Thomas M. Flynn

NBSIR 75-825

THE NATIONAL MEASUREMENT SYSTEM FOR CRYOGENICS

Thomas M. Flynn

Cryogenics Division

Institute for Basic StandardsBoulder, Colorado 80302

October 1975

U.S. DEPARTMENT OF COMMERCE, Rogers C. B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson , Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

FOREWORD

CONCEPT OF A NATIONAL MEASUREMENT SYSTEM

"Concurrently with the growth and industrialization of this nation, there has developedwithin it a vast, complex system of measurement which has made possible the verygrowth that brought the system into being. This National Measurement System (NMS)

stands today as one of the key elements in a worldwide measurement system that linksall major nations together in a consistent, compatible network for communication andtrade.

"Briefly stated, the essential function of the NMS is to provide a quantitative basis in

measurement for (i) interchangeabil ity and (ii) decisions for action in all aspects ofour daily life -- public affairs, commerce, industry, science, and engineering.

"Our National Measurement System is one of a number of mutually interacting systems withinour technologically based society that form the environment in which the individualcitizen must live and function. Familiar examples are the communication, transporta-tion, educational, medical, and legal systems, all of which may be included under the

general heading of social systems."In view of the demonstrated value of the systems approach for the understanding and improve-

ment of hardware such as computers and weapons, some of these social systems are beingsubjected to the same type of analysis. The National Measurement System, which evolvedin this country with little formal recognition as a system, is now being examined in

this way at the National Bureau of Standards (NBS) which undertook the study of NMSpartly because of a growing realization of the al 1 -pervasive nature and great economicimportance of the nation's measurement activities, and partly because of the challengeto NBS in putting its splendid new facilities to optimum use for the benefit of the

nation. Such optimum use can be approached only when NMS, of which NBS is a centralelement, and the services it requires for effective operation are sufficiently well

understood."Because the government has wisely refrained from assigning leadership of NMS to NBS by law

or executive order, the Bureau of Standards must maintain this leadership through dem-onstrated competence and general acceptance of its capability. This situation presentsboth a challenge and a responsibility. The NBS must make a continuous effort to under-stand the structure and operation of the NMS, to assess the value of its services fornational objectives, and to develop means for evaluating its effectiveness.

"Our study of the National Measurement System is still in its early stages. There remainsmuch work to characterize inputs and outputs, interactions with other social systems,involvement with national objectives, the functions of NMS elements, and couplingsbetween the elements."

This description of the National Measurement System was first published by Dr. E. D.

Huntoon in Science, 1 58 , 67-71, October 6, 1967. Dr. Huntoon at that time was director

of the Institute for Basic Standards, of the National Bureau of Standards. For the reasonsstated in the above quotation. Dr. Huntoon began and fostered systematic studies of the

National Measurement System of which the following work is a part.

CONTENTS

Pa^e

FOREWORD

EXECUTIVE SUMMARY 1

1. INTRODUCTION 3

2. STRUCTURE OF THE MEASUREMENT SYSTEM .... 4

2.1 Conceptual System 4

2.2 Basic Technical Infrastructure 5

2.2.1 Documentary Specification System 5

2.2.1.1 Standardization Institutions 5

2.2.1.2 Survey of Documentary Standards 6

2.2.2 Instrumentation System 7

2.2.2.1 Measurement Tools and Techniques 7

2.2.2.2 The Cryogenic Instrumentation Industry . . 13

2.2.3 Reference Data 17

2.2.4 Reference Materials 19

2.2.5 Science and People 21

2.2.5.1 Cryogenic Measurements in Science 21

2.2.5.2 Cryogenic Science in Measurements 22

2.3 Realized Measurement Capabilities 24

2.4 Dissemination and Enforcement Network 26

2.4.1 Central Standards Authorities 26

2.4.2 State and Local Offices of Weights and Measures . . 27

2.4.3 Standards and Testing Laboratories and Services . . 28

2.4.4 Regulatory Agencies 28

2.4.5 Industrial Trade Associations 28

2.5 Direct Measurements Transactions Matrix 28

2.5.1 Analysis of Suppliers and Users 28

2.5.2 Input-Output Direct MeasurementsTransactions Matrix 30

2.5.3 Highlights re Major Users 32

2.5.3.1 Industrial Gases and Equipment 32

2.5.3.2 Liquefied Natural Gas (LNG) 33

2.5.3.3 Research and Development 34

3. IMPACT, STATUS AND TRENDS OF THE CRYOGENIC MEASUREMENT SYSTEM . 34

3.1 Impact of Measurements 34

3.1.1 Functional, Technological and ScientificApplications 34

3.1.2 Economic Impacts--Costs and Benefits 35

3.1.3 Social, Human, Person-on-the-Street Impacts .... 36

3.2 Status and Trends of the System 37

ii i

CONTENTS (continued)

Page

4. SURVEY OF NBS SERVICES '.. 39

4.1 The Past 39

4.2 The Present-Scope of NBS Services 39

4.2.1 Description of NBS Services 39

4.2.2 Users of NBS Services 40

4.2.3 Alternative Sources 42

4.2.4 Funding Sources for NBS Services 42

4.2.5 Mechanism of Supplying Services 45

4.3 Impact of NBS Services 45

4.3.1 Economic Impact of Major User Classes 45

4.3.2 Technological Impact of Services 47

4.3.3 Pay-off from Changes in NBS Services 48

4.4 Evaluation of NBS Program 49

4.4.1 Evaluation Criteria 49

4.4.2 Evaluation Panel Role 50

4.4.3 Why NBS? 51

4.4.4 Program Evaluation 51

4.5 The Future 53

4.5.1 Technology Assessments in Cryogenics 54

4.5.2 Driving Forces 56

4.5.3 Emerging Technologies 57

4.5.4 Impacts of the National Measurement System Study . . 57

, 5. SUMMARY AND CONCLUSIONS 57

5.1 Key Developments 57

5.2 Liquefied Natural Gas 58

5.3 Hydrogen 59

5.4 Superconductivity 59

5.5 Summary 60

Appendix A. Methodology of the Study A-1

REFERENCES R-1

LIST OF FIGURES

FIGURE 1. Internal input 41

FIGURE 2. External outputs 41

FIGURE 3. External inputs 43

FIGURE 4. Outside-outside interactions 43

FIGURE 5. Industrial measurement system 44

FIGURE 6. Liquid nitrogen flow program interactions 46

FIGURE 7. Emerging technologies in cryogenics 57

iv

LIST OF TABLES

Page

Table 1-1. Organization and outputs of NBSCryogenics Division 4

Table 2-1. Instrument Society of America Ad Hoc Committee onCryogenic Flow Measurement 5

Table 2-2. Representative members of the Compressed GasAssociation 6

Table 2-3. Flowmeters in custody transfer of oxygen, nitrogenand argon 14

Table 2-4. Typical flowmeter specifications 15

Table 2-5. Typical flowmeter data 15

Table 2-5. Resistance and thermistor thermometers 16

Table 2-7. 1973 Profile: instruments for measurement, analysis,and control 17

Table 2-8 Cryogenic pressure transducers 24

Table 2-9 Some approximate characteristics of the most widelyused classes of cryogenic thermometers 25

Table 2-10. Direct measurements transactions matrix 31

Table 2-11. Net sales of major cryogenic companies in the U.S 33

Table 3-1. Instruments for measurement, analysis and control:projections 1973-80 35

Table 4-1. Funding by sources 45

Table 4-2. Distribution of effort 49

Table 4-3. The crucial role of NBS 53

V

THE NATIONAL MEASUREMENT SYSTEM FOR CRYOGENICS

Thomas M. Flynn

Cryogenics DivisionInstitute for Basic Standards

October 1975

ABSTRACT

The Cryogenics Division of NBS has evolved as the nation's centrallaboratory for cryogenics, much as NBS itself has evolved as the nation'scentral laboratory with both broad and specific responsibilities. Cryogenicmeasurement and data outputs provide the common foundation for all the insti-tutions and agencies throughout the nation employing cryogenics to solvetheir problems.

This Study of the National Measurement System showed that the CryogenicsDivision of NBS provides almost every category of measurement and data ser-vice that NBS itself provides: not just an instrumentation system (including,for example, pressure, temperature, density, liquid level, flow rate, etc.),but also properties of fluids (both thermodynamic and transport properties);properties of solids (thermal, mechanical and electrical); an interface withthe users through systems integration and advisory and consulting services;and a dissemination network through the Cryogenic Data Center.

This study documents the impact, status and trends of the cryogenicmeasurement system and specifically illustrates these characteristics whereverpossible with a specific case study, a recently completed measurements and

data program for the flowmetering of liquid nitrogen.

Key Words: Cryogenics; data; flowmeter; instrumentation; measurements;

National Measurement System.

V i

THE NATIONAL MEASUREMENT SYSTEM FOR CRYOGENICS

Thomas M. Flynn

Cryogenics DivisionInstitute for Basic Standards

October 1975

EXECUTIVE SUMMARY

The National Bureau of Standards is not

responsible for only one unit of measurement,or even a set of measurements. Rather, the

legislative mandate calls for NBS to providea base for such a system, aoordinate thatsystem, and furnish essential services. Thus

it is the responsibility of NBS to assure theproper functioning of the Nation's system of

physical measurement, the National Measure-ment System. Accordingly, the presentmicrostudy was conducted to examine anddocument the way in which the NBS CryogenicsDivision is meeting its particular responsi-bility to assure the proper functioning ofour system of cryogenic measurement.

The Cryogenics Division of NBS providesthe measurement and data services that sup-port a whole technology. Almost every cate-gory of measurement and data service is

offered that NBS as a whole provides: notjust an instrumentation system (including,for example, pressure, temperature, density,liquid level, flow rate, etc.), but alsoproperties of fluids (both thermodynamic andtransport properties); properties of solids(thermal, mechanical, and electrical); aninterface with the users through systemsintegration, and advisory and consultingservices; and our own dissemination networkthrough the Cryogenic Data Center,

This study shows that there are threespecific emerging technologies within thisbroad area of Cryogenics which need a com-plete and consistent system of measurementsand data.

For instance, a comprehensive measurementsystem for liquefied natural gas needs to bedeveloped, with special emphasis on quantitygaging in storage, flow-metering for bothmass and heating value, and basic measure-ments of thermal and mechanical propertiesof structural materials.

Basic measurements and data are requiredto support the development of hydrogen as a

fuel, to improve hydrogen liquefaction ef-ficiency, to recover liquefaction energy, todocument hydrogen-compatible materials ofconstruction, to develop improved insulationmaterials, plus measurement tools and tech-niques for the eventual commercial exchangeof liquid hydrogen.

Superconductivity connects cryogenicmeasurements and data to the electrical powerindustry, for power transmission, generation,and storage. Knowledge needed here includesheat transfer rates, behavior of helium re-

frigerant flow systems, and the degradationof the superconductors with time and stress.Other practical uses of superconductivity arebecoming apparent, such as the application ofSuperconducting Quantum Interference Devices(SQUIDs) to problems ranging from mineralprospecting to magnetocardiography . Accord-ingly, the needs to support this technologyencompass instruments and techniques forphysical measurements plus a technical database.

The technologies discussed above show theimportance of cryogenics in commerce in theU.S. today, and also show its truly diverseapplications. If there were a "GeneralCryogenics Corporation" like a GeneralMotors, it would appear in the top 10% of theFortune list of the 500 largest U.S. Indus-trial Corporations. But it is important to

note that there is not a "Cryogenics Corp-oration", per se. Cryogenics is an infra-structure industry. Similarly, the nationalsystem of cryogenic measurements is an infra-structure of cryogenic technology itself.The crucial question of this report is, howwell does the measurement and data structuresupport the technology as a whole?

This study shows that some parts of thecryogenic measurement system seem to becharacterized by adequate services and qual-ity assurance (cryogenic temperature mea-surements, for instance). It appears oneshould have less confidence in other parts ofthe system. Pressure measurements, forinstance, which are probably the measurementmost widely made in all of cryogenics,appear not nearly so well supported, espec-ially pressure measurements in extremeenvironments. Attention by NBS to theseissues is in order.

Especially apparent at this time is the

need for a different kind of measurement,namely one that describes the quality oravailability of the commodity. Specifically,we refer not so much to the flow measurementof liquefied natural gas, for example, as to

the need to measure its potential heatingvalue.

It appears that one component of the prob-lem of cryogenic measurement is that thefield is somewhat static. There has been no

concerted national effort since the peak ofthe space program.

A second part of the problem arises fromthe way cryogenic measurements fit into theNational Measurement System. As long as onlya single agency or one sector of our economy(National Aeronautics and Space Administra-tion, the aerospace industry) was using es-sentially all of the results of its own mea-surements, then that part of the NationalMeasurement System was internally consistentand in harmony with itself. Now, however,cryogenics is becoming more commercializedand moving to the market place, and thusexternal consistency as well as internalconsistency is required to make this part ofthe National Measurement System work.

The third part of the problem is perhaps a

derivative of the first. Because the fieldis relatively static, a crucial question is

not being asked: are there predictable tech-nological developments that will eithercreate a need for new cryogenic instruments,or possibly provide an altogether new mea-surement means?

Certain parts of the cryogenic measurementsystem at the national level seem to be dis-connected, or working independently of oneanother at this time. For instance, ourperception is that the U.S. Coast Guard has

the necessary authority to regulate certainaspects of liquefied natural gas transporta-tion by setting certain physical standards,measurement codes, and practices. They may dothis without necessarily having recourse to

the NBS. Other national authorities, espe-cially in the area of public safety come to

mind. Accordingly, it appears that this partof the measurement system is disjointed.There is no objective reason why it shouldremain so. It would be in accord with theNBS mission and tradition to pursue theseissues and resolve them.

A goal of this study was to achieve bothconceptual breadth and depth by examining ourrole in the national measurement system as a

whole, and illustrating this role with a

specific case study, the liquid nitrogenflowmetering program. This program wasinstigated by the needs of state weights andmeasures officials, the industry concerned,and the public for confidence in the custodytransfer of liquid nitrogen. This effort usednearly every competence and capability thatNBS has developed: measurement services(tests and calibrations of meters), propertydata (thermodynamic property data for cryo-genic fluids), standard codes and practices(Handbook 44), dissemination services (Officeof Weights and Measures, the National Con-ference of Weights and Measures), and bothvoluntary and regulatory standards activities(through the most relevant industry groupconcerned - the Compressed Gas Association,and by adoption in state codes).

The general conclusion of this study is

that the cryogenic measurement system is

doing its job adequately at reasonable cost.There is no widespread feeling of inadequacy,such as that which led to the creation of theNational Bureau of Standards seventy-fiveyears ago. On the other hand, there are bothsystematic and specific deficiencies that canand should be corrected. Further, there areseveral areas in which the cryogenic measure-ment system will be subjected to severestrains in the foreseeable future, unlessappropriate responsive steps are taken soon.

Specific needs and responses, which areonly summarized here, are documented withinthe body of the report.

2

1. INTRODUCTION

National commerce in cryogenics, a vital

outgrowth of the chemical industry, exceeds

$2 billion annually. It is both a domesticand international business, which may be

broken down into three areas. They are:

- Industrial Gases and Equipment- Liquefied Natural Gas- Superconductivity.

Industrial Gases and Equipment . Indus-trial gases provided by cryogenic techniquesare very important commodities. According to

the most recent Department of Commerce sur-

vey, the annual production of liquid oxygenis about $300 million, 50% used in the produc-tion of steel and 20% in the chemical indus-try. Aerospace use is less than 2% -- evenless than that used for sewage disposal.Minneapolis, Tampa, New Orleans, and FairfaxCounty, Va. are among the many places thatuse oxygen to speed up sewage treatment by

factors of 3 to 5. More than 50 oxygenplants are planned or under construction in

the U.S. for sewage treatment.Fifty to sixty percent of all the hospi-

tals in the U.S. presently store theirbreathing oxygen as liquid, and the AmericanHospital Association states that every newhospital costing $1 million or more usesliquid oxygen.

Annual sales of liquid nitrogen are about$150 million, with over $50 million beingused for food freezing.

One major airline uses 1.8 million poundsof liquid nitrogen per year for galley cool-ing. Company officials claim that "theprocedure is wondrously simple and reliableand that the experience has been so favorablethat all future aircraft will use the sametechnique." The Department of Transportationhas watched this system closely to get a

"feel" for the logistics of supplying cryo-genics necessary for ground transportationsystems

.

Recently, a 400 ton-a-day liquid nitrogenplant was opened at Stafford, Texas to supplynitrogen to a major semiconductor devicemanufacturer to protect electronic parts fromimpurities during manufacture. Similar faci-lities exist in the Bay Area of California tosupport the electronics industry there.

Liquefied Natural Gas (LNG) . It is pre-dicted that by 1985 10% of our natural gaswill be imported as LNG from Alaska orforeign sources. There are approximately 19

applications pending before the Federal PowerCommission for permission to import LNG or toliquefy and store it for interstate use.

These applications are not trivial. To il-

lustrate, one peak shaving facility in Iowawill cost $23 million. Import terminals,including ships and pipelines have beendescribed at costs for $2 to $6 billion.

Superconductivity . Although practicaluses of superconductivity are not extensiveat present, we expect these applications togrow and mature in the next few years. Pres-ent day superconducting magnets for liquidhydrogen bubble chambers rank as the largestsolenoid magnets in the world.

Cryogenic processes seldom result in anend product in themselves, but rather play anessential supporting role in other more visi-ble industries. As mentioned, 50% of the liq-uid oxygen production goes into steel makingand another 20% into chemicals. Forty per-cent of the space industry is cryogenicbased. The steel, chemical, and space indus-tries are highly visible, but the cryogenicsindustry is not. If one were to go shoppingfor cryogenic merchandise, he would findlittle, for cryogenics is indeed an infra-structure industry.

It is thus the nature of cryogenics thatit be largely hidden and obscure to most ob-servers, while at the same time occupying a

central position of great potential leverageon the nation's essential industries - steel,chemicals, space, transportation, agricul-ture, sewage disposal, and so forth. Itwould therefore be imprudent to leave theworkings of cryogenics to chance, and ac-cordingly this study of the National Measure-ment System was undertaken to document andevaluate the adequacy of our measurementand data services to this vital technology.

In making an inventory of all of our mea-surement services, we find that we offernearly every type of service that NBS as a

whole does, e.g., conceptual knowledge, in-

strumentation, reference materials, standardsamples, reference data, and specifications.We have also documented our operations throughthe dissemination network, e.g., regulatoryagencies, state offices, and central standardsauthorities. We have achieved both concep-tual breadth and depth by examining first ourrole in the National Measurement System as a

whole, and then illustrating this role witha specific case study.

3

2. STRUCTURE OF THE MEASUREMENT SYSTEM

The National Bureau of Standards is notresponsible for only one unit of measurement,or even a system of measurements. Rather,our legislative mandate calls for NBS to

provide a base for such a system, coovdinatethat system, and furnish essential services.Examination of these statues shows that theNBS has both unique and special responsibil-ities in relation to the Nation's science andtechnology, and very broad responsibilitiesas wel 1

.

So it is with the cryogenics at NBS. Weare not responsible for "a" unit of measure-ment or even a tidy set of measurements.Just as it is a general NBS role to make sci-ence useful, so it is our role to make cryo-genics useful. We do not develop technology.We do help others with applied research ser-vices to produce, diffuse, and enhance thevalue of practical knowledge. Our goal is tostrengthen and advance the Nation's cryogenicscience and technology— in short, make cryo-genics useful.

Accordingly, since we do help support a

whole technology, we find that we must pro-vide almost every measurement and data servicethat NBS as a whole provides: not just aninstrumentation system (including, for example,pressure, temperature, density, liquid level,flow rate, etc.), but also properties offluids (both thermodynamic and transport prop-erties); properties of solids (thermal, me-chanical and electrical); an interface withthe users through systems integration, andadvisory and consulting services; and our owninformation dissemination network through theCryogenic Data Center.

Table 1-1. Organization and outputsof NBS Cryogenics Division

Functional Organization

MetrologySolids PropertiesFluids PropertiesSystems Integration!Data Center

Outputs

Measurement TechniquesData for Decision MakingData for Reliable DesignTechnical AnalysesSafety CriteriaImpartial AssessmentInformation ServicesTechnology TransferNational Standards

ACentralizedNationalEffort

We are organized by function to providethese outputs (see table 1-1). We have foundthat such a functional approach generallyserves us better than a programmatic one.Cryogenics is an evolutionary technology andour strength lies in being able to meet chang-ing programmatic needs. We have in factevolved as the Nation's central laboratory forcryogenics, much as NBS itself evolved duringits early years as the Nation's central tech-nical laboratory with both broad and specificresponsibilities. Our outputs provide thecommon foundation for all the institutionsand agencies throughout the nation employingcryogenics to solve their problems. The fol-lowing sections will illustrate how we pro-vide these services in practice.

2.1 Conceptual System

The Cryogenics Division of NBS is the onlyfederal laboratory exclusively in cryogenicsdedicated to helping develop and promote thesuccessful application of all aspects of thisscience. As such, the conceptual system thatencompasses our work ranges from the genera-tion of basic, conceptual knowledge (e.g.,fundamental constants, superconducting quan-tum interference phenomena) to specific prob-lem solving for government agencies andother public institutions (e.g., technicaladvice to the Electric Power Research Insti-tute on refrigerators for cooling supercon-conducting electric power transmission lines).The specific quantities and phenomena thatneed to be measured relate to the propertiesof liquids and solids needed by engineersfor design and construction purposes and alsoby scientists to improve the understandingof the physics of fluids. These properties(see also Section 2.2.3) include, but arenot limited to, the thermodynamic property offluids (compressibility, entropy, enthalpy,specific heats, sound velocities); electro-magnetic properties (diekectric constant,refractive index); and transport properties(viscosity and thermal conductivity coeffi-cients). The data required on solids (metals,alloys, and composites) used at low tempera-tures include the mechanical, thermal, andelectrical properties.

Effective and reliable measurement systemsare required for certain physical parametersat low temperatures, notably: pressure, tem-perature, density, liquid level, quantity,and flow rate, and, more often than not a verydifficult parameter to realize in practice,the total "usable" mass.

The conceptual system also encompasses theuse of low temperature phenomena as tools forthe measurement of other physical parameters(see section 2.2.5.2) such as the electricalvolt, noise, current, power, flux magnitude,etc.

2.2 Basic Technical Infrastructure

As indicated in Section 1., the cryogenic

measurement system supports an international

technology that ranges from multinational

trade in liquefied natural gas to supplying

breathing oxygen for hospitals. Accordingly,

the technical infrastructure that supports

this system in turn runs from the Interna-

tional Organization of Legal Metrology to

state weights and measures officials, as a

minimum. The following sections will describesome of the more important institutions and

systems that help make this part of the Na-

tional Measurement System function.

2.2.1 Documentary Specification System

2.2.1.1 Standardization Institutions

Several states, an industry association,and national and international organizationsrecently cooperated in a technical program to

assure adequate quality control in one part

of the cryogenic measurement system, namelythe flowmetering of liquid nitrogen. We

shall use this example to highlight the vari-

ous standardization institutions that mustinteract to assure effective measurement con-

trol in even so small a part of the cryogenicmeasurement system.

Background . Liquid nitrogen is an impor-

tant article of commerce--approximately$150 million worth per year changes hands.

Its uses include food freezing, airline gal-

ley cooling, and providing a protective atmo-sphere for semiconductor manufacture andfloat glass production. Regardless of its

wide use, it is a difficult commodity to

measure for it is nearly always a boiling,two-phase mixture, whose value depends in partupon its density and in part upon its re-frigeration capability. Commonly used prac-tices of custody transfer had a vague techni-cal basis, which inhibited both complianceand regulation, regardless of how well inten-tioned either party may have been.

In 1966, at least three groups took thisproblem under consideration. The descriptionbelow is in approximate chronological order,but no great significance should be attachedto the dates. The three groups did initiatetheir work separately, but eventually workedtogether toward a common solution, and oftenwith overlapping membership. This exampleis presented to show an institutional struc-ture through which standards are effected.

The Instrument Society of America Ad Hoc

Committee on Cryogenic Flowmetering . Thedecision of the Instrument Society of Americato establish this Ad Hoc Committee was based,in part, on a recommendation for "CalibrationStandards for Turbine and Mass Flowmeters,

Particularly for Cryogenic Fluids" from the

first ISA Standards and Practices Panel Ses-sion held in conjunction with the 1965 AnnualConference. The committee membership was

broadly representative of all concerned--States weights and measures officials, cryo-

genic fluid buyers and sellers, and metermanufacturers. The membership is shown in

table 2-1.

Table 2-1. Instrument Society of AmericaAd Hoc Committee on

Cryogenic Flow Measurement

University of ColoradoNational Bureau of Standards

Transcontinental Gas Pipe Line CompanyMissiles & Space Division, Douglas Aircraft

Cox InstrumentsWyle LaboratoriesPotter Aeronautical

Air Reduction CompanyNASA - MSFC

California Bureau of Weights & Measures

The abstract of the final report by the

Ad Hoc Committee recommended: (a) a nationalstandard and transfer standards; (b) an ac-cepted methodology; (c) a national authorityto develop the standards, transfer standards,and methodology; and (d) educating all per-sonnel in the state-of-the-art of cryogenicfluid flow measurements.

The Compressed Gas Association Model Code .

The Compressed Gas Association is a non-profitmembership corporation chartered in the Stateof New York that represents all segments ofthe compressed gas industry in the UnitedStates, Canada, and Mexico. They also haveassociate members in European and Asiancountries. Among its membership are over 250companies (including North America's largestfirms) devoted primarily to producing anddistributing compressed, liquefied, and

cryogenic gases, as well as leading chemicalindustry corporations that have compressedand liquefied gas divisions. A few of themembers of the Compressed Gas Associationwho were most interested in liquid nitrogenflowmetering are shown in table 2-2.

It is estimated that the domestic companieslisted below produce in excess of 95 percentof the cryogenic fluids marketed in this coun-

try.

In June 1967, the Compressed Gas Associationproposed to the National Conference on Weightsand Measures a model code for flow metering of

cryogenic fluids. Although the Conference on

Weights and Measures noted that cryogenic flowmeasurement problems were, at that time, cen-tralized only in a few states, the CompressedGas Association proposal was a significantstep in national recognition of cryogenicflow measurement problems.

Table 2-2. Representative members of the

Compressed Gas Association

Domestic:

Air Products and Chemicals, IncorporatedAir Reduction CompanyLiquid Carbonic CorporationLinde Division - Union Carbide CorporationNational Cylinder Gas Div. - Chemetron Corp.

International Oxygen Manufacturers Assoc.CVI Corporation - Pensalt Chemical

Foreign:

British Oxygen CompanyL'Air LiquideLinde AG (Lotepro)Messer-Griesheim

The California Code on Cryogenic Measur-ing Devices . The regulatory agencies saw a

real need for traceability to a national stan-dard since they are usually obligated by law

to perform "type approval" inspections. In thefall of 1967, the State of California Bureauof Weights and Measures began hearings on

its own proposed code for cryogenic fluidmeasurement devices used in California. Afterseveral hearings in the fall and winter of1967-68, the code was adopted and made law in

California on June 1, 1968.

The State of New Jersey was not far behindCalifornia with respect to such regulations.New Jersey officials stated that with the

introduction of sales of cryogenic fluids to

the trucking industry for use as a refriger-ant, they would be forced to find some meansof developing an acceptable proving method.Further, with the advent of the Sales Tax in

the State of New Jersey, and no exceptionsbeing known at that time given to the sale of

cryogenics at the retail level to trucks, it

was felt that the commodity would be subjectto that tax.

Because such state agencies are obligatedto promulgate regulations controlling the use

of any commercially used weighing or measuringdevices, including those used in cryogenicfluid commercial sales or custody transfers,the needs of these agency officials as expres-sed by them are pertinent and important to

the subject at hand. They summarized theirneeds as follows:

"(1) With respect to standards, thereshould be a national "facility", a final

"authority", a "referee" that would not be

in competition with private industry.

(2) This "agent" should provide the neces-sary methodology to preserve the accuracyand precision of field measuring methods.

(3) This "agent" should continue to inves-tigate new measuring methods in order to

advance the state-of-the-art."

The International Organization of LegalMetrology . Just as the States preferred a

central authority to coordinate these acti-vities on a national scale, the gas pro-ducers themselves desired to coordinatesuch a standardizing activity on an inter-national scale. Accordingly, the Inter-national Organization of Legal Metrologywas brought into the program at the be-ginning to facilitate the adoption of thefindings of this program as an internationalcode. The collaborating countries areAustria, France, India, Italy, Japan, Nether-lands, Poland, United Kingdom, Switzerland,Czechoslovakia, and the USSR.

2.2.1.2 Survey of Documentary Standards

Measurement accuracy must be assured to

avoid failure in complex engineering designsand sophisticated experiments. But accuracyis even more important when quantities ofgoods or services in commerce are beingmeasured. If a free-enterprise economic sys-tem is to thrive in a modern industrial so-ciety, buyers and sellers in the marketplaceneed to have as much confidence in the quan-tity and performance of goods exchanged as

they do in the amount of moneys paid.

We will continue to use the liquidnitrogen flowmetering program as a specificexample of the process by which practicesand data become codified and have theeffect of law.

As mentioned. State regulatory agencieshave a real need for traceability to a

national standard since they are obligatedby law to perform type approval inspections.This is clearly outlined, for example, in

the Business and Professions Code of the

State of California. One provision of thiscode reads as follows:

"2500.5. The directory by rules and reg-ulations shall provide for submission for

approval of types or designs of weights,measures, or weighing, measuring, or

counting instruments or devices, used forcommercial purposes, and shall issue cer-

tificates of approval of such types or

design as he shall find to meet the re-

quirements of this code and the tolerancesand specifications thereunder.

"It shall be unlawful to sell or use forcommercial purposes any weight or measure,or any weighing, measuring, or countinginstrument or device, of a type or designwhich has not first been so approved by the

department; provided, however, that any

such weight, measure, instrument, or devicein use for commercial purposes prior to the

effective date of this act may be continuedin use unless and until condemned under the

6

provisions of this code. (Added by Ch. 893,

Stas. 1949.)"

After the hearings described in Section2.2.1.1 had been held, the code was adoptedand made into law in California on June 1,

1968. Of the code specifications, one of the

most significant was tolerance.

"The maintenance tolerance shall be fourpercent (4%) of the indicated delivery on

underregistration and two percent (2%) of

the indicated delivery on overregistration.The acceptance tolerance shall be one-halfthe maintenance tolerances."

The State of California also suggested that"best values" of data be included in the Cali-fornia Code. The gases under considerationwere limited to oxygen, nitrogen, argon, andhydrogen. The scope of the data required wasincreased to include saturation densities overa broad range of pressure and temperature foreach gas. At the request of both the Com-pressed Gas Association and the State of

California, a document was produced specifi-cally to allow traceability of selectedvalues

.

These properties data are specificallycalled out in the California Code and accord-ingly has the same weight of law as the flow-meter calibrations and tolerances themselves,viz.

:

"3081.2.6 Saturated Liquid Densities.Saturated liquid densities of Oxygen,Nitrogen, Argon, and Parahydrogen asprepared by the National Bureau of Stan-dards, Boulder, Colorado, shall apply(Refer to National Bureau of Standards,Technical Note No. TN-361)."

This program on cryogenic fluid transferis only one of the most recent instances wherecommon data have proven beneficial to indus-try and Government. Many other times govern-ment agencies with to evaluate efficiencyclaims and production capacities projected by"paper studies". A complete and consistentset of design data is essential to this pur-pose. The National Aeronautics and SpaceAdministration, National Accelerator Lab-oratory, Navy and other government agencies,for instance, specify that a common data basebe used in its proposals to provide a soundbasis for evaluation. Data so codified arein a very real sense "documentary standards",although not strictly speaking de curestandards.

2.2.2 Instrumentation System

Cryogenic instrumentation as a disciplineis primarily concerned with the condition orstate of cryogenic fluids, such as pressureand temperature. Such information is typi-cally required for process optimization andcontrol. In addition, as cryogenic. fluidsbecome increasingly commercially important,there is the question of "how much" is there?Accordingly, the instrumentation system mustbe able to provide answers in terms of liq-uid level, density, and flow rate.

A derivative question is arising more andmore frequently, namely, of what utility orquality (in the same sense as thermodynamicavailability) are the goods? As it is not"good enough" to count BTU's alone in energyconservation questions (the level of thermo-dynamic availability must be considered), soit is that the "availability" of the cryo-genic fluids must be taken into account.

This was a nagging question during thespace program when a so-called "empty" tankof liquid hydrogen could still contain 2% orso of its original mass, as a dense but un-usable fluid. It is of importance today in

the metering of liquefied natural gas, forinstance, where the integrated heatingvalue--which depends upon composition--isthe preferred unit of commerce, rather thanjust the volume that has changed hands.This section addresses the measurement toolsand techniques that are currently used to

probe this part of the cryogenic measurementsystem.

2.2.2.1 Measurement Tools and Techniques

(1) Pressure . Of all the measurementsmade on cryogenic systems, surely one of themost common must be that of pressure measure-ment. Pressure measurements are made not onlyto determine the force per unit area in a

system, but also to determine flow rate (headtype meters), quantity (differential pressureliquid level gages), and temperature (vaporpressure or gas thermometers). Pressuremeasurements are thus fundamental to thesmooth running of much of this part of theNational Measurement System.

Pressure measurements in cryogenic systemshave, for years, been made by simply runninggage lines from the point where the pressuremeasurement is desired to some convenientlocation at ambient temperatures and attach-ing a suitable pressure-measuring device, suchas the familiar Bourdon gage.

This system works quite well for most ap-plications; however, there are disadvantagesto this straightforward approach that mayintroduce problems in many systems. The two

most important are: (1) reduced frequencyresponse and (2) thermal oscillations. In

addition, heat leak, uncertainties in hydro-static head within gage lines, and fatiguefailure of gage lines could become significantin some applications. Such problems associ-ated with pressure measurement at cryogenictemperatures could be eliminated by installingpressure transducers at the point of measure-ment, thereby doing away with gage lines.

Like all instruments, the output of a pres-sure transducer depends not only on the pri-mary input, in this case pressure, but alsoupon extraneous effects, such as the effect oftemperature on its various components. Erro-neous pressure readings can be caused by bothsteady state temperature effects and tempera-ture gradient, or thermal shock effects.

While it is agreed that some availablepressure transducers are capable of perform-ing satisfactorily at low temperature, othertypes, e.g., piezoelectric, diode, inductance,reluctance, and electrokinetic devices, mayperform equally well or better. It is there-fore necessary, for the purpose of comparison,that all types of pressure transducers betested at low temperature and at various fre-quencies to determine their potential forcryogenic use. Because pressure sensing de-vices often behave quite differently in a

cryogenic medium, a systematic, well docu-mented testing program is presently neededbefore all types can be evaluated and com-pared.

A cryogenic calibration system with variedcapabilities is essential for the successfulcompletion of such a program described above.The details of such a system have been de-scribed by Arvidson and Brennan [2].

(2) Temperature . Most engineering mea-surements are made with metallic resistancethermometers, non-metallic resistance ther-mometers, or thermocouples. Gas thermometersand vapor pressure thermometers find littlepractical engineering application, and henceare mentioned only briefly in the followingparagraphs. A recent compilation of thecommercial availability of thermometers is

given in "Measurements and Data" [3].Gas Thermometry . Constant-volume gas

thermometry is familiar as a technique foraccurate realization of the thermodynamictemperature scale. In such work, thepressure-temperature behavior is made as

linear as possible by minimizing the ex-traneous volumes in the manometer and theconnecting tubing. Troublesome correc-tions for these extraneous volumes decrease

with decreasing bulb temperature, inasmuchas the proportion of gas in the bulb in-

creases. On the other hand, gas imperfec-tion increases with decreasing temperature.

If, however, the sensing bulb is made small,as compared to the external volume of thesystem at ambient temperature, the character-istic is far from linear, the sensitivityincreasing greatly as the bulb temperaturedecreases. By using a Bourdon gage to showthe pressure in this device, a simple gasthermometer is achieved that is useful forsuch purposes as monitoring the cool-down ofcryogenic apparatus.

In order to obtain accurate results in gasthermometry, it is necessary to make many cor-rections. One must account for at least:the imperfection of the gas; the effect ofthe volume of the gas that is not at thetemperature being measured; and the change ofvolume of the bulb with changing temperature.Accordingly, for engineering applications,gas thermometry is recommended only for in-dicating the approximate temperature or tem-perature trend.

Precision gas thermometry falls in thecategory of fundamental thermometers ratherthan empirical thermometers. It is much toodemanding for common use.

Vapor-Pressure Thermometry . As is wellknown, vapor pressure is a sensitive butnonlinear function of temperature, providingconvenient means for thermometry in limitedranges of temperature that unfortunately,do not join to provide continuous coverage ofcryogenic temperatures. For example, therange from 40 K to 50 K is above the range ofneon and below that of oxygen and nitrogen.Within its limits, however, this type ofthermometer is very accurate.

These thermometers are most accurate in

the area of the normal boiling point of theliquid used, and hence could be very useful,albeit over a very limited temperature range.

Advantages of this type of thermometry arethat it is sensitive, can have good timeresponse, is not affected by magnetic fields,and needs no calibration. The primary disad-vantage is that it can be used only betweenthe triple point and critical point of thefill liquid.

Metallic Resistance Thermometry . Sincethe resistivity of an element or compoundvaries with change in temperature, it has in

many instances been used as a simple andreliable temperature-measuring device.

While there exist a number of metals thatare more or less suitable for resistancethermometry, platinum has come to occupy a

predominant position, partly because of

excellent characteristics, such as chemicalinertness and ease of fabrication, and

8

partly because of custom: that is, certain

[desirable features such as ready availability'in high purity and the existence of a large

body of knowledge about its behavior have

come into being as its use grew and have

tended to perpetuate that use. Its sensi-

tivity down to 20 K and its stability are

excellent.A variety of platinum resistance thermom-

eters designed for engineering applica-tions is now available. As with other trans-ducers, these devices are subject to extra-neous effects (noise). In this case, we wishto measure only the temperature dependence of

the resistivity. However, we may also unwit-tingly measure the strain dependency as well.

To avoid this, the engineering thermometersare built to imitate the strain free con-struction of the precision laboratory typethermometers.

There are two basic designs for engineer-ing use: immersion probes and surfacetemperature sensors. The inmersion probesfeature a high purity platinum wire encapsu-lated in ceramic or securely attached to a

support frame. Features such as repeat-ability after thermal shocks, time responsein different environments, interchangeabil-ity, and mechanical shock tolerance differbetween companies and specific designs.

The second type of industrial sensor is

ibroadly known as a surface temperaturesensor, whose geometry is such that they makegood thermal contact with surfaces of variousshapes. Sensors are available for clampingaround small tubing, fitting into milledslots, and clamping under bolt heads. Theprinciple advantages of these thermometersare that they are small, typically 0.25 cm x

1.25 cm X 1.25 cm, with perhaps a factor oftwo variation in any dimension.

Non-Metallic Resistance Thermometry . Anumber of semiconductors also have usefulthermometric properties at low temperatures.A semiconductor has been defined as a ma-terial whose electric conductivity is muchless than that of a metallic conductor, butmuch greater than that of a typical in-sulator. The most promising semiconductorsseem to be germanium, silicon, and carbon.The latter, though not strictly a semicon-ductor, is included in this group because ofits similarity in behavior to semiconductors.

Of the three, germanium has received byfar the most attention, and germanium re-sistance thermometers are now available fromseveral comnercial sources. The resistanceelement is usually a small single crystal.Inasmuch as the resistivity is high, theelement can be short and thick. It is

mounted strain-free in a protective capsule.|Because of this combination of features, the

germanium thermometer is both rugged andreproducible.

The major disadvantage associated with theuse of germanium thermometers is the lack ofa simple analytical representation. Eachthermometer must be calibrated by comparisonat many points in the range of interest if

the inherent reproducibility of the thermom-eters is to be utilized.

Thermistors. Thermistors (thermally sen-sitive resistors) are essentially resistorsmade up of sintered metal oxides. Frequentlyused materials are nickel, manganese, andcobalt oxides. The fact that these resistorsare becoming increasingly popular in measure-ment and control circuits is attested to bythe number of companies selling them [3].The reasons for the increasing use are in

part: 1) they are small, which tends to makethe time response significantly less than onesecond; 2) they are typically high resistanceunits, which reduces the overall effect oflead resistances, and 3) their temperature-resistance characteristics are dependent onmaterials and procedures which allows thermo-meters to be developed that are particularlysensitive in limited ranges of temperature.

Thermocouples . Thermocouples have thefamiliar advantage that the temperature-sensing junction can be reduced in size toalmost any desired extent, so that thedisturbance to the object being sensed can bemade very slight, and the response time canbe very fast. They also have a familiardisadvantage; rather small voltages must bemeasured. In addition, they have a lessfamiliar but very serious disadvantage; thenet emf depends not merely on the materialsnominally used for the two wires, but alsoon material inhomogeneities which, if locatedin a temperature gradient, will introduceparasitic voltages. These inhomogeneitiesmay arise from variations in chemical compo-sition or may consist of crystal lattice im-perfections introduced, for example, bykinking the wires. Their presence can bedetected by various tests but cannot readilybe corrected for, so that testing merelyserves to indicate whether a given wireshould be discarded or not.

(3) Quantity or Liquid Level . Liquidlevel is but one link in a chain of measure-ments necessary to establish the contents ofa container. Other links may include volumeas a function of depth and density as a func-tion of physical storage conditions. For-tunately, the actual discernment of the liquidvapor interface (liquid level) is often thestrongest link in this measurement processdue to the significant progress made here inthe course of the Nation's space program. Asa result of this intense interest, liquid

level measurements can be made with an

accuracy and precision comparable to thatof thermometry, for instance, and often withgreater simplicity.

This period of development led to manydifferent physical embodiments of liquidlevel sensors, and there are as many ways ofclassifying these devices as there areauthors who write about them. We shall clas-sify them according to whether the output is

discrete (point level sensors) or continuous.Point Liquid Level Sensors . All liquid

level sensors depend for their operation onthe fact that there can be a large propertychange at the liquid vapor interface, a

significant change in density, for example.This may not always be the case if the fluidis stored near its critical point, forinstance, or if stratification has built upafter prolonged storage. Be that as it may,point level sensors are tuned to detect a

sharp property difference and given an on-offsignal. Several of the more commonly usedtypes are described below.

The thermal or hot wire type senses thelarge difference in the heat transfer coef-ficient between liquid and vapor. Since theheat transfer coefficient is much larger in

the liquid than it is in the vapor, one canexpect, for a given power input, that thetransducer will have a different temperatureand hence resistance, in the liquid than in

the vapor. It is this change in electricalresistance that is actually sensed in a

bridge circuit, and hence these devices canbe made both simple and fast. Small platinumwires, solid carbon resistors, and thin-filmcarbon resistors are examples of sensingelements that are used.

The capacitive type depends upon thedifference in dielectric constant between theliquid and vapor, which is essentially a

function of the fact that the liquid is moredense than the vapor. This sensor is usuallymade in the form of a bulls-eye, with alter-nate rings forming the plates of the capaci-tor, and are installed so that the plane ofthe rings is parallel to the liquid vaporinterface.

The optical type senses the change in

refractive index between the liquid andvapor, which of course is closely related to

the dielectric constant and density.This type of transducer contains a light

source and a light sensitive cell that areisolated from one another, but which do com-municate down a prism. The prism is cut in

such a way as to have total internal reflec-tion when in gas, and yet let the lightescape when in liquid. This is possiblesince there is a difference in the index ofrefraction of the liquid and the vapor, and

since the critical angle for total internalreflection depends upon the index of refrac-tion. This type of transducer has a veryhigh in-out signal ratio, for the light de-tector is almost totally illuminated ortotally dark.

There are also several acoustic or ultra-sonic devices that depend upon the fact thatthe damping of the vibrating member is

greater in the liquid than in the vapor.Often, a magnetostrictive element is drivenat a constant power and is more or lessdampened, depending whether it is in liquid orin vapor. The end of these sensors is aboutthe size of a quarter dollar, but this doesnot in any way indicate the limit of itsresolution. These devices can be tuned to

detect only a fraction of the total dampingthat would occur upon total immersion, so thattheir sensitivity can be much smaller thanthe total end of the device. Piezoelectricversions of this acoustic type liquid levelsensor are also available.

Continuous Liquid Level sensors take manyforms. Some methods determine mass, whileothers are merely interface following, andusually are just continuous analogs of somepoint sensor. Among the mass sensors are thedirect weighing schemes, nuclear radiationattenuation, and RF techniques. The interfacefollowing types include differential pressuresensors, capacitance and acoustic techniques.These are described below.

Direct weighing schemes have been used foroxygen, nitrogen and other dense fluids, buthave been handicapped in hydrogen use by thefact that the weight of the container is

often large compared to the weight of thecontents. In modern weigh-faci 1 ities how-ever, the weight of the tank rarely exceedsthe weight of the contents (when the tank is

full). Calibrated balance weights andstrain-gage load cells are most commonly usedin this application.

Nuclear Radiation Attenuation has foundsome success in oxygen and nitrogen systems,but comparatively little use for hydrogen.This is so because hydrogen is nearly trans-parent to the commonly available sources of

nuclear radiation, while the tank walls arerelatively "thick" to the same radiation.Hence the fundamental signal to noise ratiois inherently low. Hydrogen does absorbbeta radiation rather well, but then "windows"of beryllium or equivalent light metals mustbe placed in the tank walls. On the whole,this technique appears too sophisticated for

simple engineering measurements.RF Cavity Detection . In this system,

microwave energy is introduced into a tankto energize it by setting up electro-magnetic fields throughout the entire volume

10

i

of the tank. The tank interior is a di el ee-

rie region completely surrounded by conduct-

ng walls. Such a system is called a cavity,and the resonant frequencies established are

the normal theoretical modes of the cavity.Considerable development work has been donerecently on both uniform density fluids andnon-uniform density fluids, and this techniquecontinues to show considerable promise forboth mass-gaging and level-gaging in a vari-

ety of cryogenic fluids, including hydrogen.RF transmission characteristics through co-axial cables can also be used to detectliquid levels by measuring the time of flightof a RF pulse through the cable [4,5]. Thislatter technique is called time domain re-

flectometry.Differential pressure measurements are

simple to visualize, but difficult to realizein practice. "Noise" is always high due to

boiling and potential thermal oscillations atthe lower pressure tap. Also, the unknownlevel of the liquid in the gage lines canintroduce hydrostatic head errors. In thecase of hydrogen, the "signal" is low due to

the unusually low density of hydrogen.Better success is obtained with other cryo-gens of higher density.

Capacitance sensors are widely used forthe continuous measurement of the level ofcryogens. They do not truly follow thenterface, but sense the total contents ofhe container. That is, the dielectric

constant of the gas phase contributes to theoutput signal, as well as that of the liquidphase. This can be a serious source of errorin hydrogen because the density of the coldgas (and hence its dielectric constant) is

significant compared to that of the liquid.This problem is especially troublesome innearly empty tanks, but is often compensatedfor by either: a) segmenting the capacitorand ignoring the output from those sensorsections located in the vapor phase as theliquid level drops, of b) installing a fewpoint sensors at critical levels and routinelycalibrating the continuous sensor againsttern. Rod-to-blade and concentric tube con-figurations are most common in this type ofsensor.

In the acoustic devices, the liquiditself is used as the transmitting medium.A transmitter feeds an electric pulse to a

transducer where it is converted to anacoustic pulse traveling at sonic velocity tothe liquid-vapor interface, reflected back atthe same speed to the transducer, where it isreconverted to an electric pulse, and finallysent to a receiver. Knowing the velocity ofsound in a given liquid, the pulse transittime from transmi tter-to-interface-to-recei verecomes an indication of liquid level. Some-imes an acoustic racetrack of known path

11

length and variable time of flight is in-cluded to provide a measure of the density ofthe fluid. The product of the two measure-ments tends to give an indication of the massof the fluid contained in the tank.

(4) Density measurements are closely akinto quantity and liquid level measurementsbecause: 1) both are often required simul-taneously to establish the mass contents of a

tank, and 2) the same physical principle mayoften be used for either measurement, since,as noted, liquid level detectors sense thesteep density gradient at the liquid-vaporinterface. Thus, the methods of densitydetermination include the following tech-niques: direct weighing, differential pres-sure, capacitance, optical, acoustic, andnuclear radiation attenuation. In general,the comments made above about the variousliquid level principles apply to densitymeasurement techniques as well.

Two exceptions are noteworthy. In thecase of homogeneous pure fluids, density canusually be determined more accurately by anindirect measurement; namely, the measurementof pressure and temperature which is thencoupled with the analytical relationshipbetween these intensive properties and den-sity through accurate thermophysical prop-erties data.

The case of non-homogeneous fluids is

quite different. Liquefied natural gasis often a mixture of five or more componentswhose composition and hence density varieswith time and place. Accordingly, tempera-ture and pressure measurements alone will notsuffice. A dynamic, direct measurement is

required, embodying one or more of the liquid-level principles described above. Such"densitometers" are presently under develop-ment, and it is premature to discuss theircapability at this time.

(5) Flow . There are three basic types offlowmeters which are useful for cryogenicliquids. These are the: 1) pressure drop or"head" type, 2) turbine type, and 3) momen-tum type. We shall discuss each in turn.

Head Meters . This type of meter embodiesthe oldest method of measuring flowing fluids.The distinctive feature of head meters is thata restriction is employed to cause a reductionin the static pressure of the flowing fluid.This pressure change is measured as thedifference between the static heads on theupstream and downstream sides of the restric-tion.

Theoretical development of the flow equa-tions for head type meters may be found in

publications of the American Society ofMechanical Engineers [6].

The appeal of these meters in cryogenicsis more than simplicity, and stems from thepossibility of eliminating the necessity for

calibration, if proper design, applicationtheory, and practices are followed. Designmethods for orifices, flow nozzles, andventuri tubes are available in publicationsof the American Society of Mechanical Engi-neers [6]. Recommended practice for flange-mounted sharp-edge orifice plates can befound in publications of the InstrumentSociety of America [7] and the InternationalStandards Organization [8].

The characteristics of the head meter areas follows. The device is strictly a volu-metric meter; that is, it can of itself giveno information regarding mass flow rate.With appropriate pressure sensing, the rangecan be extended up to 10 to 1. It is thevery nature of these devices that theygenerate a decrease in pressure by accelerat-ing the fluid. If we are dealing with a

saturated cryogen, then this sudden decreasein pressure could lead to vapor formation(cavitation) in the flowing stream and anerroneous flow measurement. Many experiments[9], however, have failed to show any ill-effects attributable to cavitation. Nonethe-less, it is good design practice to maintainstatic liquid pressures within the meter wellabove the fluid saturation pressure. In

spite of all shortcomings, head meters arewidely used and quite reliable.

The turbine-type volumetric flowmeter is

probably the most popular of the variousflowmeasuring instruments, principally due to

their simple mechanical design and demon-strated repeatability. The turbine- typevolumetric flowmeter is a simple mechanismthat consists of a freely spinning rotorhaving a number of blades, each inclined atan angle to the axis of flow. The rotor is

supported in guides or bearings mounted in a

housing that forms a section of the pipe-line. The angular velocity (rpm) of the rotormay be detected by one of a number of methods;e.g., a permanent magnet encased in a rotorbody will induce an alternating voltage in aninductive pickup coil mounted on the housing,or the core of the pickup coil may consist ofa permanent magnet and the rotor constructedof a magnetic material so that the change in

magnetic circuit reluctance, as each rotorblade passes the coil core, causes an alter-nating current to be induced in the coil.Capacitive and photoelectric methods ofobserving rotor rpm have also been used. Theprimary requirement, however, is that theangular velocity of the rotor be directlyproportional to volumetric flowrate, or moreaccurately, to some average velocity of thefluid in the pipe.

A variation of the turbine type meter is

the "twin turbine" type. In this case, twoturbines of different blade pitch are coupled

together by means of an elastic restraint.Because of the difference in pitch, theywould tend to revolve at different speeds.However, this is prevented by the elasticcoupling so that they do revolve at the samespeed, but with a "phase angle" between them.The magnitude of the phase angle is a measureof the flow rate and is said to be, in fact,a measure of the mass flow rate.

The vortex shedding meter is also a

single-phase fluid rate-velocity meter, likethe turbine meters, but in a distinct classby itself. The phenomena upon which it is

based is the Karman vortex trail and itsapplication to the measurement of flow ofliquids and gases is fairly recent [10],probably because only recently have sensorsbecome available to detect the vortices.

The Karman vortex trail is used to explaincertain phenomena associated with the flowaround cylinders, ellipsoids, and flatplates. For flow around an object, eddysbreak off alternately on either side in a

periodic fashion. Behand the object is a

staggered, stable arrangement or trail ofvortices. The alternate shedding produces a

periodic force acting on the object normal tothe undisturbed flow. The force acts firstin one direction and then in the oppositedirection, setting up a natural frequency ofvibration.

If the frequency of the vortex peelingapproaches or equals the natural frequency ofthe elastic system, consisting of the bluffobject and its supports, the object may havea small alternating displacement normal tothe stream flow. (The vibration of somesmoke stacks, the vibration and the fatiguefailure or progressive fracture of sometransmission lines have been attributed tothis resonance phenomenon).

The vortex sensors consist of electron-ically self-heated resistance elements whosetemperatures and therefore resistances varyas a result of the velocity variationsadjacent to the body. These velocity varia-tions reflect directly the action of thevortices as they peel off from the downstreamedge of the bluff body. The meter factor(pulses/gallon) depends only on the insidediameter of the pipe and the width across thebluff body face. Cryogenic evaluation is

limited, to date, but performance on liquidnitrogen and oxygen shows promise.

Momentum Mass Flowmeters . Mass reactionor momentum flowmeters are of three types.There are those in which an impeller impartsa constant angular momentum to the fluidstream, and then the variable torque on a

turbine which removes this momentum, is mea-sured. There are those in which an impelleris driven at a constant torque, and then the

12

variable angular velocity of the impeller is

measured. And there are those in which a

loop of fluid is driven at either a constantangular speed or a constant oscillatory motion,and then the mass reaction measured.

The performance of such flowmeters wasdetermined in a National Aeronautics and

Space Administration sponsored flowmeterevaluation program [11 J. From the results of

this program, it appears that several cryo-genic mass flowmeters have been developedthat are capable of liquid hydrogen mass flowmeasurement accuracies on the order of ±0.5percent. There appears to be degradation of

mass flow measurement accuracy, however, whensubjected to a two-phase flow.

There are several other concepts of cryo-genic fluid flowmeters that are available or

are in development. Since they were notevaluated in the previously mentionedNational Aeronautics and Space Administrationsponsored program, definitive performanceresults, on the scale of the previously dis-cussed mass flowmeters, are not yet avail-able. These flowtieters are inferential massflow measurement devices, having in commonmeasurements of fluid density and fluid vol-ume flow or fluid volume flow- induced mo-mentum.

(6) Summary, Measurement Tools and Tech-niques . Since measurements are the basis oftechnology and dictate the fineness of ourphysical observations and control, it appearsthat this part of cryogenic technology may belagging. One may conclude: 1) little is

being done to bring the cryogenic instrumen-tation technology of the space program to themarket place, 2) if it were, adequate primaryinstruments and facilities do not exist tobring this part of the National MeasurementSystem under control, and 3) no concertedeffort exists to explore the consequences orexploit the opportunities of new technologi-cal opportunities.

These conclusions appear to apply gener-ally to each area of cryogenic instrumenta-tion, although, of course with varyingdegrees of severity. Specific analyses andconclusions appear in each major instrumen-tation area in Section 2.3, "Realized Mea-surement Capabilities."

2.2.2.2 The Cryogenic InstrumentationIndustry

Commerce in cryogenics is largely anextension of the chemical process industry(SIC Major Group 28). Even such specialgovernment programs as the space effort werebuilt upon the existing foundation of theindustrial gases and equipment industries tosupply liquid hydrogen in unprecedented

quantities of many tons per day. Similarly,there is no such entity as a cryogenic in-strumentation industry. Rather, those samefirms that supply instrumentation to thechemical processes industries modified andextended their existing capabilities intothe cryogenic regime. In a few instances,largely due to unique requirements or limitedapplications, the airframe companies devel-oped a special measurement capability them-selves (e.g., measurement and control systemsfor liquid oxygen in life support systems).The result has been the measurement tools andtechniques described earlier in Section2.2.2.1.

Economic Magnitude . The economic magni-tude and rate of growth of cryogenic instru-ment sales would be interesting to note.However, as indicated above, there is no suchentity as a cryogenic instrument industry.Hence the data we might desire are obscuredby the data on the measurement industry it-self, SIC Major Group 38: Measuring, Ana-lyzing, and Controlling Instruments; Photo-graphic, Medical, and Optical Goods; Watchesand Clocks.

Close inspection of SIC Group 38 revealsthat cryogenic instruments for laboratory useare found in Code 3811: Engineering, Labora-tory, Scientific, and Research Instrumentsand Associated Equipment. Some of the instruments found in this category are:

ChemicalLaboratory apparatusGas analyzing equipmentLaboratory testing and scientific instru-

mentsPhysics laboratory apparatus and instru-

ments, andStandards and calibrating equipment.

By far the greater number of cryogenicinstruments will be found in Group 382:Measuring, Analyzing and Controlling Instru-ments. For instance, Group 3822--AutomaticControls for Regulating Residential andCommercial Environments and Appliances--includes:

Float controlsIn-built thermostats, filled system, and

bimetal typesLiquid level controlsRefrigeration controls (pressure)Refrigeration thermostatsTemperature controls, automaticThermocouples, vacuum: glass.

Group 3823--Industrial Instruments forMeasurement, Display, and Control of ProcessVariables; and Related Products--includesestablishments primarily engaged in manu-facturing industrial instruments and related

13

products for measuring, displaying (indicat-ing and/or recording), transmitting, andcontrolling process variables in manufactur-ing, energy conversion, and public serviceutilities. These instruments operate mechan-ically, pneumatically, electronically, orelectrically to measure process variablessuch as temperature, humidity, pressure,vacuum, combustion, flow, level, viscosity,density, acidity, alkalinity, specificgrav-ity, gas and liquid concentration, sequence,time interval, mechanical motion, and rota-tion. Some specific examples pertinent tothis study are:

Flow instruments, industrial process typeLevel and bulk measuring instruments,

industrial process type.Liquid level instruments, industrial

process typeMagnetic flow meters, industrial process

typePressure gages, dial and digitalPressure instruments, industrial process

typePrimary elements for process flow measure-

ment: orifice plates, etc.Resistance thermometers and bulbs, indus-

trial process typeTemperature instruments: industrial

process type, except glass and bimetalThermistors, industrial process typeThermocouples, industrial process typeThermometers, filled system: Industrial

process typeTurbine flow meters, industrial process

type.

The final classification of interest to us

is Group 3824: Totalizing Fluid Meters andCounting Devices, which includes establish-ments primarily engaged in manufacturingtotalizing (registering) meters monitoringfluid flows, such as watermeters and gas-meters; and producers of mechanical and

electromechanical counters and associatedmetering devices. Instruments of interestfound here are:

Counter type registersGages for computing pressure- temperature

correctionsImpeller and counter driven flow metersMeters: gas, liquid, tallying, and mechan-

ical measuring - except electricalPositive displacement metersPropeller type meters with registersTotalizing meters, consumption register-

ing, except aircraftTurbine meters, consumption registeringVehicle tank meters.

Close inspection of the 1967 census ofmanufacturers reveals the not surprising factthat all temperature sensors or all pressuregages are lumped under one code, regardlessof their use. Accordingly, one cannot di-rectly get at the magnitude of the cryogenicinstrument business through such conventionalmeans, and other means must be found.

For instance, an industry association oc-casionally has found it useful to look at a

specific segment of their industry. TheInstrument Society of America specialcorrmittee mentioned in Section 2.2.1.1 madesuch a survey of flow meters, and theirfindings are shown in table 2-3.

Table 2-3 makes no allowance for the flow-meters that may be employed for liquid hydro-gen and LNG custody transfers from trucks ortrailers. The total investment of flowmetersis based on a price range of $700 to $2500per flowmeter.

These figures refer only to the custodytransfer (sale) of cryogenic fluids. Muchmore is at stake if one considers the totalproduction of industrial gases, which are in

fact made by cryogenic processes and includein-plant process transfers.

Table 2-3. Flowmeters in custody transfer of oxygen, nitrogen, and argon

Year Total No. Total Investment Custodyof Flowmeters Flowmeters in Millions Transfer/Year

1966 1000 $ 1.6 200,000

1967 1140 1.8 228,000

1968 1300 2.1 260,000

1969 1482 2.4 296,400

1970 1689 2.7 337,800

1971 1925 3.1 385,000

14

These figures were developed by the Instru-

ment Society of America to help demonstrate

that flowmetering had an economic magnitudesuch to merit attention, and that, in fact,

this part of the measurement system couldnot be certified to be in control.

Substructure and Composition; Firms In-

volved . Several very recent and comprehen-sive reviews of specific cryogenic instru-ments and measurement systems have been pre-pared by the Cryogenics Division of the

National Bureau of Standards for the NationalAeronautics and Space AdministrationAerospace Safety Research and Data Institute.This series includes flow measurement tech-nology [12], low temperature measurements[13], density and liquid level measurements[14], and pressure measurements [2]. Theseare truly benchmark publications that discussnot only the technology of the measurement,but also give specific performance data.The data below are typical of the level ofdetail that may be found in all of the re-

ports. They are taken from the treatise on

flow measurement [12] for an oscillatingpiston volumetric flowmeter, as an example:

"The name plate specifications on the 1-1/2inch meter are:

size - 0.0381 meters (1-1/2 inch)

maximum flow rate - 0.0044m s (70 gal /mi n)

minimum flow rate - 0.0088m s (14 gal /mi n)2

maximum pressure - 2.413 MN/m (300 psia)

material - aluminum piston, brass case.

Table 2-4. Typical flowmeter performance

Flow Rate LO2 Water Deviation LO2Gal/h Deviation Deviation from water

300 -0.4 -0.53 +0.13

450 -0.55 -0.47 -0.08

800 +0.8 -0.5 +1.3

1700 +0.35 -0.7 +1.05

2100 +0.22 -1.05 +1.27

"From this table, the mean deviation of LO2from water calibration is equal to 0.73percent (deviation from standard 14.67counts per gallon). It may be expectedthat water can be used for the routinetesting of meters of this type and a

factor applied to obtain the correctliquid oxygen calibration.

Table 2-5. Typical flowmeter performance

1-1/2 InchOscillating

Piston

Precision (3a) at Start, %

Precision (3a) at End, %

Bias at Start, %

Bias at End, %

3Vol . Metered, m (gal

)

3Max. Flow Rate, m /s (gpm)

Min. Subcooling, K

±0.63

±0.54

+1.33

+0.61

1225 (323,800)

0.0044 (70)

5

"Data on only one of the 1-1/2 inch nominalsize meters are presented as a secondmeter underwent a reduction in registrationby about 1 percent during these tests andwas replaced. The change in bias is signi-ficant and indicates wear."

This level of detail is typical of all ofthe studies mentioned above, and accordinglythey are highly recommended as source docu-ments .

Certain trade journals also review theinstrumentation field. Measurements andData Journal is published bi-monthly by theMeasurements and Data Corporation, 1687 Wash-ington Road, Pittsburgh, PA 15228. In 1974,for instance, this journal published annualstaff surveys on:

Piezoelectric pressure transducersForce measurementReluctive, inductive, and eddy-

current pressure transducersMass flowCapacitive pressure transducersThermocouples and accessoriesResistance and thermistor thermometryStrain-gage pressure transducersTurbine flowmetersPotentiometric pressure transducers.

These commercial surveys usually includea glossary of terms, physical theory,range, sensitivity, stability, cost, andaccuracy. A small part of a typical tableon resistance and thermistor thermometersfrom Measurements and Data , Vol. 8, No. 2,

(March/April 1974), is given in table 2.6to illustrate the very practical and com-prehensive data that may be found.

15

Table 2-6. Resistance and thermistor thermometers

riuuc 1 r r I VrfC

Thermal Systems1001 Ni, Pt -100/600F Industrial probe; 100 ohms $32

Hpriprril niimn<ip RTD $125

Model 5004 -100/500F Etched Balco, thin surface sensor $25

Model 5001-19 -260/400C General purpose surface sensor; $50500 Ohm

Model 1064 -452/500F .. Cryogenic platinum RTD $400

1 lUUC 1 1 U 1 VJ $Rnn

1 sjKj/ uuu

r

i?5Mnrlpl RIdR1 lUUC 1 J I to riiiticiLurc pruuc

ThoKTnn Plo^'f"^'!^ PrililcilllU QfcV.'Ul 1^ UU« 9 1 t 11., •

16301 Pt Sensor -200/500C 0.26C at OC for 50-ohm element; 3 C at 500C

Thermometries, Inc.

Series. P20, P30^ -100/300C To +.5% thermistor probe $1 (Quantity)P60, PlOO

Series HTP60, -100/450C Same; hi temp thermistor probes $5 (Quantity)

HTPlOOSeries B10,B14,B43 -100/300C To +.5% thermistor beads $l-$4

Series HTB43 -100/450C Same; hi temp thermistor beads $5Series 1F,2F, FM -50/150C To +.5% thermistor flakes $3-$20Series FM Same Same $.60

Every manufacturer that wishes to cooper-ate is included. Coverage is very close to

100% indeed. The above data were chosensimply as an illustrative but not nearlyexhaustive example.

Trends. Trends in instruments for mea-surement, analysis»and control as a wholecan be a helpful indicator even though theactual value of the cryogenic instrumentsspecifically may evade use. The followingdiscussion of trends is taken almost en-tirely from the "U. S. Industrial Outlook,1974, with Projections to 1980", a U. S.

Department of Commerce annual publication.

"Total industry shipments by manufacturersof measuring and controlling instrumentsare expected to reach $1.92 billion in

1974, a 7 percent rise over the $1.8billion estimated for 1973. Industrialprocess instruments compose approximately50 percent of this composite group.Business prospects for process instru-ments are closely related to the trendin capital expenditures for plant andequipment. Major sectors of the processgroup are the petro'leum and chemicalindustries, prime markets for industrialprocess instruments.

"Additional industrial instruments are

needed for the construction of plants to

manufacture synthetic natural gas (SNG)

from light oil, and for the facilities

required to process and transport {at

avyogenia temperatures in liquid form)natural gas from overseas sources to

depots in the U.S.

"Maintaining the pace required of a dynamichigh-technology industry, manufacturersof measuring and control instruments

continue to make substantial investmentsin newly designed products. Thesedevelopments reflect customer demands

for monitoring and control systems that

improve process management, maintaintighter product specifications, achieve

economy in production, enhance operating

safety, and add to the protection of the

environment. New high-temperature and

cryogenic technology imposes require-

ments for innovative measuring instru-

ment sensors capable of performing

dependable and accurate measurements of

ultra-hot and super-cold processes."

16

International Trade . With respect to

international trade patterns, the samesource continues:

"Technology continues to foster automated

monitoring and control of industrial

processes, and residential and com-

mercial facilities in the U.S. andworld-wide. The automatic temperaturecontrol industry, and manufacturers ofmeasuring and control instruments,produce and distribute instruments whosecommon technology crosses national bound-

aries.

"Industrial processes and building methodsare universal, and can be served through-out the world by instrumentation of sim-

ilar design. Global leadership demandsalert attention to chanqinq reauirementsin various market sectors, and continuousadvances in new product design. Manufac-

turers in these industries take part in

numerous trade shows and exhibits in the

U.S., and actively participate in sched-uled trade shows and trade missionsorganized by the Office of InternationalMarketing to reach foreign markets.

Exports by both sectors of the instru-ment industry have steadily increasedsince 1968, with exports of the measur-ing and control instrument group pro-

gressing at an annual growth rate of 9

percent from 1967 to 1973.

"The Office of International Marketing hasprepared a Global Market Survey onIndustrial and Scientific Instruments ,

depicting business prospects in se-

lected foreign markets: Global MarketSurvey, Industrial and Scientific Instru-ments, Office of International Marketing,1972, U.S. Department of Commerce."

Examples of specific international inter-actions may be found in Section 2.2, wherethe NBS cryogenic flowmetering program is

used to illustrate the process. In thisprogram alone, the NBS Cryogenics Division:cooperated with the International Orga-nization of Legal Metrology (OILM) to

facilitate final adoption of our technicalrecommendations; performed "type testing"of meters of foreign manufacture -- affil-iates of U.S. concerns; and encouraged andfacilitated the visits and participation ofinternational observers from the PTB;

Linde, AG; Messer-Griesheim GMBH; CompteursSchlumberger, France; and the British Oxy-gen Co. , London.

The Industry as a Whole . A profile ofthis industry as a whole is given in theBox:

Table 2-7. 1973 Profile:instruments for measurement,

analysis and control

SIC code 3821 3822Value of industry shipments $1800 $740

(millions)

.

Number of establishments 661 105Total employment (thousands) 67 40Exports as a percent of 27.8 4.3

product shipmentsImports as a percent of 5.5 n.a.

apparent consumptionCompound annual average

rate of growth 1967-73(percent)

:

Value of shipments 3.6 3.0(current dollars)Value of exports 9.4 4.2(current dollars)Value of Imports 25.7 n.a.(current dollars)Employment 9.2 0.8

n.a.= Not available.

2.2.3 Reference Data

Reference data are needed by the cryo-

genic community on both fluids and solids.

The following sections describe some dataproducing activities, their users, and the

principal means of dissemination.Properties of Fluids . Pure fluids of

interest in the Cryogenic MeasurementSystem include helium, neon, argon, hydrogen,deuterium, nitrogen, oxygen, fluorine,

methane, ethane, ethylene, propane, carbonmonoxide and carbon dioxide.

The mixtures include air (N„, O^, Ar),

natural gas (CH4, other hydrocarbons, nitro-gen), synthetic natural gas (CH4, H2, CO,

CO2), FLOX (F2, O2) and GDL laser fluids(He, N?, CO2).

Properties of interest are the thermo-dynamic properties (compressibility, entropy,enthalpy, specific heats, sound velocities);electromagnetic properties (dielectricconstant, refractive index); and transportproperties (viscosity and thermal conduc-tivity coefficients).

17

Properties of Solids . The solids (metals,alloys and composites) used at low tempera-tures include aluminum and aluminum alloys,copper and copper alloys, nickel and nickelalloys, the austenitic stainless steels,titanium alloys, selected ferritic steels, a

variety of superconducting materials, glassepoxy composites, and many more. The data onthese materials at the required low operatingtemperatures include the mechanical, thermal,and electrical properties.

Needs for Data and Their Users . Thesedata are required for many, and often diffuse,purposes including: a) data for materialselection in the decision-making phase pro-grams; b) data for equipment or process de-sign and optimization (for example, refrig-erator and liquefaction equipment, separationof gases, and storage and transport of liq-uids); c) data for analysis of the system orexperiment, including safety criteria; and d)

data for instrumentation and gaging, in-cluding sale or custody transfer.

It is important to note that these dataare used by the entire cryogenic community,the $2 billion per year industry that sup-ports a wide variety of technologies. Toillustrate, the use of less expensive butstructurally adequate metal could save $0.3million on the cost of a single liquefiednatural gas storage tank or $1.0 million onthe cost of a single ship carrying liquefiednatural gas--a total cost saving of as muchas $15 million per year. In addition, eco-nomic analyses show that the value of thethermodynamic data to the design of a plantor facility is worth 1 percent or more of thecapital cost of the entire unit—of consider-able value when used for the design of largecryogenic units, many of which run into tensof millions of dollars [15].

A less quantifiable but equally importantuse of the reference data base is in estab-lishing codes, standards, and recommendedpractices. These data often form the tech-nical foundation for regulatory decisions by

such agencies as the Federal Power Conmis-sion, the Department of Transportation, andthe Office of Pipeline Safety, as well as theNational Fire Protection Agency.

Methods of Acquisition . Data on fluid andsolid properties at cryogenic temperaturesare obtained by a wide variety of groups in

industrial, government, university, and non-profit laboratories. These data are ref-erenced, compiled, correlated, and criticallyevaluated by our staff and form the basis fordeciding what new measurements are requiredand which ones are not needed. Our staffperforms comprehensive accurate measurementsto fill important da£a gaps and reconcileinconsistencies where necessary.

Methods of Dissemination . The NBS Cryo-genic Data Center [16] was established in1958 and publishes a bi-weekly currentawareness list of articles in the fields ofcryogenic engineering and cryogenic physicswhich have appeared in the open literature.In collaboration with the Standard Refer-ence Data Program, an accumulated total ofnearly 100,000 technical articles have beenreceived, cataloged and indexed for readyaccess. In addition, specialized quarterlybibliographies are prepared for: Super-conducting Devices and Materials; LiquefiedNatural Gas; and Hydrogen as a Future Fuel.The cryogenic community, including libraries,purchase these documents on a subscriptionbasis, which covers the NBS cost of prepara-tion. Subscriptions to these periodicalstotal nearly 1300 [17].

In addition, the staff of the Data Centerresponds to over 500 technical inquirieseach year. Some of these requests requirethe use of an automated information system,in which case the user pays a fee for justthe costs involved in the automated search.

The Cryogenics Division is the focal pointfor the measurement and data requirements ofthe cryogenic community. We established theNational Cryogenic Engineering Conferences(CEC), now in their 20th year and NBS con-tinues to be the secretariat. The 20 vol-umes of the conference proceedings "Ad-vances in Cryogenic Engineering" are majorresource documents for the workers in thisfield. In addition, we sponsor specializedconferences, like the International CryogenicsMaterials Conference, and workshops to aid in

dissemination of data.The most prestigious of our outputs are the

individual research publications, approxi-mately 60 per year, or roughly one open-literature publication per professional man-year. Special purpose publications are muchmore numerous, and often more specific andtimely. For instance, progress reports andNBS Technical Notes are frequently distrib-uted directly to other agency sponsors andknown users on a quarterly basis.

Pattern of Use of the Data in the Mea-surement System . As mentioned, the users ofreference data by the cryogenic communityare many and varied. Selected examples havebeen chosen to illustrate these uses.

a) Nat. Bur. Stand. (U.S.) Tech. Note No.

361 "Standard Liquid Densities of Oxygen,Nitrogen, Argon and Parahydrogen" by Roder,McCarty and Johnson, was prepared in 1968 at

the request of the Compressed Gas Associationand the State of California, Office of Weightsand Measures. Subsequent revisions (1972 and1974) have extended the range of data and

(

18

provided a metric supplement. The latterwas requested and paid for by the GermanGovernment for use in the European trade in

cryogenic fluids. These data have now beenadopted as a tentative code (law) by the

"57th National Conference on Weights andMeasures" and are now used as the data basefor custody transfer (sale) in all commercein the Western World for these fluids.

b) A comprehensive program on the thermo-physical properties of pure methane has

recently been completed. Nat. Bur. Stand.

(U.S.) Tech. Note No. 653 "The ThermophysicalProperties of Methane, from 90 to 500 K at

pressures to 700 Bar", by R. D. Goodwin,contains the most comprehensive and accuratetables and interpolation functions availablefor methane, and NBS has already convincedthe American Gas Association to accept thesereference data as "agreed upon" data for theNation's gas industry. NBS has made similarrecommendations to the American NationalStandards Institute (ANSI) and the Interna-tional Liquefied Natural Gas Conference,LNG-4, held in Algiers in the Suirmer of 1974.

c) A compilation and critical evaluationof data: "Thermal Conductivity of Solids atRoom Temperature and Below" by Chi Ids,

Ericks and Powell, NBS Circular 131, is thebasic reference document for all thermalconductivity data in this field. In additionto presenting the available data, it pointsto the data gaps and guides future research,

d) Many times NBS is called upon by othergovernment agencies to evaluate efficiencyclaims and production capacities projected by"paper studies". A complete and consistentset of design data is essential for thispurpose. The National Aeronautics and SpaceAdministration, Department of Defense and theEnergy Research and Development Agency, forinstance, specify that NBS data be used inits proposals to provide a coninon, soundbasis for evaluation. Similarly, our recom-mendations to the regulatory agencies wouldbe open to question if it were not for a

sound foundation of valid and consistent data.e) Accurate density measurements and cal-

culation methods for liquefied natural gasmixtures are being obtained to provide a

basis for custody transfer agreements and formass, density, and heating value gagingthroughout the fuel gas industry.

The basis for the custody transfer ofliquefied natural gas is its heating value.It is difficult to determine and agree on theheating value of extremely large volumes ofnatural gas in the liquid state. For example,methods for calculating the heating value ofa liquefied natural ^as mixture require know-ing its density, which in turn depends on itscomposition, temperature, and pressure.

As the composition of LNB mixtures varyconsiderably, depending on the sources of thegas and the processing conditions, accuratemethods are needed for calculating liquiddensities at arbitrary compositions, temper-atures, and pressures. The accuracy is impor-tant because of the extremely large volumesof liquid involved (e.g., 125,000 cubic metersper ship). This project is being funded andguided by a consortium of 18 energy compa-nies, and the results will be the industry"agreed upon" reference data.

2.2.4 Reference Materials

Reference materials are well characterized(and sometimes certified) materials producedin sufficient quantity to assure long termintegrity of the measurement process. Refer-ence materials for low temperature applica-tions are continually being developed andcharacterized to help fulfill our goal offurnishing complete and comprehensive serviceto the cryogenic coimunity. The materialsstudied are primarily metals, alloys, andcomposites. The electrical, thermal, andmechanical properties are the prime charac-terization parameters. These activities aredescribed below.

Nature of the Data . Reference materialsfor cryogenic measurement standardization areprincipally solids, especially pure metalsand alloys. Because of the economic signi-ficance of heat loss minimization and energyconservation, insulating reference materialsare also of considerably importance at thistime.

Properties of interest include the thermalconductivity, thermal diffusivity, thermalexpansion, specific heat, and electricalresistivity. These properties are among thosethat depend significantly on variable ma-terial production factors,

A broad range of reference materials foreach useful property is required to includethe range of measurements encountered in

practice. For example, thermal conductivityreference materials are required to spanconductivities from the low conductivityinsulating materials to the very high con-ductivity pure metals, a range of one millionor more. The reference data for these ref-erence materials must be accurate to nearstate-of-the-art levels. At this stage in

the evolution of cryogenic technology, how-ever, the prime requirement is for charac-terizing more new materials, rather thanhigher accuracy measurements on "older"materials

.

19

It should be noted that reference data maybe of little use without corresponding ref-erence materials. Reference data of mate-rial properties can be grouped into two broadcategories: those which are not significantlyaffected by variations in production tech-niques and those which are. The latter classof reference data require reference materialsfor their continued usefulness and are ofprincipal importance at low temperatures.

Need for Data and Their Users . Referencematerials and concomitant reference data arerequired primarily for three purposes, all

of which form a basis for our national cryo-genic measurement system's compatibility andaccuracy: 1) to perform comparative mea-surements in which the measured propertyvalue is given directly in terms of thestandard; 2) to perform apparatus check-out,thus basing the performance of the apparatuson the standard; and 3) to train new person-nel, thus propagating a high level of reli-ability and expertise. We must be preparedto fulfill all three of these requirements to

ensure compatibility within the Nation'smeasurement system and to promote meaningfulmeasurements.

Methods of Acquisition . Reference mate-rials are produced by industry and governmentunder carefully controlled production condi-tions to assure maximum homogeneity of thematerial lot. The NBS Office of StandardReference Materials (OSRM) produces, certi-fies, and issues reference materials and, as

such, is the world's largest. Reference datafor these materials must be determined by

standards laboratories of the highest recog-nized expertise in order to realize theirfull utility.

The Properties of Solids Section of theCryogenics Division of NBS has been active in

establishing thermal conductivity, electricalresistivity, and thermoelectric reference ma-terials. Recent efforts have resulted in

establishing three metal reference materialscovering a wide range of conductivity andtemperature. These reference materials havebeen described by Hust, Sparks, and Giarratano[18, 19, 20, 21]. Another pertinent cryo-genic reference device, and associated ref-erence materials for measuring very low temp-eratures, has been described by Schooley [22].Current plans are to extend this effort toinsulating materials and other solid mate-rials. One program to establish severalinsulating reference specimens, in conjunc-tion with the National Aeronautics andSpace Administration space effort, was under-taken by this laboratory, but remains in-

complete at this time..

20

The NBS Office of Standard Reference Mate-rials, as the world's largest source of ref-erence materials, offers approximately 850different items for sale. About 33,000 unitsworth approximately $1.6 million are soldannually. Information regarding these ref-erence materials is available directly fromthe Technical Representative of the Office ofStandard Reference Materials, Mr. R. W.

Seward, phone (301) 921-2045, and also bycatalog [23].

Certificates are issued with these mate-rials listing the property and their ac-curacies .

"Uncertified" reference materials, usually .

known as research materials, are also pro-vided by this office and other components ofNBS. They serve a very valuable purpose ascommon source materials in round-robin inter-comparison, as do the Standard ReferenceMaterials. They also play a unique role in

the calibration of research apparatus andmethods, as opposed to engineering, or processquality control uses. These research ma-terials are especially valuable as a founda-tion for comparing data obtained from dif-ferent sources or by different means duringthe course of an experimental program.

Patterns of Use of Materials in the Mea-surement System . A few specific examples maybe helpful to illustrate how reference ma-terials are used. For instance, Hust [18]describes the preparation and character-ization of an electrolytic iron. Thisthermal conductivity sample was characterizedover the range 4 to 300 K to meet industryand government needs in 1971. The tempera-ture range of this material was just recentlyextended by Hust and Giarratano [21] to 1000 K.

Only a few of these materials are sold annu-ally, especially when compared to the largevolume of chemical composition samples thatare distributed. However, the impact ofthis small number of samples may nonethelessbe comparable, if one considers the improvedreliability and confidence in the data thatare subsequently published, following the

common use of these materials in many labora-tories employing many different procedures.

Many research groups routinely "prove"

their apparatus with these research materials

before publishing any data. In the past,

discrepancies of 50% in thermal conductivitydata were not uncommon. In one documentedinstance, a team at a major Mid-WesternUniversity has spent two years improvingtheir data accuracy and credibility throughthe use of precisely the research material

just described. In another instance, duringthe late 1960's, NBS was requested to provideconsultation services for a thermal and elec-trical properties project in conjunction witha nuclear powered rocket program for the

National Aeronautics and Space Administration.

Several measurement laboratories were in-

volved, and the question of data accuracybetween laboratories became a significantproblem. To answer this question, we ar-

ranged a round-robin study on four referencematerials. The results of this study were

essential to the laboratories involved. In

general, it showed that good agreement could

be expected, but it also showed that largediscrepancies could occur, even with simple

measurements such as electrical resistivity.For instance, one of the four laboratoriesreported vastly different results that werelater proven to be erroneous.

NBS has initiated a conscious and delib-erate program of establishing selected re-

search materials. These are referred to as

"uncertified reference materials" since theyare not accompanied by reference data. Theyare, however, highly characterized from the

standpoint of homogeneity. These materialsprovide an excellent basis for intercom-parisons of data. Subsequent studies per-formed on them allow a more logical inter-comparison of data, thus improving ourtheoretical knowledge of the behavior ofmaterials. This program is still in its

infancy, and while much remains to be done,it also shows much promise.

2.2.5 Science and People

2.2.5.1 Cryogenic Measurements in Science

Cryogenics and measurements at cryogenictemperatures are widely used in research andinvestigation in basic science. Many NobelLaureates received their honors either be-cause of work directly in cryogenic sciencesor because of work in which cryogenic mea-surements were indispensable. An imposinglist of such Nobel Prize winners follows:

1902 Pieter ZeemanInfluence of magnetism uponradiation

1904 Lord RayleighDensity of gases and hisdiscovery in this connectionof Argon

*1910 Johannes Van der WaalsFor his work concerning theequation of state of gasesand liquids

*1913 H. Kammerlingh OnnesFor his investigations into theproperties of bodies at lowtemperature that led, amongother things, to the preparationof liquid helium

1920 Charles GuillaumeFinding cheaper materials fornational prototype standards(Ni-Steel) INVAR

*1934 H. C. UreyDiscovery of D2--was producedby distillation

1936 P. J. W. DebyeDebye theory of specific heats

*1949 W. F. GiauqueFor his contribution in thefield of chemical thermometry,particularly concerning thebehavior of substances atextremely low temperatures

*1957 T. D. Lee and C. N. YangUpsetting the principle ofconservation of parity as a

fundamental law of physics

1960 D. A. GlaserInvention of bubble chamber

1961 R. L. MossbauerRecoilless nuclear resonanceabsorption of gamma radiation

*1962 L. D. LandauPioneering theories of condensedmatter, especially liquid helium(He^)

*1968 Luis W. AlvarezDecisive contributions to ele-mentary particle physics, in

particular "for his discoveryof resonant states" through his

development of hydrogen bubblechamber techniques and dataanalysis

*1972 John Bardeen, Leon N. Cooper,and J. Robert SchriefferExposition of the "B-C-S" theoryto explain superconductivity on

a microscopic basis

*1973 B. D. Josephson, Ivar Giaever,and Leo Esaki

The discovery of tunnellingsupercurrents (the Josephson-Junction)

Cryogenics crucial to the investigation

The kinds of people working in this partof the National Measurement System, and thefields of science that support it, are in

part illuminated by the above list, espe-cially during the last decade or so. Theremay be a trend away from the very basic workof Mossbauer and Landau, for example, to workof almost immediate practicality (BCS, Joseph-son, etc.). This is probably only an ap-parent trend, for who is to say that any workmeriting the Nobel prize in physics is notbasic?

Of more immediate concern to us is notonly the ubiquitous nature of cryogenics in

basic science, but also how often NBS hasdirectly played a key role. For instance,the Lee-Yang parity hypothesis was experi-mentally proven by an NBS team--Dr. E.

Ambler, and others. The BCS Theory wassupported in part by the "isotope effect"experiments by Emmanuel Maxwell at NBS in the1950's. Luis W. Alvarez, in his Nobel ac-ceptance speech, said in part:

".. . problems involved in building andhousing the 72-inch bubble chamber. Wewere also extremely fortunate in beingable to interest the National Bureau ofStandards in the Project. Dudley Chelton ,

Bascom Birmingham , and Doug Mann spent a

great deal of time with us, first edu-cating us in large-scale liquid hydrogentechniques, and later cooperating with us

in the design and initial operation of thebig chamber."

(The first publication on the 72-inch bubblechamber was authored by NBS CryogenicsDivision Staff.

)

2.2.5.2 Cryogenic Science in Measurements

This list of Nobel Laureats may also serveto illustrate the use of cryogenic science in

measurements--employing cryogenics per se todevelop new or improved measurement technol-ogy in fields outside of cryogenics.

For instance, Donald Glaser inventedthe bubble chamber that won him his NobelPrize. Glaser recognized the principal limi-tation of the Wilson cloud chamber namely,that the low density particles in the cloudcould not intercept enough high-energy par-ticles that were speeding through it from thebeams of powerful accelerators- Glaser'

s

first bubble chamber operated near roomtemperature and used liquid diethylether. Toavoid the technical difficulties presented by

such a complex target as diethylether. Pro-fessor Luis Alvarez of the University ofCalifornia devised a bubble chamber chargedwith liquid hydrogen. Since hydrogen is the

simplest atom, consisting only of a protonand an electron, it interferes little withthe high-energy processes being studied withthe giant accelerators, although it is read-ily ionized and serves well as the detectorin the bubble chamber.

The first large liquid hydrogen bubblechamber was installed at the Lawrence Ra-diation Laboratory of the University ofCalifornia and first operated in March 1959.A remark was made that this 72-inch liquidhydrogen bubble chamber would be the equiv-alent of a Wilson cloud chamber one-half milelong. They could not really be equal,however, because the cloud chamber does nothave the great advantage of utilizing thesimplest molecules as the detector.

The most recent application of cryogenicphenomena to measurement science involves theso-called Josephson junction. Some of themost exciting phenomena worth, exploiting in

instruments and devices occur at weak elec-trical contacts between superconductors,known as Josephson junctions. They can be

simple structures, consisting only of twopieces of superconducting metal lightlytouching together. Often one of them is a

fine wire reminiscent of the "cat whisker" ofthe early days of radio. Sometimes thestructures are thin evaporated films, withbarriers consisting of very thin layers ofinsulating material (or normal metal) or verynarrow constrictions. The importance ofJosephson junctions arises from the extra-ordinary way they respond to voltage andmagnetic flux.

Under the influence of a small appliedvoltage, the current through a Josephsonjunction oscillates at a frequency strictlyproportional to the voltage. The factor ofproportionality (about 484 MHz per yV) is

a fundamental constant of nature; twice the

electric charge of the electron divided by

Planck's constant. It has been measured withhigh accuracy (about one part in 10^) by

Langenberg and his group at the University of

Pennsylvania. The accuracy of this measure-ment was limited at the time by the defini-tion of the volt. Frequency was (and still

is) the quantity which could be measuredbest, and the standard volt was maintained by

a group of chemical cells. However, the

Josephson junction has proven itself, and the

legal volt has been maintained by this meanssince July 1 , 1972.

If a Josephson junction serves to close a

small superconducting loop, it becomes sen-sitive to magnetic flux as a result of

quantum mechanical interference betweenelectrons travelling around the loop. Thisresults in a periodic response to magneticflux, the period being the magnetic flux

quantum (h/2e, or about 2 x10"^ ^W),

22

another fundamental constant of nature.

This device has come to be known as a SQUID,

an acronym for Superconducting QUantum Inter-

ference Device. It is the world's mostsensitive magnetic sensor.

A most promising application of the SQUIDis in magnetocardiography . The action of a

beating heart generates small electriccurrents that can be magnetically recordedwith the aid of a SQUID. The resultingrecord bears a strong resemblance to an

electrocardiogram, but no electrodes are used

to obtain it. Mere proximity of the instru-ment is sufficient. It has been discoveredthat, in addition to the short pulses of

current generated by normal action of the

heart, steady currents associated withvarious kinds of injury may also be detected.This may give useful diagnostic informationthat is not readily obtainable in any otherway without surgery.

Another application that has been estab-lished in the field is electromagneticsounding to depths of a few kilometers in theearth. A SQUID magnetometer has proven to bethe best instrument for these measurementsand has been used to map a geothermal energybasin in California.

Other applications of these very sensitivemagnetometers include magnetoencephalography

,

geomagnetism, and conmiuni cation throughground or water at frequencies of a fewhertz, which would rapidly attenuate signalsat higher frequencies.

The periodic response of the SQUID to

magnetic flux suggests a new style of elec-trical metrology. One could measure currentby counting off magnetic flux quanta in thesame way that we measure length by countingoff wavelengths of light. The Cryoelectron-ics Section at NBS is working on this now.Preliminary results indicate that it will bea powerful technique both for direct currentand for radio frequencies up to the microwaverange. Another advantage of electricalmeasurements employing cryogenic devices in

general is the high sensitivity attainablebecause of the freezing out of thermalbackground noise.

The last area of activity to mention in

applying cryogenics to other measurements is

the extension of radio technology into thesubmi 1 1 imeter-wave to far-infrared range offrequency. Possibilities include communi-cation, radar, and astronomy. The recentdevelopment of powerful, coherent sources(such as the hydrogen-cyanide, water-vapor,and carbon-dioxide lasers) has stimulatedexploration in this field. Receivers havelagged behind the development of transmit-ters, but with Josephson junctions we canhope for receivers of the same quality as we

have at normal radio frequencies. Thepioneering work was done by Grimes, Richards,and Shapiro when they were all at the BellTelephone Laboratories. An NBS team, notablyMcDonald and Evenson, are synthesizing sig-nals of stable and accurately known frequencythroughout this range by using Josephsonjunctions to generate harmonics and mixturesof signals from the primary sources. One oftheir objectives is to extend this activityup to the range of visible light (usingdevices other than Josephson junctions forthe final stages) and to measure the fre-quency of visible light of a well definedwavelength, such as is used for the standardof length. This raises the possibility ofusing a single standard for both length andtime. Such a standard will have practicaladvantages as well as satisfying admirers ofthe theory of relativity. The technologythey are generating will be directly usablefor the other purposes mentioned.

These are just a few examples of the manyexisting and future applications of cryo-genics, especially superconductivity, appliedto electronics. The first few commercialinstruments are appearing on the market; wecan expect their number to grow.

One of the barriers to the widespreadapplication of superconducting devices is ofcourse the need to provide a liquid-heliumenvironment. For small instruments, dis-sipating minute quantities of power, this is

not such a severe problem as it might be forbig machines. Liquid helium is widelyavailable. Compact, portable containerscan be engineered to run for several daysbetween refills. In fact, the development ofthe SQUID, which has an established reputa-tion as the world's most sensitive magneticsensor, has now reached the stage that it is

becoming the most convenient and portableinstrument for many geophysical measurements.In collaboration with the United StatesGeological Service, a SQUID magnetometerwas tested for electromagnetic prospectingfor geothermal sources in the geyser basinnear Clear Lake, California. It provedto be a handy instrument for this purpose.The same instrument was also taken as air-line hand luggage to the Republic of Chadin Africa to make magnetic observationsduring the solar eclipse. Weighing only10 kg, the instrument gave no trouble andshowed that it is ready for use in even themost remote parts of the world.

23

2.3 Realized Measurement Capabilities

This section summarizes state-of-the-art

technology for cryogenic instruments.

Pressure transducers are normally placed

in a temperature controlled environment near

room temperature. Some available pressure

transducers are capable of performing satis-

factorily at low temperatures, but new types

such as piezoelectric, diode, electrokinetic,

etc., may perform equally well or better. In-

formation on their performance is needed.

For a detailed review of the ranges,

accuracies, and precisions attained in

pressure measurements, see the comprehensive

review by Arvidson [2]. Table 2-8 below is

reproduced from that work.

Temperature measurements are unquestion-

ably in better shape than any other cryogenic

measurements. Adequate calibration facili-

ties exist, as well as a large body of know-

ledge that together help keep this part of

the National Measurement System in control.

Industrial type platinum resistance ther-

mometers are routinely used, for instance.

Improvements in their interchangeabi 1 ity

would be desirable, as well as some simple

thermometry for crude temperature indications

and the monitoring of process trends.

Table 2-9 summarizes some representative

characteristics of the best known types of

cryogenic thermometers.The terms "reproducibility" and "accuracy"

require some explanation. Reproducibility

means the variability observed in repeat-

ing a given measurement using the best

present-day laboratory techniques. Changes

produced on thermal cycling of the thermom-

eter to and from ambient are included in this

parameter. Accuracy means the significance

with which the thermometer can indicate the

absolute thermodynamic temperature. This

includes errors of calibration and as

errors due to nonreproducibil ity, the

Table 2-8. Cryogenic pressure transducers.

Characterlitic > Strain Cage Capacitance Crystal Reluctance

Frequency rciponse, Hz to 40 k Hs to 500 K Hs 0. 5 to 1 M Ha 1 K Hz (approx.

)

Nominal •ensitivlty,

% full (cale

0.5 1.0 0.5 1.0

Thermal stability Excellent for compensatedbridge winding

Approx. temperaturedrift; 0.025 % per deg F

Good Approx. 0.02% per deg F

Linearity, % < 0.1 -1.0 0.5 -1.0

Response to vibration,

noise, acceleration

Negligible for light-dia*

phragm and fully-rigid

types

Low, but noticeable Can be appreciable; also

highly sensitive to

electrical "noise"

Low, but noticeable; about

1.0% per 100 G

Drirt, % negligible 1.0 (excluding temperaturedrift)

2.0

Hysteresis, % Approx, 0. 2 1.0 negligible 0. 5

Open-circuit full-scale

output

Order of 50 mv Order of 5 v Order of 1 mv Order of 5 v

Overload, % Generally about 100; to

500 for special types

Order of 100 Satisfactory for elastic

limit of crystal; poor for

liigher loads

Order of 100

Ease of calibration straightforward straightforward No static calibration

possible; dynamic calibra-

tion tricky

slraightforward

Typlcal^resBure sensing

device

tube or diaphragm diaphragm c rystal fliaplira);m or twisted

torsion tube

Cooling Some designs air or watercooled (special types have

heat-transfer rates to

about 7.0 nxU/lnV"

Some designs air or watercooled (special types haveheat-transfer rates to

about 7.0 DTU/inV»

Generally none possible Generally none possible

Remarks and limitations Good all-around. Expensivic

repair and replacement of

parts on high-performancedoflign.s

Excellent instrument ex-

cept for drift. Larger andmore complex than strain

Rage

Unique In ultra-high fre-

quency range. Not use-

able below about 5 tiz.

Maximvmi (cmpcralure200 F. Low frequency

rt-sponHO

24

former usually being much more significant.

The approximate numbers given for these

quantities represent good current practice.

It may be possible to do better by extreme

care. On the other hand, in most engineering

measurements a lower order of accuracy is

permissible, and this may allow relaxation of

certain requirements such as strain-free

mounting of resistors, homogeneity of ther-

mocouple materials, purity of vapor-pressure

fluid, sensitivity, and accuracy of associated

instruments, etc.

For temperatures above about 20 K, the

metallic resistance thermometers are more

sinsitive than the nonmetallic resistance

thermometers. Temperatures above 20 K can

be measured routinely with an industrial type

platinum resistance thermometer with an accu-

racy of better than 100 mK and time responses

somewhat better than 1 second. Accuracy at

the millidegree level requires a precision

capsule type platinum resistance thermometer

and careful calibration.

Carbon thermometers are generally used for

low temperature measurements (T < 80 K) when

accuracies of ± 0.1 K or ± 1% of the absolute

temperature are needed. Millidegree accuracy

is attainable using germanium resistance

thermometers at temperatures below 20 K. The

primary drawback to germanium thermometers is

that no simple analytical representation is

available that represents the resistance

versus temperature characteristics, even for a

given class of doped germanium crystals. A

many point comparison calibration is required

if all the inherent stability of the resistor

is to be utilized.

Vapor pressure and gas thermometry offer

sensitive methods of temperature measurement

with the advantage that no calibration is

necessary. Further advantages are that these

transducers are not sensitive to magnetic

fields or electric fields. In the case of

vapor pressure thermometers, the time re-

sponse may be made comparable to the resis-

tance thermometers.A sensible recommendation about which type

to use cannot be made without knowing the

specific measurement requirements. The

generalization most likely to hold true,

however, is the following: for crude temp-

erature indications and monitoring trends, a

gas thermometer will probably be suitable;

for more accurate work, vapor pressure or

resistance thermometry is recommended; for

engineering application in this latter area,

the need is for inexpensive devices that do

not call for unique calibration.

An outstanding review of cryogenic temp-

erature measurements has recently been

published by Sparks [13]. The above material

borrows freely from this excellent benchmark

study.Level detectors for cryogenic fluids were

extensively developed during the space

program, but it is remarkable how little

Table 2-9. Some approximate characteristics of the mostwidely used classes of cryogenic thermometers.

BEST BEST RESPONSETYPE RANGE REPRODUCIDILXTY accuracy" TIME

K K S

RESISTANCE THERMOMETERSPlatinum 10-900 io"3-io-^ 10-2-10"* 0.1-10

Carbon 1-30 io"2-io-3 10-2-10-3 0.1-10

Gcrraanlum 1-100 io"3-io"* 10-2-10-3 0.1-10

THERMOCOUPLESCold-Cobalt va Copper A-300

-1 -210 -10 10-1 0.1-1

ConstanCan V3 Copper 20-600 10-1-10-2 10-1 0.1-1

VAPOR PRESSUREUcllum 1-5 lO'-'-io"* 10-3 0.1-100

Hydrogen 14-33 10-3 10-2 0.1-100

Nitrogen 63-126 10-2-10-3 10-2 0.1-100

Oxygen 54-155 10"2-10-3 10-2 0.1-100

a-Includlng nonreproduclbllltyt calibration errors and tcmperoture scale uncertainty

25

space hardware is actually used in thecommercial sector. A deliberate effort to

adapt space instrumentation to commercial and

industrial applications may be worthwhile.Primary instruments and facilities to

calibrate liquid level devices do not exist,and accordingly it is questionable whetherthis part of the National Measurement Systemis in control. Furthermore, a large body ofknowledge and experience needs to be devel-oped to move with assurance from this rela-tively clean measurement to the practicalmeasurement question of "how much does thetank really contain?"

Performance characteristics vary widely,depending upon the fluid being measured, its

temperature, pressure, and even orientation.Accordingly, no brief summary is possible.The best complete review of this measurementmay be found in the work of Roder [14].

Density is an inferential measurement and,

as such, it should be traceable to a nationalstandard, such as a national density refer-

ence system. Primary instruments to cali-brate densitometers do not exist.

Several physical principles of cryogenicdensity measurement have been brought wellforward by the space program. Notable arethe capacitance, vibration, and nuclearradiation attenuation schemes. Microwavemethods are recently moving to the forefront.Roder [14] has recently summarized this fieldas wel 1

.

Flow . There is no shortage of physicalprinciples upon which to base a cryogenicflowmeter. Depending on the need, they rangefrom simple pressure drop meters to sophis-ticated mass reaction types. Flow, however,is a derived quantity, and as such flowmetersrequire traceability to a reference system to

establish credibility.Summary . One component of the problem of

cryogenic instrumentation is that it is

largely static. Not much has been accom-plished technically since the peak of the

space program. There is little evidenceof the commercialization of these instru-ments .

A second part of the problem arises fromthe way cryogenic measurements fit into the

National Measurement System. As long as onlya single agency or one sector of our economy(National Aeronautics and Space Administration,the aerospace industry) were using essentiallyall of the results of their own measurements,then that part of the National MeasurementSystem was internally consistent and in har-

mony with itself. Now, however, the prospectsare that cryogenics is becoming more commer-cialized and moving tq the market place andthus external consistency as well as internalconsistency is now required to make this part

of the National Measurement System work.Primary instruments and facilities to

calibrate the derived quantities--liquidlevel, density, and flow--do not exist.

Accordingly, there is less confidencethat this part of the cryogenic measurementsystem is as well under control as tempera-ture is.

The third part of the problem is perhapsa derivative of the first. Because the fieldis static, a crucial question is not beingasked: are there predictable technologicaldevelopments that will either create a needfor new cryogenic instruments or possiblyprovide an altogether new measurement means?

2.4 Dissemination and EnforcementNetwork

Standards are the means used to judgesomething as authentic, good, or adequate.They are the measures to determine what a

thing should be, or whether it is correct.Thus, there are standards for measurements--prototypes, artifacts, the physical real-

ization of a conceptual measurement--stan-dard constants, including property data;

standards of quality, of performance, and of

practice (codes). The public outputs are

usually pieces of paper--documentary stan-

dards. Behind all of these paper standards

are the physical measurement standards that

national authorities keep in their custody as

artifacts, or that they define in terms of

some physical phenomena.Every form of standard, from the docu-

mentary standards to the physical embodiments,

are essential to the proper functioning of

the measurement system. In the discussionbelow, the word standard will be used delib-

erately ambiguously to indicate that all

types of standards are involved in the

dissemination and enforcement network.Much of the Dissemination and Enforcement

Network has been discussed in Section 2.2,1.1,"Standardization Institutions" and 2.2.1.2,

"Survey of Documentary Standards." Here, we

shall highlight this network with a specific

case study, the Cryogenics Division's liquid

nitrogen flowmetering program.

2.4.1 Central Standards Authorities

National Conventions . In the case chosen

as the illustrative example, NBS itself was

the relevant national authority.This came in part because NBS has the

ability to provide both national standards

and international standards through such well

established NBS mechanisms as NBS Handbook

44. It also came in part because our mostuseful and important type of standard setting

activities may be the de facto standards --

26

which exist and are accepted just because NBS

exists and is accepted -- such as the thermo-dynamic properties work mentioned in Section2.2.1 .2.

The State of California, during thehearings in the fall and winter of 1967-68,

clearly developed and documented their needfor a central, national authority. Therecord shows in part:

"With respect to standards, there should be a

national facility, a final authority, a

referee, that would not be in competitionwith private industry."

This expresses rather clearly the need fora centralized national effort in such mattersthat at first do not appear to transcendstate boundaries.

International Conventions . The Com-pressed Gas Association was stronglymotivated to deal with one national labora-tory rather than 50 state laboratories.Recognizing this problem on an inter-national scale, we at NBS have:

• Cooperated with the InternationalOrganization of Legal Metrology (OILM) to

facilitate the adoption of the findings ofthis program as an international code;

• Performed type testing of meters offoreign manufacture as an integral part ofthe program. (See for instance, NBS Tech.Note 624, "An Evaluation of Several Cryo-genic Turbine Flowmeters");

•Promoted and facilitated a six weekvisit by Dr. Josef A. Eberle of thePhysi kal i sch-Techni sche Bundesanstal

t

(PTB). One result of Or. Eberle's visitwas his translating into German of our NBSReport 9778, "Cryogenic Flow ResearchFacility Provisional Accuracy Statement"to be used as a model by the PTB. Otherinternational observers included Dr.

Walter Linde and Dr. Klaus Schmidt ofLotepro, Inc., (a subsidiary of Linde,Germany); Dr. Helmut Peter and Dr. S. K.

Windgassen of Messer-Griesheim, Germany;Dr. Heribert Wenzel of Linde (Munich,Germany); Dr. Jacques Hermel of CompteursSchlumberger, France; and Dr. J. B. Gardnerof the British Oxygen Co., England.

•One of the most important trans-actions occurred in an un-official way.Specifically, the Compressed Gas Associa-tion, which supported the eventual flow-metering program, formed a steering com-mittee to help provide a degree of qualitycontrol to the program, but especially tohelp substantially b^ providing guidanceand advice at critical stages of planningand implementation of the program. Thiscommittee met three to four times a year

27

during the nearly eight year life of theprogram. In addition, state weights and

measures officials routinely attendedthese meetings, which provided an invalu-able forum for the cooperative solution of

vexing problems. The real impact of this

type of program may indeed lie in this

kind of cooperation and communication.NBS-Infrastructure . Within the NBS it-

self, there is a very strong and viableinfrastructure that undergirds the wholestandards setting activity. In this case,for instance, it included:

•The Institute for Basic Standardsitself, whose statutory responsibility to

provide basic measurements and standardsmade the cryogenic flowmetering programpossible.

•The Office of Measurement Services,which provided guidance on accuracy state-ments, and experience in conducting roundrobins

.

•The Patent Advisor, who provided guide-lines for handling proprietary information on

the performance of specific flow meters.

•The Office of Weights and Measures,(OWM), which publishes Handbook 44 and pro-vides the secretariat to the National Con-ference on Weights and Measures (NCWM). TheOWM gave our program the direction and

mechanism to make its results have the effectof law.

•The Applied Mathematics Division, whichhelped plan experiments for statisticalsoundness and assisted in analyzing theresults. This provided a scientific basisfor interpreting claims in the trade litera-ture of "accuracy" and "repeatability".

• The Cryogenics Division itself providedthe essential technical base and resources.It is true time and again that the soundfixing of standards cannot occur in an ivorytower. It requires good judgment, and this

can be applied only when there is soundcomprehension not only of the science in-

volved, but also of the ways in which it is

being applied, and more subtly, of the waysin which it is likely to be applied in thefuture.

2.4.2 State and Local Offices of Weights andMeasures

The state regulatory agencies saw a real

need for traceability to a national standardsince they are obligated by law to perform"type-approval" inspections. In the fall of1967, the State of California Bureau of

Weights and Measures began hearings whichhave already been described in Section2.2.1.1. With the assistance of NBS, a code

was adopted that was felt to representequitably the capability of the meters thenused in commerce. It must be admitted, how-ever, that the tolerances chosen were arbi-trary, with little or no cryogenic testing to

back them up. The State of California,frustrated by their legal requirement toregulate the sale of liquid nitrogen, butwith no technical capability to do so, essen-tially had no other choice. They set thesame standard for liquid nitrogen as was thenin force for gasoline. The suppliers, in

effect, said "prove it". This impasse wasresolved by the liquid nitrogen flow program.

Fortunately, perhaps, the original toler-ances proposed by the State of Californiawere later demonstrated by NBS to be rea-listic and feasible, a finding which facil-itated the early adoption of the code. Theproducers were especially pleased to be

able to deal with one central laboratoryrather than 50 separate state labs. Weregard this as a good example of "NewFederalism" at work--as NBS competence is

directly transferred to the states.

2.4.3 Standards and Testing Laboratoriesand Services.

Round-robin intercomparisons are at theheart of transferring the NBS measurementcapability to the states, producers, andmeter manufacturers. For instance, espe-cially in the earlier stages of the physicalevaluation of our own flow system, round-robins were conducted with industrialtesting laboratories. These included thefacilities of the Linde Co. at Tonawanda,N.Y., Air Liquide near Paris, The BritishOxygen Co. in London, and Messer-Griesheimat Dusseldorf, Germany. This cooperationnot only gave us a feeling of confidencein our own facility, but also opened thedoor for international agreement (via theOILM, for instance).

In addition, it is known that the Stateof California has already calibrated over95% of all the meters used there in liquidnitrogen commerce. To further facilitatesuch intercomparisons, NBS has built andis currently proving a transfer standardof its own.

2.4.4* Regulatory Agencies

For this case study, consumer organiza-tions per se , federal agencies (regulatoryand otherwise), and the National Confer-ence of Standards Laboratories (NCSL), a

quasi -governmental regulatory unit, didnot play a major role, although theysurely would in other types of studies.This is so because the specific programhighlighted here, concerning the meteringof liquid nitrogen, was prompted by an

28

unresolved technical controversy betweencertain state weights and measures bodiesand the producers of a specific commodity.Accordingly, federal agencies, other thanour own, had little or no interest or partto play; direct contact with the consumerwas not necessary. The consumer's view-point was adequately represented by theState bodies, and in fact, the Californiahearings deliberately solicited the con-sumer's opinion. The National Conference ofStandards Laboratories (NCSL) as a whole wasof little interest to this particularstudy, for a much more narrow and intenseresource existed as a sub-set of the NCSL,namely the ISA Ad-Hoc committee alreadymentioned.

2.4.5 Industrial Trade Associations

An unusually significant and interestinginteraction occurred in the following way.

The Compressed Gas Association, which sup-ported the eventual flowmetering program,formed a steering committee to help provide a

degree of quality control to the program, butespecially to help substantially by providingguidance and advice at critical stages ofplanning and implementation of the program.As mentioned, this committee met three to

four times a year during the nearly eight-year life of the program. In addition, stateweights and measures officials routinelyattended these meetings at our request, andoften with our financial support. Thisprovided an invaluable forum for the co-

operative solution of vexing problems. Thereal impact of this program may indeed lie in

this kind of cooperation and communication--structured yet unofficial.

2.5 Direct Measurements TransactionsMatrix

Understanding the National CryogenicMeasurement System is closely related to

understanding the cryogenic community, whichis largely related to the production and use

of cryogenic fluids. The following sectionprofiles the supply and use of cryogenicfluids.

2.5.1 Analysis of Suppliers and Users

The cryogenic fluids with the largestdollar value of sales are: oxygen, nitrogen,helium, hydrogen, argon, and liquefied nat-

ural gas. Krypton, neon, and fluorine are

also considered to be cryogenic fluids, but

the quantities produced are very small and

are not discussed here.

The value of the six fluids consideredhere was about $166 million in 1960. By 1968

the value had tripled to about $532 million.(These are values of liquids and gases pro-

duced by cryogenic processes and do not

include low-purity gases or gases produced by

electrolysis.) From 1960 to 1968 the annual

growth rate averaged about 15%. However, the

market began leveling off at $795 million in

1973. By examining each fluid and its marketin turn, we see that it is not reasonable to

expect both a constant and uniform growthrate for all fluids. The arguments for this

less optimistic projection follow for each

fluid.Oxygen . High purity (greater than 99.5%

pure) 1 iquid oxygen is mainly produced by

cryogenic air separation processes (elec-

trolytic oxygen amounts to much less than 1%

of high purity production). Low purityproduction (less than 99.5% pure) is about1/6 of the high purity oxygen production.

A major use of oxygen is in the basicoxygen process for steel, which consumesabout 80 X 10^ std ft^ per year, andopen-hearth steelmaking where oxygenlances use over 50 x 10^ std ft^ annually.These uses are the main factors in thegrowth of oxygen production in recent years.The chemical industries come next, usingsome 15% of production, followed by welding,nonferrous metal refining, aerospace andbreathing uses. It might be pointed outthat the chemical industry is growing muchfaster than most segments of the UnitedStates economy and thus might be expectedto contribute even more to the growth ofoxygen production than does steel.

Shipments^ of liquid oxygen are de-creasing as a fraction of total produc-tion. This can be attributed to the factthat more liquid oxygen facilities arebeing built right at the users' doorsteps,and also that National Aeronautics andSpace Administration consumption of liquidoxygen is decreasing.

Looking ahead, the industry itselfpredicts annual growth rates of 5-15% forthe coming decade [24]. Using an averageof 10%, we should reach 10^^ std ft^ by1983.

New uses of oxygen could change thisoutlook materially. For example, thetreatment of sewage and wastes by bubblinglarge amounts of oxygen through the tanksoffers cleaner discharge, better phosphateand nitrate removal, and reduces the needfor agitation, which speeds the sludgeseparation process. Approximately fourtimes the oxygen concentration can beachieved in this way as compared to air

Shipments is used in the special sensethat it occurs in the Census of Manufactur-ers. It means the value of shipments,which is the net selling value, f.o.b.plant, after discounts and allowances andexcluding freight charges and excise taxes.

bubbling, thus improving the bacterialdegradation rate and helping the environ-ment support aquatic life. The amounts ofoxygen needed for this purpose in two orthree decades could equal the amounts nowused in steel

.

Nitrogen . The economic importance ofnitrogen is about half that of oxygen. It

is the fastest growing of the major indus-trial gases. Nearly all high puritynitrogen is produced by the air separationprocess. More liquid nitrogen is shipped(as opposed to in-plant transfers) than is

the case with oxygen. This is apparentlyso because the producers (often located nearoxygen consumers) are not always locatedclose to the nitrogen consumers, such as thefood freezing industry. Nitrogen is used asan inert atmosphere in many metal, electro-nic, chemical, and aerospace industries.(See Section 1 .0)

.

Looking beyond 1975, industry spokesmenfeel that the past rate of growth will not bemaintained, but will be greater than that ofoxygen [24]. From 1960 to 1968, the rate wasabout 26%, but this is predicted to level outat 15-20% in the next decade.

Nitrogen is already widely used for foodpreservation, refrigerated transportation,and cryo-biology. Practically all the frozenshrimp in the U.S. are processed in this way,and nearly all the west coast lettuce shippedto the East comes under a cold nitrogenblanket. There are now approximately 500truck stops in the U.S. where a truck cantake on diesel fuel at one end, and liquidnitrogen at the other. The essential featureis that each truck now carries a simple tankof liquid nitrogen instead of a mechanicalrefrigerator.

Hel ium . The great majority of the proven,economically recoverable helium sources in

the Western Hemisphere are found in the

Texas-Oklahoma-Kansas area of the UnitedStates. These known reserves are estimatedat over 150 x 10^ std ft^

Most of the helium used in the UnitedStates has gone to government agencies suchas the National Aeronautics and Space Admin-istration, the Department of Defense, and theAtomic Energy Commission, which are requiredto buy their helium from the Bureau of Minesin order to finance the conservation program.Private producers entered the market withdeliveries almost equal to that of the Bureauof Mines in 1967. The decreasing aerospacebudget has resulted in smaller deliveries by

the Bureau of Mines, which means less heliumcan be bought for conservation. (Each cubicfoot of lost sales reduces the reserve pur-chases by 2.4 cubic feet.) These factorsindicate that a readjustment of helium pricestructures may occur in the near future.

29

One of the first tasks assigned by theCongress to the newly created Energy Re-search and Development Administration is to

conduct a thorough study of the need forhelium in energy applications (e.g., super-conducting electrical power systems). Therecommendations of this study will doubt-lessly have a profound effect upon futurehelium conservation efforts in the UnitedStates.

Hydrogen . Liquid hydrogen productiondepends more on defense and aerospace acti-vity than does oxygen or helium. Sincethe National Aeronautics and Space Adminis-tration used between 1/3 and 1/5 of thehydrogen produced, its variations had a largeeffect on the total picture. While theaverage rate of annual growth was greaterthan 30% during the 60' s, it would appearthat 10% is more likely during the 70's.Fields of hydrogen use, which seem likely togrow, are hydrogenation of edible oils,atmospheric control in the electronic andelectrical machinery industries, and de-oxidation in heat treating of metals. If

hydrogen realizes its potential as a fuel,there may be explosive growth here (SeeSection 5.0).

Argon . Some 70% of the argon producedis used for welding reactive metals, butthe continuous casting process of steelproduction could potentially use manytimes the current production (worth around$32 million in 1968) as a blanketingagent. Argon has shown an historicalgrowth of about 17% annually from 1960 to

1968, matching the growth rate of oxygenfor the same period. This is logical,since argon is produced cryogenically as a

by-product in the air separation processfor oxygen. If the continuous castingtechnology develops sufficiently to createa huge demand for argon, it would alsogive impetus to the oxygen producerslocated near the steel mills. If this newmarket does not develop, the growth ofargon will probably be held to about thesame rate as oxygen, or 10%.

Liquefied Natural Gas (LNG) . In 1968,the least economically important of thecryogenic fluids was LNG, worth about $24million. However, in 1972 it had alreadygrown {o third place and may be first short-ly after 1976. LNG is used mainly forpeak shaving purposes in areas where largevolume gas reservoirs are unavailable, andalso for base load supplies where pipelinegas is not feasible. It is predicted thatLNG produced in the United States will havea value of about a billion dollars a yearby 1976 [25], or over^ 10% of the totalnatural gas production of the country.

LNG is used as a replacement for gaso-line in some vehicles to reduce pollutionand gain in operating economy. All thefleet vehicles of San Diego Gas and Elec-tric run on LNG, as well as about half thebuses of the Chicago Transit Authority.All the off-the-road equipment of U.S.

Steel in the Mesabi range likewise useLNG.

Other uses investigated include tem-porary consumer supply during pipelinedisruption or maintenance, as a petro-chemical feedstock, desalinization of seawater through freezing, and refrigerationand power supply for food freezing plants.The concept of clustering several industriesthat need refrigeration around a re-gasifi-cation facility should be considered morethoroughly. Many re-gasification plantswaste the huge cold-potential by absorbingtheir heat from the air or ocean.

Profile Summary . In conclusion, then, it

would appear that the growth of the cryogenicfluids industry will continue, but at a ratesomewhat smaller than during the past decade,LNG excepted. A growth rate of around 10%seems a reasonable expectation, arrived at by

weighting the growth rates of the individualgases according to the 1968 production fig-ures. However, if LNG fulfills its promise,the rate could be much higher.

2.5.2 Input-Output Direct MeasurementsTransactions Matrix

General . A matrix has been constructed to

show the transactions between suppliers andusers. The elements indicated on table 2-10

include, for instance: The knowledge com-munity, standards organizations, the instru-ment industry, NBS, regulatory agencies at

all levels, industrial associations, and the

general public. The entries in the inter-section boxes describe the interaction as a

whole within the Cryogenics MeasurementSystem, not just those involving the Cryo-genics Division of NBS alone, and certainlynot just the flowmetering program usedelsewhere in this report as a specific ex-

ample.Format . In the center of each box is a

numeral indicating the magnitude of the

transaction on a semi -quantitative "volume"basis:

0 = Trivial1 = Minor2 = Moderate3 = Important4 = Major

In the lower left hand corner , there is a

digit describing the rate of change of trans-actions at this intersection:

30

Table 2-10. Direct measurements transactions matrix

DIRECTI'lCMOUnLI lull 1 o

TRANSACTIONSMATRIX FOR

U

S

pt.

R

SKnowledge

Community

International

Metrological

Organizations

Documentary

OJ

Standards

Organizations

Instrumentation

Industry

(/Icaz.

5^

Other

U.S.

Nat'l.

Stds.

Authorities

-J

State

&

Local

OWM's

^

Private

Stds.

Laboratories

1

.D

Regulatory

Agencies

oDepartment

of

Defen-

j

_,

Other

Federal

Agencies

j

_

State

&

Local

Govt.

Agencies

i

_,

Industrial

Trade

"

Assoc.

_,

Misc.

Industrial

&

Commercial

i

Q_

(Uc<uC3

15SUPPLIERS \1

Knowledge Community4 1

2

?

4 1

2

4 1

2

2 1

3

4 1

4

3 1

1

2

3

2

2

2 1

3

3 1

2

2

2 1

3

2

3 1

2

2

2

1

2

2

4

2

3

2lnternationalMetrological

Organizations

4 1

2

4

4

4 1

2

2 1

2

N

4 3

4

2

3 1

1

2

2

1

N

2

2

N

3

2

3

1

2

1

1

2

1

2

3DocumentaryStandards

tlrganizatinns

4 1

2

4

2

4 1

4

3 1

3

?

4 1

3

7

3 1

1

2

3 1

3

2

2 1

2

3 1

4

2

3

1

2

2

2

2

2

2

2

2 1

3

2

2

3

2

2 1

1

4Instrumentation

T nH 1 1 c "f" 1'* \y1 ilUUb LI jr

2 1

3

2 1

3

3 1

3

2

2

3

3 1

3

2

3 1

1

2

3 1

2

2

2

4

3 1

2

2

2

3

2

2

2

1

2

3

1

3

1

5

NBS

4 1

4

4 3

4

2

4 1

3

2

3 1

3

2

4 1

3

?

3 2

1

2_

3 1

2

2,

2

1

2

2

2 1

1

2

3

4

Z

2 1

4

2

2 1

2

2^

2 1

4

2

2 1

3

2

1 2

1

2

^Other U.S. Nat'l.

JLU^> MULrlUl ILICD

3 1

1

2

3 1

?.

3 1

1

2

3 1

1

2

3 2

1

2

3 2

3

2

1

2

2

2

3

3

2

2 1

2

2

1

1

2

2 1

2

2

2

1

2

7

state & Local OWM's3

2

2

3 3 1

3

2

3 1

2

2

3' 1

2

2

3

1

4 1

4

2 1

3

3 1

1

2

1

1

2

2 1

3

2

2 1

1

2

2 1

1

oPrivate Stds.

Laborator i es

2 1

3

2 2 1

2

2

4

2

2

2

1

1 3

1

2

2

1

2

1

2

2

2

2

2

2

2

2

1

1

9

Regulatory Agencies3 1

2

2

3

2

3 1

2

2

2 1

1

2

2

2

2

3 1

1

2

2

1

2 1

2

2

1 1

1

2

1 1

2

2

1 1

2

2

2 1

3

2

2 1

2

2

2 2

1

2

10

Department of Defense2 1

3

2

3 3

1

2

2

3

3

4

2

3

3

2

2

1

1 1

1

2 1

4

2

2 1

3

2

1 1

1

2

2

1

1

1

2

1

1

^^Other Federal

Agencies

3 1

4

2

2 2

2

2

2

2

2 1

4

2

2 1

2

2

2

2

1 1

2

2

2 1

3

2

2 1

3

2

2 1

2

2

2 1

3

2

1 1

1

2 2

1

2

^^State & Local Govt.

Agencies

2

1

?

2

2

?

2

1

2 1

2

2

1

1

2

1

1

2

2

2

1 1

2

2

1 1

1

2 1

2

2

2 2

2

2

%'2

1 1

1

2

2 2

2

2

13Industrial TradeAssoc.

2

4

1

3

2 1

3

2

2

3

2 1

4

2

2 1 12 1

2 3

2 2

2

2

2 1

3

2

2

1

2

2 1

3

2

2 1

3

2

2 1

2

2

2 1

3

2

2 2

1

2

14Misc. Industrial &

Commercial

2

3

1

1

2

3

2

1

3

2 1

3

2

2 2 1

11

1

2 12

2

2

2 1

2

^2_

1 h 1

1 ! 1

!

1 1

1

2 1

3

2 2

3

2

1

1

15

General Public2 1 jl

1

'

i

1 2

1

2

2 1

1

T 2

1

2

1 ^ 2

1 1

2

\ -t2

2

It1

2

1

1

KEY TO MATRIX ENTRIES

IMPORTANCE OF TRANSACTIONS

1 = Purely convenience2 s= Strongly desirable3 = No real alternatives4 = Essential

B - RATE OF CHANGE

N = Declining0 = Stable2 = Growing4 = Growing explosively

Unknown, X = Not studied, Blank = 0

USERS

C D

SUPPLIERS A-

—

B

D - (IN)ADEQUACY OF SERVICES

0 = No improvements needed1 = Could be improved2 = Marginal3 = Serious deficiencies4 = Out of control

MAGNITUDE OF TRANSACTIONS

0 = Trivial1 = Minor2 = Moderate3 = Important4 = Major

31

N = Declining volume or needs0 = Stable2 = Growing4 = Explosive growth or discontinuity on

hand

In the upper left hand corner , a digit indi-

cates the importance or critical ity of thetransaction

:

1 = Purely a matter of convenience;transaction not essential;reasonable alternatives readilyavailable

2 = Economically important; stronglydesirable

3 = No satisfactory alternate source;legally required

4 = Essential; sole source; mattersof life and death

In the upper right hand corner , anotherdigit indicates the (in)adequacy of the

transaction goods or services:

0 = No foreseeable improvementsneeded or desirable

1 = Under control, but could be

improved2 = Only marginally O.K.; significantly

inadequate3 = Seriously deficient4 = Out of control ; thoroughly un-

satisfactory

The general code for a stable field is

a zero. For ease in reading, all zeroshave been suppressed in the table. Thereare no intentional omissions, as an "X"

would have been used to indicate a factordeliberately excluded.

Double-lines are used to help subdividethe large matrix into smaller ones. For

instance, double lines are found on eitherside of "NBS", and they are also usedbetween the Department of Defense Sectorand the Regulatory agencies.

Hiqhl iqhts . International MetrologiaalOrganizations and NBS, in the field ofthis microstudy , have only a moderatevolume of transactions between them, hencethe "2" in the center of the box. Thesetransactions are growing -- "2" in the

lower Jeft hand corner -- as the importationof LN6 increases. The interaction is

essential -- "4" in the upper left corner.They are under control, but could be

improved as the volume and variety of the

transaction increases -- "1" in the upperright corner.

NBS and Other U.S. National StandardsAuthorities. A useful example here is ourinteraction with the'U.S. Coast Guard,which is indeed a national authority that

sets minimum specification and performancestandards for ships that may use U.S.

ports. We help by supplying technicalinformation on the properties of LNG,

potential hazards, handling procedures, andstructural materials. The volume of thistransaction is minor at present (1, center);is growing (2, lower left); is stronglydesirable (3, upper left); and could be

significantly improved (2, upper right).It appears that the U.S. Coast Guard has

final legal authority to set the standardsrequired and to define the measurementcodes and practices to test whether or notthe standards are being met. The U.S.

Coast Guard may do this without neces-sarily having recourse to the NBS. Accord-ingly, it appears that this part of themeasurement system is disjointed at thepresent time. There is no objective reasonwhy it should remain so.

Item 12, State and Local GovernmentAgencies, for this microstudy includes: TheNew York City Fire Department and similarjurisdictions concerned with the safety of

LNG.

The General Public has little directcontact with cryogenics, since it is essen-tially an infrastructure industry. However,transactions do occur in such diverse areas

as liquid oxygen for breathing therapy,artificial insemination, cryo-embalming, and

questions of safety regarding the storage and

transportation of cryogenic fluids.

2.5.3 Highlights re Major Users

It has been claimed that cryogenics is

nearly a $2 billion industry, and that thereis widespread interest in it. The discussionbelow gives a few indicators leading to theseclaims and highlights the major users.

2.5.3.1 Industrial Gases and Equipment

Industrial gases are at present the back-

bone of this industry, and will continue to

be while the liquefied natural gas componentbuilds up. At some time in the future, LNG

may surpass industrial gases (Carbon Dioxide,

Acetylene, Nitrogen, Oxygen, Argon and Hydro-

gen --SIC Code 2813), but the value of ship-

ments of industrial gases was $795 million in

1974, produced in 507 establishments employ-

ing 9,000 people [26]. A "rule-of-thumb" for

this industry is that it has roughly three

equal components: liquids, gases, and equip-

ment. Therefore, if the liquids and gases

sold were worth about $800 million, then the

cryogenic equipment is worth about half of

this again, $400 million, making the total

about $1.2 billion.The annual investment in capital equip-

ment is at least 15% of sales [27] or about

32

$280 million. Thus the total expenditure in

cryogenics is about $1.5 billion per year.

These figures exclude LNG, but it is not hard

to imagine the value of LNG bringing the

total close to $2 billion.In order to be more specific, we have

analyzed the public Annual Reports of a fewof the major corporations engaged in cryo-genics. The findings are given below, and wemay safely assume that the figures given arerealistic, as such reports are carefullycontrolled by the Securities and ExchangeCommission (SEC). Not all of the reports arefrom the same year. One is from 1971, forinstance, but this discrepancy will onlyserve to make the figures conservative, as

newer figures would be greater due to real

growth, inflation, etc.

Table 2-11. Net sales of major cryogeniccompanies in the U.S.

Corporation Net Sales

Chemtron Gases Group, $ 156.4 Mformerly National CylinderGas (1972)

Union Carbide, Linde Div. 581.0Gases and related products(1973)

Air Products and Chemicals, 209.6Gases and Equipment Group(1971)

Airco, Industrial Gases and 240.0Cryogenics Group, formerlythe AiReduction Co. (1972)

Cryogenic Technology Inc. 33.0(1974)

Total $1,220.0 M

These are not all the companies doingbusiness in cryogenics, but they arerepresentative of the principal ones.(Note that this demonstrable figure of$1.22 billion compares favorably with ourprevious "rule-of-thumb" estimate of $1.20bi 1 1 ion.

)

We can still add approximately 15% [27]for the annual capitalization rate, or$183 million, and thereby get $1,403billion as the annual size of the cryo-genic gases, liquids, and equipment indus-try.

2.5.3.2 Liquefied Natural Gas (LNG)

The following is a brief summary fromthe published literature that tends toestablish the dollar value of the LNG in-dustry on an annual basis.

Import-Export . The Minerals Yearbook[28J states that 2.2615 billion cu. ft. of

natural gas was imported as liquid fromAlgeria and Canada in 1972. In addition,it states that 47.9 billion ft^ of LNG wasexported to Japan from Alaska during 1972.Therefore, 50 billion ft^ of natural gas in

liquid form was involved in import-exportcommerce in 1972. By applying a conservative$1 per thousand std ft\ it is possible toestimate a value of $50 million for the LNGimport-export trade.

LNG Produced for Internal Consumption .

We may estimate the value of LNG producedfor internal consumption from the grossliquefaction capacity of peak shaving andsatellite liquefaction facilities presentlyoperating. Although LNG is generally notconsidered a cormodity in peak shavingoperations, it is nonetheless possible toestimate its value from the size of thenational liquefaction capacity by assumingthe market value of LNG at $1 per thousandstd ft^ equivalent. "Gas Facts" [29]cites gross liquefaction capacity of 206million ft^ per day which computes to be 75billion ft^ per year with a dollar valueof $75 mill ion.

LNG Ship Building Construction . There arepresently 16 LNG ships under construction in

the U.S. [30]. It is assumed that theseships were ordered in the period 1973-1974for delivery in the five year period 1975 to1980. We estimate each ship's value at $90million [31]. Assuming that these 16 shipswill be delivered over the five-year periodmentioned, we thus derive an average yearlyvalue of $288 million for LNG ship construc-tion.

LNG Storage and Peak Shaving Plant Con-struction . Hale [32] states that up to 10 ormore LNG peak shaving plants will be builteach year for the next 10 years. Furthermore, there are 19 applications pendingbefore the Federal Power Commission forpermission to import LNG or to liquefy andstore it for interstate use alone. Theseapplications are not trivial. To illustrate,one peak shaving facility in Iowa is esti-mated to cost $23 million. The import ter-minals proposed by Western LNG is estimatedto cost $1.7 billion, and the El Paso-Alaskaexport terminal to supply part of the westcoast (including 11 ships and a pipeline) is

estimated to cost $5.6 billion. Hale [32]cites a recent Northern Natural Gas Companyplan for a $20 million facility. With his

value as a conservative average, we mayestimate investment in peak shaving faci-lities to be at a level of $200 million perannum. The size of the U.S. LNG industry is

therefore approximately:

33

Component Value, $ M/yr

1. Import-Export Trade $ 50

2. LNG produced for Internal 75

Consumption3. LNG Ship Construction 2884. Peak Shaving Plant 200

Construction$613 M

Therefore, the approximate size of the

cryogenic industry in the United States is

$1,403 million plus $613 million or $2,016bil 1 ion.

2.5.3.3 Research and Development

None of the above includes research anddevelopment, or any estimate of the future.There are a few indicators in this area:

About $26 million per year is spent on

superconductivity programs in the U.S. [33].This total includes: $3 to 4 million forelectrical generators; $3-1/2 to $4 millionfor electrical power transmission; $6 millionfor electrical propulsion systems; $6-1/2million for energy storage, magneto-hydro-dynamics and controlled thermonuclear re-

actors; $7-1/2 million for high energy physicsexperiments; and $2-1/2 million for basicresearch on superconducting materials.

The importance of helium is noted in

the Energy Research and Development Admin-istration (ERDA) legislation, which directsthe Administrator to conduct a study ofthe potential applications of helium, andto report his recommendations to thePresident and the Congress within sixmonths of enactment. These recommendationswill concern the management of the heliumprogram from the standpoint of energy R&D[34].

The Institute of Gas Technology reportsthat the natural gas utilities feel theneed to demonstrate to their investorsthat they have prospects for participatingin a "perpetual" energy industry, notsubject to depletion. They see hydrogenas a substitute fuel gas to move throughtheir pipelines [35].

Many feel that cryogenics may be to thesecond half of the twentieth century whathigh temperature processing was to thefirst^half. We at NBS certainly agreethat at least it is an important, large,growing and dynamic industry.

3. IMPACT, STATUS AND TRENDS OF THECRYOGENIC MEASUREMENT SYSTEM

3.1 Impact of Measurements

3.1.1 Functional, Technological, and Scienti-fic Appl ications

The impact of cryogenic measurements maybe illustrated by some examples where cryo-

genics plays a crucial role in the advance-ment of national programs. In the examplesbelow, the measurement infrastructure sup-ports the commerce in cryogenic fluids, al-though measurements per se may be peripher-al to the applications listed. They arementioned primarily because of their in-

herent interest.In the area of health: blood for trans-

fusions can be stored at. liquid nitrogentemperature for extended periods of time,while storage for over 2 weeks at 4°C is themaximum allowed with conventional technology.Recently, the Food and Drug Administrationhas approved such blood as a commodity forinterstate commerce.

Biological samples (like tissue, cancercells, tumors, cornea, and bone marrow) canbe stored without serious degradation forstudy and inter! aboratory comparison. TheNational Cancer Institute maintains just suchan archive.

There are several applications in agricul-ture, but one of the most noteworthy is thatmore than 50% of all cattle are bred by

artificial means with the bull sperm storedand transported at liquid nitrogen tempera-ture.

Another agriculture related use of liquidnitrogen is in food freezing, a well estab-lished technology--over $50 million worth ofliquid nitrogen is used for this purposeannually. Since the use of liquid nitrogenhas been so advantageous, developments are

underway to extend its use further back into

the food chain. For instance, sweet corn and

sweet peas are being harvested experimentallywith the aid of cryogenics. This process is

said to enhance their value by retaining the"field sweetness" of the produce. Soybeans,a valuable source of protein, are beingcryogenical ly harvested also. It is saidthat the objectionable (to some) flavor ofsoybeans is due to the highly perishablenature of the newly picked beans. Cryogenicharvesting is said to enhance the value of

this product several times over by helping to

retain the highly desirable fresh-pickedflavor.

In transportation there are already a

limited number of cars and trucks using LNGand hydrogen, but the auto industry does use

cryotechniques extensively, including oxygenfor steel making, grinding paint pigments,and deflashing parts at low temperatures.In addition, float glass is inerted with

gaseous nitrogen. Even the reclamation of

scrap metal from old cars and tires uses

cryogenic technology—cooling to low

temperature permits fracturing and componentseparation.

34

The aerospace industry is committed to

cryogenics and about 40% of the National

Aeronautics and Space Administration'sbudget is cryo-related.

In research, the National AcceleratorLaboratory (NAL) has recently purchased15,000 lbs. of NbTi ingots at a cost of

approximately $500,000 to build a supercon-ducting energy doubler. This amount of

material is enough for only 1/6 of the

magnets around the 4 mile ring, or $3million worth of raw NbTi. Other scien-tific applications of cryogenics y/ere dis-

cussed extensively in Section 2.2.5.

The Navy is building 3000 HP supercon-ducting motors and generators for ship pro-

pulsion and has design studies underway for a

30,000 HP version. These motors couldrevolutionize the use of hydrofoils and evenconventional ships.

In some of these examples, the NBS roleis rather diffuse and indirect, while in

other cases, our aid is quite explicit.In all cases, cryogenic measurements arecentral to the infrastructure that supportsthe technological and scientific applica-tions mentioned.

3.1.2 Economic Impacts--Costs and Benefits

Some examples of the value of cryogenicmeasurements were given in Sections 2.2.2.2and 2.5.2. We shall highlight a few ofthese values again below, and concludewith a specific case study sponsored byThe Instrument Society of America.

•Approximately 2,000 cryogenic flow-meters are in use today with a value ofover $3 million, making approximately400,000 custody transfers per year.Flowmeters are considerably less numerousand less widely used than other cryogenicinstruments

.

•In terms of rate of growth, theindustry as a whole, of which cryogenicmeasurements are a part, ranked 59th out

of 130 industries surveyed by the Depart-ment of Commerce during 1973-74. Theaverage growth rate was 7%.

The two principal subcodes within thisgroup are 3821 and 3822. Projections [36]through 1980 are shown in table 3-1.

A specific example of benefit-cost esti-mation may prove useful at this point andhelp bridge the gap between instrument anduser. Our example shall turn around thecryogenic flowmetering program, especiallythe summary report [37] prepared by TheInstrument Society of America Ad Hoc Com-mittee mentioned in Section 2.2.1.1.

As mentioned, NBS contributed to thisreport and excerpts are given below:"The previous section has developed some

of the needs for cryogenic fluid flowmeasurement and standards. However,it is one thing to have needs and anotherto economically justify the solution ofthese needs. Since this was part of thecharge to the Ad Hoc Committee, an attemptwas made to come up with an economic justi-fication. As in many situations suchas this, this economic justification is

not easy to prove and verify by actualnumbers because so many intangibles mustbe considered as part of the economics of

such a problem. However, using statementsand estimates from various Ad Hoc Commit-tee members and other interested contrib-utors, plus statements and estimatesgathered from technical papers, letters,and telephone conversations, a briefreport has been prepared in an attemptto at least demonstrate the economic mag-nitude of cryogenic fluids. For the pur-

poses of this section of the report, thecryogens of concern at this time areoxygen, nitrogen, argon, hydrogen, and

liquefied natural gas."The report continues in this realistic

fashion and estimates the value of cryogenicfluids. It continues:

Table 3-1

Instruments for measurement, analysis and control:

projections 1973-80(value of shipments in millions of dollars)

SIC Industry 1973 1974 Percent Percentcode increase increase

1973-74 Low High3821 Measuring and controlling

instruments 1,800 1 ,920 7 4.8 6.0

3822 Automatic temperaturecontrols 740 780 5 5.2 6.5

35

"A study of this table indicates that if the

custody transfer of these fluids were in

error by only one percent (present codes

allow two percent), a billing error couldamount to more than 15 million dollars.This point is emphasized in the tablebelow.

"

Year PossibleBilling Error/Yr

1966 $ 2,158,0001971 5,705,0001976 15,372,000

In Section 2.2.2.2, we estimated thatthe total value of flowmeters in servicein 1971 was about $3.1 million. Onecan choose for himself whether or notto divide the figures above by oneanother. If he does, a ratio of between2 and 4 to 1 is obtained.

The report continues on another tack:

"Previous discussion has outlined the econo-mic worth of the cryogenic fluids in termsof custody transfer. However, this is notthe only place where an increased cryo-genic fluid meter calibration certaintywould be desirable. For example, in theaerospace industry an increase in fluidmeter calibration certainty would go a

long way to guarantee engine performance.Present uncertainties in the factorsinvolved in mixture ratio trim causeapproximately a 2% uncertainty in guaran-teed engine performance. Accordingly,guaranteed engine performance is down-graded by 2% in order to insure overallmission success when engine and vehicleare mated. Any decrease in this 2% un-

certainty would raise the mission capabil-lity by some corresponding amount.

"In the case of one oxygen-hydrogen engineunder development, the 3a error in flowmeasurement is 0.433 and 0.541% for fueland oxygen, respectively. The corres-ponding percent error in mixture ratio(3o) is 0.727%, which is clearly a sub-stantial portion of the overall 2%

uncertainty."If a facility were available that could

reduce the flowmeter calibrationuncertainty to 0.2% each, the correspond-ing percent error in mixture ratio (3o)

would be reduced from 0.727 to 0.282%.Hence, the uncertainty in engine perfor-mance is reduced by 0.444%. If the spe-cific impulse of the engine is around 350seconds, the corresponding increase in

engine performance certainty is (350)(0.444%) or 1.56 seconds.

"In the special case under considera-tion, each second of additional guaranteedperformance is equivalent to a 25 lbs in-

crease in payload for a given booster.Accordingly, the improvement in flowmetercalibration assumed here reflects an

increase in payload capability of (1.56)(25) = 39 lbs for a given booster.

"The value of increased flowmeter cali-bration certainty may be reflected in

other ways. The above example indicatesan increased payload capability of nearly40 lbs. This also means that for a givenpayload, the booster has a payload capabil-ity of 40 lbs more than necessary, due to

flowmeter calibration uncertainty. Bydecreasing this uncertainty to the levelsassumed, the booster size can be decreasedby 40 payload-lbs equivalent.

"In a typical system, each pound of payloadrequires some 60 lbs of additionalpropel lant. Decreasing the flowmeteruncertainty means that, in this case, the

booster size could be reduced by (40) (60)= 2,400 lbs of propel lant. Correspondingreduction in tankage, lines, valves,engines, launch facilities, personnel,liquefier capacity, test sites, boostertransportation, etc., occur.

"If the economic worth of cryogenic fluids,the possible billing error to consumers,the improved rocket performance, the

improved regulatory agency relations,the improved customer relations, etc.,are considered, it is safe to assumethat the net value of improved flow

, measurements in custody transfer,diagnostics, and standards is a multi-million dollar per year proposition .

"

Please recall that all of the above is quotedfrom the ISA report.

3.1.3 Social, Human, Person-on-the-StreetImpacts

We have already mentioned in Section2.2.5.1 that 15 Nobel prizes in physics wereawarded for work in or related to cryogenics.While these are hardly "man-on-the-street"impacts, it must be recognized that cryo-genics has had significant impact on basic

research and education, which does affect us

all.

A much more down-to-earth educationalneed involves the plant operators, truckdrivers, police and fire departments. The '

following statements have been collectedto help reinforce this point.

"There is a broad feeling among those

responsible for the measurement of LNGthat much needs to be learned as to the

best methods for measuring and calibrat-ing flowmeters, tank level gauges, and

densimeters. Plans for LNG measurementtechniques and standards, at this

point, are nebulous. It is probably a

36

case in which operating experience is

expected to focus attention on the needfor specific programs in this area by

the operating companies." M. H. November,Potter Aeronautical .

"It is a responsibility of the program of

the NBS to train county personnel in

the proper procedures of inspection."W. Watson, California Bureau of Weightsand Measures .

"— that a committee or organization(possibly such as the CGA) work closelywith the regulatory agencies and cryogenproducers to educate both to the prob-lems and to develop any necessaryguides for product handling and meter-ing." G. C. Nubel , Air ReductionCompany .

"The cryogen producers also need moreinformation for fire prevention codes.This information is needed by thepublic, such as fire department andpolice department officials." W. Spencer,American Cryogenics .

To cite educational needs (almosteveryone agrees to education) is onething, but to meet these needs is another.These needs are not essentially simpleones easily met by bulletins, pronounce-ments, or regulations, but rather they arecomplex ranging from technical and scien-tific down to operational. Some of thesecomplex educational needs include: (1)study of safety practices; (2) educationof police and fire officials; (3) educa-tion of driver-operator in proper proce-dures -- the why and how of these proce-dures, and so forth. Measurements areneeded to help develop educational programs,specify codes, etc., which have the directhuman/man-on-the-street impact.

The point of the cryogenic measurementsystem is to foster and help develop a newtechnology, the infrastructure technologyof cryogenics itself. It is generallyaccepted that such technological innovationcan help us expand our markets at home andabroad, strengthen old industries, createnew ones, and generally provide more jobsin the labor market.

The direction of private technologicalactivities is determined in large measure bythousands of private decisions -- and thisshould always be the case -- but we cannotignore the fact that federal policy, such asundergirding a new technology, also has a

profound effect upon what happens in theprivate sector.

3.2 Status and Trends of the System

Several special studies have been preparedto characterize the cryogenic measurement

system (See Section 4.5.1).The Overview . Two overviews have been

made to document the infrastructure positionof cryogenics in large national programs(space, health, transportation, etc.) and toidentify leading indicators of trends of thehealth of cryogenics.

Applications for Specific Customers . Oncethe network of cryogenics in technology as a

whole had been defined and tested, it wasuseful to look at specific functional rela-tionships between terminals in that network,or the leverage of cryogenics in specificapplications. Such studies were made on theapplication of cryogenics in atomic energyprograms, transportation, biology, and waterpollution abatement.

Applications to a Specific National Need -

Energy . Technology assessments have beenprepared in three energy areas -- LNG, hydro-gen, and superconductivity.

Analysis of Major Technical Threats .

Since cryogenics is a rather well bounded andself contained technology, it is not likelyto be replaced by a competing technology.The principal threats are from among therivals within the technology itself, as fromabroad. Two foreign technology assessmentshave been made.

Analysis of Major Technical Barriers . Thequestion of reliability and cost is alwaysraised whenever a commercial application ofcryogenics is suggested. Accordingly, a

survey of the state-of-the-art of commercialrefrigerators was first published in 1969 andupdated in 1973.

Analysis of Major Technical NewOpportunities . Assessments of cryoelectro-nics, superconducting engineering and thecommercialization of cryogenics have alsobeen prepared.

The synthesis of these studies is that themajor developments in cryogenics in the nextfew years that will have significant impacton the technology of the country and its

balance of trade are the widespread inter-national use of liquefied natural gas

potential uses of hydrogen, and applicationsof superconductors. These developmentsare a result of the national sense ofurgency regarding energy problems and theestablished trends toward the uses of: (1)liquefied natural gas to meet local peakenergy requirements (peak shaving) and toaccommodate the transportation of naturalgas in the dense cryogenic form; (2)

liquid hydrogen as a potential syntheticfuel of the near future; and (3) super-conductivity in applications for electricpower generation, transmission, and storage.The cryogenic measurement system mustrespond with design data, metrology, andrelated applied cryogenic research.

37

Along with this "commercialization" ofcryogenics comes a new role that giveseven greater leverage to the measurementsand data, and which is one way to assurethe effective transfer of measurementsinto the hands of the users. This newrole is a partnership between cryogenicsand the regulatory agencies. For in-

stance, results of the NBS flowmeteringprogram (e.g., tolerances and basic prop-erty data) have been adopted into NBSHandbook 44 as a result of cooperativework with the states of California and NewJersey. The Maritime Administration andthe U.S. Coast Guard are interested in

new, inexpensive, but safe materials forseagoing tankers. The Federal PowerCommission (FPC) needs cryogenic mea-surements and data on the cryogenic safetyand design aspects of current applicationsbefore the FPC for authorization of LNGterminal and storage facilities. Under-lying and supporting each of the specifictechnologies of LNG, hydrogen, and super-conductivity is the necessity of: (1)establishing and providing an informationbase for cryogenic measurements and prop-erties of materials at low temperatures;and (2) characterizing the behavior ofmaterials at low temperatures by definitivestudies involving mechanical, thermal, andelectrical property measurements. Some ofthe strengths and weaknesses of the currentcryogenic measurement system are describedbelow.

Liquefied Natural Gas (LNG) . Over 30percent of the basic energy supply in theU.S. is provided by natural gas. Thedemand for this relatively inexpensive,ecologically satisfactory fuel has sub-stantially exceeded the domestic supply.Even with responsible conservation anddevelopment of alternative sources, largequantities must be secured not only throughforeign importation, but also from Alaska,by 1985. Domestically, major facilitieshave been established in large populationcenters to permit peak shaving and redistri-bution. These large scale applications re-

quire handling the natural gas in liquidform. New measurements and data are re-

quired, to permit the U.S. to participatesuccessfully in domestic and imported lique-fied natural gas programs in order todevelop; (1) advanced concepts, (2) environ-mental impact statements, (3) regulations,(4) economics, (5) safety, and (6) reliabi-lity. Accordingly, a complete and com-prehensive physical measurement system forLNG needs to be developed.

Today, quantity gaging in storage andship tanks is uncertain and requires accu-racy statements and traceability yet to be

developed. Flowmetering for commoditytransfer and equity in trade has been de-veloped for more conventional cryogens(Handbook 44). An equivalent program forLNG will be unique in conception becauseit will require the integration of massand heating value measurements. Nonethe-less, traceability to national standards(NBS) is already written into existing inter-national agreements (El Paso Gas-Algeriaand Algonquin Gas-Algeria) with little orno technical basis in fact.

Basic measurements of the thermal andmechanical properties of structural mate-rials are the key to realizing the potentialof LNG as a major source of fuel . Forinstance, the fatigue crack growth rate andfracture toughness of many potential con-struction materials have not yet been mea-sured for cryogenic applications. Suchdata are essential to ship construction as

well as to stationary storage of LNG.

Hydrogen . Hydrogen is a prime candidateto satisfy many long-term national (and

international) fuel requirements. It seemsno longer necessary to justify the relevanceof hydrogen fuel research since hydrogen is

a clear contender for the synthetic fuel

market of the future -- only the time scalefor implementation of this fuel is uncer-tain. Its use in the period 1985-2000appears guaranteed. Thus basic measurementsand data are required now.

Priority research elements that have been

identified are: (1) improve hydrogen lique-

faction efficiency, (2) evaluate methods of

recovering liquefaction energy, and (3)

evaluate hydrogen compatible materials of

construction. Longer term priorities includethe development of improved insulation sys-tems and the establishment of instrumentationand measurement methodology for commercialexchange of liquid hydrogen.

Superconductivity . Cryogenic measurementsand data are intimately bound together withthe electrical energy industry through the

application of superconductivity to powertransmission, generation, and storage.All three applications have at least three

problems in common. First, conductorstailored to each of the above areas are

still under development, and their perform-ance depends in part upon the rate of heattransfer to the helium heat sink undertransient conditions. Second, the behaviorof the entire helium refrigerant flowsystem, including responsiveness to instabil-ities must be known (pressure, tempera-ture, and flow rate vs. time). Third,degradation, or aging, of the superconduc-tor may result from the various differentstresses -- thermal, electrical, or mechani-cal -- with long term reduction of system

38

capacity. The problem areas -- refrigerationand superconductor behavior -- are commonto each and every superconducting applica-

tion and at present represent a weaknessin the cryogenic measurement system.

Helium is, of course, the indispensablerefrigerant for all known superconducti-vity technology. The importance of heliumwas recognized in the bill creating the

Energy Research and Development Adminis-tration (ERDA), which directs the Adminis-trator to conduct a study of the potentialenergy applications of helium and to

report his recommendations to the Presidentand the Congress within six months afterthe enactment of this Act. These recommen-dations will concern the management of thehelium program from the standpoint ofnational energy research and development,and will undoubtedly have a profoundeffect upon the future of the cryogenicmeasurement system.

4. SURVEY OF NBS SERVICES

4.1 The Past

Ever since the Federal Government estab-lished the Bureau, NBS has been involved in

cryogenic measurement science and has fre-quently been sought out to settle technicalcontroversies or to solve problems whosesophistication lay beyond the capabilitiesof other agencies.

In fact, the NBS program in cryogenicsitself dates back to 1904 when Congressapproved the purchase of a hydrogen lique-fier exhibited by the British at the St.

Louis world's fair. A somewhat largerfacility was established in Boulder in 1952at the request of the AEC, and ever sincethen, the Cryogenics Division of NBS hasparticipated significantly at the criticalstages of planning and execution of everymajor national program using cryogenics. Abrief historical background follows:

- Established the National CryogenicEngineering Conferences, now in their 20thyear.

- Assisted in the development of thefirst large liquid hydrogen bubble chamber,which won for Dr. Luis Alvarez the NobelPrize in Physics in 1968 and also a commen-dation 'for the NBS team.

- Developed the OP catalyst essential tothe long term storage of hydrogen.

- Produced the first text book in cryo-genic engineering; co-edited the firstjournal of cryogenics and taught the firstcollege accredited course in cryogenicengineering.

- Received the DoC Gold Medal for Mea-surement and Publication of DefinitiveProperties of Hydrogen.

- Assisted in 1970 in the investigationof the cause of the Apollo 13 cryogenictankage failure and helped to establish thebasis of safe redesign.

Thus it is apparent that NBS has providedcryogenic measurements, data, and servicesfor nearly 70 years. The present holdsevery bit as much promise as cryogenicsmatures and finds more and more use.

4.2 The Present Scope of NBS Services

The present scope of NBS services to thecryogenic measurement system is indeed sig-nificant. We have already indicated thatcryogenic measurement and data services areoffered in nearly every field that NBS as a

whole does: conceptual knowledge, instrumen-tation, reference materials, standard samples,reference data, and specifications (SeeSection 1.). Accordingly, it may be moreedifying at this time to illustrate theseservices with our case study, the liquidnitrogen flowmetering program. We shallattempt to illustrate not only the NBSservices, but also their uses and interactionsthrough an Input-Output analysis. Thismatrix is essentially a four terminal networkto describe the flow of information betweenNBS and various users.

Block I is "from NBS to NBS", or InternalInput.

Block II is "from the outside to NBS" orExternal Input.

Block III is "from NBS to the Outside" orExternal Output.

And Block IV, since it describes inter-actions "from the Outside to the Outside"and does not involve NBS per se, appearsto hold little interest for us at themoment.

4.2.1 Description of NBS Services

A description of NBS services should notonly include those services that NBS suppliesto the outside, but to internal users as

well. Accordingly, we shall subdivide thissection into two parts: Internal Inputs--NBS to NBS; and External Outputs--NBS tothe outside.

Internal Inputs: NBS to NBS . This blocki ncludes, for instance (Figure 1 )

:

•The Institute for Basic Standards--whose statutory responsibility toprovide basic measurements and standardsmade the program possible.

•The Office of Measurement Services -

provided guidance on accuracy state-ments, and experiences in conductinground robins.

•Patent Advisor--guidel ines for hand-ling proprietary information on theperformance of specific flow meters.

39

•The Office of Weights and Measures--publishes Handbook 44 and provides thesecretariat to the National Conferenceon Weights and Measures (NCSM). Gaveour program the direction and mechanismto make its results have the effect oflaw.

•Applied Math Division--planning experi-ments for statistical soundness andanalyzing the results.

•Cryogenics Di vision--provided theessential technical base and resources.

For more detail on these Internal Inputs,see Section 2.4.1, especially NBS Infra-structure .

External Outputs: NBS to the Outside .

The analogy has been drawn that basic mea-surements and standards are the "currency"or medium of exchanges in business. Theanalogy may be broadened by recognizing thata currency has no intrinsic value of its

own, but is only as good as the user'sconfidence. The same is true for basicmeasurements and standards.

Standards as the "currency" of science canbe a revealing analogy, for standards are thekey to the commercialization of science.Each scientist works within a self containedsystem using "his" thermometer, "his" balance,and "his" meter, which could be the distancebetween two marks on a barn door, as far as

he is concerned. As long as his measurementsystem is internally consistent, he has no

need to refer to or compare against an ex-ternal set of standards. Only when he stepsout of his system to put his work into generaluse, to gain general acceptance, to put hiswork into circulation, as it were, does heneed to refer to a set of external standards.Basic standards then are not the analog ofcurrency, but are the currency of fact, sincethey are indeed the medium of exchange thatcauses the scientific work to become commonlyaccepted, used, and repeated. Thus, basicstandards are the transfer agent from whichthe benefits of science are derived.

It is a paradox that "basic" has come tomean in the minds of some "undirected" or"exploratory", for indeed the sole need forstandards is to communicate with others. In

this sense, standards provide the dictionaryof tedinology and commerce.

Standards are the means used to judgesomething as authentic, good, or adequate.They are the measures to determine what a

thing should be, or whether it is correct.Thus, there are standards for measurements(property data) for performance (tolerance)and for products (type testing). In thisprogram, these standards were embodied as

"External Outputs" (Figure 2).

•Codes, Standards, and Recommended Prac-tices, such as adopted in Handbook 44.

•Properties Data. The NBS property datafor liquid nitrogen were also adopted in

Handbook 44. See Sections 2.2.1.2 and 2.2.3.•International Conventions. As mentioned

earlier, the Compressed Gas Association wasstrongly motivated to deal with one nationallaboratory rather than fifty state labora-tories. We extended this philosophy on aninternational scale via the lOLM. SeeSection 2.4.1

.

•Performed type testing of meters offoreign manufacture as an integral part ofthe program. (See Tech. Note 624, "An

Evaluation of Several Cryogenic TurbineFlowmeters"

.

)

•Promoted and facilitated many visits byinternational observers. The result of onesuch visit was the direct translating intoGerman of NBS Report 9778, "Cryogenic FlowResearch Facility Provisional AccuracyStatement" to be used as a model by the PTB.

For more discussion, see Section 2.4.1.

4.2.2 Users of NBS Services

The principal users of NBS services, in

the representative sample chosen for illus-tration, can readily be identified by theinputs they had to the program. This may atfirst seem to be a backward approach, but it

is surely the most direct way to identifythose who needed the services the most - namelythose who helped influence and "design"those services. We call these ExternalInputs

.

External Inputs: Outside to NBS . Theprincipal external inputs (Figure 3) came fromregulatory agencies, and trade associations.Their role was fundamental in both initi-ating and guiding the program and was de-scribed in detail in Section 2.2.1.1. Theseincluded the Instrument Society of America(ISA) Ad Hoc Committee on Cryogenic FlowMetering, The Compressed Gas Association,and the State of California. There arethree factors in common between NBS andthese groups that bear further comment.

1. The regulatory agencies need a soundtechnical basis for their codes so that theyare feasible as well as enforceable. TheNBS, having no regulatory authority (and

desiring none), needs the leverage of regu-latory agencies for its basic measurementsand standards to be adopted rapidly anduniformly.

2. Because the NBS has no regulatoryfunctions, our basic measurements and stan-dards must stand on their own merit. Theymust be the best in the country to be accept-ed, for they are not promulgated by law.

40

INFORMATION INPUT - OUTPUT MATRIX

NBS To OUTSIDE

OUTSIDE

INTERNAL INPUT

• IBS

• OMS• Patent Adviser

• OWM• Applied Math Division

• Cryogenics Division

FIGURE 1. Internal input.

NBS To OUTSIDE

NBS

OUTSIDE

INTERNAL INPUT

• IBS

• OMS• Patent Adviser

• OWM• Applied Math Division

• Cryogenics Division

EXTERNAL OUTPUTS• Codes• Standards• Recommended Practices• Properties

• Measurement Techniques

• Correlations

• Literature Services

• MAP• International Conventions

FIGURE 2. External outputs.

41

(The analogy has already been drawn thatbasic measurements and standards are the"currency" or medium of exchanges in busi-ness).

3. Because of our unbiased outlook, theparties involved, each with his own selfinterest or view points, feels free to cometo us as the impartial third party. The ISA

specifically recommended recourse to a na-

tional laboratory. The State of Californiaalso expressed the need for traceability to

a national standard, since they are obligatedby law to perform type approvals. The CGAwas strongly motivated to come to a centrallaboratory, for the alternative was to deal

with fifty state laboratories.Our responsibility lies not only in

providing the competence in advance of need,but also making that aompetenae known toour customer's^ and making it easy for him todo business with us.

4.2.3 Alternative Sources

We offer to the Cryogenic MeasurementSystem essentially every service that NBS as

a whole offers to the entire measurementsystem. Therefore, the list of every actualor potential alternate source is, for all

practical purposes, endless. We have at-tempted to tether such a discussion by

tying it to a specific scenario: namely,what would happen if NBS were to stop its

cryogenic measurement services tomorrow?This scenario is developed in Section 4.3"Impact of NBS Services", especially Section4.3.1.

Here, we shall limit our discussion to

means of identifying user needs possibly notbeing met, and the NBS role vis-a-vis suchneeds. One way to do this is to identifythe Outside-Outside interactions. By def-inition, these interactions do not involveNBS, but perhaps they should.

Outside-Outside Interactions . The input-output functions of Block IV at first do notappear to interest us, for they do notinvolve NBS per se . They include, for in-

stance (Figure 4)

:

Regulatory Agencies - California and NewJersey state weights and measures officialscollaborating on a model code in order to

facilitate trade among their states, as wellas intra-state commerce.

Meter Manufacturers--an instrument makerplanning his flow meter design and distri-bution to conform not only with U.S. conven-tion, but also with that of the PTB, forinstance.

Fluid Producers--especial ly those in

interstate or international commerce.Professional Societies--such as non-

technical policy board meetings of the ISA.

Note that these examples are essentiallynon-technical policy level determinations,and accordingly appear not to be the concernof NBS. But note these common traits.

1. Vantage points of enormous leveragewhere the most fundamental decisions aremade.

2. Opportunities of largest possibleeconomic impact (it is more economical foreveryone concerned to get a code that is

feasible in the first place, rather thantesting and re-writing the code after thefact.)

3. Taken as a whole, they represent the"Industrial Measurement System", a sub-setof the National Measurement System. (Figure5).

This is the arena where decisions are themost fundamental, and where the opportunitiesand problems originate. Accordingly, it is

not only in our sphere of responsibility, butalso in our own interest, to consciously and

systematically monitor and influence thecourse of technology in the political (people),technical, economic, ecological, and socialenvironments. If we are to serve the cryo-genic measurement system adequately, then wemust continuously identify, analyze, evaluateand participate in the transactions occurringin this essential, but sometimes overlookedpart of the measurement system.

4.2.4 Funding Sources for NBS Services

In Section 3.1 we identified the impactof our measurement services, and noted thatin some of the examples given (health,agriculture) the NBS impact had been ratherdiffuse and indirect. In other cases (space

exploration, LNG), the NBS cryogenic measure-ment services were explicit and direct. So

it is with the funding sources for ourservices. Some services result in widepublic benefit, meriting wide public support(e.g., appropriated funds). On the otherhand, where specific beneficiaries can be

identified, then these beneficiaries havepaid, because "full recovery of costs" is

the rule. A few specific examples may provehelpful and are given below.

Cryogenic Flowmetering . We have usedthis specific case study throughout ourmicrostudy to help illuminate general princi-ples. As discussed in Section 2.2.1.1, the

Compressed Gas Association was a specificbeneficiary, and the member companies mostinterested in the problem (see Table 2-2)

contributed funds and helped provide program

definition that allowed the program to

proceed to its ultimate technical conclusion.

Reference Data . Accurate density mea-surements and analytical calculation methodsfor liquefied natural gas are essential to

42

INFORMATION INPUT

NBS To

OUTPUT MATRIX

OUTSIDE

NBS

From

OUTSIDE

NBS

From

OUTSIDE

INTERNAL INPUT

• IBS

• QMS• Patent Adviser

• OWM• Applied Math Division

• Cryogenics Division

EXTERNAL OUTPUTS• Codes• Standards

• Recommended Practices

• Properties

• Measurement Techniques• Correlations

• Literature Services• MAP• International Conventions

EXTERNAL INPUT• National Conference on Weights

& Measures

• Federal Agencies

• Trade Associations

(C6A, AGA)

• Regulatory Agencies

(State, National, International)

FIGURE 3. External inputs.

NBS To OUTSIDE

INTERNAL INPUT

• IBS

• QMS• Patent Adviser

• OWM• Applied Math Division

• Cryogenics Division

EXTERNAL OUTPUTS• Codes• Standards• Recommended Practices

• Properties

• Measurement Techniques

• Correlations

• Literature Services

• MAP• International Conventions

EXTERNAL INPUT

• National Conference on Weights

& Measures

• Federal Agencies

• Trade Associations

(CGA, AGA)

• Regulatory Agencies

(State, National, International)

• Regulatory Agencies

• Meter Manufacturers

• Fluid Producers

• Consumer

• Professional Societies (ASTM)

FIGURE 4. Outside - outside interactions.

43

INFORMATION INPUT

NBS To

OUTPUT MATRIX

OUTSIDE

NBS

From

OUTSIDE

INTERNAL INPUT

• IBS

• QMS• Patent Adviser

• OWM• Applied Math Division

• Cryogenics Division

EXTERNAL OUTPUTS• Codes• Standards• Recommended Practices• Properties

• Measurement Techniques• Correlations

• Literature Services

• MAP• International Conventions

EXTERNAL INPUT

• National Conference on Weights& Measures

• Federal Agencies

• 1 race Associaiions

(CGA, AGA)

• Regulatory Agencies

(State, National, International)

INDUSTRIALMEASUREMENT SYSTEM

• Regulatory Agencies

• Meter Manufacturers

• Fluid Producers

• Consumer

• Professional Societies (ASTM)

FIGURE 5. Industrial measurement system.

provide an unequivocal basis for custodytransfer. These same data provide the basisfor mass, density and heating value measure-ments throughout the fuel gas industry. Atechnical program to meet these needs is

presently underway, funded and guided by a

consortium of 18 energy companies (SeeSection 2.2.3 for technical description).

Hydrogen-Future Fuel . In the fall of1972 the NBS Cryogenics Division NAS-NAE-NRCevaluation panel recommended renewal of a

modest effort on hydrogen fuel technology.The scientific staff responded enthusiasti-cally and a state-of-the-art evaluation wasreleased in the summer of 1973. An economicanalysis of hydrogen-fueled electricalutility systems was published in March 1974,and a benchmark literature bibliography wascompleted in June 1974. The work describedbelow was initiated in July 1973, and effortswere accelerated by support of managementat all levels of the NBS , e.g.. Institute ofBasic Standards Director's Reserve fundswere made available to initiate this study.

The goal of this work is to provideinnovative cryogenic technology so thathydrogen may be liquefied, stored, and dis-tributed efficiently on an unprecedentedscale and with safety and fairness to theconsumer. Specifically, analyses and sum-mary reports were prepared on the following

topics: (1) cost and availability of hydro-gen, (2) hydrogen in the electrical utilityindustry, (3) applications of hydrogen in

transportation, (4) survey of materials for

hydrogen service, (5) instrumentation forcryogenic hydrogen fuel, (6) transmissionand distribution of energy, (7) solar energyliquid hydrogen, (8) industrial applicationsof hydrogen, and (9) hydrogen fuel literature

These analyses demonstrated, among otherthings, that even now hydrogen appearsattractive as an aircraft and aerospacefuel, in certain integrated utility systems(e.g., use of hydrogen to store solarenergy), for transport of energy from nuclearor solar sea power plants and is already an

essential ingredient in a wide variety of

industrial processes (ammonia synthesis,hydrocracking, hydrotreating, and methanolsynthesis). This example was chosen to

illustrate how internal re-direction of

funds by an alert management can quicklyproduce results not otherwise possible.

Liquefied Natural Gas . This presentstudy of the cryogenic measurement system(now in its second year) has helped documentfor us the complete process that must be

undertaken to provide a complete measurementservice. Specifically, our LNG BudgetInitiative submitted in the Spring of 1974

was deliberately constructed to include all

44

three necessary elements: measurementscience, data base, and technology transfer

(includes safety, interstate and inter-

national cooperation, effective use of

Office of Weights and Measures and training).

Thanks (in part) to the National MeasurementSystem study, new work proposals now use the

guidelines so developed to assure a completeand comprehensive approach.

Even though this particular initiativedid not survive the government budget process,we are nonetheless pursuing other avenues of

funding, perhaps even multiple sources, butwith the objective of nothing less than a

comprehensive program. This example waschosen to illustrate the course of a newbudget initiative pf potentially large publicbenefit, which could reasonably be assumedto merit public support (appropriated funds).

Thus the answer to "Sources of Funds forNBS Services" is: "It depends". Table 4-1

gives a more explicit answer.

Table 4-1

Funding by sourcesFiscal Year 1974

NBS PercentDirect appropriation 31

Postdoctoral s 01

Standard Reference Data 03Standard Reference Materials 01

NBS TOTAL 36%

OTHER AGENCY R&DNational Aeronautics and

Space Administration 11

Atomic Energy Commission 05Department of Defense 23Maratime Administration 05Navy 01

Federal Power Commission 02National Science Foundation 01

OTHER AGENCY TOTAL 48%

INDUSTRIAL ASSOCIATIONSAmerican Gas Association 11

International CopperResearch Association 01

Other 01

INDUSTRIAL ASSOC. TOTAL 13%

TESTING, CALIBRATION, SERVICES 03

GRAND TOTAL 100%

4.2.5 Mechanism of Supplying Services

Dissemination mechanisms are as varied asthe services themselves.

Calibrations, and Maps were described in

Sections 2.2.1.1 and 4.2.1 in conjunctionwith the cryogenic flowmetering program.

Reference Data , whether distributed in anunstructured way by individuals, or in a

systematic way by the Cryogenic Data Center,were discussed in Section 2.2.3. Publi-

cations, special bibliographies. StandardReference Data, and several Current Awarenessservices were described there.

Reference Materials were described in

section 2.2.4. These included the StandardReference Materials incorporated in the NBSprogram of that name. Also mentioned was theimportance of corollary reference data andround robins utilizing "uncertified" refer-ence materials.

National trade associations, other federalagencies, and international mechanisms weredescribed in Section 2.4, "Dissemination andEnforcement Network".

These descriptions, while as complete andcomprehensive as possible, nonetheless appearrather sterile compared to actuality. Sup-plying services is never "pure". Usually a

mix of services, e.g., reference data alongwith reference materials, must be supplied toa mix of users, e.g., several laboratories in

a round robin interchange. The cryogenicflowmetering program serves well again as an

example of the mechanisms required in prac-tice.

Figure 6 illustrates the truly staggeringnumber of mechanisms for supplying servicesthat came into play. Note for instance:

Regulatory Agencies--StateRegulatory Agencies--ForeignProfessional SocietiesIndustrial Meter Manufacturers--DomesticIndustrial Meter Manufacturers--ForeignIndustrial Producers--DomesticIndustrial Producers--Foreign.

Specific detail is given in Figure 6.

4.3 Impact of NBS Services

We shall attempt to examine the impact ofNBS services by following a specific scenarionamely, what would happen if NBS were to stopits cryogenic measurement services tomorrow?For this approach, we are indebted to Pro-fessor Charles Howe, who is Chairman of theEconomics Department at the University ofColorado. Professor Howe is a consultant to

the State Legislature of Colorado and his

specialty is establishing criteria for publicsupported programs. He has served as a

consultant in this capacity to Ghana, Kenya,Botswana, and lately to the Cryogenics Divi-sion of NBS.

We shall try to follow this scenario downtwo roads, one leading to the potentialeconomic impact; the other to the techno-logical impact.

4.3.1 Economic Impact of Major User Classes

One possible scenario is that cryogenicswould simply disappear. We believe, however,that cryogenics is here to stay; we haveshown that it is an infrastructure technology

45

NBS

Institute for Basic StandardsPatent AdvisorOffice of Measurement ServicesApplied MathematicsMechanicsQuantum ElectronicsElectromagneticsCryogenicsInstrument ShopsPlant DivisionOffice of Weights and MeasuresElectronics Technology

Regulatory Agencies - State and Federal

Office of Weights and MeasuresFederal Power Commission

T"

U.

—

H

Federal AgenciesNational Aeronautics and Space AdministraUnited States Air ForceAtomic Energy Commission

Industrial Trade AssociationCompressed Gas AssociationAmerican Gas Association (AGA)Pipeline Research Committee

Cryogenic Flow Research Facility

NBS

Institute for Basic StandardsPatent AdvisorManagement and OrganizationCryogenicsOffice of Weights and MeasuresConference on Weights and MeasuresElectronics Technology

Regulatory Agencies - StateCal iforniaColoradoNebraskaWyomingConference on Weights and Measures (50 States)

Regulatory Agencies - ForeignPhysi kal isch-Techni sche Bundesanstal t.

West GermanyMinistere de la Consommation et des

Corporations, Canada

Professional SocietiesAmerican Inst, of PhysicsAmerican Society of Mechanical EngineersInstrument Society of America

—J

1

—I

._L_

Industrial - Meter Manuf. - DomesticBrooks Inst. Div. Emerson Electric Co.

Daniel IndustriesEastech Inc.

ITT BartonFoxboro CompanyLiquid Controls Corp.

National Cylinder Gas, Division of

Chemetron Corp.

Union Carbide Corp. - Linde DivisionRockwell Meter Co.

Industrial - Meter Manuf. - Foreign•

IBritish Oxygen Company - London, England

1 1 Compagnie des Compteurs - Paris, FranceLinde, A.G. West Germany

Industrial - Producers - ForeignBritish Oxygen Co., LondonL'Air Liquide, Paris

Linde, A.G., West GermanyMesser-Griesheim, West Germany

Industrial - Producers - DomesticAir Products and Chemicals, Inc.

Air Reduction CompanyAmerican Cryogenics, Inc.

Burdette Oxygen CompanyNational Cylinder Gas, Division of

Chemetron Corp.

Liquid Air, Inc.

Liquid CarbonicMesser-GriesheimUnion Carbide Corp. - Linde Division

FIGURE 6. Liquid nitrogen flow program interactions.

46

that is used wherever it is more economical,

or wherever it permits some higher level of

performance. Accordingly, every user of

cryogenics would create his own in-house

competence a piece at a time. It follows

that:

Such redundant facilities and data

gathering would likely cause expensive and

slow response to national needs, while at the

same time wasting national resources .

It seems inevitable that such duplicateefforts would produce inconsistent designdata which would prevent both process opti -

mization and safety evaluation . The corrolaryquestions are: "Who is right?"; "Where is

the arbiter to judge, and how does he decide?".

It is argued by some that while propri-

etary data of a basic nature may give its

owner' a slight edge for a short time, keepingdata proprietary may sometimes impede national

technological advancement and hence our abi-

lity to compete successfully in international

trade .

In the absence of a centralized effortsuch as NBS provides, arbitrary or evenconflicting standards could be adopted,leading to questionable practices in custodytransfer and in safety evaluation . If a

free enterprise economic system is to survivein a modern industrial society, buyers and

sellers in the marketplace need to have as

much confidence in the quantity and performanceof goods exchanged as they do in the amountof moneys paid.

The government would find itself in theconflicting role of trying to regulate thevery technology it is trying to promote .

A vague technical base inhibits bothcompliance and regulation , no matter howwell-meaning or good intentioned eitherparty may be.

If there were no centralized effort,both government and commerce would findthemselves with a generally unsatisfactorybasis for decision making and impartialjudgments

.

The key to impact of NBS services appearsto lie in their centralized, coordinatednature. Our legislative mandate does indeedcall for us to provide a base for a nationalsystem of measurement, and to furnish essen-tial services. The congress has also wiselychosen language that calls for us to coordi-nate that system as well. Perhaps it canbest be summed up that "no coordinatedeffort" would lead rather shortly to dis-cordant and hence wasteful national programs.

4.3.2 Technological Impact of Services

Let us continue our scenario of:

"What if NBS were not involved? Whatwould happen if we stopped cryogenictechnology tomorrow?" There would be no

ready acceptance, no preferred alternative,and no centralized national effort. Whilethis is true, it is neither very helpful norvery satisfying. We would like to be morespecific and I believe we can be, by lookingat some specific technological examplesillustrating the points made above.

Redundant data/facilities cause expensiveand slow response to national needs . Thecryogenics measurement system is suppliedreference data by many experimental systems.One of these is our Pressure-Volume-Tempera-ture system for the thermodynamic propertiesof fluids, which was built up over many yearsby the National Aeronautics and Space Admin-istration and NBS at a cost of approximately$1.6 million. If it did not exist, somethinglike it would have to be built up many timesover by every user who needs the data; andoperated by scientists relatively "low" onthe learning curve. As it is, it is avail-able for any priority work regardless of its

origin. It is, in fact, being employed nowto produce industry wide data on LNG for theAGA.

Inconsistent design data prevents optimizationand evaluation . Many times NBS has beencalled upon by the government to evaluateefficiency claims and production capacitiesprojected by "paper studies". A complete and

consistent set of design data is essential to

this purpose. The National Aeronautics and

Space Administration, for instance, specifiesthat NBS data be used in its proposals toprovide a common, sound basis for evaluation.Similarly, NBS recommendations to the FPC

would be open to question if it were not forour sound foundation of valid, consistentdata.

Arbitrary/confl icting standards : question-able custody transfer and safety evaluation .

The State of California, frustrated by theirlegal requirement to regulate the sale ofliquid nitrogen, but with no technical backup,were forced to set arbitrary standards.Specifically, they set the same standard forliquid nitrogen as was then in force forgasoline. The suppliers demanded a technical

demonstration of the feasibility of thesestandards. This impasse was resolved by the

NBS liquid nitrogen flow program. The pro-ducers benefited dealing with one central

laboratory rather than 50 separate statelaboratories. The states benefited by not

having to construct 50 times over such a

complex cryogenic test facility. The publicbenefited by the rapid proof and adoption ofthe codes. As mentioned, we feel that this

is a practical realization of the "NewFederalism" at work - as NBS competence wasdirectly transferred to the states.

47

Conflicting government role : regulate/pro -

mote technology . The federal government hasoccassionally found itself in the awkwardposition of attempting to regulate and pro-mote a technology at the same time. Theeffective and safe use of atomic energy is

perhaps such an example. Recently, theAtomic Energy Commission as such was abolish-ed the regulatory functions assigned to a

new commission, and the technology advance-ment functions assigned to a separate energydevelopment agency.

The National Bureau of Standards, havingno regulatory function, is free of this typeof mission conflict.

Vague technical basis inhibits both compli -

ance and regulation . A liquefied natural gasexplosion in 1944 was not only the worstdisaster in Cleveland's history, but it alsohelped to set back the use of LNG for 20 or30 years.

One hundred and thirty-one persons werekilled when one of the LNG tanks failed fromlow temperature embrittlement/fatigue.Neither the plant builders and operators northe public safety agencies had an adequatetechnical basis (the properties of 3-1/2%nickel steel, in this case), although bothwere conscientious in their respectivetasks.

Unsatisfactory basis for decision making/ -

impartial judgment . Because of the enduringenergy shortage and the great potential ofhydrogen as a future fuel, a large number oflaboratories, both public and private, havemoved speedily to verify the feasibility ofhydrogen as a fuel, e.g., numerous graduatestudents have converted automobile internalcombustion engines to run on hydrogen gas.While this has been interesting and hasattracted a great deal of attention, we havepreferred to produce a benchmark study thatwill be used as th_e technological base forall further programs of any agency or uni-versity on hydrogen: future fuel. Thisreport will do much to remove most of thespeculation from this area and to provide a

sound and common basis for decision making.

4.3.3 Pay-off from Changes in NBS Services

Services provided to the National Measure-ment System for cryogenics will always beembodied in measurements, data, and technology;but the thrust of the effort may change withtime.

As mentioned, major developments in thefield of cryogenics are occurring at threedistinct regions of the cryogenic tempera-ture scale, namely: 110 K (liquefied naturalgas), 20 K (hydrogen: future fuel) and 4 K

(superconductivity technology). Thesetrends are not only valid, but also aretaking on added significance in the light of

48

the national commitment and sense of urgencyto achieve a greater degree of nationalenergy self-sufficiency in the near timeframe.

These trends represent our best informedjudgment of our prime teehniadl opportunitiesfor service over the next five years. In

addition, largely as a result of this presentstudy of the National Measurement Systemoperational opportunities are emerging.The historical role of cryogenics at NBS has

been one of technical problem solving tocomplement the monolithic mission of othergovernment agencies (e.g.. Atomic EnergyCommission, National Aeronautics and SpaceAdministration), and we continue to lookforward to this exciting and mutually bene-ficial partnership. We now see another roleemerging that gives even greater leverageto our measurements and data, and which in-deed assures the effective transfer of mea-surements into the hands of the users. Thisemerging role is a partnership with the re-rulatory agencies. For instance, the resultsof the flowmetering program (e.g., toler-ances and basic property data) have beenadopted into NBS Handbook 44 as a result ofour cooperation with the states of Califor-nia and New Jersey. A metals combustionprogram resulted from an initial Departmentof Transportation request following anoxygen tank truck disaster in Brooklyn.Much of the present LNG program came frominterests by The Maritime Administrationand the U.S. Coast Guard in new, inexpen-sive, but safe materials for seagoingtankers. Consultation and advisory servicesare provided to the Federal Power Commissionon the cryogenic safety and other technicaldesign aspects of several current applica-tions before the Federal Power Commissionfor authorization of LNG terminal and storagefacilities.

Table 4-2 shows how the beneficiaries ofour outputs are expected to change as a

consequence of the trends mentioned above.Some of the reasons behind the expected

changes shown in Table 4-2 are:

•Services to specific manufacturingfirms will increase, reflecting the fact thatcryogenics in general and superconductivityin particular are coming of age. Morepractical devices and instruments, such as

SQUID'S, will be manufactured.•Interaction with the service industries

will also increase as we interact more withthe public energy utilities (hydrogen fuel,LNG, applied superconductivity).

•We have little direct measurementcontact with the consumer per se , and expectno significant change. Contact will con-tinue to be made through service industriesand regulatory agencies.

Beneficiaries of Outputs

directly to specific manufacturing firms

or industries

directly to specific service industries

directly to the individual consumer

to the Defense Department

to Federal regulatory agencies

to State government needs

to other Federal government agencies

to other NBS groups

to university research and other researchat the frontiers of science

Table 4-2. Distribution of effort

Percent of Cryogenics Division Total EffortCurrent 5 years from now

8% 10%

5%

n30%

2%

1%

43%

5%

5%

8%

1%

33%

5%

3%

30%

5%

5%

• Direct support of the Department of

Defense mission will continue, reflectingthe fact that the Department of Defensesupports about half of all research in thiscountry [38] and that the first practicalapplications of superconductivity will

probably be to Department of Defense needs.

•Both federal and state regulatory needswill grow. The federal interest (FederalPower Commission, Coast Guard) will be in

the safe and efficient handling of cryogens.The State's interest lies primarily in

effective metering, sale and taxation ofcryogens.

•Non Department of Defense agencies willshow a decline of the total, primarily dueto the growth of the regulatory agencies.

•"Other" will remain small and constant,as instruments become standards and as

conceptual knowledge is developed to thepoint of useful research.

4.4 Evaluation of NBS Program

4.4.1 Evaluation Criteria

Needs for NBS services to the cryogenicmeasurement system fall into two majorcategories: those determined by our ownstudies and initiatives, and those broughtto our attention otherwise, such as sugges-tions from within other units of NBS orrequests from other agencies, both federaland state. In any case, however, a similardecision process is made, carefully account-ing for a balanced program, internal capa-bility and facilities, staff wisdom, and thepromotion of the mission and functions ofInstitute for Basic Standards and NBS.

Programs in support of these needs, whetherfunded by direct appropriation or by transferof funds from other agencies, must be chosenfor the same basic reasons. The Congress has

wisely chosen a statement of the Bureau'smission broad enough to allow the Bureau to

respond to changing needs. By the sametoken, such a freedom of choice demands of us

a continual appraisal of the most importantproblems to tackle. Of the criteria forchoice, and therefore for action, four seemto be vital to success:

•Needs in Relation to Mission (what is

the relevance on either a long or short rangebasis?)

•Technical Opportunity (is it timely totake on a new program; is there a good idea?)

•Resources (can we bring enough manpowerand money to bear on the problem to ensure an

adequate contribution?)•Leadership (is there an energetic "ball-

carrier" who wants to do the job?)

Unless all four criteria are met, any problemthat is tackled is not likely to have strik-ing success.

However, there are three characteristicsof our other agency work that do set themapart from our own, and these evolve in thefollowing way:

•We wish to promote the efficiency ofgovernment through effective utilization offederal laboratories. When approached forhelp by another agency, we consider what theywould have to spend to achieve our existingcapabil ity.

•The applied measurement programs ofother agencies give our staff practicalexperience with problems in the field, andthereby automatically enhance the relevanceof their work. We give priority to problemsthat add to our capabilities to carry out ourprimary statutory functions.

•We provide technical assistance to

agencies that issue regulatory standards.The appropriateness and fairness of the tests

49

and measurement standards that define suchregulations are critically important to fairand rational management of the Nation'stechnology.

If further consideration is warranted, weproceed through checklists (sometimes for-

mally and documented, sometimes informally)that include at least the following criteria:

Evaluation Criteria - External

•Appropriate federal role?^

•Match to NBS mission•Potential high impact•Leverage of NBS measurement and data

services on given sectors ofthe economy

•Importance of these services to fieldsother than immediately representedby measurements and data

•Importance of these fields within the

scope of national priorities•Absence of alternative institutions who

can provide this information

Evaluation Criteria - Internal

•Utilize unique facilities, competences,and staff wisdom

•Maintain and strengthen staff competence•Provide scientific and technical exper-

tise to NBS programs•Provide Institute for Basic Standards

and NBS programmatic coherence•Implement long-range strategic plan

Admittedly, these are only qualitativeguidelines, but since the process is iterativeand open to discussion over a period oftime, some arguments begin to take on weightand become demonstrable while others do not.

For instance, a "must" is that the programbe somehow quantifiable -- that it havemilestones for measuring progress versusplans. The decision is ultimately the linemanager's responsibility, and he must bearthe consequences. We find the above guide-lines invaluable and useful. They areespecially useful as tie points to tetherthe arguments and to make the decisionprocess open and visible.

^ This is of course, a most vexing question.Guidance is found in the NBS and Institutefor Basic Standards mission statements,several NBS internal Policy Guides, and Ad-ministration interest. Guidance is alsofound in the following statement by a pre-vious administration: "The legitimateobject of government is to do for a communityof people whatever they need to have done,but cannot do at all, or cannot so well dofor themselves, in their separate andindividual capacities". (A. Lincoln, Spring-field, Illinois, July 1, 1854).

The final key to our program evaluationis how well the proposed program fits theDivision strategic plan. This strategic planis established by the cooperative action ofsenior technical staff. Institute for BasicStandards and NBS management, and the Evalu-ation Panel. Planning is, of course, a con-tinuous process, but this strategic plan is

formally documented and articulated annuallyin the Division's Planning and BudgetingDocument (usually prepared each fall in

time for the annual Evaluation Panel meeting,and the initiation of the budget cycle).

In this part of the evaluation process,it is important to realized that both the

plan and the program are tested. Sometimeswe do modify the plan to fit the program,but if so, we try to do this consciously andsystematically, to be fully aware of why the

strategic plan needed changing and what the

consequences are.

4.4.2 Evaluation Panel Role

The Evaluation Panel always plays an im-

portant role in this evaluation process.

The background and affiliation of the membersare perhaps more germane to this presentdiscussion than the names of the membersthemselves. The affiliations of the Panel

members over the last few years (1975 backthrough 1970) are given below:

Department of Physics,University of Pennsylvania

San Diego Gas & Electric Co.

Mechanical Engineering Department,University of California,Lawrence Berkeley Laboratory

Department of Physics,University of Connecticut

Director, Superconductivity and CryogenicsPrograms,

Westinghouse Research Laboratories

Controlled Thermonuclear Reaction,Lawrence Livermore Laboratory

Department of Chemical Engineering,University of California

Department of Mechanical Engineeringand Applied Mechanics,

University of Rhode Island

Los Alamos Scientific Laboratory

The Evaluation Panel is charged with both

broad and specific responsibilities. The

Evaluation Panel

:

•Provides Bureau management assistancein planning

•Considers importance and relative

priority of projects

50

•Makes recommendations on new programinitiatives

•Identifies areas of redirection•Provides forum for technical staff

•Identifies barriers to progress

•Provides communication link with scien-

tific and industrial organizationsWe find the Panel especially valuable in

evaluating our strategic plan and promoting a

certain degree of discipline in exposing our

programs to critical review and evaluation.

4.4.3 Why NBS?

In Section 4.3, we discussed the impact of

NBS services and gave some specific examplesof the consequences of not providing thoseservices. In this Section, we shall examinesome of the factors that help make the NBS

role crucial

.

Part of the reason is historical. NBS has

supplied data and services to the cryogenicmeasurement system for nearly 70 years (see

Section 4.1). As a result, we have developedunique capabilities -- not just in facilities,but more importantly, in staff experience --

a resource difficult, if not impossible, to

duplicate elsewhere.Industry values the third party indepen-

dence and integrity of NBS, i.e., our im-

partial judgment. Companies and industrialassociations frequently plead with us toestablish a first line measurement competencein their technical area, even though they mayalready have competent research laboratories.Those industries who know they have an excel-lent product want their customers to be ableto make accurate and objective evaluations ofthat product. If their own product claimsare based on measurements traceable to NBS,customer confidence is enhanced. This is

important also in foreign trade, for theBureau is regarded as highly abroad as it is

at home. We call it neutrality and acceptance;"neutrality" in the sense of an independentthird party; and "acceptance" in two ways.Not only does the integrity, competence, andindependence of NBS often lead to the ready,universal acceptance of our work, but also weare able to accept proprietary data in con-fidence, which often facilitates the processof objective technical review and evaluation.

Providing a fast and timely response is

possible in part to this ready acceptance.NBS is also able to respond rapidly andcredibly because of the experienced staff,having diverse backgrounds, which is avail-able to assist in problem solutions requiringmany technical disciplines (as in the Apollo13 and Staten Island LNG incidents).

NBS alone has the charter to provide bothnational standards and international standardsthrough the aegis of the Treaty of the Meter.

The federal role of NBS is to provide thebasic measurements, data, and standards thatare required to support and enhance a diversenational technology --the infrastructuretechnology of cryogenics itself. NBS doesthis in part by providing a sound technicalbasis for regulations that will stand up in

court. NBS was established by the Congress to

be helpful, and this assigned function is a

critical link between the basic researchcommunity and those who have to put scienceto work.

The coordination of such a nationwideeffort as this is best centralized so thatthe Nation can have a strategic and inte-grated program rather than a piecemeal one,and can further benefit from the synergismthat naturally occurs in a centralized,coordinated effort.

These principles are the lifeblood of theNational Bureau of Standards and are stronglyand deeply felt by each and every one of theCryogenics Division's professional staffmembers, just as they are by every member ofthe NBS as a whole.

Table 4-3 summarizes the crucial role ofNBS. (See page 53).

4.4.4 Program Evaluation

"We judge ourselves by what we feel capable

of doing; others judge us by what we havedone." Henry Wadsworth Longfellow.The previous sections have described the

evaluation process; the following gives the

results of that process, in particular, thejudgment of the Evaluation Panel appointedby the National Academy of Sciences/NationalAcademy of Engineering/National ResearchCounci 1

.

The members of the Evaluation Panel are

chosen by the above associations for re-

cognized scholarly competance. The membersof the 1973-74 panel were: Donald N.

Langenberg, Chairman , University of Pennsyl-vania; Paul L. Hathaway, San Diego Gas andElectric Co.; H. Paul Hernandez, Universityof California; John L. Mason, The GarrettCorporation; John M. Prausnitz, Universityof California; Clyde E. Taylor, LawrenceLivermore Laboratory.

The following material quotes the summaryand general conclusions of the 1973-1974report.

"Summary

"The Cryogenics Division's coupling withoutside client agencies, industries, andassociations is good, though more effortshould be made to achieve visibility atthe highest managerial levels of theseorganizations

.

51

"The Panel believes that all three of

the Division's new program initiativesare timely, relevant, compatible withthe Division mission and goals, andworthy of support. On the basis of the

irmediaay of the problems beingaddressed, rather than long-term impor-

tance or quality, the Panel ranked the

initiatives as follows: (1) LiquefiedNatural Gas Technology, (2) Cryotech-nology for Superconducting Equipment,and (3) Hydrogen: Future Fuel. Withineach initiative, portions of relativelyhigher or lower priority were identi-fied and discussed.

"General Comments

"The Division's technical and managerialcompetence remains high. With the

possible exception of certain aspectsof its Liquefied Natural Gas (LNG)

Program, it maintains a good balancebetween work related to its essentialbasic-standards mission and work that

responds to national problems, such as

the energy crisis. Even in the latterarea, the proposals and activities areclearly within the basic mission of

the Division."The Division effectively maintains

close coupling with its counterpartindustries and industrial associations.Because these interactions are essentialand contribute to the Division'ssuccess, they must be continued andenhanced. The Division is well-knownat the operational level in industry.

However, the Panel does not believe thatU.S. industrial leadership at the vice-

presidential level is aware enough ofthe Division's capabilities in trouble-shooting and contributions to

engineering research. It is to the

Division's advantage to ensure thatthose individuals who are in a positionto influence policy in government and

in industrial research foundations know

about its industrially important activ-ities and well-earned internationalreputation. Accordingly, the Panel stronglyrecormends that the Cryogenics Divisionconsider ways to increase its visibilityin general and especially in high-levelindustrial management circles.

"An important Division contributionoutside NBS has been its consultativeservices to industry and other govern-men.t agencies. The Panel urges that as

many permanent technical staff,including its younger members, as

possible participate in this activityas a means of ensuring continued

effectiveness and achieving more generalrecognition of the importance of this

facet of its work."

The 1974-1975 panel members were DonaldN. Langenberg, Chairman , University of

Pennsylvania, Paul L. Hathaway, San Diego

Gas & Electric Co., H. Paul Hernandez,Lawrence Berkeley Laboratory, Paul G.

Klemens, University of Connecticut, JamesH. Parker, Jr., Westinghouse ResearchLaboratories, Clyde E. Taylor, LawrenceLivermore Laboratory.

The following sections are quoted directlyfrom the panel's 1974-1975 report:

"THE ROLE OF NBS IN CRYOGENIC TECHNOLOGY

"The Panel was informed that the involvementof NBS (primarily through the Cryogenics

Division) in cryogenic technology is some-

times questioned. The rationale for such

questions is apparently that, since cryo-

genic technology is a primary concern of

a variety of private-sector institutions,many of the cryogenic programs currentlyin progress within NBS might better be

carried out in these institutions.

"It is the view of the Panel that the currentactivities of the Cryogenics Division in

the area of cryogenic technology are en-

tirely consistent with the goals and

purposes of NBS and should not (and in

many instances could not) be left to

private sector institutions, particu-larly when the independent position and

the high quality of the Division's workis recognized.

"Let us consider some examples:

"A. Liquefied Natural Gas (LNG). The Cryo-

genics Division is studying the thermo-

physical properties of pure componentsand of mixtures of the components of

LNG. The purpose of this work is to

develop the basic reference data and

measurement techniques required to assure

equity in the handling and transfer of

LNG, an activity which is rapidly be-

coming a major factor (billions of

dollars) in our fuel importation in-

dustry. The assurance of equity in

trade and certifiable measurement of

trade quantities is sel f-evidently an

NBS function. If the LNG industry were

to assume responsibility for this program,

it could do so only be replicating,

probably several -fold and at consider-

able cost in time and money, the uniquefacilities and expertise already in

existence in the Cryogenics Division.

We would then have one party to commerc-

ial transactions specifying reliability

of the measurements involved, or two

52

parties in conflict over the applicabilityof different measurement systems. This

is just the sort of thing it is NBS's

function to avoid. That all of this is

fully recognized by the LN6 industry is

evidenced by the fact that it is providingmajor funding for the NBS program throughits trade organization, the American Gas

Association."B. Cryogenic Materials. The Cryogenics

Division is studying the mechanical and

electrical properties of a wide varietyof materials for use in cryogenic en-

vironments. The purpose here is to

develop bench mark data for use in design,

a function which could be carried outelsewhere only at considerable cost in

duplication and general credibilityand acceptability. Here again, the

special capabilities of the CryogenicsDivision are recognized in fundingsupplied by the Advanced Research ProjectsAgency and the U.S. Maritime Administra-tion.

"C. Cryoelectronics. Several divisions ofNBS are engaged in developing applica-tions of superconducting electronics.Here the primary and immediate importwill be on the Bureau's own needs forprecision measurements and standards.There simply is no other institutionwhich is in a position to supply thetechnology needed for these special needs.

"D. Properties of Cryogenic Fluids. TheCryogenic Division has provided a uniquepublic service in acquiring availablephysical properties data, in performingexperimental measurements, and in for-mulating these data for use in thermalcomputations for such fluids as helium,hydrogen, nitrogen, methane and the like.The integrity of their work is recognizedworldwide and has led to the broad accept-ance of this basic data."

Evaluation Summary . Each year, thePanel is charged with specific responsi-bilities in addition to its overall duty,and accordingly, the response each yearcenters about a different theme. Nonethe-less, some general conclusions may bedrawn from the above reports. Others judgeus as having good coupling with our out-side clients; having a timely, relevant andbalanced program; maintaining high technicaland managerial competence; and making animportant contribution through our consul-tation services. Our special capabilitiesare recognized in funding supplied bycounterpart institutions. We ai^e criticizedfor having poor visibility at high levelmanagement circles. Correcting the latterdeficiency could add leverage to our work.

On the whole, this outside review of ourprogram is rather favorable.

Table 4-3. The crucial role of NBS

• Federal Role- Need for data and services to accom-

plish a specific government function,such as health and safety regulation

- Importance of these data and serviceswithin the scope of national priorities

- Leverage of NBS data and services on

a given sector of the economy

•Diverse National Need- Lack of direct incentives to a singleorganization to perform the "services"needed

- Diffuse benefit--high risk, low gain- Multiple beneficiaries

•Provide National Standards- Model established: measurement develop-ment, plus transfer of technology

•Impartial Judgment- Neutrality- Acceptance

•Unique Capability- Unique NBS capability in equipment,

facilities, personnel, or experience- Past success; acceptance- Experience in related fields

•Fast Response Time- Ability to respond rapidly and credibly

to a recognized need

•Technology Transfer- Needs identified by cryogenic community;

well identified needs; well documentedsuccesses

•Preferred Alternative- Absence of alternative institutions who

can provide this information- Mission orientation

•Acceptance- De facto standards of measurement, of

quality, of performance, and of prac-tices

•Coordinated National Effort- Importance of these data and services

to fields other than those requestingthe data

- Other agencies conjoined; synergism

4.5 The Future

We have indicated that cryogenics is

largely an infrastructure technology. It is

by and large hidden from the casual observer,while at the same time occupying a centralposition of great potential leverage on theNation's essential science and industry. The

53

cryogenic measurement system is in turn, aninfrastructure of cryogenic technology.Therefore, to anticipate the needs of the

future, it is necessary to assess the stateof cryogenic technology itself and the stateof the measurement system within that tech-nology. Such assessments are carried outperiodically and systematically. The frame-work of the studies is discussed below.

4.5.1 Technology Assessments in Cryogenics

Overview . As mentioned briefly in Section3,2, two overviews were made at the division-as-a-whole level to document the infrastruc-ture position of cryogenics in large nationalprograms (space, health, transportation,etc.) and to identify leading indicators oftrends of the health of cryogenics.

The first, "Cryogenics and National Goals",

[39] was in 1968. At the height of the spaceeffort, it predicted the demise of thatprogram, its need for hydrogen technology,and foresaw the growing importance of a

practical helium technology and LNG as a

fuel. It is perhaps interesting to note thatthe Oil and Gas Journal at that time saidthat "The U.S. is not generally regarded as

an energy starved nation, and imports of LNGwill never be significant."

The motivation for the second overview,"Trends in Cryogenic Fluid Production in theU.S." [40], was to verify and update thefindings of the first. It seemed importantto let a little time pass, and then test thestructure and underlying assumptions of thefirst benchmark study. It was an experi-mental check of the 1968 study and diddocument the critical supporting role cryo-genics plays in essential national indus-tries.

Applications for Specific Customers . Oncethe network of cryogenics in technology as a

whole had been defined and tested, it wasuseful to look at specific functional rela-tionships between terminals in that network,or the leverage of cryogenics in specificcustomer applications. Four such studieswere formally done and published.

"Superconductivity Programs of the AEC"

[41], predicted the need for efficientcooling of long lines to helium temperaturesfor power transmission. There are now fourmajor research groups involved in the develop-ment of just such superconducting powertransmission lines in the U.S. Precisemeasurements (especially pressure measure-ments) are crucial to achieving the effectivecool-down of such long lines.

"Superconducting Levitation of High SpeedVehicles" [42], was prompted by need of theDepartment of Transportation to decide betweencompeting levitation technologies, such as

the floating of trains above a track on anair cushion, or supporting it on magneticcushions that may or may not use supercon-ducting magnets. This study documented theprecise role of cryogenics in high speedground transportation and proposed severalpossible ways to anticipate and resolvepotential cryogenic measurement problems.

"Current Developments in Cryomedicine"[43] was meant to define what role, if any,NBS should play in the field of cryo-medicine.There did not appear to be a unique opportun-ity for NBS in the field of measurementscience in cryo-biology . Accordingly, noparticular course of action was deemed to

have a striking chance of success. A con-scious decision was made not to enter thisfield.

"Water Pollution Abatement" (internalstudy by Chelton) was the Cryogenics Divi-sion's first systematic look at environmentalproblems. Again, a program was deliberatelynot recommended, although both the need andthe technical opportunity (but for others)were present. Two technical conclusions werereached: (1) The most extensive potentialapplication of cryogenics is that of supply-ing (liquid) oxygen instead of air to second-ary waste water treatment plants to acceleratedecomposition, and thus upgrade presentplants and facilities; and (2) the mostsophisticated application of cryogenics is

the use of superconducting magnets forcolloidal filtration of river water. None-theless, criteria for NBS entering the fieldwere missing. Specifically, the first casewas not really a cryogenic research problem,for the handling of liquid oxygen is a wellestablished business. Neither was the second,necessarily, since the construction of largesuperconducting magnets has been accomplishedat the national laboratories.

Applications to a Specific National Need- -

Energy . We have prepared technology assess-ments in three energy areas: LNG, hydrogen,and superconductivity. Measurement servicesand data to support these three technologiespromise to be the main enterprise of theCryogenics Division for the foreseeablefuture.

Liquefied Natural Gas was addressedat two levels — simply its peculiarities as

a cryogenic fluid, and as a commodity."LNG as a Cryogenic Fluid" [44] assumed

that the Nation is just now entering an era

of the large scale use of liquid natural gas.

This report then predicted potential LNGproblems, based on similar experience gainedwhen the Nation just began handling liquidhydrogen as a commodity. It predicted specificinstrumentation problems in measuring pres-sure, temperature, liquid level, and flow.

It also predicted specific problems from

54

property data that are insufficient, have had

insufficient analysis, or are internallyinconsistent. This study documented the

practical utility of basic measurements and

launched the American Gas Association program

on LNG.

Since LNG was a significant commodity in

trade, "Measurements of LNG in Commerce"

[45] examined the measurement basis for

purchase of LNG. This study found a six-stepmeasurement process which has, at present, no

quality control or quality assurance built

in, and which is based essentially on a bid

and barter system. For instance, tank volumesare fixed at room temperature by "strapping"the tank with a tape measure, and then estab-lishing some functional relationship betweenliquid level and volume. This paper docu-

ments the advantage of basing the commercialcustody transfer on modern mass flowmeteringand property data instead. The goal is to

establish an orderly, systematic, and scien-tific basis for LNG trade.

"Hydrogen: Future Fuel" [46] showed themany technical, economical, and ecologicaladvantages that make hydrogen a prime candi-date as a substitute chemical fuel of thefuture. It was the first step in documentingthe needs for the present technical program.

"Superconducting Electrical Power Systems"[47] was an effort to accelerate the applica-tion of this technology to an old, established,and reliable industry. It found, among otherthings, that:

•Technological leadership in supercon-ducting machinery in the United Statescan help to reduce generator importsby up to 50%.

•Technological leadership by foreigncompanies can help them to capture a

larger share of the U.S. market.•Superconducting generators may beessential to realizing the full advan-tage of the large fast breeder reactors.

Specific technical program plans weredrawn to enable the development of supercon-ducting electrical generators, in cooperationwith the large electrical machinery manu-facturers. This effort helped stimulatethe development of applied superconductivityin this country, made public much privatelyheld information, and has led to major newthrusts to provide adequate measurementservices in support of this field.

Analysis of Major Technical Threats .

Since cryogenics is a rather well -boundedand self-contained technology, it is notlikely to be replaced by a competing tech-nology, such as electrical measurements re-placing mechanical or optical measurements,or TV phones replacing business commuting.The principal threats are from among the

rivals within the technology itself, es-pecially from abroad. Since cryogenics was"invented" abroad, we have never sufferedthe delusion of thinking that NBS has theworld's supply. Instead, world-wide aware-ness is central to our supplying timely andessential measurement and data services tothe U.S. cryogenics community.

The most recent systematic foreign tech-nology assessment was the monitoring ofapplications of superconductivity in the USSR,Switzerland, W. Germany, France, England, andJapan (internal study). For instance, NBSstaff visited the Fawley (U.K.) power stationto inspect the 3250 HP superconducting motor;discussed national funding of private enter-prise with the U.K. - National ResearchDevelopment Council; discussed the Germansuperconducting levitated train in Munich;and witnessed the Japanese 4-passengerdemonstration superconducting train. Wefound foreign efforts to be aggressive, wellahead of our own, and funded in cooperationwith their national governments. This studydocumented the magnitude of the foreignexploitation of U.S. technology and helpedprovide a sound basis for designing our ownmeasurements and data program.

Analysis of Major Technical Barriers .

The question of reliability and cost is

always raised whenever a commercial appli-cation of cryogenics is suggested. Heliumsupply, management, and control lie at theheart of realizing practical superconductingsystems

.

Strobridge [48] documented that enoughexperience has been accumulated in the designand operation of low temperature refrigeratorsand liquefiers to safely assume that anycooling requirement can be met. This studyfrequently obviates proposals for new refri-geration surveys, or, in some cases, re-

frigeration development programs, and pro-vides a common data base for refrigerationdependent technologies (e.g., acceleratorsand transportation).

We have seen that cryogenics is an

infrastructure industry, serving in an

indispensable way the needs of other indus-tries. Similarly, the science of cryogenicsis an infrastructure science. Seldom arethe low temperatures themselves of interest,except perhaps to establish some record.Rather, their real importance lies in

enabling the basic understanding of otherphenomena, i.e., increasing conceptualunderstanding.

The essential point is that here, too,cryogenics plays an essential but invisiblerole. It is usually not the cryogenics perse under study, but rather that the ultralow temperatures cause basic physical

55

phenomena to be greatly simplified and thusbe more susceptible to understanding anduse.

Accordingly, we conducted in 1969 aninternal planning study to define needs in

millikelvin research and propose specificaction to meet those needs. This studyrecommended specific measurement and dataneeds in the millikelvin and sub-mi 1 1 i kelvinrange. These plans included the developmentand improvement of standards and measurementtechniques, as well as techniques forobtaining and maintaining low temperatures.

Analysis of Major Technical New Oppor-tunities . The studies above have in commonthe motivation of need in relation tomission. A parallel requirement of a soundprogram is the existence of a timely technicalopportunity, and our formal technologyassessments have not been without thiscomponent as wel 1

.

Cryoelectronics has been addressed in

this fashion twice, in harmony with thenotion of reviewing and checking our pre-dictions periodically. The first was aninternal planning study which documenteddevelopments in superconducting devices in

d.c. voltage, direct current, magneticfield, RF current, RF power, pulse technology,RF noise, and temperature (internal study).It articulated a measurement role for NBS andformed a new organization to consolidate anNBS program in cryoelectronics.

"Developments in Cryoelectronics" [49]was published to document the development ofnew electronic instrument, s taking advantageof the unique properties of superconductors.It found that commercial activity has been in

the nature of an investment in the future:very few devices have actually been sold yet.It suggested that computers, informationtransmission lines and magnetocardiographymay become commercially significant appli-cations of superconductivity.

It suggested that many other superconduc-ting devices also perform specializedfunctions uniquely, and would repay thecost of development without necessarilygenerating a large market. This study is

helping to provide the basis for futuremeasurement and data programs.

An intense and in-depth effort on super-conductivity was conducted at the requestof the President's Science Advisory Com-mittee (PSAC), which required the partici-pation of many experts outside of NBS.

In a sense, it was a conference-style Delphiexercise. The result was an oral briefing toPSAC on the current status and future promiseof superconductivity. It covered such topicsas new superconductors; magnets and theirapplication to transportation, ore benefi-cation, and water pollution; electric power

generation and distribution; and cryoelec-tronics. As a result, the President'sScience Advisor formally requested theDepartment of Commerce to take a leadershipposition for the exploitation of cryogenicsand the creation of new industries.

As a result of this briefing, a plan wasdeveloped to help assure the successfulcommercial exploitation of cryogenics. Thegoal was to assist the Department of Commerceto create its own policy for the effectiveapplication of cryogenic technology forpublic benefit.

Summary of Cryogenic Technology Assess-ments . These studies have given visibilityto our decision making, and invited staffparticipation by those most likely to be

affected by the decisions. A stronger, moretimely program has been the result.

4.5.2 Driving Forces

The overall goal of the National Bureauof Standards is to strengthen and advancethe Nation's science and technology and tofacilitate their effective application forpublic benefit. Accordingly, it is notsurprising that we find both technical andsocietal driving forces at work, influencingthe trends of our program.

Technical driving forces (applied super-conductivity, hydrogen fuel, LNG imports,etc.) were noted in the specific technicalsections above. In addition, as implied in

the NBS Goal, we must continually givespecial attention to the public and privateinstitutions through which our measurementand data services benefit people. Somenoteworthy trends in such societal drivingforces and our expected response to themfollow below:

•Services influencing the manufacturingsector will increase, reflecting thefact that cryogenics in general, andsuperconductivity in particular, arecoming of age.

•Interaction with the service industrieswill also increase as the interactionwith the public energy utilities andthe Energy Research and DevelopmentAdministration increase.

•There is little direct contact withthe consumer per se, and no significantchange is expected. Contact will

continue to be made through serviceindustries and regulatory agencies.

•Both federal and state regulatoryneeds will grow. The federal interestwill be in the safe handling of cryogens.The state's interest lies in effectivemetering, sale, and taxation of cryogens.

As a result, we shall have to maintain a

balanced program supplying both measurementservices and data to the cryogenic measure-ment system.

4.5.3 Emerging Technologies

We have seen that the major developmentsin cryogenics in the next few years that willhave significant impact on the technology ofthe country and its balance of trade are thewidespread international use of liquefiednatural gas, applications of superconductors,and potential uses of hydrogen. Cryogenicmeasurement and data services are essentialto meet the developing needs for metrology,design data and applied cryogenic research.

Figure 7 shows these technological trendsand our response to them. The check marks area qualitative representation of our presentemphasis, which is in harmony with the time-liness (or urgency) of the technologicaltrends. LNG is upon us now; superconduct-ivity is a technology that is finding wideruse; while the most pressing need for hydro-gen -- Future Fuel is data for decisions.These emerging technologies will demandcontinued NBS support for the foreseeablefuture. See Section 5. for specific re-

^commended actions.

4.5.4 Impacts of the National MeasurementSystem Study

This study of the National MeasurementSystem documented for us the completeprocess that must be undertaken to providea complete measurement service. For instance,our LNG budget initiative submitted in thespring of 1974 was deliberately constructedto include all three necessary elements:measurement science, data base, and technology

transfer (includes safety, interstate andinternational cooperation, effective use ofthe Office of Weights and Measures, andtraining). Thanks (in part) to the NMS study,new programs now use the guidelines sodeveloped to assure a complete and compre-hensive approach.

In addition, we have become more sensitiveto the measurement system concept in allour programs, not just the LNG program.For instance, we are making an inventory ofall of our measurement services. We alsoare documenting our operations throughoutthe dissemination network, e.g., regulatoryagencies, state offices, central standardauthorities, and education programs.

Left to our own devices, we would mostlikely have conducted a technologicalimpact study (the science and technologyprofile of the cryogenics industry needsupdating) and not an examination of ourpart of the National Measurement System.Left on our own, we would have benefited bydocumenting new and other needs and develop-ing programs accordingly. We would havelost the understanding we now have of a"complete" program, and our role in theinfrastructure of the National MeasurementSystem.

5. SUMMARY AND CONCLUSIONS

5.1 Key Developments

This study has shown that there are threeemerging technologies within the broad fieldCryogenics with a need for a complete and

TECHNOLOGY TRENDS |

OUTPUTS Liquefied

Natural GasSuperconductivity

Hydrogen:

Future Fuel

Physical Measurement

Materials Data Base

Cryoengineering Services

FIGURE 7. Emerging technologies in cryogenics.

57

consistent system of measurements and data.Specifical ly:

Liquefied Natural Gas . A complete and com-prehensive measurement system for the lique-fied natural gas industry needs to be de-veloped, with special emphasis on quantitygaging in storage and ship tanks, flow-metering for determination of both mass andheating value, and basic measurements ofthermal and mechanical properties of struc-tural materials.

Hydrogen . Basic measurements and data arerequired now to support the development ofhydrogen as a fuel, in such areas as improve-ment of hydrogen liquefaction efficiency,evaluation of methods of recovering lique-faction energy, of hydrogen-compatible ma-terials of construction, and developmentof improved insulation materials and an in-

strumentation and measurement methodologyfor the commercial exchange of liquid hydro-gen.

Superconducti vi ty . Superconductivity con-nects cryogenics measurements and data to

the electrical power industry, for powertransmission, generation, and storage.Knowledge needed includes heat transferrates, behavior of helium refrigerantflow systems (including the response toinstabilities), and the degradation of thesuperconductors with time and stress.

Superconductivity is also a means ofemploying cryogenics to develop new orimproved measurement techniques in fieldsoutside of cryogenics. The SQUID (Super-conducting Quantum Interference Device) is

demonstrating promising applications in

magnetocardiography , geothermal prospect-ing, determining molecular constants, andspectroscopy of all kinds. Indeed, theSQUID appears to be as versatile as theLaser as a measurement technique, and is,

of course, fundamentally a cryogenic device.Some of the needs of each of these parts

of the National Measurement System forCryogenics are illustrated below.

5.2 Liquefied Natural Gas (LNG)

LNG is a Cryogenic Fluid (NBP 110-140 K)

but unlike the simple fluids of our usualexperience it is:

•A non-ideal mixture of five or morehydrocarbon fluids and nitrogen;no known mixing rules exist at thistime, and therefore the mixture pro-perties are not yet predictable; all

must be measured.•Furthermore, the mixture fraction varieswith source-time-and storage treatment.

•LNG is primarily an energy storagemedia, because its energy content is

about 600 times that of natural gas atatmospheric conditions.

Peak shaving accounts for the largestnumber of LNG facilities with 106 beingcompleted within the U.S. This number includes55 actual peak shaving plants (which includeliquefaction, storage and gasification equip-ment), and 51 satellite facilities (whichcomprise a total storage capacity of approxi-mately sixty-five billion cubic feet (equi-valent gas volume) and a total liquefactioncapacity of approximately 295 million cubicfeet per day.

LNG presents not only a nationwide problem,but an international one. Contrary to

popular opinion, the U.S. is not dependentupon just one source. Imports are plannedfrom Malaysia, Australia and South America,for instance. We will also "import" fromAlaska. In fact, the U.S. is presently a

net exporter of LNG (to Japan) due to con-tracts signed in 1968.

Industry desires NBS assistance in thisnational problem. For instance, the presidentof the American Gas Association has writtenthe Secretary of Commerce, requesting mea-surements and data assistance from theDepartment of Commerce and the NBS.

The Secretary gets many such letters, to

be sure, but our study has shown that the

Department of Commerce and NBS have beenearmarked as the international and inter-

state connection agency. Internationalcontracts call out NBS as the measurementauthority. In addition, we also have an

inter-state responsibility to provide LNGassistance to a variety of federal, stateand local authorities on the inter-statetransfer of LNG.

LNG has grown so fast and to such a size

and complexity that our NMS study revealedthat it is now timely for the Departmentof Commerce to take steps to assure qualitycontrol and continuity in this part of the

NMS.

The overall measurement and data needsfor LNG identified in the course of this studyinclude:

•Heating Value (Energy) metering fornational and international trade

•Quantity gaging•Thermophysical properties•Properties of structural materials•Instrumentation and data for EnergyConservation

• Safety Criteria

The needs for the safe and effectiveutilization of liquefied natural gas are

58

most urgent. They include both tools and

techniques for physical measurements as well

as a data base for materials selection and

use.

5.3 Hydrogen

With respect to hydrogen, there seems

to be little doubt that it will become a

major source of fuel for the future. Needs

are centered about providing an adequate

data base--reference data, reference ma-

terials and performance standards--to give

a rational basis for decision making in this

field.Candidate Markets for cryogenic hydrogen,

without regard to priority or imminency,

are:

•Transportation--to fuel aircraft, autosand ships;

•Aerospace--rocket and spacecraft fuel;•Energy storage and transmission--carrierof nuclear or solar energy from sea-to-shore or overland;

•Utilities--fuel for integrated gas-electric utility operations and a

portable fuel for rural communities;and to a lesser extent:

•Superconducting and cryoresistiveelectrical power cables--to be used as

a closed-loop coolant (electricityand hydrogen are del i vered)

;

•Industrial processes--to provide highpurity hydrogen gas upon demand.

Assuming that a future market exists forliquid hydrogen we must dispense the fuel in

an efficient, fair and safe manner.The efficiency of liquid hydrogen fueled

systems can be improved on three fronts:

(1) lightweight, efficient and inexpensiveinsulation materials are needed, together withnational insulation transfer-standards;

(2) data are needed on advanced construc-tion materials that are lightweight, strong,inexpensive, resistant to hydrogen em-brittlement and brittle fracture, and hav-ing low heat capacity and thermal conductivity.

(3) liquid hydrogen handling procedures,though highly developed and successful in

the aerospace program, will have to be re-vised for commercial applications.

Liquid hydrogen enjoys an enviable safetyrecord in the aerospace industry. However,the safe use of hydrogen in commerce willrequire thorough re-evaluation of: 1) com-patible materials of construction, 2) handl-ing procedures and regulations, and 3) ex-plosion hazards.

We must also be able to guarantee equityin hydrogen commerce. Thus, traceablemeasurement standards are required for massflow, pressure, temperature, and quantity-

gaging. Liquid hydrogen instrumentationhas not significantly advanced in the pastten years since the peak of the space pro-

gram. Major efforts will be required to

meet the needs of a commercial cryogenichydrogen fuel market. Instruments suitablefor aerospace applications are not usuallyappropriate for commerce and vice versa.

Measurement standards are needed to bringall aspects of hydrogen instrumentation intoquality control within the National Mea-surement System.

5.4 Superconductivity

Superconductivity was discovered at aboutthe same time as the Wright brothers firstflight, yet remains largely an undevelopedtechnology. This is indeed curious sincethe potential practical applications of superconductivity are staggering. For instance,it is widely held that superconductors couldbe used to advantage to transmit electricalpower with almost no loss, to make magnetsof a size not heretofore possible for energystorage; to upgrade low quality iron ore in

magnetic mineral processing; to improve the

quality of kaolin; to purify water via

colloidal filtration; or to float high speed

trains on a magnetic cushion.Yet none of these possibilities are

approaching commercial realization in the

United States. The problem does not appearto lie with the superconducting wires them-

selves, as over 500 materials are alreadyknown to be superconductors. Furthermore,

a dozen manufacturers here and abroad are

producing superconducting wire and cables

in nearly commercial quantities at pricesapproximately one- tenth that of copper wire

for the same current carrying capacity.The problem appears to lie instead in

providing a reliable, safe and convenientsupporting cryogenic environment. We need

to provide the helium measurements and

data base essential to the successful develop

ment of superconductivity. NBS need not

address the applications of superconductorsmentioned above, but does need to providethe supporting measurements and data on:

1) helium heat transfer and fluid dynamics;

2) instrumentation and measurement systems

for helium management, and 3) data on the

degradation of superconductors.Since heat transfer and fluid dynamics

are strongly interrelated, a thorough under-

standing of the fluid dynamic aspects is

essential. The important consideration is

that all flow irreversibilities ultimatelyshow up in the form of heat, thus reducingthe capacity of the helium to absorb otherlosses. We need to provide basic data and

understanding on the properties and behavior

59

of helium to provide engineering and processdesigns, predictions, and scaling of equip-ment.

Effective helium management will require,at least, sensors for pressure, temperature,quantity and flow rate. We need to providesuch instruments through developments whichtake advantage of the low temperatures andoptimize the instrument output. For instance,superconductors themselves may be used forthermometers and level gages. We need a newgeneration of instruments and measurementtechniques tailored to liquid helium as a

technical fluid.The third consideration arises from the

fact that practical superconducting systemswill not operate under ideal laboratoryconditions. They will be subjected tomechanical stresses during shop and field-site fabrication; they will, at leastoccasionally, be subjected to unduly roughhandling; they will have unprogrammed ex-cursions in current, temperature, and mechan-ical stress during fault conditions. Evenmore fundamentally, they will certainlyshow typical manufacturing variabilitiesand may show time dependent deteriorationof their desired design properties.

The foregoing discussion has focused onthe physical measurements, units, standardsand essential technical data needed to

support the needs of the National Measure-ment System for cryogenics. In addition,cryogenics itself may be used to advantageto develop new or improved measurementtechnology outside of the field of cryogenics.Specifically, the SQUID is being used toimprove technology transfer from our physicalmeasurements program to other federal agencies

and industry; and to extend the impact areaof the measurement program. Since physicalmeasurements are almost always reduced to

electrical measurements, the list of cryo-electronic applications is almost endless.Accordingly, it is particularly timely to

open up the way for extensive new applica-tions of cryogenics to physical measurementsunits and standards.

5.5 Summary

Our study of the National MeasurementSystem for Cryogenics has shown that majordevelopments in the next few years will

occur in cryoelectronics, the widespreadinternational use of liquefied natural gas,potential uses of hydrogen, and applica-tions of superconductors. Major otherfederal agencies will doubtlessly continueto solve their specific cryogenic techno-logical problems through a variety ofmeans, including, but not limited to,

soliciting the services of the CryogenicsDivision. We regard this constituent ofour total program as a necessity to main-taining our institutional health, and oursustaining a current awareness of nationalneeds and goals.

However, no other instrument of the govern-ment has the prime responsibility to assurethe proper functioning of the Nation's systemof cryogenic measurement. The needs as

discussed briefly above and documented withinthe body of this study, demonstrate thatnow, more than ever, it is time for a central,coordinated, coherent national effort on thepart of NBS to bring and keep the cryogenicpart of the National Measurement System intoqual ity control

.

60

METHODOLOGY OF THE STUDY

APPENDIX A.

One purpose of the Cryogenics Division

study of the National Measurement System was

to clarify and understand what is necessary

to provide a "complete" measurement service,

and to identify the role cryogenic measure-

ments in the infrastructure of the National

Measurement System.

We hoped by this process to document the

way information was gathered, how conclusionswere reached, and how the results were vali-

dated. Such hindsight could then be appliedto the systematic development of new mea-surement services in the future, as well as

to improving present services. In the follow-ing material, we shall examine our particularmethodology in four categories:

1. Mechanism for Selection of DataSources;

2. Transmission Mechanics, the means by

which the desired data wasconveyed;

3. Contact Mechanisms, used to obtainthe desired data;

4. Sources of Information or Validation,

Table A-1 is a matrix designed by Dr. R.

C. Sangster, National Measurement SystemCoordinator, that conveys at a glance muchabout the study. The blocks in the matrix aredivided by a diagonal. The upper left cornerrefers to the process of obtaining results;the one in the lower right deals with theprocess of val idating the results. "0-L-M-H"gives a rough quantitative estimate of theimportance (to this study) of the results in

terms of zero, low, medium, or high.

The following narrative describes eachof the four tactical means listed above.

1. Mechanism for Seclection of DataSources.

An analysis of NBS clientele was veryimportant to obtaining data. Many of theclientele (state weights and measures offi-cials and compressed gas suppliers) played anessential role in validating our results. Inthe case study cited in this report, ourresults were crucial to the commerce betweenmany of our clientele. They were profoundlyaffected (by law) by the results, and there-fore had a vested interest in promoting validresults.

The NCSL membership, per se, was notused because the Instrument Society ofAmerica (ISA) had already formed an Ad Hoccommittee on a specific measurement, namelycryogenic flow measurement. This committeeprovided an extensive review and definition

of the national needs for cryogenic flowmeasurements and standards, and we used thisresource extensively to illustrate the prac-tical realization of general principles.

Invaluable help was obtained from theCompressed Gas Association (CGA). The CGA is

a nonprofit corporation which represents all

segments of the compressed gas industry in

the United States, Canada, and Mexico. Theyalso have associate members in European andAsian countries. Among its membership areover 250 companies, including North America'slargest firms, devoted primarily to producingand distributing compressed, liquefied, andcryogenic gases, as well as leading chemicalindustry corporations that have compressedand liquefied gas divisions. They contri-buted valuable insights to the mechanics ofthe National Conference on Weights and Mea-sures, especially as to how a code is devel-oped and promulgated through the documentarysystem. Perhaps prompted by the interest ofthe CGA and the states in "type approval" ofmeters, members of the instrumentation in-

dustry were very helpful.

The U.S. Department of Commerce (DoC)compiled and published many statisticalsummaries that were invaluable to this typeof study. For instance, the SIC codes leadimmediately to the "Current IndustrialReports", in our case Series M28C, whichgives frequent and accurate summaries of theproduction of cryogens. The "AlphabeticIndex of Manufactured Products" is a com-panion to the better known "Standard In-

dustrial Classification Manual " . Otheruseful Department of Commerce publicationsinclude "Industry Profiles", and the annual"U.S. Industrial Outlook". The latter is

especially useful, for it not only summarizesstatistical data, but also forecasts growthand the reasons (e.g., new uses for oldproducts) for this growth. "Mineral Factsand Problems", published by the U.S. Depart-ment of the Interior, provides a resourcesimilar to the "U.S. Industrial Outlook", butis even more exhaustive in its treatment ofcryogenic gases.

Private compilations, such as the Dunnand Bradstreet's "Million Dollar Directory",while giving a brief overview of a particularcompany, also gives the SIC codes for theproducts manufactured by that company. Forinstance, "Cryostats" do not appear in theSIC Manual, but can be found in a roundaboutway from Dunn and Bradstreet, if one knowseven the name of only one firm in the cryo-stat business. Once the SIC code is foundfor a particular product, then this resourcelists al

1

firms reporting under that code.In this way, every firm in that business is

A-1

TABLE A-1. Means used to obtain and validate data.

1. MECHANISM FOR SELECTION OF SOURCESOBTAIN^^^^-^^^-^'"^

/ALIDATE

Analyses of NBS Clientele

Analyses of NCSL Membership

Analyses of Instrumentation Industry 1^^""^

Analyses of Other, Similar List _IL-'--^''hUse of SIC Codes for Analyses

Staff Judgment/Wisdom

Analyses of Statistical Compilations

2. TRANSMISSION MECHANICS

Published LiteratureUl ^—

—

^^-^^ H

Formal Meeting PresentationLI

"

^-—^^ H

Organizational StatementUl

'—^^'^^ H

Personal Statement1L —^-^^ H

AdvertisementsM ^

—

— 0

Clientele Customer Lists1

L _^

—

^—-""^0

3. CONTACT MECHANISM

Literature Searchu —-

—

—-—^—H

Retention of ConsultantsMfl —— h

Conversation - Visitor to NBSu ^—-

—

n

H

- At off-site locationu ^—

—

n ^—

—

h

- By telephonert

_^ ^ h

- By visit to source's siteUl

—

'

—

—

^^-^^ H

CorrespondenceM ——rn ^

- M

Formal Pol 1 ing/Canvass/Questionnairen

0

Delphi Studies1

-

—

L —L

Other Formal Forecasting TechniquesUl ^—'

—

'

^-"-^""^0

Special Conferences (NBS Sponsorship)un^ H

Trade Show Exhibits by NBSU ^

—

^--^^^ 0

Round-Robin/Inter ComparisonU ^^^-^^'^

H

Training Courses ^^^^ 0

Construction of New Institution0^-^^^ 0

A-2

TABLE A-1. Means used to obtain and validate data (continued)

OBTAIN ^^^^'^^--^^/ALIDATE

Attendance at Conferences & Meetings

Statistical Compilations

4. SOURCE OF INFORMATION OR VALIDATION

Academic People & InstitutionsL —

—

M

Prof., Tech. Soc, & PublishersH ^—

H

International & Foreign Organizations ^^^^^^^^Documentary Standards Bodies

L ^^— H

Ref. Data & Mat' Is OrganizationsH^^^^^ H

Instrumentation IndustryH^^^^^ H

NBS Evaluation PanelsL

M

Other NBS UnitsH —^—-"""''^

H

Nat'l Conf. WTs & Meas/St. etc. OWM's ^^"'^ H

Nat'l Conf. of Standards Laboratories0 ^^^-^^^—^ 0

Stds & Testing Labs & ServicesM^-——"^'^ H

Governmental Regulatory Agencies0 "

0

Other Federal Government Agencies ^---^^State and Local Governmental Agencies

H ^̂ H

Trade AssociationsH ^—

"

^-^^^^ H

Trade PressM —^ 0

Private CompaniesH —

^

— H

Consumer OrganizationsL ^

—

^^^^^ 0

Popular Press0 ^^--^^ 0

Other (See Text)H ——'— H

Staff Wisdom/Previous StudiesH ^^^--^— —^ H

A-3

revealed with certain of its vital statis-tics.

The use of these statistical resourcesled us immediately to corporate Annual Re-

ports, which are required annually by theSEC, and whose accuracy must be unquestion-able. We gathered a number of such reports,and they proved to be one of our most valu-able resources of specific, fine-grainedinformation, plus giving projections for thefuture. We plan to keep a comprehensive andcurrent set of corporate Annual Reports as a

ready reference to answer "who needs it", and"what are they doing with it?"

2. Transmission Mechanisms

When the State of California beganpublic hearings on a code for fluid meteringof cryogens, it was suggested that the Cryo-genics Division of NBS provide "best values"data for inclusion in the California Code.The gases under consideration were limited to

oxygen, nitrogen, argon, and hydrogen. Atthe request of both the Compressed Gas Asso-ciation and the State of California, wegenerated skeleton tables, which were pub-lished in the California Code. In addition,the Cryogenics Division provided a sourcedocument, NBS Technical Note 361 "SaturatedLiquid Densities of Oxygen, Nitrogen, Argon,and Parahydrogen" [1]. The latter documentwas produced specifically to allow trace-ability of the selected values. It wasrevised in 1972 to include compressed liquiddensities, and again in 1974 in a metricformat. These NBS property data are spe-cifically called out in the California Codeand accordingly have the same weight of lawas the flowmeter calibrations and tolerancesthemselves.

Other transmission mechanisms include:

•Codes, Standards, and RecommendedPractices, such as adopted in Handbook44;

•Properties Data. NBS property data forseveral cryogens were adopted in Hand-book 44. In addition, there is no doubtthat the wide dissemination and know-ledge of the NBS cryogenic fluid pro-perty work was the original factorleading the regulatory agencies andthe CGA to come to NBS in the firstplace.

•International Conventions. At one timeor another, we have cooperated withthe International Organization of LegalMetrology (OILM) to facilitate theadoption of international codes; per-formed type testing of instruments offoreign manufacture as part of the

program; and promoted and facilitatedvisits by many representatives fromother nations, including Germany,France, and the United Kingdom.

•Steering Committee. In the casehistory used for illustration, theCompressed Gas Association formed a

steering committee to help providea degree of quality control to theprogram, but especially to help sub-stantially by providing guidance andadvice at critical stages of planningand implementation of the program.This committee met three to four timesa year during the nearly eight-yearlife of the program. In addition,state weights and measures officialsroutinely attended these meetings,which provided an invaluable forumfor the cooperative solution of vexingproblems.

Advertisements and other trade litera-ture were of moderate importance in locatingmeter manufacturers and documenting accuracyclaims. They played no role in validatingthe results, unless one cares to note anychanges in advertising copy that might haveoccurred after the program.

3. Contact Mechanism

Contact mechanisms may be viewed as theterminals of the transmission mechanicsdescribed above, and accordingly will not bere-addressed at any length here. Only a fewobservations may be in order:

•Conversations - especially face-to-facemeetings, such as described under "SteeringCommittee" above were a prime source ofreally useful data.

•Forecasting plays a major role. Forinstance "Normative" forecasting was per-formed by the ISA Ad Hoc committee mentionedin the study. Goals, needs, and desires werespecified, and the Ad Hoc committee thenworked backwards to the (then) present todefine what capabilities either existed or

could be extrapolated to meet the goals.Section 4.5 described the major role fore-casting plays in developing the Division'stotal program of measurement and data ser-vices .

•Round-robin intercomparisons are at theheart of transferring the NBS measurementcapability to the states, producers, andmeter manufacturers. For instance, the Stateof California has now calibrated no less than58 out of the 60 meters used there in liquidnitrogen commerce by this means. To furtherfacilitate such intercomparisons, NBS has

built and is currently proving a transfer

A-4

standard of its own. Similar round-robins

have been conducted for years on thermocouple

materials. Section 2.4 describes otherinter-comparisons accomplished through the

use of other reference materials.

Numerous contacts were made within the NBS

and described in Section 2.4.1, under

NBS Infrastructure .

4. Sources of Information or Validation

Many sources of information were of

necessity described in the previous threesections. Accordingly, the purpose of this

section will be to summarize the above, and

to comment in a general way on the utility ofsome of the sources.

For this particular study, the PopularPress, Consumer Organization per se the TradePress, Federal Agencies (regulatory andotherwise), the National Conference ofStandards Laboratories (NCSL) and academicinstitutions did not constitute a majorresource, although they surely would in othertypes of studies.

Some groups ranked low as input sources,but were virtually indispensable to validat-ing the results. Such groups include inter-national and foreign organizations and do-cumentary standards bodies (the NCWM providedlittle input, but was essential to codifyingthe results); the main contribution of theNBS Evaluation Panel was in providing anoverview of the study as a whole and aidingin the technical quality control.

A third group could be ranked as "medium"on the input side, but "high" in terms ofvalidation. For instance, especially in theearlier stages of the physical evaluation of

our flow system, round-robins were conductedwith industrial testing laboratories. Thiscooperation not only gave us a head start in

our own facility, but also opened the doorfor eventual international agreement (via theOILM, for instance).

The fourth group ranks "high" on bothinput and validation, and accordingly wasincluded in the previous sections. Forcompleteness, they may be listed as: pro-fessional and technical societies (e.g..Instrument Society of America, CompressedGas Association); reference data organiza-tions (e.g., the National Conference ofWeights and Measures for Handbook 44; andour own Tech. Note No. 361); the instru-ment industry (via the Instrument Societyof America and instrument manufacturers).Other NBS units were invaluable in helpingdesign the experiments (e.g., Applied MathDivision), in codifying the results (e.g..Office of Weights and Measures) and in

furnishing other essential services (patentadvice). The role of state agencies, tradeassociations (Compressed Gas Association)and private companies (cryogen producers,instrument makers) have already been men-tioned. The Annual Reports of these pri-vate companies have proven to be gold minesof documented needs and opportunities.

Finally, we come to "staff wisdom".This study of the National MeasurementSystem is based on 20 years of work by

literally hundreds of men and women in theCryogenics Division of NBS. This resource,especially in terms of accumulated experi-ence, would be impossible to duplicateelsewhere. Accordingly, "staff wisdom" wasof inestimable value throughout the study.

A-5

REFERENCES

[I] Roder, H. M., Standard Liquid Densitiesof Oxygen, Nitrogen, Argon and Para

Hydrogen, Nat. Bur. Stds. (U.S.) Tech.

Note No. 361 (1968) (Revised-1972; MetricSupplement-1974)

.

[2] Arvidson, J. M., and Brennan, J. A.,

Pressure Measurement, ASRDI TechnologySurvey, (to be published).

[3] Measurements and Data 1_, No. 2, 101-112

(Mar-Apr 1973).

[4] Cruz, J. E., Rogers, E. H., and Heister,A. E., Continuous Liquid Level Mea-surements with Time-Domain Reflecto-metry. Book, Advances in CryogenicEngineering, 18, 323-(Ed.) K. D.

Timmerhaus (Plenum Press, Inc., NewYork, N.Y., 1973).

[5] Willis, W. L., Disturbance of CapacitiveLiquid Level Gauges by Nuclear Radia-tion, Book, Advances in CryogenicEngineering, 12^, 665-72, (Ed.) K. D.

Timmerhaus (Plenum Press, Inc., NewYork, N.Y., 1967): See also, Willis, W.

L., and Taylor, J. F., Time DomainReflectometry for Liquid Hydrogen LevelDetection, Unclass. Rept. LA-3473-MS,Los Alamos Scientific Laboratory, LosAlamos, New Mexico (Feb. 1966).

[6] ASME, Fluid Meters, Their Theory andApplications, 6th Edition (ASME, NewYork, N.Y., 1971).

[7] ISA, Standard Practices for Instru-mentation, Instrument Society ofAmerica, Pittsburgh, PA. (1970).

[8] ISO Recommendation R541 , Measurement ofFluid Flow by Means of Orifice Platesand Nozzles (Jan. 1967).

[9] Richards, R. J., Jacobs, R. B., andPestalozzi, W. J., Measurement of theFlow of Liquefied Gases with Sharp-edgedOrifices, Book, Advances in CryogenicEngineering, 4, 272-285 (Ed.) K. D.

Timmerhaus, (Plenum Press, Inc., NewYork, N.Y., 1960).

[10] Rodeley, A. E., Vortex Shedding Flow-meter, Measurements and Data, No. 18,

(Nov. -Dec. 1969).

[II] Wyle Laboratories, Final Report, Con-tract No. NASB-1526, Liquid HydrogenMass Flowmeter Evaluation (Jan. 1965).

[12] Mann, D. B., ASRDI Oxygen TechnologySurvey, Flow Measurement Instrumenta-tion, NASA SP-3084 (1974). (For saleby the National Technical InformationService, Springfield, VA 22151, Price$4.50).

[13] Sparks, L. L., Low Temperature Mea-surement, ASRDI Oxygen TechnologySurvey, Volume IV, NASA SP-3073 (1974).(For sale by the National TechnicalInformation Service, Springfield, VA22151, Price $3.75).

[14] Roder, H. M., ASRDI Oxygen TechnologySurvey, Volume V: Density and LiquidLevel Measurement Instrumentationfor the Cryogenic Fluids Oxygen,Hydrogen and Nitrogen, NASA SP-3083(1974). (For sale by the NationalTechnical Information Service, Spring-field, VA 22151, Price $3.75).

[15] Zudkevitch, D., and Gray, R. D., Jr.,Impact of Fluid Properties on Designof Equipment for Handling LNG, Ad-vances in Cryogenic Engineering, 20,

(Ed.) K. D. Timmerhaus (Plenum Press,Inc., New York, N.Y., 1967).

[16] Olien, N. A., The Cryogenic Data Center,An Information Service in the Field ofCryogenics, Cryogenics Vol. 11, No. 1,

11-8 (Feb. 1971).

[17] Mendenhall, J. R., Johnson, V. J., andOlien, N. A,, Publications and Servicesof the National Bureau of Standards,Cryogenics Division, Institute forBasic Standards, Boulder, Colorado80302 1953-1972, Nat. Bur. Stand.

(U.S.) Tech. Note No. 639 (Aug. 1973).

[18] Hust, J. G., and Sparks, L. L., ThermalConductivity of Electrolytic Iron,

SRM 734, from 4 to 300 K, NBS SP 260-31

(1971). This work has been extendedto include temperatures from 4 to

1000 K by J. G. Hust and P. J. Giarratano(In press).

[19] Hust, J. G., and Sparks, L. L., ThermalConductivity of Austenitic StainlessSteel, SRM 735, from 5 to 280 K, NBSSP 260-35 (1972). This work has beenextended to include temperatures from4 to 1200 K by J. G. Hust and P. J.

Giarratano (In press).

R-1

[20] Must, J. G., Electrical Resistivity ofElectrolytic Iron, SRM 797, and Auste-nitic Stainless Steel, SRM 798, from 5

to 280 K, NBS SP 260-47 (1973). Thiswork has been extended to include tem-

peratures up to 1200 K by J. G. Mustand P. J. Giarratano (In press).

[21] Hust, J. G., and Giarratano, P. J.,

Thermal Conductivity and ElectricalResistivity Standard Reference Materials:Arc cast and Sintered Tungsten, SRM's730 and 799, from 4 to 3000 K, NBSSP-260-XX (In review).

[22] Schooley, J. F., et al . , Preparation andUse of Superconductive Fixed PointDevices, SRM 767, NBS SP 260-44 (1972).

[23] Standard Reference Materials 1973Catalog, National Bureau of StandardsSpecial publication No. 260 (availablefrom the U.S. Government PrintingOffice, Washington, D.C. 20402, Price$1.25 ; or through the Office ofStandard Reference Materials, NationalBureau of Standards, Washington, D.C.

20234).

[24] Curto, J. M., Growth of the CompressedGas Industry, Paper presented at 55thAnnual Meeting, Compressed Gas Assoc.,5-21 (Jan. 1968).

[25] Lofstrom, J., Uses of LNG for the Future,Pipe Line Industry 29, No. 4, 95-97(Oct. 1968).

[26] U. S. Industrial Outlook 1974, U.S. Dept.of Commerce (available from USGPO,Stock No. 0325-0004).

[27] Industry Profiles, U.S. Dept. ofCommerce (available from the USGPO).

[28] Minerals Yearbook - 1972, Vol. I, Metals,Minerals, and Fuels, Dept. of theInterior, Bur. of Mines, p. 807 (1974).

[29] Gas Facts - A Statistical Record ofthe Gas Utility Industry, 1972 data,

p. 58, table 53 (The American GasAssociation, 1973).

[30] Hale, D., Editor, World LNG Carrier FleetGrowing, Pipeline and Gas Journal,

pp. 42-44 (June 1974).

[31] National Gas Survey, Federal PowerCommission, Vol. II, Supply Task ForceReports, p. 390; Federal Power Com-mission, 1973).

[32] Hale, D., Editor, LNG Growth Continuesto Escalate, Pipeline and Gas Journal,

pp. 27-32 (June 1974).

[33] Programs on Large Scale Applicationsof Superconductivity in the UnitedStates, by Powell, Fickett andBirmingham. Appears in SuperconductingMachines and Devices, Proc. NATO Ad-vanced Study Institute, Plenum Press

(1974).

[34] Weekly Energy Report, Vol. 2, No. 41

(October 14, 1974).

[35] Weekly Energy Report, Vol. 2, No. 48(Dec. 2, 1974).

[36] U.S. Industrial Outlook 1974, withProjections to 1980 (for sale by theSuperintendent of Documents, U.S.

Government Printing Office, WashingtonD.C. 20234, Price $3.40).

[37] Instrument Society of America Ad HocCommittee Report on Cryogenic FlowMeasurement, prepared under the Spon-sorship of the ISA Technical Department,T. J. Kehoe, Vice President (June

1967).

[38] Federal Funds for Research, Developmentand other Scientific Activities,Fiscal Years 1972, 1973 and 1974,

(the National Science Foundation,NSF-74-300, Vol. 22, Dec. 1973).

[39] Flynn, T. M., Cryogenics and NationalGoals, paper A-1 in Advances in Cryo-genic Engineering, (Proc. 1968 Cryo-genic Engineering Conf.), Vol. 14,1-12. Plenum Press, New York (1969).

[40] Flynn, T. M., and Smith, C. N., Trendsin Cryogenic Fluid Production in the

United States, Bull. Inst. Int. Froid,

Annexe 1970-2 (Proc. Comm. I, Conf.

on Cryophysics and Cryoengineering,Tokyo, Japan, Sept. 11-12, 1970)

p. 241-7.

[41] Birmingham, B. W., SuperconductivityPrograms of the AEC, Special Publica-tion of the AEC, WASH-1081 (June 1967).

[42] Arp, V. C, Clark, A. F., and Flynn,T. M., Superconducting Levitation ofHigh Speed Vehicles, Transp. Eng. J.,

Vol. 99, No. TE4, 873-85 (Nov. 1973).

R-2

[43] Smith, R. V., Current Developments in

Cryomedicine, Cryogenics, 7_, No. 2,

84-9 (April 1969).

[44] Mann, D. B., and Roder, H. M. , LiquefiedNatural Gas as a Cryogenic Fluid--Instrumentation and Properties, Proc.

Transmission Conf. of AGA, New Orleans,La., (May 26-27, 1969).

[45] Mann, D. B., Diller, D. E., and Olien,

N. A., Measurements of Liquefied Na-

tural Gas in Commerce, Proc. Distri-bution Conf. of AGA, Washington, D.C.,(May 1973).

[46] Hord, J. (Ed.), Selected Topics on

Hydrogen Fuel, Nat. Bur. Stds. (U.S.)

Spec. Publ. No. 419 (May 1975). Avail-able from the USGPO, Stock No. C-13.

410:419, $2.80.

[47] Flynn, T. M. , et al.. SuperconductingElectrical Generators of Central PowerStation Use, Advances in CryogenicEngineering, j[9, (Ed.) K. D.

Timmerhaus (Plenum Press, Inc., NewYork, N.Y., 1974).

[48] Strobridge, T. R., Cryogenic Refrigerators--An Updated Survey, Nat. Bur. Stand.(U.S.), Tech. Note No. 655, (June 1974).Available from the USGPO Stock No.

C13. 46:655, $0.30.

[49] Kamper, R. A., and Sullivan, D. B.,

Developments in Cryoelectronics,Nat. Bur. Stand. (U.S.), Tech. NoteNo. 630, (Nov. 1972). Available fromthe USGPO, Stock No. C13. 46:630,$0.70.

R-3 ISCOHX - IRL

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U.S. DEPT. OF COMMBIBLIOGRAPHIC DATA

SHEET

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The National Measurement System for Cryogenics

7. Al l llOKis)

T. M. Flynn9. PI I<I (.)KM1NC. ORCANI/A I ION NA.Ml ANH ADDHr.Ss

NATIONAL BUREAU OF STANDARDSDEPARTMENT OF COMMERCEWASHINGTON, D.C. 20234

12. Spou'-onni; t Vj; .in i / ,it i on N.imo .inJ < oniplcu AJi|ris>. (Sfrevt. City, Stale. /.IP)

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16. .AHs'l KA( r (A 200-\\ord or /e.s.s- factual nummary ol mo.s ( >,i^ilicanl in lorwd tton. U doLunn-n I includt.-s j .^i^nitnonl

bibl lofiraphy or literature survey, mention it here.)

The Cryogenics Division of NBS has evolved as the nation's central laboratory forcryogenics, much as NBS itself has evolved as the nation's central laboratory with bothbroad and specific responsibilities. Cryogenic measurement and data outputs providethe common foundation for all the institutions and agencies throughout the nationemploying cryogenics to solve their problems.

This Study of the National Measurement System showed that the Cryogenics Divisionof NBS provides almost every category of measurement and data service that NBS itselfprovides: not just an instrumentation system (including, for example, pressure, temp-erature, density, liquid level, flow rate, etc.), but also properties of fluids (boththermodynamic and transport properties); properties of solids (thermal, mechanical andelectrical); an interface with the users through systems integration and advisory andconsulting services; and a dissemination network through the Cryogenic Data Center.

This study documents the impact, status and trends of the cryogenic measurementsystem and specifically illustrates these characteristics wherever possible with a

specific case study, a recently completed measurements and data program for the flow-Tietering of liquid nitrogen.

17. Kl > WORDS (.SIX to twelve entries; alphabetic al order, capitalize only the first letter of the first key uord unless a proper

nawe; separated by semicolons )

Cryogenics; data; flowmeter; instrumentation; measurements; National Measurement System.

18. AVAII AHII.I 1 V 1 X Unlimited 19. SlX URllV CLASS(THIS REPORT)

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jUSCOMM- DC ^- _i 4. -'' .'4

YEARS

1901-1376