Attachment C NIST hb-105-3-2010.pdf

Specifications and Tolerances for Reference Standards and

Field Standards Weights and Measures

105-3 February 2010

Specifications and Tolerances for Graduated Neck Type

Volumetric Field Standards

NIST Handbook

RFQ Attachment C

Specifications and Tolerances for Reference Standards and Field Standards Weights and Measures

Specifications and Tolerances for Graduated Neck Type Volumetric Field Standards

Editors:

L. F. Eason (Contract) Georgia L. Harris Val R. Miller

Carol Hockert, Chief Weights and Measures Division National Institute of Standards and Technology Gaithersburg, MD 20899-2600

U. S. Department of Commerce Gary Locke, Secretary

National Institute of

Standards and Technology Patrick D. Gallagher, Director

NIST

Handbook 105-3

February 2010 Edition Supersedes June 1997 Edition

Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose.

National Institute of Standards and Technology Handbook 105-3, 2010 Edition Natl. Inst. Stand. Technol. Handb. 105-3, 2010 Ed., 49 pages (February 2010)

CODEN: NIHAE2

WASHINGTON: 2010

Preface

The 2010 revision of Handbook 105-3 includes the following changes since it was last published in 1997:

No retroactive requirements have been added to this revision of the document.

The definitions have changed. Volumetric field standards are considered test measures if they are hand held and considered provers when mounted. A number of references and defined terms have been expanded.

Test measures are described as typically 20 L (5 gal) or smaller instead of 40 L (10 gal) or smaller due to ergonomic concerns. Bottom drain 5 gal (19 L or 20 L) test measures were added.

High resolution volumetric field standards are no longer covered in the document.

Definition of these laboratory volumetric standards is beyond the requirements of NIST Handbook 105-3 and is left to the manufacturer and the laboratory.

Data plate no longer is required to include reference temperature or material thickness.

Method of use only has to be on the scale plate.

It is the responsibility of the user to ensure that a volumetric field standard is appropriately labeled when necessary to prevent cross contamination of products measured.

Inside diameter and wall thickness were standardized for sight glasses. Sight glass ID for 10 gallon and smaller is 13.0 mm (0.5 in) and 16.0 mm (approximately 5/8 in) for larger volumetric field standards. The minimum nominal wall thickness for sight glasses is

3.2 mm (approximately 1/8 in).

Clear coated aluminum allowed for the scale plate material. Markings must be permanent (allows silk screen).

A non-accredited manufacturer of volumetric field standard must make it clear that calibration is required before use for Weights and Measures applications.

Scale plate graduations must be no smaller in height than 2 mm (approximately 0.1 in).

The total span of graduations on volumetric field standards smaller than 3800 L (1000 gal) has to be at least 1.5 % of the nominal volume. For 3800 L (1000 gal) and larger volumetric field standards, the total span of graduations must be at least 1.0 % of nominal volume.

Three thermometer wells are required for 3800 L (1000 gal) and larger volumetric field standards.

Fast acting, full port valves (rather than gate valves) are required on drain lines.

A new requirement for sight flow indicators (near the drain valve) has been added.

Though not retroactive, these indicators should be added to existing volumetric field standards anytime a major repair of the standard is performed.

NIST Handbook 105-3 iii

Provers larger than 20 L (5 gal) used for top load applications are required to have fill pipes.

Bleed lines are required (instead of bleed valves) on all new provers where air may be entrapped in the dry break coupler and lines going to it.

The level condition of volumetric field standards must be determined by using levels to plumb the neck rather than depending on the top of the neck to be level. The levels on volumetric field standards will be adjusted to agree with this level condition.

In harmony with OIML R 120, the tolerances for volumetric field standards (test measures and provers) have been changed to ± 0.05 % of the nominal capacity. All points on the neck scale must be within this tolerance for the entire volume (not the neck volume). An additional neck uniformity tolerance of 1 minor scale division (subdivision) from the nominal/zero to any point on the scale also applies.

Values in the four tables have been updated and the minor scale division (subdivision) is defined as the neck uniformity tolerance.

An optional evaluation checklist has been added to provide a reference for uniform evaluation of volumetric field standards.

NOTE Regarding Units of Measure:

The SI unit of volume is the cubic decimeter (dm3) or the cubic centimeter (cm3). The Twelfth General (International) Conference on Weights and Measures redefined the litre [herein spelled liter] as a “special name for the cubic decimeter,” but agreed to permit the continuance of the terms liter (L) and milliliter (mL), except in association with measurements of the highest precision. The commercial measurement system in the United States continues to use gallons and cubic inches for practical applications and manufacturers in this industry continue to use U.S. Customary dimensions. Since commercial applications in the United States use units other than SI or other accepted metric units, this document references common units in current use.

Acknowledgment:

The first edition of this Handbook was written by Blayne C. Keysar of NBS in 1979. The 1997 edition was updated with assistance of Karl Herken (KS). This 2010 edition was finalized through a work group consisting of those who provided comments on draft versions, compilation and draft responses of all comments by Michelle Foncannon, with the final review and editing effort led by L.F. Eason. Special acknowledgment is given to Seraphin Test Measure for preparing updated drawings and schematic diagrams. Thanks are also given to numerous metrologists (of both state and industry laboratories) for their technical review of several drafts.

*Trade names used in this Handbook do not imply recommendation or endorsement by the National Institute of Standards and Technology.

NIST Handbook 105-3 iv

Table of Contents

Preface .........................................................................................................................................................iii NOTE Regarding Units of Measure: ............................................................................................................................iv Acknowledgment:.........................................................................................................................................................iv

INTRODUCTION

1 ..........................................................................................................................................................1 Scope

1.1 ..................................................................................................1 “Volumetric Field Standard” Classification

1.1.1 ...................................................................................................................................2 Test Measures

1.1.2 ..............................................................................................................................................2 Provers

1.2 .....................................................................................................................................2 Laboratory Standards

1.2.1 .......................................................................................................................2 High-Resolution Type

1.3 ..................................................................................................................................................2 Retroactivity

1.4 ...............................................................................................................................................3 Future Designs

1.5 ....................................................................................................................................3 Safety Considerations

2. ......................................................................................................................................3 Reference Documents

2.1 ..............................................................................................................3 American Petroleum Institute (API)

2.2 ...................................................................................3 American Society for Testing and Materials (ASTM)

2.3 ......................................................................................................................4 Factory Mutual Research (FM)

2.4 ....................................................................................4 International Organization for Standardization (ISO)

2.5 ...............................................................................4 National Institute of Standards and Technology (NIST)

2.6 ...............................................................................4 International Organization of Legal Metrology (OIML)

3. ....................................................................................................................................................4 Terminology

4. ..................................................................................................................................................6 Specifications

4.1 ..................................................................................................................................................6 Physical Size

4.1.1 ................................................................................................................................6 Size Declaration

4.1.2 .........................................................................................................................6 Special Applications

4.1.3 ................................................................................................................................6 Size Limitations

4.2 ..................................................................................................................................6 Reference Temperature

4.3 .................................................................................................................................7 Identification Markings

4.3.1 ...................................................................................................................7 Identification Placement

4.3.2 ..............................................................................................................................................7 Content

4.3.3 ............................................................................................................................8 Limitations on Use

4.4 ..........................................................................................................................................................8 Material

4.4.1 .............................................................................................................................8 Steel Construction

4.4.2 .............................................................................................................8 Intended Use Considerations

4.4.3 ........................................................................................8 Material and Cross Contamination Safety

4.4.4 .....................................................................................................8 Non Steel Construction Materials

4.5 ..............................................................................................................9 Physical and Mechanical Properties

4.5.1 ..................................................................................................................................................9 Body

4.5.2 .................................................................................................................................................9 Shape

4.5.3 .......................................................................................................................9 Top and Bottom Cone

4.5.4 ..................................................................................................................................................9 Neck

4.5.5 ..................................................................................................................11 Sight Glass Gauge Tube

4.5.6 .................................................................................................................12 Scale Plate Construction

4.5.7 .......................................................................................................................13 Scale Plate Markings

4.5.8 .............................................................................................................................14 Scale Plate Units

4.5.9 ..................................................................................................................14 Scale Plate Graduations

4.5.10 ............................................................................................................................................15 Support

4.5.11 .........................................................................................................................15 Thermometer Wells

4.5.12 ..............................................................................................................................................17 Drains

4.5.13 ........................................................................................................................17 Sight Flow Indicator

4.5.14 ........................................................................18 Minimization of Product Vaporization or Foaming

4.5.15 ...........................................................................................................................................18 Fill Pipe

4.5.16 ..............................................................................................................................18 Bottom Loading

4.5.17 ................................................................................................................................19 Air Entrapment

NIST Handbook 105-3 v

4.5.18 ..................................................19 Bleed Line for Prevention of Air Entrapment During Calibration

4.5.19 .............................................................................................................20 Bleed Valves Not Allowed

4.5.20 ..............................................................................................................................20 Vapor Recovery

4.5.21 .........................................................................................................................................21 Hardware

4.5.22 ...............................................................................................22 Volumetric Field Standard Leveling

4.5.23 ..............................................................................................................................................22 Levels

4.6 .......................................................................................................23 Workmanship, Finish, and Appearance

4.6.1 ..............................................................................................................................23 Finished Quality

4.6.2 ..........................................................................................................................................24 Coatings

4.6.3 ....................................................................................................................24 Ladders and Platforms

4.7 .....................................................................................................................................24 Other Requirements

4.7.1 ....................................................................................................................................24 Return pump

4.7.2 .......................................................................................................................................25 Grounding

4.7.3 .............................................................................................................................................25 Wiring

4.7.4 ..........................................................................................................25 Electronic Overflow Systems

4.7.5 ...............................................................................................................................25 Braking System

4.7.6 ..................................................................................................................25 Labeling and Placarding

5. ...................................................................................................25 Tolerances (Maximum Permissible Errors)

5.1 ......................................................................................................................................25 Capacity Tolerance

5.2 ............................................................................................................................................25 Neck Tolerance

5.2.1 ............................................................................................................25 Neck Calibration Tolerance

5.2.2 ............................................................................................................26 Neck Uniformity Tolerance

5.3 ...................................................................................................................................................26 Adjustment

6. ............................................................................................................................26 Verification Requirements

6.1 .....................................................................................................................................26 Legal Requirements

6.2 ..................................................................................................................................................26 Traceability

6.3 ......................................................................................................................................26 Calibration Reports

6.4 ..................................................................................................................26 Initial and Periodic Verification

6.5 ..................................................................................................................27 Calibration of Metering Devices

6.5.1 .......................27 Using Volumetric Field Standards Without Application of Calibration Correction

6.5.2 ............................27 Using Volumetric Field Standards With Application of Calibration Correction

7. ........................................................................................................................27 Test Methods and References

7.1 ....................................................................................................................................28 Calibration Methods

7.1.1 .....................................................................28 NIST IR 7383 Selected Volume Procedures, SOP 18

7.1.2 .....................................................................28 NIST IR 7383 Selected Volume Procedures, SOP 19

7.1.3 .......................................................................28 API, Manual of Petroleum Measurement Standards

7.2 .........................................................................................................................................28 Field Calibrations

8. ..................................................................................................................................................28 Uncertainties

8.1 .......................................................................................................................................28 Legal Applications

8.2 ....................................................................................................................................29 Sources of Variation

8.2.1 .........................................................................................................................................29 Accuracy

8.2.2 ...................................................................................................................................30 Repeatability

Table 1a. ...................................................31 Dimensional requirements for metric volumetric field standards Table 1b. ......................................32 Dimensional requirement for U.S. customary volumetric field standards Table 2a. ....................................33 Tolerances and scale plate volumes for metric field standards and provers Table 2b. ...............................34 Tolerances and scale plate volumes for customary volumetric field standards Appendix 1. .......................................35 Optional HB 105-3 Volumetric Field Standard Specifications Checklist Figure 1. ......................................................................37 Hand-held volumetric field standard (test measure).

Figure 2. ...............................................................38 Small truck mounted volumetric field standard (prover).

Figure 3. ..................................................................................39 Mounted volumetric field standard (prover).

Figure 4. .....................................................................................................................40 Sight gauge assembly.

Figure 5. .......................................................................41 Trailer mounted volumetric field standard (prover).

Figure 6a. ........................................................................42 Limiting vapor loss with fill attached to drain line.

Figure 6b. ........................................................................42 Limiting vapor loss with fill entering bottom cone.

References

NIST Handbook 105-3 vi

NIST Handbook 105-3 1

SPECIFICATIONS AND TOLERANCES

FOR REFERENCE STANDARDS AND FIELD STANDARD

WEIGHTS AND MEASURES

3. Specifications and Tolerances for Graduated Neck Type Volumetric Field Standards

These specifications and tolerances are recommended as minimum requirements for standards used by state and local weights and measures officials and others in the regulatory verification of meters used in quantity determination of liquid commodities. Other users may find this handbook helpful in the design of volumetric standards, but the requirements should not be considered mandatory for special applications outside of the scope of regulatory weights and measures.

Key words: bottom loading; provers; specifications; standards; test measures; tolerances;

vapor recovery; volumetric field standards; volumetric specifications and tolerances; weights and measures.

INTRODUCTION

Graduated neck type volumetric field standards (test measures and provers) are used primarily to test liquid measuring devices for compliance with commercial requirements. Use of these standards at all appropriate levels of manufacture, distribution, and weights and measures inspection will help promote accuracy and uniformity in commerce. Volumetric field standards covered by this handbook include standard resolution models only. These include hand-held test measures, free-standing and mounted test measures, and provers. The breadth of topics in this handbook is intended to provide information for manufacturers, calibration staff, and weights and measures officials. Other end users may use this handbook for guidance in the design of special application volumetric standards. Deviations from the design specifications in this handbook may require additional tests to ensure the modified standard design meets the performance requirements of the specific application. Deviations from the requirements of this handbook must be clearly noted on any calibration report stating (or implying) compliance to the standard. References are provided when additional information may be useful to the reader.

1. Scope

1.1 “Volumetric Field Standard” Classification

These specifications are limited to non-pressurized, graduated neck type metal field standards, with or without vapor recovery capabilities where the volume is established between a shut-off valve (or bottom-neck zero graduation) and an upper-neck nominal graduation. The term “volumetric field standard” as used in this publication refers to all sizes in general.

1.1.1 Test Measures

Test measures are small (typically 20 L (5 gal) or smaller) hand-held volumetric measures, with or without a graduated bottom-neck (also called bottom-zero or wet-bottom).

1.1.2 Provers

Provers are large (typically 20 L (5 gal) or larger) bottom-drain volumetric measures with or without a graduated bottom-neck (also called bottom-zero or wet-bottom). Provers may be free-standing or permanently mounted on a truck, platform, or trailer.

1.2 Laboratory Standards

Test measures and provers may be used in a laboratory setting as primary or secondary standards. Additional specifications and tolerances may be applicable in those situations.

Slicker plate type laboratory standards are not addressed in this handbook.

1.2.1 High-Resolution Type

High-resolution volumetric standards are considered to be laboratory standards and are outside of the scope of this document. These test measures and provers are designed with a small diameter neck and are used to achieve greater neck volume resolution. This type of volumetric laboratory standard may also be characterized by the terms “high-accuracy,” “high-sensitivity neck,” or by the abbreviation “HSN.” Typically high resolution volumetric standards have approximately twice the resolution (i.e., the scale plate graduations are half as large for the same linear distance) of a normal volumetric field standard of the same nominal volume. Since these high resolution standards are specialty items, the neck diameter, resulting resolution, and other design elements must be specified based on the application, agreed to by both customer and manufacturer, and are generally outside the scope of this handbook.

1.3 Retroactivity

These specifications are not intended to make obsolete those field standards fabricated to meet prior specifications. All new test measures and provers placed in service after March 1, 2010, must meet these requirements prior to certification for regulatory Weights and Measures (legal metrology) use.

Volumetric field standards fabricated to meet prior specifications may be used as long as they 1) maintain the current tolerances, 2) meet calibration repeatability requirement of 0.02 % of nominal volume, and 3) their performance is adequate to meet NIST Handbook 44 fundamental considerations (volumetric correction plus uncertainty is less than one third of the tolerance for the device being tested).

The new requirements in this document are not retroactive. However, it is recommended that volumetric field standards be retrofitted to meet new requirements when major repairs or other modifications are made to an older standard.

Leveling volumetric field standards (section 4.5.22) to adjust replacement levels shall be performed by plumbing the neck on two axes separated by 90 degrees. This method shall be used to establish the reference level condition of all volumetric field standards.

NIST Handbook 105-3 2

1.4 Future Designs

These specifications are not intended to limit innovation made possible by advances in technology or changes in the commercial field devices they are used to test. All design revisions should be evaluated by NIST Weights and Measures Division for accuracy, repeatability, and suitability for task. Approved design revisions may be included in future editions of this document.

1.5 Safety Considerations

This documentary standard may involve hazardous materials, operations, and equipment and does not purport to address the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety information is documented in the API references. Specific items of safety concern are included in Section 4.7.

Commercial liquid measuring devices, tested with volumetric standards, are typically used to measure quantities of petroleum products. Petroleum products are known hazardous materials and hazardous wastes. The user is encouraged to obtain Material Safety Data Sheets (MSDS) from the manufacturer of any product encountered. Federal, state and local safety and disposal regulations concerning hazardous materials encountered should be reviewed and followed by the user.

2. Reference Documents

2.1 American Petroleum Institute (API)1

2.1.1 Manual of Petroleum Measurement Standards, Chapter 4, Proving Systems.

2.1.1.1 Section 1, Introduction (2005).

2.1.1.2 Section 4, Tank Provers (2005).

2.1.1.3 Section 7, Field-Standard Test Measures (2003).

2.1.1.4 Section 8, Operation of Proving Systems (2007).

2.1.1.5 Section 9, Methods of Calibration for Displacement and Volumetric Tank Provers.

2.1.1.6 Chapter 11, Physical Properties Data (Volume Correction Factors).

2.1.1.7 Chapter 12, Calculation of Static Petroleum Quantities.

2.1.2 RP 1004, Bottom Loading and Vapor Recovery for MC-306 and DOT-406 Tank Motor Vehicles.

2.2 American Society for Testing and Materials (ASTM)2

2.2.1 D 1250, Standard Guide for Use of the Petroleum Measurement Tables.

2.2.2 Table 24, Volume Reduction to 60 °F.

2.2.3 Table 24B, Generalized Products, Correction of Volume to 60 °F against Relative Density 60/60 °F.

NIST Handbook 105-3 3

2.2.4 Table 34, Reduction of Volume to 60 °F against S.G. 60/60 °F for Light Petroleum Gases.

2.3 Factory Mutual Research (FM)3

2.4 International Organization for Standardization (ISO)4

2.4.1 ISO 45 Aircraft Pressure Refueling Connections, 1990.

2.4.2 ISO Guide to the Expression of Uncertainty in Measurement, 1993.

2.5 National Fire Protection Association (NFPA)5

2.5.1 NFPA 58, Liquefied Petroleum Gas Code.

2.6 National Institute of Standards and Technology (NIST)6

2.6.1 Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, see current edition, published annually.

2.6.2 NISTIR 7383, Selected Procedures for Volumetric Calibrations, 2006.

2.7 International Organization of Legal Metrology (OIML)7

2.7.1 OIML R 117-1 (E), Dynamic Measuring Systems for Liquids Other Than Water; Part 1: Metrological and Technical Requirements, 2007.

2.7.2 OIML R 120, Standard Capacity Measures for Testing Measuring Systems for Liquids Other Than Water, 1996.

3. Terminology

Bleed line. A small bore line that automatically prevents air entrapment in a pipe, valve, dry break coupling, or other fitting that is part of the calibrated volume of the field standard during calibration and top loading applications.

Bleed valve. Valve used during calibration and top loading applications to manually release entrapped air from a pipe, valve, or fitting that is part of the calibrated volume of the field standard.

Bottom drain. Volumetric field standard design that permits draining the contained liquid without lifting and tipping the prover. Volumetric field standards with a bottom drain are commonly referred to as provers.

Bottom loading. Method of filling a volumetric vessel from below. Intake is made through piping at the bottom part of the vessel with connection through a dry-break coupler (also called a bottom-load adaptor). This method of loading tankers is prevalent at large petroleum terminals and must be used for the volumetric field standards used to test the meters at these terminals.

Bottom-load adaptor. See dry-break coupler.

Capacity, nominal. The nominal capacity of a volumetric field standard is the volume used to designate the test measure or prover (e.g., 5 gal test measure). The nominal volume is defined by the nominal mark on a graduated upper neck gauge on a test measure. The nominal volume is defined between the nominal mark on the graduated upper neck gauge and the lower shut off valve (or zero mark on a lower neck gauge) on a prover.

NIST Handbook 105-3 4

Cubical coefficient of thermal expansion. Three dimensional expansion or contraction of a material due to temperature change, expressed °C−1 or °F−1 (/°C or /°F).

Dry-break coupler. A spring loaded device on a volumetric field standard that is designed to connect to and disconnect from a loading rack arm or aircraft fueler hose without leaking. The same type of adapter is used on petroleum (or other fluid tankers) to connect to the loading arm or on aircraft to attach to the fueler hose.

“High Resolution” volumetric standard. A standard with a small diameter neck for improved resolution in reading the meniscus. Generally used in the laboratory as a standard or check standard.

Main flow cessation. The moment when a full discharge stream "breaks" and becomes a trickle or a drip.

Plumb. The condition of being perpendicular to a horizontal plane, vertical.

Prover. A mounted volumetric field standard (truck, trailer, or stationary); typically greater than or equal to 20 L (5 gal). Provers are not hand held and bottom drain is implied. Provers may be filled from the top or bottom loading, depending on intended use.

Reference temperature. The temperature at which the measure is intended to contain or to deliver its nominal capacity.

Sight-flow-indicator. A fitting with windows that allows visual observation of the flow through a pipe.

Submerged fill pipe. Pipe used in top filling to minimize foaming of liquids, such as fuel oil and milk, by discharging the product into the bottom of a prover.

Test measure. A hand held volumetric field standard that is typically less than or equal to 20 L (5 gal) and without a bottom drain.

To contain. An indication that the measure is adjusted to contain its intended volume when filled from its empty and dry condition at a reference temperature. These measures are typically marked “To Contain” or “Contain.” Test measures and provers are generally not used in this condition.

To deliver. An indication that the measure is adjusted to deliver its intended volume when filled from its empty and “wet” condition at a reference temperature. The “wet” condition is obtained by filling the measure to its nominal capacity and emptying it in conformance with procedural requirements, leaving a reproducible reference residual amount of liquid in the measure.

Volumetric field standards (test measures and provers) are generally used in this condition.

These are typically marked “To Deliver” or “Deliver.”

Tolerance (also Maximum Permissible Error). Extreme value of measurement error, with respect to a known reference quantity value, permitted by specifications or regulations for a given measurement, measuring instrument, or measuring system.

Vapor recovery. A system for entrapping and collecting vapors for return to the tank to prevent expulsion into the atmosphere.

NIST Handbook 105-3 5

4. Specifications

4.1 Physical Size

4.1.1 Size Declaration

The recommended sizes of metric and U.S. Customary (inch-pound) test measures and provers are shown in Tables 1a, 1b, 2a, and 2b. Nominal volumes in each system are ideally selected in multiples of 1, 2, and 5 (liters or gallons) to facilitate calibration. However, a prover may be built to any size to meet specific needs. Non-standard size volumetric field standards that comply with all other requirements shall be considered to be in full compliance with this standard.

NOTE: Users must ensure that the intended metrology laboratory is able to calibrate non-standard sizes prior to obtaining a new field standard.

4.1.2 Special Applications

Test measures and provers are generally selected to minimize the number of deliveries required for volume transfer calibration. Selection may be for use as a laboratory standard for calibration of other test measures or provers, for calibration of LPG provers, or for calibration of dynamic small volume provers. Fifteen is the maximum recommended number of deliveries from a standard to a prover under test to minimize calibration uncertainties. Selection of provers as laboratory standards should take into consideration the largest size of unknown prover that is likely to be tested.

4.1.3 Size Limitations

The 5000 L (1500 gal) prover, which is the largest of the provers described in this publication, is typically the largest size which can be mounted vertically on a truck or trailer and meet highway height and width requirements. Larger volumetric field standards may be built based on design considerations within this document, but they are not specifically covered. Additional performance, structural integrity, stability, and safety issues applicable to these larger standards, though outside of the scope of this handbook, must be considered.

4.2 Reference Temperature

The temperature at which test measures and provers are referenced during calibration and during use for testing petroleum products is generally 15.56 °C (60 °F). International standards reference petroleum products to 15 °C. Provers may be used for applications other than petroleum products or in areas where a different reference temperature is used for petroleum products. In such cases, the appropriate reference temperature for the application should be identified and used. For example, the reference temperature for provers used in testing milk is

4.44 °C (40 °F).

NOTE: Any time the prover is used at a temperature different than the reference temperature the prover volume must be corrected from the reference temperature using the following equation:

1 ttVVV ref Sindicatedgaugecalibratedcorrected where:

= cubical coefficient of expansion for the prover material (units must match units used to measure prover temperature and tref S);

NIST Handbook 105-3 6 indicatedt = temperature of the prover, typically estimated by measuring the temperature of the prover contents through the thermometer wells, when so equipped;

ref St = reference temperature of prover calibration;

calibratedV = calibrated volume of the prover at the reference temperature;

gaugeV = indicated gauge reading at the time of use;

correctedV = actual volume of prover contents when corrected from the reference temperature, tref S.

This temperature correction must be performed to determine the correct volume of the prover at time of use. This temperature correction does not in anyway correct for the expansion/contraction of the measured commodity (commonly known as temperature compensation.)

4.3 Identification Markings

4.3.1 Identification Placement

Identification information shall be engraved, embossed, or affixed by some other permanent means directly on the standard or on a metal plate that is permanently attached to the standard in an area that is relatively protected from damage or normal wear. All lettering shall be permanent, durable, weather resistant, impervious to the liquids the volumetric field standard is intended to measure, and of a contrasting color to that of the background. This information (however placed) should be either laminated or coated with a clear protective coating to preserve its legibility indefinitely.

NOTE: The permanence of adhesives used to attach data plates to volumetric field standards has proven to be problematic in the extreme conditions under which these standards are often used.

Therefore, the data plate must be attached by weld, solder, or another means that is more permanent than adhesives.

4.3.2 Content

Each standard shall bear in a conspicuous place the following information:

4.3.2.1 Nominal capacity;

4.3.2.2 Name and address of the manufacturer;

4.3.2.3 Model number;

4.3.2.4 Non-repetitive serial or identification number and year of manufacture;

4.3.2.5 Material identification and cubical coefficient of thermal expansion per °C (°F);

4.3.2.6 “10 sec drain after 30 sec delivery” for hand-held volumetric field standards (test measures) or “30 sec drain after main flow cessation” for bottom-drain volumetric field standards (provers).

NOTE: The year of manufacture may be included as part of the serial number if it is easily identifiable to the user.

NIST Handbook 105-3 7

4.3.3 Limitations on Use

Any limitations on use shall be clearly and permanently marked on any volumetric field standard (but not necessarily on the data plate) by either the manufacturer or the user. Examples include volumetric field standards intended to measure accurately only:

4.3.3.1 Products having particular properties (e.g., a volumetric field standard for food product testing with a plastic sight glass and alternative reference temperature);

4.3.3.2 Under specific installation or operating conditions; or

4.3.3.3 When used in conjunction with specific accessory equipment.

4.4 Material

4.4.1 Steel Construction

Unless approved by the Weights and Measures Division, National Institute of Standards and Technology (NIST), volumetric field standards shall be constructed of low carbon steel or 300-series stainless steel. All parts of a test measure or prover (i.e., neck and integral hardware) shall be made of identical material. Non-integral hardware may be of other materials provided the hardware is durable and suitable for its intended purpose.

4.4.2 Intended Use Considerations

Material must be chosen based on intended use and shall be thermally stable. The use of oxygenated fuels, chemicals (e.g., fertilizers, pesticides), or food products may dictate the type of metal that may be used. Laboratory standards should be made of 300 series stainless steel.

NOTE: The materials used in volumetric field standards used for special applications must comply with regulations governing the specific application. In case of conflict, legal requirements supersede the requirements of this handbook.

4.4.3 Material and Cross Contamination Safety

Care should be taken to ensure that the materials used for the volumetric field standards, or any subsequent contamination of such materials, do not create a safety hazard, especially when the measures may be used for the measurement of food, petroleum, or chemical products. It is the responsibility of the user to ensure that a volumetric field standard is appropriately labeled when necessary to prevent cross contamination of measured products.

4.4.4 Non Steel Construction Materials

Proposals for the exemption of material requirements and for use of other suitable materials must be submitted to the Weights and Measures Division of the National Institute of Standards and Technology (NIST). All applicable physical property data shall be accurately documented for any material chosen. The proposed material will be evaluated to determine the suitability for the intended use, and the requestor will be informed in writing of the decision.

EVALUATION NOTE: An unduly high coefficient of thermal expansion (e.g., such as for plastic or aluminum) is inappropriate for field use in meter verification and will not be approved.

Uncorrected thermal expansion introduces an error or uncertainty that is statistically significant.

NIST Handbook 105-3 8

4.5 Physical and Mechanical Properties

4.5.1 Body

Any cross section taken in a plane perpendicular to the vertical axis shall be circular. The volume of a standard shall be established without the use of fillers, adjusting plugs, or cavities of any kind.

4.5.2 Shape

The shape of the test measure or prover shall ensure complete emptying, draining, and the prevention of air entrapment.

4.5.3 Top and Bottom Cone

4.5.3.1 Cone pitch

Recommended top and bottom cone pitches are provided in Tables 1a and 1b. Cone pitches are intended to facilitate complete emptying and draining. The bottom of hand-held test measures shall be concave to prevent the distortion of the measure during filling due to the weight of the liquid.

NOTE: Deviation from the recommended cone pitch requires a laboratory evaluation of repeatability and assurance of no air entrapment. Repeatability criteria requiring the agreement between calibration runs are established in the appropriate calibration procedures. A complete evaluation of repeatability for non-standard cone pitches may require additional runs to verify acceptable repeatability. The metrologist should also examine the surface properties of the cone as roughness will affect drainage characteristics, especially when pitches are less than those specified. Visual examination for places air might be entrapped and agitation of water in the filled vessel to reveal air pockets should be done to ensure there is no air trapped in the volumetric standard.

4.5.3.2 Bottom cone anti-vortex design

An effective anti-vortex device shall be attached to the bottom cone of a prover to minimize liquid swirl during emptying. A prover or test measure must be designed to prevent the trapping of air, whether top or bottom filled.

NOTE 1: Fins or plates are often used to limit circular product motion that creates a vortex.

NOTE 2: Calibration of provers generally requires top filling regardless of top or bottom fill applications to allow for delivery by gravity drain from the laboratory standard.

4.5.3.3 Cone trough

Where a support band extends above the joint between the body of the prover and the top cone, the trough shall have a suitable drain.

4.5.4 Neck

The neck (upper and/or lower) of a volumetric field standard shall be inspected for uniformity in its circular cross section. If the graduated section of the neck is “out-of-round” (e.g., oblong or dented), this is indicative of damage and the volumetric standard should be rejected during inspection/calibration by the weights and measures enforcement agency. The neck axis shall be perpendicular to a level horizontal plane.

NIST Handbook 105-3 9

4.5.4.1 Neck reinforcement

The opening at the top of the neck shall be reinforced to retain a circular cross section by using a rolled bead or a band welded to the neck. As much as practical, this reinforcement and the lip of the neck shall be shaped to facilitate a controlled, single stream pour of liquid from test measures. (See Figures 1, 2, and 3.)

4.5.4.2 Neck diameter

Maximum neck diameters are specified in Tables 1a and 1b. Neck diameters may vary; the critical factors related to neck diameter are the cross sectional area of the fluid in the graduated section of the neck, the volume above and below the nominal zero level, the graduation sizes, the space between graduations, and the clarity and permanence of the markings.

4.5.4.3 Cross sectional area

The cross sectional area of the liquid in the graduated area of the neck of a volumetric field standard is the critical factor in the evaluation of the neck. Therefore, the cross sectional areas of the sight glass and any top fill pipes must also be considered when applicable (i.e., when determining the space between scale plate graduations).

4.5.4.4 Access for cleaning

The neck diameter of a test measure shall be sufficient to permit cleaning and inspection. Small capacity volumetric field standards may have neck diameters that are too small to allow adequate visibility for inspection or space to insert a hand for cleaning. In these cases, a small inspection mirror, fiber optic or miniature camera, and a flexible bottle brush may be necessary to inspect and clean the measure.

4.5.4.5 Neck attachment to cone

The upper neck and lower neck (when present, i.e., bottom zero) shall be attached flush with the cone seam and in such a way that the neck does not project into either cone, thus preventing air or liquid entrapment at the joint.

4.5.4.6 Upper neck drain valve

Volumetric field standards used for meter proving shall not have a drain valve on the upper neck of the standard. Provers used as laboratory standards may have a drain valve on the upper neck to be used for adjusting the delivery from the standard to a nominal volume.

4.5.4.7 Lower neck drain valve

A small drain valve on the gravity discharge line of a volumetric field standard is permitted to adjust the level of a bottom-zero (when present). This drain should be installed before the shut off valve, below the bottom-zero level, and shall not interfere with use of the prover for meter verification.

4.5.4.8 Automated bottom-zero option

Internal piping to the bottom-zero setting valve may be constructed so that the drained level of the liquid is even with the zero level of the lower neck gauge plate. If this is the case, the bottom zero must be adjusted to agree with this fluid level and verified at each calibration.

NIST Handbook 105-3 10

4.5.4.9 Access to drain

If a lower neck drain valve is present, there must be adequate space for a drain bucket (or other appropriate container) under this valve. Alternatively, the drain valve output may be piped back into the main drain line at a point beyond the shut off valve.

4.5.4.10 Operation

Operator control of the lower neck drain valve must allow simultaneous visibility of the bottom sight gauge.

4.5.5 Sight Glass Gauge Tube

Field standard volumetric standards shall be equipped with a gauge tube mounted on the side of the neck to clearly indicate the level of fluid in the standard.

4.5.5.1 Material

Unless prohibited by the intended application (i.e., testing meters or tanks for milk or other products for human consumption), the gauge tube shall be made of borosilicate glass and be clear and free of any markings, irregularities or defects which distort the appearance of the liquid surface.