standards.

It is the policy of the National Bureau of Standards to use the International System

of Units (SI) in its reports unless this usage would lead to confusion or a lack of understanding. In this report SI units have not been used because it is standard practice in

the industry to use English units and the use of SI units would be unduly cumbersome.

The following conversions are given so the reader can convert the values in the report

if he desires.

3 3 feet x 0. 028317 = meter

3 gallons x 0. 0037854 = meters

3 gallons /minute x 0. 00006309 = meters /second

inches x 0. 0254 = meters

pounds x 0. 45359 = kilograms

2 2 pounds /inch x 6894. 757 = newtons /meter

The authors wish to thank Dr. Peter Tryon of the NBS Statistical Engineering

Laboratory for his assistance in this program. The test schedules he prepared and the

assistance in analyzing the data have been invaluable.
TABLE OF CONTENTS

ABSTRACT 1

1. Introduction 1

2. Cryogenic Flow Research Facility 1

3. Meter Description 2

4. Method of Meter Evaluation 4

5. Data Analysis 6

6. Meter Performance Summary 7

7. Flowmeter Methodology 8

8. References 11 APPENDIX A. Rangeability Test Plan A-l

APPENDIX B. Performance of an Inferred Mass Turbine Meter System

(Meters N and O) B-l

APPENDIX C. Performance of a Volumetric Turbine Meter (Meters P and Q) • • • C-l

APPENDIX D. Performance of a Volumetric Turbine Meter (Meters R and S) • • • D-l

APPENDIX E. Performance of Volumetric Turbine Meter (Meter V) E-l

APPENDIX F. Performance of an Inferred Mass Turbine Meter System

(Meter Z) F-l

LIST OF FIGURES

Figure 1. Schematic of Flow Loop.

Figure IB. Volumetric Meter N, First Rangeability Test B-5

Figure 2B. Volumetric Meter N, First Rangeability Test B-6

Figure 3B. Volumetric Meter N, Boundary Test B-7

Figure 4B. Volumetric Meter N, Stability Test B-8

Figure 5B. Volumetric Meter N, Second Rangeability Test B-9

Figure 6B. Volumetric Meter N, Second Rangeability Test B-10

Figure 7B. Mass Meter N, Variable Flow Test B-ll

Figure 8B. Volumetric Meter O, First Rangeability Test B-12

Figure 9B. Volumetric Meter O, First Rangeability Test B-l

3

Figure 10B. Mass Meter O, Variable Flow Test B-14

Figure 11B. Meters N and O, Pressure Drop B-15

iv
LIST OF FIGURES (continued)

Figure 1C. Meter P, Variable Flow Test C-4

Figure 2C. Meter P, Variable Flow Test C-5

Figure 3C. Meter P, First Rangeability Test C-6

Figure 4C. Meter P, First Rangeability Test C-7

Figure 5C. Meter P, Boundary Test C-8

Figure 6C. Meter P, Stability Test C-9

Figure 7C. Meter P, Second Rangeability Test C-10

Figure 8C. Meter P, Second Rangeability Test C-ll

Figure 9C. Meter Q, First Rangeability Test . C-12

Figure IOC. Meter Q, First Rangeability Test C-13

Figure 11C. Meters P and Q, Pressure Drop C-14

Figure ID. Meter R, Variable Flow Test D-4

Figure 2D. Meter R, Variable Flow Test • D-5

Figure 3D. Meter R, First Rangeability Test D-6

Figure 4D. Meter R, First Rangeability Test D-7

Figure 5D. Meter R, Boundary Test D-8

Figure 6D. Meter R, Stability Test D-9

Figure 7D. Meter S, First Rangeability Test D-10

Figure 8D. Meter S, First Rangeability Test D-ll

Figure 9D. Meters R and S, Pressure Drop D-12

Figure IE. Meter V, First Rangeability Test E-3

Figure 2E. Meter V, First Rangeability Test E-4

Figure 3E. Meter V, First Rangeability Test E-5

Figure 4E. Meter V, Variable Flow Test E-6

Figure 5E. Meter V, Variable Flow Test E-7

Figure 6E. Meter V, Pressure Drop E-8

Figure IF. Volumetric Meter Z, First Rangeability Test F-5

Figure 2F. Volumetric Meter Z, First Rangeability Test F-6

Figure 3F. Volumetric Meter Z, Boundary Test F-7

Figure 4F. Volumetric Meter Z, Stability Test F-8

Figure 5F. Volumetric Meter Z, Second Rangeability Test F-9

Figure 6F. Volumetric Meter Z, Second Rangeability Test F-10

Figure 7F. Mass Meter Z, First Rangeability Test F-ll

Figure 8F. Mass Meter Z, First Rangeability Test F-12

Figure 9F. Mass Meter Z, Boundary Test F-13

Figure 10F. Mass Meter Z, Stability Test F-14

v
LIST OF FIGURES (continued)

Figure 11F. Mass Meter Z, Second Rangeability Test F-15

Figure 12F. Mass Meter Z, Second Rangeability Test F-16

Figure 13F. Volumetric Meter Z, Pressure Drop F-17

LIST OF TABLES

Table 1. Descriptive Meter Characteristics 4

Table 2. Meter Test Record 8 Table 3. Turbine Meter Performance Summary 9 Table 1A. Rangeability Random Test Plan A-2

Table 2A. Rangeability Test Schedule A-3

Table IB. Fit of Model to Meter N, First Rangeability Test Data B-2

Table 2B. Fit of Model to Meter N, Second Rangeability Test Data B-2

Table 3B. Fit of Model to Meter N, "Variable Flow Test Data B-3

Table 4B. Fit of Model to Meter O, Rangeability Test Data B-3

Table 5B. Fit of Model to Meter O, Variable Flow Test Data B-4

Table 1C. Fit of Model to Meter P, Variable Flow Test Data for Flow

Rates above 40 gpm (2. 5 tls) C-l

Table 2C. Fit of Model to Meter P, First Rangeability Test Data for

Flow Rates above 40 gpm (2. 5 t/s) C-2

Table 3C. Fit of Model to Meter P, Second Rangeability Test Data for

Flow Rates above 40 gpm (2. 5 -t/s) C-2

Table 4C. Fit of Model to Meter Q, Rangeability Test Data for Flow

Rates above 40 gpm (2. 5 t/s) C-3

Table ID. Fit of Model to Meter R, Variable Flow Test Data D1

Table 2D. Fit of Model to Meter R, Rangeability Test Data D-2

Table 3D. Fit of Model to Meter S, Rangeability Test Data D-3

Table IE. Fit of Model to Meter V, Rangeability Test Data E-l

Table 2E. Fit of Model to Meter V, Variable Flow Test Data E-2

Table IF. Fit of Model to Meter Z (Volumetric System), First Rangeability

Test Data F-2

Table 2F. Fit of Model to Meter Z (Volumetric System), Second Rangeability

Test Data F-2

Table 3F. Fit of Model to Meter Z (Mass System), First Rangeability Data,

for Flow Rates above 4 lbs/s (1. 8 kg/s) F-3

Table 4F. Fit of Model to Meter Z (Mass System), Second Rangeability

Test Data F-4
AN EVALUATION OF SEVERAL CRYOGENIC

TURBINE FLOWMETERS

J. A. Brennan, R. W. Stokes, D. B. Mann, and C. H. Kneebone

The National Bureau of Standards (NBS) and the Compressed Gas

Association (CGA) have jointly sponsored a research program on cryogenic

flow measurement. A cryogenic flow research facility was constructed

and has been used to evaluate cryogenic flowmeters operating on several

different principles.

The operation and the accuracy of the flow facility is briefly

described. The performance of the flowmeters in liquid nitrogen is described by reporting the precision and bias of the meters before and

after an 80-hour stability test and by defining the existence of temperature,

pressure, flow rate, subcooling, and time order (wear) dependencies.

Meters were evaluated with flow rates ranging from 20 to 210 gpm

(1. 3 to 13. 2 Lis), pressures ranging from 32 to 112 psia (0. 22 to 0. 77

MN/m ), and with temperatures ranging from 72 to 90 K.

Key Words: Cryogenic; flow; liquid nitrogen; mass; mass flowmeters;

measurement; turbine flowmeters; volume flowmeters.

1. Introduction

The National Bureau of Standards and the Compressed Gas Association have jointly

sponsored a program of cryogenic flow research. A dynamic gravimetric flow facility

has been constructed at NBS Boulder and flowmeters operating on several principles have

been evaluated. This report describes the results of the evaluation of several volumetric

and mass cryogenic turbine type flowmeters. This group represents those meters or meter systems which have not been widely used commercially in the United States either

because they are new or not readily obtainable in this country. The group includes flowmeters from England and Germany, as well as domestic flowmeters. The commercial

meters commonly used in the United States have been tested and reported earlier by

Brennan et al. [1971],

Meters were submitted for testing as a result of joint recommendations of the

Compressed Gas Association Subcommittee on Cryogenic Liquid Flowmetering and the

National Bureau of Standards, Cryogenics Division. The meters were intended to be

representative of those available from industry. The results presented in this report

only show the capability of each individual meter tested to measure flow of liquid nitrogen.

2. Cryogenic Flow Research Facility

A continuous flow loop has been constructed that allows the dynamic gravimetric

measurement of liquid nitrogen flow. The continuous flow loop, shown schematically

in figure 1, allows the establishment of constant pressures, temperatures, and flow rates over a long period of time. Liquid is pumped out of the catch tank through a heat ex- changer where the pump and heat energy are removed. Liquid then passes through the
test section, 'weigh tank, and back to the catch tank. A measurement is taken by closing

the flow diverter valve, weighing the fluid that passes through a meter under test located

in the test section, recording the meter registration, and timing the test interval. When

the tank is filled to a preset level the flow diverter valve is opened automatically without

interrupting the flow. A more complete discussion of the design of the facility is given

by Dean et al. [ 1969].

The principle operating criteria of the flow research facility during the period of

these meter evaluations were:

1) Ability to establish and maintain thermal and pressure equilibrium during test.

2) Operation with temperatures ranging from 72 to 90 K and with pressures from

32 to 112 psia (0. 22 to 0. 77 MN/m2

).

3) Usable weigh tank volume from 50 to 100 gallons (189 to 379 I).

4) Flow rates cover the volume flow range from 20 to 210 gpm (1. 3 to 13. 2 £/s).

A detailed description of the accuracy statement for the flow facility has been

presented by Dean et al. [1971]. In that report the uncertainty of the measurement of

total mass flow was estimated to be ±0. 18 percent. This figure includes an allowance

of ±0. 12 percent for known sources of systematic errors, plus an allowance of ±0. 06

percent for random error. The estimated uncertainty due to random error was based

on three times the standard deviation calculated from 23 applications of the calibrated

masses over a period of three months. An additional uncertainty was specified for

total volume flow which was caused by the uncertainty in the thermodynamic properties

data. However, when a consistent set of data is used by all meter users this additional

uncertainty need not be considered.

Continued analysis of the system has not revealed any reasons for changing the

uncertainty values at this time. The random error determination can now be based on many more applications of the calibration masses but the values are approximately the

same as reported by Dean.

3. Meter Description

Test results are presented for eight meters representing five different manufactuerers. In most cases, more than one meter of the same size and model was

submitted for testing. A brief description of each meter type is included in the following

text. A detailed description is presented in the appendices.

Five of the turbine meters were standard volumetric meters. Three were standard

volumetric meters combined with a compensation device that measured or inferred the

fluid density at the flow conditions whereby the volumetric output from the turbine meter

was converted to a mass output.

2

A summary of descriptive meter characteristics is presented in table 1.

Table 1. Descriptive Meter Characteristics

Manu- Meter Operating

facturer De signation Principle

1 N, O Compensa

Turbine

2 P,Q Turbine

3 R,S Turbine

4 V Turbine

5 z Compensa

Size

in (cm)

PrimaryElement

1| (3. 81) Volume

1| (3. 81) Volume

2 (5. 08) Volume

Compensated 1^ (3.81) Volume

Turbine

Register

Mass

Volume

Volume

Volume

Mass

4. Method of Meter Evaluation

The performance of each meter was evaluated by comparing the amount of liquid

registered by the meter over the test interval to the liquid mass accumulated in the weigh

tank for a wide range of liquid conditions. The mass of liquid metered by the volumetric

meters was calculated from the expression.

where

M

P

V

R

K

M

R

= P.VK

.p

mass calculated from the volume registered by the meter (lb)

pulses, or meter counts

volume meter factor (gal/P)

liquid density (lb/gal).

(1)

The volume meter factor, V , is the volume registered by the meter per count. The

volume meter factor normally used in this calculation was supplied by the meter manufacturer. Usually the factors were determined in a non-cryogenic fluid such as water

or oil. The measurement of the liquid mass accumulated in the weigh tank was started

and terminated on integer meter counts.

The mass of liquid registered by the mass meters tested was calculated from the

expression

where

MK

M = P«MT, R K

mass meter factor (lb/P)

(2)
The mass calculated from the meter pulses is then compared to the mass

accumulated in the weigh tank and the percent deviation calculated as follows:

M - M„TT,„ R NBS

percent deviation = — • 100 (4) MNBS

where

M = mass calculated from the meter pulses R

M = mass measured by NBS.

The Cryogenic Liquid Flowmetering Subcommittee of the CGA and NBS jointly

decided to subject each meter to three types of test: a rangeability test, a long term

stability test, and a boundary test. Another test, the variable flow test, is used in some

cases for special purposes.

The purpose of the rangeability test is to subject the meter to a variety of conditions

and to observe the response of the meter to these conditions. This test was statistically

designed so the effect of various parameters could be separated. The temperature range

explored was from 80 to 90 K in 2. 5 K increments. The pressure range was 62 to 112

psia (0. 427 to 0. 772 MN/m2

) in increments of 12. 5 psi (0. 86 MN/m2). Flow rates

depended on the meter capacity with the flow range being divided into four equal increments

if the meter did not have significant flow rate dependencies. The flow range was divided

into twelve equal increments in most cases where it was necessary to closely examine

these dependencies. A schedule of variables, based on a table of random numbers, was

selected for all meters. A typical schedule is given in Appendix A.

An 80-hour stability test was designed to determine the effect of wear on the meter

performance. The stability test was run in eight hour shifts at flow rates near the

maximum rated capacity and at a convenient temperature near 80 K. The meter was

allowed to warm up overnight between shifts.

The boundary test was performed with the liquid conditions at the bounds of what

the Cryogenic Liquid Flowmetering Subcommittee and NBS judged to be well beyond the

normal operating range for most meters and within economic operation of the flow facility.

The upper boundary was set at a pressure of 112 psia (0. 772 MN/m ) with the temperature

varying from about 72 to 85 K. The lower pressure boundary was set at 32 psia

(0. 22 MN/m^) with the temperature ranging from 72 K to a temperature as close to the

saturation temperature as could be obtained without excessive cavitation occurring in the

meter. The purpose of these bounds -was to establish a wide range of liquid subcooling

conditions.
A first rangeability test is conducted for each type of meter before the 80-hour

stability test is performed, and a second rangeability test is generally performed at the

conclusion of the stability test. The boundary test is performed before the start of the

stability test. In certain situations where a retest of a meter did not warrant a complete

rangeability test, a variable flow test was used. In this test only the flow rate is varied over the flow range and all other parameters are held constant.

5. Data Analysis

The criteria for evaluating meter performance are the precision and bias of the

meter and the existence of flow rate, temperature, subcooling, pressure and time order

(an indication of meter wear) dependencies. The bias is defined as the mean percent

deviation from the measured NBS mass for repeated measurements at a specified set of

flow conditions. The precision is a measure of the ability of the meter to reproduce

the same bias for repeated measurements at the same flow conditions. The

precision is reported as three times the standard deviation and, for a meter with no

significant order, flow rate or temperature dependencies, is calculated from the

following expression:

i=i (y-*) 100

where

a = standard deviation (percent) n = the number of separate measurements over a range of flow conditions

y = mean bias of the repeated measurements over the same conditions

(percent)

a- = bias of each single measurement (percent).

For a meter that has significant dependencies, the precision is reported as three times

the residual standard deviation after the data have been fitted to a mathematical model.

The residual standard deviation represents the precision at a single set of conditions,

whereas, the standard deviation represents the precision over a range of conditions. The

reported bias of the meter was obtained by evaluating the mathematical model at the rated

maximum flow rate of the meter under test at a temperature of 80 K. The bias may also

be calculated from the mathematical model for any desired combination of parameters

that are within the range of the experimental data.

The mathematical model for a mass flowmeter is

2 . 2 y = p, + aT + bT + cm + dm + eG

6
where

y = bias in percent

u = constant

T = temperature

m = mass flow rate in lb/s

= time order term.

The coefficients a, b, c, d, and e give an indication of the dependency of the corresponding

terms and are reported for each rangeability test when they are significant. This model

can be used for volumetric meters by substituting the volume flow rate, q in gallons per

minute, for the mass flow rate terms. Pressure terms are not included in the model

since, on examination, the data did not indicate a dependency for any of these meters.

In the case where terms did not prove to be significant, they were removed from the

model. In the majority of cases, reduced linear models have been used.

A subcooling term has not been included in the model. The subcooling effect may

be seen by examining the boundary test data. Similarly, the effect of wear is best seen by

examining the stability test data.

When the meters showed a strong flow rate dependency at the low or high extremes

of the flow range, that portion of the data was not fitted to the model. The model then can

be considered a mathematical expression of the bias over the useable flow range of each

meter. The primary criterion in determining the significance of each parameter was the

residual standard deviation after fitting. If the standard deviation did not change by more

than 0. 02, then the parameter was not considered significant.

6. Meter Performance Summary

A meter test record is presented as table 2. This represents the meters whose

performance is reported. As will be noted in the appendices, meters H, I, and Y were

submitted and partially tested, but the results are not reported.

The general CGA-NBS committee policy is to have two meters available for testing.

One of the two is subjected to the first rangeability test, the boundary test, the stability

test, and the second rangeability test. The second meter is subjected only to a rangeability test. By then comparing the rangeability tests of the two meters an insight is gained into the meter manufacturers ability to reproduce his meters.

There are exceptions to this policy. Meter V was not solicited through the normal

procedures. It was obtained by NBS as a transfer meter for a liquefied natural gas flowmeter calibration facility. Since the liquid nitrogen tests, which were subsequently done,

were of interest to the Compressed Gas Association, the results are reported.
Table 2. Meter Test Record

Meter

Manufacturer

Number Meter

Variable

Flow

First

Range

1 N X X

1 O X X

2 P X X

2 Q X

3 R X X

3 S X

4 V X X

5 Z X

d j cl u-1-.l Second Boundary Stability- Range

X XX

X XX

X X

X XX

A detailed description of the meters and their performance is given in the

appendices. Wherever possible meter performance is plotted using a six percent range

in deviation. This range was chosen since the tentative code for Cryogenic Liquid

Measuring Devices adopted at the 1972 Conference on Weights and Measures (4) specifies

a maintenance tolerance of + 2 percent and - 4 percent. The deviation was calculated from

the K-factor supplied with the meter which resulted in some meters having a large bias.

This bias can be changed, of course, by using the proper K-factor. As long as the meters

operated normally, all reported here had sufficient precision to satisfy the tentative code.

A summary of the meter performance is given in table 3. The precision reported is three

times the residual standard deviation calculated from the data taken during the rangeability

test. The precision at the start is calculated from the first rangeability test data taken

before the stability test, while the precision at the end is calculated from the second

rangeability test data taken after the stability test. The meter bias is reported for each

rangeability test. The minimum subcooling required for consistent meter performance,

as determined in the boundary test, is reported.

7. Flowmeter Methodology

The accuracy that may be achieved with each of these meters is dependent to some

degree on the manner with which they are used. An effort was made during the testing of

these meters to observe and record any operational procedures or circumstances that

may have a detrimental effect on the accuracy. Those observations are included here.

All meters tested showed a tendency toward overregistration and a loss of precision

as the subcooling was decreased. With the exception of meter N, they required from 14

8
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to 20 K minimum subcooling. Meter N showed only a slight loss of precision down to 6 K

subcooling although considerable cavitation was observed downstream of the meter.

Turbine meters are sensitive to overspeeding during cooldown and if this situation

is not considered during installation, damage to the bearings may occur. All meters

were installed so that they could be cooled down to liquid nitrogen temperature before any

fluid passed through them.

Turbine meters are known to exhibit K-factor shifts when the meters are operated

in fluids other than liquid nitrogen. It has also been observed during these tests that the

K-factor will shift from meter to meter in the same fluid. It, therefore, should be noted

that if these meters are to be operated at the maximum accuracy inherent in them, they

must be individually calibrated with the fluid in which they will be used.

10
8. References

1. J. W. Dean, J. A. Brennan, and D. B. Mann, "Cryogenic Flow Research Facility

of the National Bureau of Standards, " Advances in Cryogenic Engineering , Vol. 14

(Plenum Press, New York 1969), p. 299.

2. J. W. Dean, J. A. Brennan, D. B. Mann, and C. H. Kneebone, "Cryogenic Flow

Research Facility Provisional Accuracy Statement, " National Bureau of Standards,

Tech. Note 606 (1971).

3. J. A. Brennan, J. W. Dean, D. B. Mann, and C. H. Kneebone, "An Evaluation

of Positive Displacement Cryogenic Volumetric Flowmeters, " National Bureau of

Standards, Tech. Note 605 (1971).

4. 57th National Conference on Weights and Measures, Washington, D. C. , July 10-14,

1972. To be published in "Specifications, Tolerances, and Other Technical

Requirements for Commercial Weighing and Measuring Devices, " National Bureau

of Standards, Handbook 44,1972 edition.

11

APPENDIX A. Rangeability Test Plan

The purpose of the rangeability test is to investigate the performance of cryogenic

liquid flowmeters when the flowmeters are subjected to the following conditions:

1) Temperature varying from 80 to 90 K.

, 2 2) Pressure varying from 50 to 100 psig (0. 427 to 0. 772 MN/m ).

3) Flow rates from 20 gpm (1. 3 l/s) to the maximum rated capacity in either

four or twelve steps.

/ 2 4) Average barometric pressure of 12. psia (82. 7 kN/m ).

The liquid density resulting from the chosen pressure and temperature ranges

from 6. 7 lbs/gal (0. 803 kg/*,) to 6. 2 lbs/gal (0. 743 kg/ 1).

In addition, it is desired to keep the subcooling, which is a function of temperature

and pressure, above 8 K.

It is time consuming and inefficient to change the temperature of the flow system,

so temperature changes consequently are kept to a minimum. Pressure changes also are kept at a minimum to conserve helium. The flow rate may be changed easily and

quickly.

An example of a test plan is presented in table 1A. This particular plan was

designed for a meter with a flow range from 20 gpm (1. 3 t/s) to 130 gpm (8. 2 Lis). The

flow range has been divided into twelve equal increments in this example; however, a similar plan has been used that divides the flow range into four equal increments. The

test draft weight was included as a parameter and was varied as shown in four increments.

Points at high temperatures and low pressures are not included because of the subcooling

requirement.

Numbers and arrows at the top of each column indicate the sequence in which the

columns were executed and the points were taken.

The test plan was then used to generate an operator test schedule which is presented

in table 2A. In order to conserve time, the approximate values of these parameters are

set and held constant. The actual values are then measured and recorded.

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Table 2A. Rangeability Test S<:hedule

Run Temperatu re Pressure Test Draft Fl«dw Rate

Number K psig lbs gpm

1 85 100 520 30

2 85 100 460 110

3 85 8 7. 5 520 50

4 85 87. 5 400 90

56 82. 5 87. 5 580 130

57 82. 5 87. 5 400 20

58 82. 5 100 520 80

59 82. 5 100 580 60

A-3

APPENDIX B. Performance of an Inferred Mass Turbine

Meter System (Meters N and O)

This meter system consists of a standard turbine meter, a platinum resistance

thermometer that is mounted upstream of the meter in the liquid stream, and an electronics

package. The turbine meter rotor speed is monitored by a pickup coil mounted on the

turbine housing. The volumetric flow rate is then a function of the frequency generated by

the pickup coil. This frequency is an input to the electronic package. The other input

is provided by the thermometer whose resistance is a function of the liquid temperature

and, consequently, density. The influence of pressure on the density is neglected. The

electronics package converts the input volumetric frequency and the temperature to a pulse output that reads directly in mass units.

The meter manufacturer specifications are:

fluid - liquid nitrogen

maximum flow rate - 79. 25 gpm (5 l/s)

minimum flow rate - 3. 08 gpm (0. 2 t/s)

volumetric K-factor - 242. 3 P/gal (64 P/l)

registration - electrical pulse output, one pulse is equivalent to one cubic

meter of gaseous nitrogen at 750 torr (99. 99 kNAn2

) and 288. 16 K.

Initially the flowmeter electronics package was not compatible with the NBS

electronics system. Since the functioning of the mechanical system depends almost

entirely on the performance of the turbine meter, volumetric tests were performed

first on both turbine meters without temperature compensation. Once the electronics

problems were resolved, additional variable flow tests were performed on both meters

to determine the ability of the meter systems to register inferred mass. Only one thermometer and one electronics package was tested. No adjustment was made in the

electronics to take into account the different volumetric K-factors of the two meters.

Meter N

This meter was subjected to a first rangeability test, a boundary test, a stability

test, and a second rangeability test. These were volumetric tests involving only the

turbine meter. These tests were followed by a variable flow test, which as previously

explained, was designed to test the system as an inferred mass meter.

The results of the first rangeability test are shown in figures IB and 2B. These

data were fitted to the mathematical model and the results are shown in table IB.

B-l
Table IB. Fit of Model to Meter N, First Rangeability

Test Data

Model y

= 3. 82

Bias, y = +3 82%

Standard Deviation = ±0. 23%

Number of Points = 45

There were no significant dependencies observed during this test. The bias of these

data is +3. 82% and the precision based on three times the standard deviation +0. 69%.

The results of the boundary test are shown in figure 3B. There was no significant

loss of accuracy down to six degrees of subcooling. At this point there was extensive vapor

formation downstream of the turbine meter as observed during the test through the sapphire

window in the flow system. Since the vapor was not affecting the performance of the turbine,

it was being formed in the piping downstream of the turbine.

The results of the stability test are shown in figure 4B. Approximately 384 000

gallons (1 453 600 -t) of liquid nitrogen were metered during this test. There was no indication of wear occurring during that period.

The results of the second rangeability test are shown in figures 5B and 6B. These

data were fitted to the model and the results are shown in table 2B.

Table 2B. Fit of Model to Meter N, Second Rangeability

Test Data

Model y = 3. 85

Bias, y

= 3. 8 5%

Standard Deviation = ±0. 22%

Number of Points = 57

There were no significant dependencies observed during this test. The bias of these

data is +3. 85% and the precision based on three times the standard deviation is ±0. 66%.

It should be mentioned that there was no significant change in the precision or bias

of this meter after having metered 384 000 gallon (1 453 600 I) of liquid nitrogen.

The last test performed on this meter was the variable flow test of the mass system.

The test was done by initially establishing a temperature of 80 ±0. 2 K and a pressure of

92 ±5 psia. The flow rate was then varied over the meter range while holding all other

parameters constant. The sequence was then repeated at a temperature of 90 ±0. 2 K. This test provided an insight into the ability of the system to register mass over a range

B-2
of flow rates and the temperature extremes of the rangeability test. The results are shown in figure 7B. These data were fitted to the model and the results are shown in

table 3B.

Table 3B. Fit of Model to Meter N, Variable Flow Test Data.

Model y = -6. 786 + 0. 06197 T + . 6307 m - 0. 03766

. 2 m

Bias at m = 8. 8 lbs/s and T = 80 K, y = +0. 80%

Residual Standard Deviation = ±0. 24%

Number of Points - 16

This mass meter system shows significant dependencies on temperature, T, mass

flow rate, rh in lbs/s, and mass flow rate squared. The bias at a flow rate of 8. 8 lbs/s

and a temperature of 80 K is +0. 80 percent. The precision based on three times the

residual standard deviation is ±0. 72 percent.

The mean bias of these data without fitting them to the model is +0. 56 percent. The

standard deviation of these data without the model is ±0. 65 percent and the precision based

on three times the standard deviation is ±1. 95 percent.

Since this meter has significant dependencies, the bias must be calculated from the

model to obtain the precision of ±0. 72 percent. If the bias is not calculated from the model

then the precision can be no better than ±1. 95 percent.

Meter O

This meter was subjected to a rangeability test and a variable flow test. As

previously explained the rangeability test was performed only on the turbine meter. It was

a volumetric test. The variable flow test was performed on the mass system.

The results of the rangeability test are shown in figures 8B and 9B. These data

were fitted to the model and the results are shown in table 4B.

Table 4B. Fit of Model to Meter O, Rangeability Test Data

Model y = 2. 20

Bias, y = +2 20%

Standard Deviation = ±0. 28%

Number of Foints = 56

There were no significant dependencies observed during this test. The bias of these

data is +2. 20 percent and the precision based on three times the standard deviation is

±0. 84 percent.

B-3
The results of the variable flow test are shown in figure 10B. The test was done

by initially establishing a temperature of 80 ±0. 2 K and a pressure of 94 ±10 psia. The

flow rate was then varied over the meter range while holding all other parameters constant

The sequence was then repeated at a temperature of 90 ±0. 1 K. These data were fitted to the model and the results are shown in table 5B.

Table 5B. Fit of Model to Meter O, Variable Flow Test Data

Model y = -2. 691 + 0. 5852 m - 0. 04023

. 2 m

Bias at m = 8. 8 lbs/s, y = -0. 66%

Residual Standard Deviation = ±0. 31%

Number of Points = 16

This mass meter system has significant dependencies on mass flow rate, m in lbs/

and mass flow rate squared. The bias at a flow rate of 8. 8 lbs/s is -0. 66 percent. The

precision based on three times the residual standard deviation is ±0. 93 percent.

The mean bias of these data without fitting them to the model is -0. 92 percent.

The standard deviation of these data without the model is ±0. 47 percent and the precision

based on three times the standard deviation is ±1. 41 percent.

Since this meter has significant dependencies, the bias must be calculated from the

model to obtain the precision of ±0. 93 percent. If the bias is not calculated from the mode'

the precision can be no better than ±1. 95 percent.

Typical pressure drop data are shown in figure 11B for both meters N and O.

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B-15

APPENDIX C. Performance of a Volumetric

Turbine Meter (Meters P and Q)

This meter is a standard turbine flowmeter in which a rotor is actuated by the

moving liquid. The volumetric flow rate is a function of the speed of rotation of the rotor. The rotor revolutions are translated into voltage pulses by a pickup coil mounted on the

meter housing. These pulses are then counted by means of an electro-mechanical digital

totalizer.

The meter manufacturer's specifications are:

fluid - liquid nitrogen

maximum flow rate - 180 gpm (11. 3 l/s)

minimum flow rate - 30 gpm (1. 9£/s)

volumetric K-factor - 25 P/gal

registration - electro-mechanical digital totalizer which registers one

pulse for every eight meter pulses.

Two meters (P and Q) were tested and exhibited similar characteristics.

Meter P

This meter was subjected to a first rangeability test, a boundary test, a stability

test, a second rangeability test, and a variable flow test in that order.

The results of the variable flow test are shown in figures 1C and 2C. The temperature was 80 ±0. 5 K, and the pressure was 98 ±5 psia during this test. The figures show

a strong underregistration tendency below 40 gpm (2. 5 lis). The data above 40 gpm

(2. 5 l/s) were fitted to the flow model and the results are shown in table 1C.

Table 1C. Fit of Model to Meter P, Variable Flow Test Data

for flow rates above 40 gpm (2. 5 lis)

Model y

= 0. 02

Bias y = +0. 02%

Standard Deviation = ±0. 21%

Number of Points = 30

There were no significant dependencies above 40 gpm (2. 5 l/s). The bias of these data is

±0. 02 percent and the precision based upon three times the standard deviation is ±0. 63

percent.

The results of the first rangeability test are shown in figures 3C and 4C. Three

points were removed from these plots. They were very low deviation points and it was

felt that something was retarding the rotor that could have been attributed to the system.

C-l
The data above 40 gpm (2. 5 lis) were fitted to the flow model and the results are shown in

table 2C.

Table 2C. Fit of Model to Meter P, First Rangeability Test Data

for flow rates above 40 gpm (2. 5 Lis)

Model y

= 0. 10

Bias y = +0. 10%

Standard Deviation = ±0. 18%

Number of Points = 39

There were no significant dependencies above 40 gpm (2. 5 lis). The bias of these

data is +0. 10 percent and the precision based on three times the standard deviation is

±0. 54 percent.

The results of the boundary test are shown in figure 5C. A loss of precision and

a tendency to overregister is evident below fourteen degrees of subcooling. The probable cause was the formation of vapor in the meter or the flow system which was observed

during this test through the sapphire window downstream of the flowmeter. No explanation can be given for the high deviation at 2 5 K.

The results of the stability test are shown in figure 6C. Approximately 810 000

gallons(3 066 200 I) were metered during this test. The meter did not show any wear

during that period.

The results of the second rangeability test are shown in figures 7C and 8C. The

data above 40 gpm (2. 5 I) were fitted to the flow model and the results are shown in

table 3C.

Table 3C. Fit of Model to Meter P, Second Rangeability Test Data

for flow rates above 40 gpm (2. 5 lis)

Model y = 0. 09

Bias, y : = +0. 09

Standard Deviation = ±0. 16%

Number of Points = 41

There were no significant dependencies above 40 gpm (2. 5 lis). The bias of these

data is +0. 09 percent and the precision based on three times the standard deviation is

±0. 48 percent.

It should be noted that there was no significant change in the precision or bias of

this meter after having metered 810 000 gallons (3 066 200 I) of liquid nitrogen.

C-2
The pressure drop data for meter P are shown in figure 11C.

Meter Q

This meter was subjected only to a rangeability test. The results of this test are shown in figures 9C and IOC. The data above 40 gpm (2. 5 -t/s) were fit to the flow

model and the results are shown in table 4C. The five low deviation points above 40 gpm

(2. 5 t/s) were removed from those points included in the fit. As the points were in

consecutive order it was felt the possibility existed that something was retarding the

rotor that could be attributed to the system.

Table 4C. Fit of Model to Meter Q, Rangeability Test Data

for flow rates above 40 gpm (2. 5 -t/s)

Model y = 0. 8468 + 0. 00251C q Bias at q

= 180 gpm, y = +1. 30%

Residual Standard Deviation = ±0. 19%

Number c f Points = 37

Meter Q was dependent on the volume flow rate, q in gpm, as the model indicates.

The precision based on three times the residual standard deviation is ±0. 57 percent and

the bias at a flow rate of 180 gpm (11. 3 t/s) is +1. 30 percent.

The mean bias of these data without fitting them to the model is +1. 16 percent.

The standard deviation of these data without the model is ±0. 22 percent, and the precision

based on three times this standard deviation is ±0. 66 percent.

Since this meter has a signficant flow rate dependency, the bias must be calculated

from the model to obtain the precision of ±0. 57 percent. If the bias is not calculated

from the model, then the precision can be no better than ±0. 66 percent.

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C-14
APPENDIX D. Performance of a Volumetric

Turbine Meter (Meters R and S)

This meter is a standard turbine flowmeter in which the rotor is actuated by the

moving liquid. The volumetric flow rate is a function of the speed of rotation of the rotor. The rotor revolutions are translated into voltage pulses by a pickup coil mounted on the

meter housing. This system includes an electronic package with a manually adjustable

meter K-factor and a digital register. By selecting the proper meter factor, the register

will read directly in gallons.

The meter manufacturer's specifications are:

fluid - liquid nitrogen

maximum flow rate - 120 gpm (7. 6 -C/s)

minimum flow rate - 12 gpm (0. 8 l/s)

nominal size - 1-1/2 inch (0. 038 m)

Volumetric K-factor - Meter R - 433 P/gal

Meter S - 425 P/gal.

The test results of two meters (R and S) are reported. Both meters were a modified

version of an earlier design. Two meters of the earlier design (meters H and I) were

tested previously but are not reported. All four of these meters failed mechanically during

the tests. The failure mode in all four cases was an apparent bearing failure which allowed

the rotor blades to contact the meter housing. The meter failure was detected by a large

underregistration accompanied by a high frequency audible response. In case of meter R,

the meter performed satisfactorily with no loss of accuracy up to the point of failure.

Meter S showed a slight order dependency in the rangeability test data which may have been

symptomatic of the ensuing failure.

Meter R

This meter was subjected to a variable flow test, a rangeability test, a boundary test,

and a stability test.

The results of the variable flow test are shown in figures ID and 2D. The temperature was 80 ±0. 2 K and the pressure was 99 ±2 psia during this test.

The data were fitted to the model and the results are shown in table ID.

Table ID. Fit of Model to Meter R, Variable Flow Test Data

Model y = 1. 082 4 0. 006578 q Bias at q = 120 gpm, y = 1. 87%

Residual Standard Deviation = ±0. 10%

Number of Points = 21

D-l
This meter showed a significant dependency on volume flow rate, q in gpm, during

this test, which is indicated by the model. The precision based upon three times the

residual standard deviation is ±0. 30 and the bias at a flow rate of 120 gpm (7. 6 l/s) is

+1. 8 7 percent.

The mean bias of these data without fitting them to the model is +1. 47 percent. The

standard deviation of these data without the model is ±0. 21 percent, and the precision

based on three times this standard deviation is ±0. 63 percent.

Since this meter has a signficiant flow rate dependency, the bias must be calculated

from the model to obtain the precision of ±0. 30 percent. If the bias is not calculated from

the model, then the precision can not be better than ±0. 63 percent.

The results of the first rangeability test are shown in figures 3 D and 4D. These

data were fitted to the model and the results are shown in table 2D.

Table 2D. Fit of Model to Meter R, Rangeability Test Data

Model y = 1. 139 + 0. 006626 q Bias at q = 120 gpm y = +l. 93%

Residual Standard Deviation = ±0. 34%

Number c f Points = 57

The meter showed essentially the same flow rate dependency during this test as during the variable flow test. The precision based on three times the residual standard

deviation was ±1. 02 percent. This is significantly higher than the precision during the

variable flow test; however, this is expected as all parameters are varied during this

test while only flow rate is varied during the variable flow test.

When the data are not fitted to the model, the mean bias is ±1. 56 percent. The

standard deviation of these data without the model is ±0. 42 percent and the precision

based on three times the standard deviation is ±1. 26 percent.

The results of the boundary test are shown in figure 5D. A loss of precision and

a tendency to overregister is evident below twenty degrees of subcooling.

The results of the stability test are shown in figure 6D. This test was terminated

after approximately twenty hours when the meter failed. At the point of failure 280 000

gallons (1 059 900 I) of liquid nitrogen had been metered. The last data point taken on

this meter had a deviation of minus twenty-five percent and is not shown on figure 6D.

Meter S

A rangeability test was completed on this meter, however, at the start of the

boundary test the meter failed.

D-2
The results of the rangeability test are shown in figures 7D and 8D. These data

were fitted to the model and the results are shown in table 3D.

Table 3D. Fit of Model to Meter S, Rangeability Test Data

Model y = 2. 166 - 0. 010530

Bias at 9 = 57, y = +1. 57%

Residual Standard Deviation = ±0. 26%

Number of Points = 57

As noted previously, this meter has an order dependency which may have been a symptom of the failure which was to follow. The bias was calculated from the model at the last data point taken and was +1. 57 percent. The bias at the beginning of the rangeability test, as calculated from the model, was +2. 16 percent. The precision based on

three times the residual standard deviation is ±0. 78 percent.

The mean bias of these data without fitting them to the model is +1. 86 percent.

The standard deviation of these data without the model is ±0. 31 percent and the precision

based on three times the standard deviation is ±0. 93 percent.

The pressure drop data for meters R and S are shown in figure 9D.

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D-12
APPENDIX E. Performance of Volumetric

Turbine Meter (Meter V)

This meter is a standard turbine flowmeter in which the rotor is actuated by the

moving liquid. The volumetric flow rate is a function of the speed of rotation of the rotor. The rotor revolutions are translated into voltage pulses by a pickup coil mounted on the

meter housing. This meter system was not equipped with a counter or a register. This

system did include an integral signal conditioner which amplified the voltage pulses and

re- shaped them from a sinusoidal to a square wave pulse form.

The meter manufacturer's specifications are:

fluid - liquid nitrogen

maximum flow rate -225 gpm (14. 2 Lis)

minimum flow rate - 22 gpm (1. 4 Lis)

volumetric K-factor - 147. 1 P/gal

nominal size - 2 inch (0. 051 m)

The results of one meter (V) are reported. This meter was subjected to a rangeability test and a variable flow test.

The results of the rangeability test are shown in figures IE, 2E, and 3E. These

data were fitted to the mathematical model and the results are shown in table IE.

Table IE. Fit of Model to Meter V, Rangeability Test Data

Model y = -135. 87 + 3. 1874 T - 01852 T

2 + 0. 006078 q

-0. 00003047 q

2

Bias at q

= 225 gpm and T - 80 K, y

= +0.42%

Residual Standard Deviation = ±0. 37%

Number o f Points = 59

This meter shows significant dependencies on temperature, T, temperature

squared, volume flow rate, q in gpm, and flow rate squared. The flow rate dependency

is evident in figure IE and the temperature dependency can be seen in figure 3E. The

bias at a flow rate of 225 gpm (14. 2 t/s) and 80 K is +0. 42 percent. The precision

based on three times the residual standard deviation is ±1. 11 percent.

The mean bias of these data without fitting them to the model is +1. 19 percent.

The standard deviation of these data without the model is ±0. 46 percent and the precision

based on three times this standard deviation is ±1. 38 percent.

E-l
Since this meter has significant dependencies, the bias must be calculated from

the model to obtain the precision of ±1. 11 percent. If the bias is not calculated from the

model, then the precision cannot be better than ±1. 38 percent.

The results of the variable flow test are shown in figures 4E and 5E. The temperature was held constant during this test at 82. 5 ±0. 2 K and the pressure at 108 ±4 psia.

These data were fitted to the model and the results are shown in table 2E.

Table 2E. Fit of Model to Meter V, Variable Flow Test Data

Model y

= 1. 138 + 003148 q

- o. 00001876

2 q Bias at 22 5 gpm, y = +0. 90%

Residua1 Standard D eviation = ±0. 055%

Number of Points = 17

This meter shows a significant dependency on volume flow rate, q in gpm, and

on volume flow rate squared. The bias at a flow rate of 225 gpm (14. 2 t/s) is +0. 90 percent. The precision based on three times the residual standard deviation is ±0. 16 percent.

It should be noted that this variable flow test will only detect dependencies in order and

flow rate. It is necessary to refer to the rangeability test data to examine the results or

other dependencies such as temperature.

The mean bias of these data without fitting them to the model is +1. 17 percent. The

standard deviation of these data without the model is ±0. 13 percent and the precision based

on three times this standard deviation is ±0. 39 percent.

Since this meter has significant dependencies, the bias must be calculated from

the model to obtain the precision of ±0. 16 percent. If the bias is not calculated from the

model then the precision cannot be better than ±0. 39 percent.

The pressure drop data for meter V are shown in figure 6E.

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E-8
APPENDIX F. Performance of an Inferred Mass

Turbine Meter System (Meter Z)

This system consists of a standard turbine meter, an in-line densitometer, an

electro-mechanical register and an electronics package. The turbine meter rotor speed

is monitored by a pickup coil mounted on the meter housing. The volumetric flow rate is

a function of the voltage pulse rate generated in the pickup coil. This voltage pulse is one input to the electronics package. The other input is the signal from the densitometer.

This device measures density directly by monitoring the damping effect of the liquid on a vibrating element in the flowing liquid stream. The electronics package converts the

volumetric pulse rate and the densitometer output to a pulse output that is proportional to the mass flow rate. This pulse output is converted to a direct reading in pounds by the

electro-mechanical register.

The meter manufacturer's specifications are:

fluid - liquid nitrogen

maximum flow rate - 130 gpm (8. 2 -t/s)

minimum flow rate - 11 gpm (0. 7 t/s)

mass meter factor - 10 lbs/P (4. 5 kg/P)

volumetric K-factor - 315. 2 P/gal

nominal turbine meter size - 1-1/2 inch (0. 038 m)

The test results of one meter are reported. Two meters were submitted for

testing; however, one (meter Y) of the two had been subjected to substantial preliminary

tests at another facility and did not function satisfactorily at NBS.

The meter was subjected to a first rangeability test, a boundary test, a stability

test, and a second rangeability test in that order.

Two sets of data were collected simultaneously during all tests. One set was

volumetric data from the turbine meter only, and the other was mass flow rate data from

the complete system. Both sets of results are reported.

Meter Z (Volumetric System)

The results of the first rangeability test are shown in figures IF and 2F. These

data were fitted to the mathematical model and the results are shown in table IF. The

four outlying points were removed from the data prior to the fit because it was felt these

points may have been influenced by the malfunctioning densitometer.

F-l
Table IF. Fit of Model to Meter Z (Volumetric System),

First Rangeability Test Data

Model y = -2. 353 + 0. 04287 T

Bias at T = 80 K, y = +1. 08%

Residua1 Standard Deviat ion = ±0. 19%

Number of Points = 54

This volumetric meter displayed a significant temperature dependency. The bias

at a temperature of 80 K is + 1. 08 percent. The precision based on three times the

residual standard deviation is ±0. 57 percent.

The mean bias of these data without fitting them to the model is +1. 27 percent.

The standard deviation of these data without the model is ±0. 24 percent and the precision

based on three times this standard deviation is ±0. 72 percent.

The results of the boundary test are shown in figure 3E. The accuracy seems to remain unaffected by subcooling above approximately sixteen degrees of subcooling.

Below that point there is a noticeable change in bias and a loss of precision. The amount

of subcooling was determined at the inlet to the metering system; therefore, the turbine

meter performance may have been affected by the pressure drop across the densitometer

and the interconnecting piping.

The results of the stability test are shown in figure 4F. Approximately 624 000

gallons (2 362 100 -t) of liquid nitrogen were metered during this test with no apparent

wear occurring.

The results of the second rangeability test are shown in figures 5F and 6F.

These data were fitted to the model and the results are shown in table 2F. Two

points with the highest deviation were removed before fitting because of possible influence

of the densitometer.

Table 2F. Fit of Model to Meter Z (Volumetric System)

Second Rangeability Data

Model y = 1. 23

Bias, y = +1. 23%

Standard Deviation = ±0. 29%

Number of Points = 57

There were no significant dependencies exhibited during this test. The bias is

±1. 23 percent and the precision based on three times the standard deviation is ±0. 87

percent.

F-2
Typical pressure drop data for meter Z is shown in figure 11F.

Meter Z (Mass System)

The results of the first rangeability test are shown in figure 7F. The data above

4 lbs/s (1. 8 kg/s) were fitted to the model and the results are shown in table 3F. The

data below 4 lbs/s (1. 8 kg/s) were removed from the model because of the strong flow

rate dependency and the loss of precision. One other point was removed at 14 lbs/s

(6. 3 kg/s) and 6 percent deviation because the densitometer was not functioning properly

at that time.

Table 3F. Fit of Model to Meter Z (Mass System), First

Rangeability Data, for flow rates above 4 lbs/s (1. 8 kg/s)

Model y = 156. 62 - 3. 5366 T + 0. 019865 T

2

Bias at T = 80 K, y = +0. 83%

Residua1 Standard Deviation = ±0 60%

Number of Points = 48

These data show significant dependencies on temperature, T, and temperature

squared. The bias at a temperature of 80 K is +0. 83 percent and the precision based on

three times the residual standard deviation is ±1. 80 percent.

The mean bias of these data without fitting them to the model is -0. 147 percent. The

standard deviation of these data without the model is ±0. 84 percent and the precision based

on three times the standard deviation is ±2. 52 percent.

There appeared to be a calibration error in the densitometer which can be seen in

figure 8F. Since the density is relatively insensitive to pressure, this calibration error appears in the model as a temperature dependency.

The results of the boundary test are shown in figure 9F. The eight high deviation

points at approximately eight degrees of subcooling are the result of the turbine meter

subcooling dependency observed on figure 3F. The three high deviation points at approximately twenty-four degrees subcooling are a result of the behavior of the densitometer.

Below a liquid temperature of 74 K (high subcooling), the densitometer became erratic

and gave erroneous data.

The results of the stability test are shown in figure 10F. The imprecision was due

in large part to the erratic behavior of the densitometer. There did not appear to be any

change in the turbine meter during this test.

The results of the second rangeability test are shown in figure 11F. The data below

4 lbs/s did not exhibit the same loss of precision as was observed during the first rangeF-3
ability test and they were included in the fit to the model. The results of the fit are presented intable 4F.

Table 4F. Fit of Model to Meter Z (Mass System),

Second Rangeability Test Data

Model y = 15. 29 - 0. 1786 T - 0. 1136 m

Bias at T = 80 K and m = 14. 5 lbs/s, y = -0. 64%

Residual Standard Deviation - ±0. 80%

Number of Points = 58

During this test, the mass meter system shows significant dependencies on temperature, T, and mass flow rate, m. The bias at a flow rate of 14. 5 lbs/s and a temperature of 80 K is -0. 64 percent. The precision based on three times the residual

standard deviation is ±2. 40 percent.

The mean bias of these data without fitting them to the model is -0. 69 percent.

The standard deviation of these data without the model is ±1. 10 percent and the precision

based on three times the standard deviation is ±3. 30 percent.

Since this meter has significant dependencies, the bias must be calculated from

the model to obtain the precision of ±2. 40 percent. If the bias is not calculated from the

model then the precision can be no better than ±3. 30 percent.

The density dependency is shown in figure 12F.

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F-17

orm NBS-114A d-71)

2. Gov't Accession No.

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBS TN 624

3. Recipient's Accession No.

.TITLE AND SUBTITLE

An Evaluation of Several Cryogenic Turbine Flowmeters

5. Publication Date October 1972

6. Performing Organization Code

. AUTHOR(s) J". A- Brennan, R. W. Stokes, D. B. Mann, and"

C. H. Kneebone

8. Performing Organization

10. Project/Task/Work Unit No. 2750360

PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS, Boulder Labs.

DEPARTMENT OF COMMERCE

Boulder, Colorado 80301

11. Contract/Grant No.

!. Sponsoring Organization Name and Address Co-Sponsored by

The Compressed Gas Association, Incorporated

500 Fifth Avenue

New York, New York 10036

13. Type of Report & Period

Covered

Interim - 1971

14. Sponsoring Agency Code

i. SUPPLEMENTARY NOTES

• ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) he National Bureau of Standards (NBS) and the Compressed Gas Association (CGA)

ive jointly sponsored a research program on cryogenic flow measurement. A cryoenic flow research facility was constructed and has been used to evaluate cryogenic

owmeters operating on several different principles.

he operation and the accuracy of the flow facility is briefly described. The perforiance of the flowmeters in liquid nitrogen is described by reporting the precision and

.as of the meters before and after an 80 -hour stability test and by defining the existenc

'temperature, pressure, flow rate, subcooling, and time order (wear) dependencies.

Meters were evaluated with flow rates ranging from 20 to 210 gpm ( 1. 3 to 13. 2

/s) , pressures ranging from 32 to 112 psia (0. 22 to 0. 77 MN/m 2

), and with tempera

res ranging from 72 to 90 K.

• KEY WORDS (Alphabetical order, separated by semicolons)

"yogenic; flow; liquid nitrogen; mass; mass flowmeters; measurement; turbine

>wmeters; volume flowmeters.

AVAILABILITY STATEMENT

fXI UNLIMITED.

I I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

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90

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NBS Special Publication 305, Supplement 2, Publications of the NBS, 1970. When ordering, include Catalog No. C13.10: 305/Suppl. 2. Price $3.25 ; 85 cents additional for foreign mailing.

Order NBS publications (except Bibliographic Subscription Services)

from: Superintendent of Documents, Government Printing Office, Washington, D.C. 20402.
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, D.C. 20234

OFFICIAL BUSINESS

Penalty for Private Use. S300

POSTAGE AND FEES PAID US. DEPARTMENT OF COMMERCE

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