National Bureau of Standards

Library, N.W. Bldg (/ (j MAY 1 1963

NBS MONOGRAPH OZ

Testing of Metal

Volumetric Standards

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress,

March 3, 1901, as amended by Congress in PubHc Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means

and methods for making measurements consistent with these standards; the determination

of physical constants and properties of materials; the development of methods and instruments

for testing materials, devices, and structures; advisory services to government agencies on

scientific and technical problems; invention and development of devices to serve special needs

of the Government; and the development of standard practices, codes, and specifications.

The work includes basic and applied research, development, engineering, instrumentation,

testing, evaluation, calibration services, and various consultation and information services.

Research projects are also performed for other government agencies when the work relates to and siipplements the basic program of the Bureau or when the Bureau's unique competence

is required. The scope of activities is suggested by the listing of divisions and sections on

the inside of the back cover.

Publications

The results of the Bureau's research are published either in the Bureau's own series of

publications or in the journals of professional and scientific societies. The Bureau itself publishes three periodicals available from the Government Printing Office: The Journal of Research, published in four separate sections, presents complete scientific and technical papers;

the Technical News Bulletin presents summary and preliminary reports on work in progress;

and CRPL Ionospheric Predictions provides data for determining the best frequencies to use for radio communications throughout the world. There are also five series of nonperiodical

publications: Monographs, Applied Mathematics Series, Handbooks, Miscellaneous Publications, and Technical Notes.

A complete listing of the Bureau's publications can be found in National Bureau of

Standards Circular 460, Publications of the National Bureau of Standards, 1901 to June 1947

($1.25), and the Supplement to National Bureau of Standards Circular 460, July 1947 to June

1957 ($1.50), and Miscellaneous Pubhcation 240, July 1957 to June 1960 (Includes Titles of Papers Published in Outside Journals 1950 to 1959) ($2.25); available from the Superintendent

of Documents, Government Printing Office, Washington 25, D.C.
UNITED STATES DEPARTMENT OF COMMERCE • Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Testing of Metal

Volumetric Standards

J. C. Hughes and B. C. Keysar

National Bureau of Standards Monograph 62

Issued April 1, 1963

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 2S, D.C. - Price IS cents
Library of Congress Catalog Card Number: 63-60025
Foreword

This Monograph is intended primarily as a guide in the purchase and use of metal volumetric standards by weights and measures officials, by oil, gas, and pipeline companies, and

by others who measure fluid products by volume.

The measures described herein are used principally as reference standards in the calibration

of working standards. For this reason, specifications and tolerances have been established to insure that standards purchased are of suitable quality.

The courtesy of equipment manufacturers who have supplied photographic material and

drawings is greatly appreciated.

m
Contents

Page

Foreword in

1. Introduction

1.1. Purpose

1.2. Organization

1.3. Scope 1

2. Liquid measures

2.1. General specifications

2.2. "Slicker plate" liquid measures 2

2.3. Graduated-neck liquid measures 3

2.4. Other liquid measures 5

3. Gas measures 5

3.1. General specifications 5

3.2. Immersion bottle 6

3.3. Portable cubic-foot (Stilbnan) standard 7

3.4. One-tenth cubic-foot bottle 9

4. Dry measures 10

5. Directions for submitting apparatus for test

5.1. Application for test

5.2. Shipping directions..

5.3. Damage to apparatus

5.4. Address

5.5. Remittances

6. References

7. Appendix

7.1. Change in capacity caused by change of temperature

7.2. Correction for difi^erence in temperature 12

7.3. Correction for difference in thermal expansion of measures 12

IV
Testing of Metal Volumetric Standards

J. C. Hughes and B. C. Keysar

The National Bureau of Standards has for many years calibrated and certified metal

measures which are used as standards by weights and measures officials and others in the

calibration of instruments for measuring the volumes of fluids. No complete specifications or tolerances for these standards have ever been published, however, nor have standardized

procedures for the calibration and use of the liquid measures been available. The information contained in this Monograph should assist in the purchase of quality

instruments and the proper use of the standards in calibrating other measures for liquids

and gases.

1. Introduction

1.1. Purpose

The specifications and tolerances contained in

this Monograph should be of assistance to purchasers of metal capacity standards. The information on methods of calibration and use of these measures should prove valuable to weights and

measures officials and those persons in industry

who are concerned with measurements of volumes

of fluids. 1.2. Organization

I Although some repetition may result, it is

I believed that the separate and complete treatment

j of each type of measure will be more convenient to

j| those who use this publication as a reference.

1.3. Scope

It is recognized that some types of metal capacity measures will not be covered by this publication; however, it has been deemed advisable to provide specifications and tolerances for only those

types which the National Biireau of Standards is called upon to calibrate. The principles involved

in the design, calibration, and use of these basic

standards are generally applicable to all types of

metal capacity measures. Measures submitted to the Bureau for certifi- cation should conform with the specifications

contained herein; however, certificates may be

issued to state agencies when required by state law

whether or not the item complies in all respects

with these specifications, if it is apparent that the

item will perform its designed function.

The Bureau does not desire that the specifications contained herein work a hardship on the owner of costly equipment. Therefore, any metal

capacity standard which has been previously

certified will be accepted for recalibration as long

as it is in good condition.

2. Liquid Measures

, 2.1. General Specifications

' a. Units of Capacity

' The great majority of metal liquid measures

i used in this country are in units of a gallon, which

li is defined as 231 in.^ Metal measures are made in

[ sizes as small as 1 gill, or 4 fluid ounces. Other

;j units used are listed below with their equivalents.

|j 1 liquid pint =4 gills

I 1 liquid quart=2 liquid pints

1 gallon =4 liquid quarts

1 liter = 1 .05672 liquid quarts =61.0254 cubic inches

!j b. Standard Temperature

Metal capacity measures are usually standardized at 60 °F for use in the oil industry or at 68 °F

(20 °C) for milk and other food products.

c. Design and Workmanship

The cross section of any metal capacity standard

must be circular, and the shape must permit

complete emptying and draining. When a bottom

drain extends outward from the center of a

standard, it must slope at least 5 deg.

Instruments having a base must stand solidly on a level surface. If provided with a bail handle, a measure must hang with its axis vertical. The

inside surface must be corrosion resistant, and all inside seams must be smoothly filled with metal

to eliminate pockets where air or Hquid may be

trapped when the measure is used.

All measures must be sufiiciently strong and

rigid to prevent distortion of the vessel when fuU

of liquid. Reinforcing bands, properly used, will

eliminate the necessity for excessively heavy

construction.

Valves must operate freely and positively, and

there shall be no leakage from seams or fittings.

1
Adjustable legs must be capable of easy operation when the measure is filled. A capacity measure must be completely as- sembled before calibration or before shipment to the National Bureau of Standards. Anything

which will extend through the wall must be in place. Volume-adjusting plugs must have provision for sealing.

The possibility of making certain types of

liquid measures of materials other than metal has

been under study. Nothing in these specifications is intended to preclude the use of other

suitable materials, provided measures made of

such materials conform with applicable parts of

these specifications.

2.2. "Slicker Plate" Liquid Measures

a. Design

The most accurate metal measures for liquids are those in which the capacity is limited by a

glass plate, commonly called a "slicker plate,"

which is slid into place on top of the measure. The top edge of the measure must be carefully

machined so that there will be no leakage between the metal edge and the glass plate.

Cylindrical measures of this type have been

used for many years; but the conical shape with

a smaller top, because of its improved handling

ease, is rapidly replacing the older and heavier

cylindrical shape. The conical design, illustrated

in figure 1 , is used almost exclusively for measures

of 1 gill to 1 gal. The 5-gal stainless steel smaUFiGTJRE 1. Conical measure.

neck measure illustrated in figure 2 has proved

very satisfactory as a standard for calibrating measures used in the field. ti Slicker-plate measures larger than 1 gal are j usually made with a bottom drain and a plug » valve. Those of 1 gal or less can be manipulated « without difficulty by means of the handle provided.

i b. Special Requirements

The bottom of a conical measure, which has a

relatively large area, should be designed so that ; it will resist denting or displacement in use. Final adjustments of the capacity should not be

made by adding an excess of soft metal to the ^ inside. jj The inside diameter of the top opening should

not be less than 1 in. for any size. ' The nominal capacity of a slicker-plate measure

shall be prominently engraved on the outside

wall. If in units of a pint or a quart, the word

"liquid" or the abbreviation "liq" shall be in- ' eluded in the inscription. The manufacturer's

name or trademark and a serial number should be L shown less conspicuously.

c. Capacity Tolerances

National Bureau of Standards certificates will s be issued to cover the calibration of slicker-plate '

Figure 2. 5-gallon ^'slicker plate'' measure.
capacity standards when the corrections to the

indicated capacities are not greater than the

tolerances listed below. These tolerances represent the maximum errors that may be disregarded in normal use. When the corrections

exceed the tolerances, but are not more than

twice the tolerances, the results will be given on

a Report form.

Capacity Tolerance

Customary units

Less than 1 pint

1 pint or larger

1 part in 1000

1 part in 2000

Metric units

Less than 5 decihters

5 deciUters or larger

1 part in 1000

1 part in 2000

d. Calibration and Use At the National Bureau of Standards, slickerplate measures are usually calibrated by weighing.

After cleaning with an organic solvent, the measure is filled with distilled water until the

water level is slightly below the top edge of the

measure, and a thermometer inserted to determine the temperature. After removal of the

thermometer, more water is added to raise the

level above the top of the measure, and the glass

slicker plate is pushed from one side across the

top edge of the measure until the plate covers the

opening completely. The excess of water is thus

cut off and the measure should then be completely

fuU. There should be no air bubble beneath the

slicker plate ; if one is present more water must be

added.

All water on the outside of the measure and the

exposed surfaces of the slicker plate is then re- moved with absorbent paper, and the fiUed measure is placed on the pan of a balance of

adequate capacity. The tare is adjusted until

the balance is in equilibrium. The measiire is removed from the balance and emptied (in the

case of a measure without a drain) by tipping

until its axis is approximately horizontal and then

carefully sliding the slicker plate upward to allow

the water to flow out. The plate is slid completely off as soon as convenient, and after the

main outflow has ceased the measure is held in a nearly inverted position and allowed to drain for 10 sec. It is then righted, the slicker plate re- placed, and the measure returned to the balance

pan. The weight which must be added to the same pan to restore equilibrium is the apparent

weight of the water delivered by the measure. The weight of water delivered is converted to volume by means of prepared tables which include

corrections for temperature, atmospheric pressure, and humidity.

A slicker-plate measure having a bottom drain

is emptied by moving the plate just far enough

to allow air to enter the measure wlien the valve

is opened, sliding it completely off after flow has

started. The drainage time for measures of this

type is 30 sec.

If provided with means of adjustment, a

slicker-plate measure wiU be sealed after calibration. An identifying number is applied by the

National Bureau of Standards, and the actual

volume delivered is reported as indicated in section 2.2.c. In using a slicker-plate standard to calibrate

another measure, it is filled as described in the

method of calibration. It is not necessary to dry

the outside so completely; however, it must be

sufficiently dry that no water will run off into the measure being calibrated. The standard is emptied as described in the calibi'ation method.

2.3. Graduated-Neck Liquid Measures

a. Design

These measures are made in a wide range of

capacities, from a quart or less to thousands of

gaUons. They have a relatively small neck on

which is mounted a gage glass and a graduated

scale. A typical measure is shown in figure 3.

Figure 3. Graduated-neck measure.
Measures of 1-gal to 10-gal capacity are usually

made with a closed bottom and equipped with a

bail or other form of handle for lifting and emptying. Measures of more than 10-gal capacity are usually made with a bottom drain and a valve.

The larger measures are often equipped with

adjustable legs for leveling.

b. Special Requirements

A bail handle should be attached to the neck

rather than to the conical part of the body, to minimize any possibility of distortion.

The bottom should be designed so as to resist distortion when filled and to provide protection

against damage in use. The gage glass should be of clear glass tubing,

free of any irregularities or defects which would

distort the appearance of the liquid surface, and

having an inside diameter of approximately }i in. If plastic tubing is used, it should be resistant

to the chemical action of petroleum products.

The mounting should be designed so that it will not interfere with brush cleaning of the inside of

the tube. The bottom mounting of the gage

glass should be made leakproof without the use of

cement; that is, replacement of the glass tube

should present no difficulties. A scale of corrosion-resistant metal should be

mounted approximately on a tangent to the front

of the gage glass. It should not be more than

in. from the gage glass. In most cases, the nominal

capacity is designated by a zero line near the center

of the scale, with at least 15 graduations above and

15 below the zero line. In special-purpose provers,

such as those for high-vapor-pressure liquids, the

design of the gage and scale may differ from that

recommended above. The scale should be as near

as possible to the recommended position, however.

Numbering should be in whole units. The minimum distance between adjacent lines should be

}U in. When two scales are used, the graduation

lines representing equivalent volumes must lie in the same plane. Provision shaU be made for

finely adjusting, locking, and sealing the scale so that it cannot be moved.

The type of gage which is merely a window with

a scale on the side is not considered suitable for use on a standard. The top edge of the meniscus

appears as a distinct line on the window, while the

bottom of the meniscus, which is the reading level,

is barely discernible. For this reason, the Bureau

does not accept for calibration measures equipped

with this type of gage.

All measures should be level when the gage is read. Large measures (commonly called provers)

which are to be used in a fixed location should

be leveled when installed. Provers which may be

moved must be equipped with a means of determining when they are level. The use of two small

spirit levels, permanently mounted at right angles

to each other, has proved satisfactory for this

purpose. Leveling devices are not required on

measures of 10 gal or less, as they are either

placed on a level surface or suspended by the bail

j handle in use. ; A bottom drain on a prover should be equipped

with a quick-acting leakproof valve.

Each measm"e submitted to the Bureau for calibration must bear the maker's name or trades

mark and an identification or serial number. *

c. Capacity Tolerances

Capacity Tolerance

Customary units

Over 1 gallon (graduated neck)

1 gallon or less (graduated neck)

1 gallon (cylindrical-graduated in fl oz) _ _ 1 quart (cylindrical-graduated in drams).

1 pint (cylindrical-graduated in drams) _ _ pint (cylindrical-graduated in drams) —

_

1 part in 2000

1 part in 1000

0.25 fl oz

0.5 dram

0.5 dram

0.5 dram

Metric units

Over 5 liters (graduated neck)

5 liters or less (graduated neck)

1 liter (cylindrical-graduated in ml)

1 part in 2000

1 part in 1000

2 ml

d. Calibration and Use i

I At the National Bureau of Standards, graduated-neck measures of capacities up to and in- cluding 10 gal are calibrated by weighing. After ij cleaning with an organic solvent, the dry measure j, is placed on the pan of a suitable balance together j with enough weights to equal or exceed the weight 1, of the water which the measure will contain. ( Weights are added to the other pan until equilibj riiuTX is established. The measure is removed , from the balance and filled with distilled water

until the level is slightly above the zero mark on

the scale. The water temperature is taken by

lowering a thermometer approximately to the

center of the measure, and the meniscus is set on

the zero mark by withdrawing water in a suitable

syringe. Before the final setting, the measure

should be tilted toward the observer to wet the

tube 1 or 2 cm above the zero mark.

When the water level is set or read in the gage, the line of sight must be horizontal. A convenient

aid to a proper setting is a rectangular piece of j white paper with a pencU line drawn through the ,

'.^ center. The paper is slipped into place between i

|| the scale and adjusting rods and in back of the

gage glass, the pencil line being alined exactly

with the zero line on the scale. When the water level has been adjusted to the

zero mark, the measure is placed on the balance

pan and equilibrium restored by removing weights

from the pan bearing the filled measure. The ;i total weight removed is the weight of water contained in the measure. If it is desired to deter- - mine what volume the measure will deliver, the i

4
water is poured out and the measure is allowed to drain in a nearly inverted position for 10 sec. It is again placed on the balance pan and weights

added to the same pan until equilibrium is restored.

The weight added is equal to the weight of the

water delivered.

The weight of water contained in or delivered by

the measure is converted to volume by means of prepared tables, which include corrections for

temperature, atmospheric pressure, and humidity.

A measure of more than 10-gal capacity, com- monly known as a "prover," is calibrated by the

use of standards of appropriate size. A graduated-neck measure may be calibrated

either to contain or to deliver the nominal volume.

A request for calibration should specify which is desired; when it does not, the measure will be

calibrated "to deliver." A measure calibrated

"to contain" must be completely emptied and

dried before each filling, while a measure calibrated "to deliver" may be used to receive its nominal

volume if it is filled and emptied, then drained

for the prescribed time (10 sec for measures of 10

gal or less; 30 sec for larger measures) before each

measurement.

2.4. Other Liquid Measures

There are other metal liquid measures designed

for special purposes, such as the meter provers

described in API Standard 1101 [1].^ Some are

similar in design to the measures described in

' paragraph 2. 3. a, while others differ greatly.

Proving systems entirely closed to the atmosphere

' are essential for liquids of high vapor pressure. A widely used portable prover for liquefied petroleum gas meters is shown in figure 4. It is built

to withstand pressures up to about 300 lb/in.

I The hose connected at the top permits vapor to

jl pass freely between the prover and the supply

3. Gas

j 3.1. General Specifications

a. Units of Capacity

li Gas is measured almost exclusively in cubic

' feet in the United States. A few meters reading

! in liters are made here, principally for sale abroad.

I The relationship between these units is

1 cubic foot =28.31605 liters.

L b. Standard Temperature

I The standard temperature for volume measureiments of gas is 60 °F.

' Figures in bracltets indicate tlie literature references on page 11.

Figure 4. Liquefied petroleum gas meter prover. tank, thus maintaining a constant pressure within

the system while proving a meter. When calibrating a closed prover under internal

pressure, the drop in liquid level as pressure is applied is a combined result of tank expansion and

decrease of liquid volume. To determine the

change in tank volume, the change in gage reading

must be reduced by the change in liquid volume.

This change in liquid volume may be computed

easily if the compressibility factor is known.

Measures

c. Design and Workmanship

Certain required features of design and workmanship are common to the three types of gas- measuring standards.

(1) The cross section shall be circular, and the

shape shall permit complete emptying

and draining.

(2) The instruments must be sufficiently sti'ong

and rigid to resist denting or distortion.

(3) The materials used in their construction

must be corrosion resistant.

(4) All seams shall be smoothly filled with

metal to eliminate crevices and pockets

and to prevent leakage.

(5) Valves or cocks must operate smoothly and

must not leak under maximum operating

5
pressures. Three-way valves shall be

marked to indicate the position of the

plug openings.

(6) Volume-adjusting devices, whether indices,

collars, or sleeves, must be provided

with means for locking in place. The

set screws provided for locking the adjusting sleeves on cubic-foot bottles,

immersion and portable, should be drilled

to receive sealing wires.

(7) Inscriptions shall include the maker's name

or trademark, a serial number, and the

nominal capacity.

3.2. Immersion Bottle

a. Design

The 1-ft^ immersion bottle shown in figure 5 is used for calibrating gas-meter provers (gasometers). It has an opening about 2}^ in. in diameter on the lower end, while the upper end

is equipped with a gage glass with adjustable

index, a 3-way control cock, and a hose fitting.

A hose connects the bottle with the prover (gasometer), and lowering the bottle into the liquid

(water or oil) to the gage index displaces 1 ft^ of air at atmospheric pressure. After fabrication

of the bottle, adjustment of the capacity is made

by means of an adjustable collar on the open

end.

b. Special Requirements

The bottom edge of the adjustable collar mentioned above must be smoothly finished, at

right angles to the axis of the bottle. The collar must have provision for sealing gastight to the

neck of the bottle. If this is accomplished by a packing ring above the collar, both ring and

collar should be drilled in three or more places on the periphery so that spanner wrenches may

be used to tighten or loosen the seal. The gage glass shall be of clear glass tubing,

sealed gastight within a gage body so designed

that the liquid level may be easily observed.

The gage marker or index shall be so constructed

and mounted that it will resist bending or breaking. It should preferably be made of stainless 5 steel.

c. Capacity Tolerances Ij The capacity of a 1-ft^ immersion bottle is adjusted so that the volume of water delivered at

60 °F between the gage index and the open end,

allowing 3 min for emptying and an additional;

3 min for draining, is 1.000 ft^, with a tolerance

of ±0.05 percent, or ±0.0005 ft^

It is now the practice at the National Bureau

of Standards to adjust these bottles so that the

volume of water delivered under the above condi

tions is slightly more than 1.000 ft^; for example,

1.0003 ft^. If the bottle is used iii oil instead oi water, the volume of oil delivered will then be

only slightly less than 1.000 ft^; for example,

0.9997 ft^. The best available data on the comparative drainage of water and the light oi. recommended for use in gasometers indicate that,

under the conditions outlined above, the volume

of oil remaining on the inner wall of the bottle is approximately 0.0006 ft^ more than that of water

d. Calibration and Use 2

ise

Figure 5. immersion bottle.

(Courtesy of American Meter Company)

The calibration described in section 3.2.c. accomplished by weigliing on a sensitive balance

The rate of emptying is controlled by an orifice plate attached to the open end.

For the standardization of a prover it is essential

to have the temperature of the room constanti

throughout the test. If water is used in thei prover (or bottle tank), evaporation from the wefcl sides of the bell (or bottle) as it is raised may cool

the air within sufficiently to cause an appreciable

error. There are two ways in which this troubles may be overcome. One is to saturate the air in, the room with water vapor. The other method,\

which is recommended as preferable, is to use ini place of the water a light clear oil of low vaporc

pressure. The calibration of a prover by the cubic-foot

bottle can be made either by measuring the airi into the prover 1 ft'^ at a time until the proveij

is filled, or by filling the prover and measuring

the air out 1 ft^ at a time. There is no inherent, reason why the two methods should not agree J

2 Much of the material on the use of the cuhic-foot standards is taken front' NBS Circ. 309 [2].

6
Successive calibrations should agree within 0.2 percent.

The bottle and prover should be kept near each

other for a long enough period before the test (preferably overnight) so that they will be at the same temperature.

To test bottle and connections for leaks, the

counterweights of the prover are adjusted until

the pressure in the prover is about 1 in. of water. The bottle is lowered into the tank and connected

with the prover. The valves between bottle and

prover are opened until the pressure in the system

is the same as that in the prover. The prover

valve is then closed and the setup allowed to stand for 5 or 10 min. If the temperatures of

the air and bottle do not change, the pressure, as indicated by the gage on the prover connection,

should remain constant. The prover bell can also be tested for leaks

during this interval by raising it and noting its position. If the temperatures of the air and

prover do not change, the bell should remain

stationary.

(1) Bottling Out oj the Prover. Bottling out of a prover with an immersion bottle may be done

either at atmospheric pressure or at the usual

prover pressure. The procedure for calibrating at the usual prover pressure will be described first. After making sure that all connections are tight,

and with the bell raised as high as possible without

unsealing, the valve between prover and bottle is opened, making the pressure within the bottle the same as in the prover. The quantity of liquid in the bottle tank is then adjusted until the surface

of the liquid within the gage glass of the bottle is in the plane of the gage mark. There may be some

difficulty in making this adjustment because the

surface of the liquid in the tank, outside the bottle,

will be above the gage mark by an amount suffi- cient to balance the pressure of the prover. By

manipulation of the prover slide valve the zero of

the prover scale is now brought exactly opposite

the pointer. The bottle is now raised steadily

from the tank, thus drawing into it air from the

i prover. Since the test is being made at the usual

prover pressure, the opening of the lower neck will

still be submerged by an amount sufficient to equal the pressure of the prover when the bottle is filled with air. It will be necessary, therefore, to

raise the bottle very slowly when it is nearly filled

I with air and to stop the instant the first small

bubble breaks out from the bottom of the bottle.

. If the work is done carefully, there is no need of

I losing more than one or two very small bubbles

I of air.

j Now that a cubic foot of air has been removed

i from the prover, the prover valve is closed and the

' reading of the scale is noted. A small amount of

air is then returned from the bottle to the prover

'i so as to raise the 1-ft mark of the prover scale

above the index mark. The bottle is then subiij merged after opening its valve to the atmosphere.

The prover bell is now adjusted so that the 1-ft

scale mark coincides with the pointer and another

cubic foot of air may be bottled out.

If the test is made at atmospheric pressure the

procedure will be substantially the same as tfiat just described. The special precautions occasioned

by the prover pressure will now be unnecessary.

However, it would be advisable when raising the

bottle from the tank not to unseal the bottom of the lower neck until after closing the valve between the prover and the bottle in order to guard

against accidental shifting of the prover bell.

(2) Bottling Into the Prover. This method is the

reverse of the preceding with the exception that it

is practically necessary to use atmospheric pressure

in the bottle and prover during the test. This

merely requires that the counterweights of the

prover be increased until the bell is just balanced.

3.3. Portable Cubic- Foot (Stillman) Standard

a. Design

A portable cubic-foot standard (also called a

Stillman cubic-foot standard) is illustrated by

figures 6 and 7. The essential details of construction (shown by fig. 7) are as follows: the bell a

fits into the annular tank h, guided by the tele- scoping tubes c and d and the collars e and /. Collar e is threaded onto the inner tube d and

serves as both a guide ring and a stop to limit

Figure 6. Portable standard.

(Courtesy of American Meter Company)
Figure 7. Diagram of portable 1-ft^standard.

the upward travel of the bell. Collar / and stop

ring I are fixed to the inside of the outer tube.

By changing the position of collar e on tube d the

height to which the bell may be raised is changed.

It is by this means that the displacement of the

bell is adjusted to exactly 1 ft^. The cap h

forms a gastight seal. The tube i serves as an

inlet to or outlet from the interior of the bell. A flexible hose connecting this standard with a prover or other instrument is attached at j, and

the flow of gas into or out of the standard is controlled by a 3-way valve k. Water or a light oil may be used as the sealing

liquid in the annular tank h; however, if water i^ used, this standard will be subject to the same

disadvantages as were mentioned in the discussion

of the immersion type of cubic-foot bottle, which

may be overcome by the same methods as then? suggested. The quantity of sealing liquid re-, quired is a little over 1 gal.
b. Special Requirements

Portable cubic-foot standards are equipped with

a circular type spirit level mounted on top of the

beU. The level must be carefully mounted so

that its indication is correct. The tank rests on

three leveling screws. The stop ring I and collar e (fig. 7) which limit

travel of the bell must meet squarely. They

must be free of solder or other foreign matter on

the contact surfaces. This requirement applies

also to the shoulder where tube d is joined to the

beU, and the collar /, which serve to limit the

J downward travel of the beU. The tank, bell, and

guide tubes must be truly concentric in order

that there will be no binding at any point and the

bell will not depart from a level condition as it

is raised.

A drain cock shaU be provided at the bottom

of the tank, while the inlet-outlet tube must have

a drain hole fitted with a gastight plug. If there

is a bleed hole in the flared ring at the top of the

tank, this hole must also be fitted with a leakproof

plug.

The bottom cap on the outer guide tube shall be

fitted with a gasket which will provide a positive

seal when tightened by hand.

The adjusting sleeve must be carefully machined

so that it turns easily.

c. Capacity Tolerance

A certificate will be issued for a portable cubicfoot standard of the Stillman type if the error in

the volume of air delivered at 60 °F by a full stroke of the bell does not exceed 0.05 percent or

0.0005 ft^

d. Calibration and Use

For adjusting a portable standard to receive

or deliver 1 ft^ of gas, an accurately adjusted

I immersion-type bottle is connected to the standj ard. The stroke of the bell is then so adjusted

! that, upon discharging 1 ft^ of gas from the immer-

' sion bottle into the portable standard essentially

; no change of pressure takes place within the system.

Actually a small change of pressure will result

from the drainage of the sealing fluids, but this

I need be taken into account only for calibrations

of the highest accuracy. Both the portable standiard and the immersion bottle must, of course, be

I at the same temperature.

j This standard may be operated at atmospheric

I pressure or slightly higher. In either case it is essential to have the pressure within the standard

jand apparatus under test the same at the end of

the bell stroke as at the start. The bell should be in the same position relative

, to the tank when at the bottom and top of its stroke. Current production models are equipped

with a device which allows vertical movement

I only.

' The bell should rest tightly against the stops

when at either the upper or lower position, but

should not be allowed to strike either stop hard;

the bell should be raised and lowered evenly and

without undue force. This portable standard has the important advantage of being very easily moved. If provided

with a suitable case it may be shipped from place

to place without danger of injury. The method

of operation is very easy and rapid. When used

to calibrate a meter prover the ordinary prover

pressure may be used, a practice that is not always

possible when using other types of cubic-foot

bottles. The Bureau has found that it is possible

to calibrate meter provers with this type of standard to practically the same degree of ac- curacy as is obtained when the older forms of

cubic-foot bottles are employed.

3.4. One-Tenth Cubic- Foot Bottle

a. Design

The l/lO-ft^ bottle illustrated by figures 8

and 9 is used principally for setting the water

level in, or calibrating, small water-sealed rotat- ing-drum meters (commonly called wet-test meters). It has gage glasses on top and bottom,

fittings for hose of approximately % in. i.d. on top

and bottom, and a 3-way valve, or cock, on the

top. The gages are provided with adjustable

markers, or indices, to mark the capacity limits.

b. Special Requirements

The gage markers, or indices, are normally supported on a guide rod at one point only; therefore,

they must be of rigid construction to prevent

bending.

c. Capacity Tolerances

A certificate will be issued for a 1/10-ft^ bottle

if, with the gage markers set within the middle half

of the exposed gage glass length, the bottle delivers

0.10000 ±0.00005 ft^ at 60 °F. The capacity

is reported to 0.00001 ftl

d. Calibration and Use

Calibration of a fractional cubic-foot bottle is accomplished by weighing the water delivered.

A stopcock is clamped to the lower hose fitting

and the bottle filled from the bottom until the level

is slightly above the upper gage index. A few

blows on the bottle with the palm of the hand

wiU displace air bubbles which may collect on the

inside walls. The bottle is then clamped in a stand and water is drained out through the stopcock until the level is exactly at the upper index.

Any excess water on the tip is touched off against

the inside wall of the receiving vessel, which is then replaced with a weighing flask. With the stopcock fully open, the water is dis- charged against the inner wall of the flask neck

until the level in the bottle approaches the lower

index. The discharge is slowed, and stopped when

the level is exactly at the index. The rate of

9
I

Figure 8. One-tenth ft^ bottle.

(Courtesy of American Meter Company)

outflow is controlled by the size of the opening

in the tip so that the time of outflow is approximately equal to that required in use plus the 30-sec

drainage time prescribed in ASTM Standard

Method D 1071 [3] (about 2 min). Any excess water at the stopcock tip is touched off against

the inner wall of the flask, after which the flask

is stoppered and weighed.

The method of using a 1/10-ft^ bottle to cali- brate a 1/10-ft^ wet-test meter is described in detafl in ASTM Standard D 1071 [3].

4. Dry

The use of dry measures is prohibited by law in some jurisdictions. The sale of dry commodities

by weight has become so prevalent that the use

of dry measures is rare even where permitted.

For completeness, however, there is presented here

a brief discussion of standards of dry measure.

4.1. Design

Standards of dry measure are cylindrical in shape, with sizes ranging usually from 1/2 pt to

1/2 bu. The capacity is defined by the top edge

of the standard.

)

Figure 9. Diagram of 1/10 ft^ bottle. ] p

, I II

Measures

j

4.2. Special Requirements '

Measures must be sufficiently strong and rigid

to prevent distortion of the vessel when filled. The top edge of a standard must be machined; ; true, so that a watertight closure may be obtained

with a glass "slicker plate."

The nominal capacity shall be prominently en- graved on the outside wall. If in units of a pint, or a quart, the word "dry" shall be included in the

inscription. The manufacturer's name or trade-Jj

mark and a serial number should be shown less conspicuously.

10
4.3, Capacity Tolerance

The capacity tolerance for standards of dry measure shall be 1 part in 1,000.

4.4. Calibration and Use

The capacity of a dry measure is computed from

the weight of water which it will contain, using a

slicker plate to determine when it is filled exactly

to the top. The use of these measures with dry

commodities is described in NBS Handbook

45 [4].

5. Directions for Submitting Apparatus for Test

5.1. Application for Test

The request for test should be made in writing

and should include a list of the apparatus, the

method of calibration desired (to contain or to

deliver), the standard temperature (if not marked

on the apparatus), and the material of which the

instruments are made, if known.

Representatives of state institutions entitled to

tests free of charge must make application in writing for each test in order to avail themselves

of the privilege.

Patrons should always examine apparatus care- fully before submitting it for test to ascertain if it complies with the construction specifications, is free of dents and rust, does not leak, and is in good condition generally. Delay and cost of transportation on apparatus not entitled to verification will thus

be avoided.

The Bureau does not sell volumetric apparatus.

It may be purchased from manufacturers or jobbers and submitted for test. Purchasers of apparatus to be submitted to the Bureau for test should so specify to the dealer in order to avoid

unnecessary delays and misunderstandings.

5.2. Shipping Directions

The apparatus should be securely packed in cases or packages which will not be broken in trans- portation and which may be used in returning the

tested material to the owner.

Transportation charges are payable by the

party requesting the test. The charges for shipment to the Bureau must be prepaid; and, unless

otherwise arranged, articles will be returned or forwarded by express collect. After the material is received at the Bureau,

the shipper will be notified of the test number

assigned. This number should be mentioned in

any correspondence pertaining to the test. When submitting immersion bottles for calibration, do not include the tank. It is not used in

the calibration, and the crating and shipping would

involve a considerable expense.

5.3. Damage to Apparatus

In spite of reasonable care in handling, it is possible that damage may occur during testing.

There is no legal way in which the Bureau can make reimbursement for damage of this kind. It

is therefore a matter of necessity, and not of choice,

that the Bureau makes those who send apparatus

for test assume all the risks involved.

5.4. Address

Articles and communications should be

addressed, National Bureau of Standards, Washington 25, D.C.

6.5. Remittances

Payment of test fee should be made promptly

upon receipt of bill. Remittances may be made

by money order or check drawn to the order of the

"National Bureau of Standards."

Copies of the current Test Fee Schedules may

be obtained from the Bureau upon request.

6. References

[1] API Standard 1101, American Petroleum Institute, [3] ASTM Standard D 1071, Amer. Soc. for Testing and

New York, N.Y. (1960). Materials, Philadelphia, Pa.

[2] NBS Circ. 309 (1926). Gas measuring instruments. [4] NBS Handb. 45, p. 198 (1951). Testing of measuring

equipment.

7. Appendix

7.1. Change in Capacity Caused by Change

of Temperature where

If the capacity of a measure at any temperature,

for example 60 °F, is known, the capacity at another temperature may be determined by the use of the following formula:

Vt=V,, [1+a (^-60)] (1)

V(= capacity at t °F,

1^60= capacity at 60 °F,

q: =coefficient of cubical expansion

of the material of which the measure is made, per degree

F.

11
Average coefficients (per °F) for the metals

most widely used in capacity standards are: Brass 0.000030

Copper .000028

Low carbon steel .000018

18-8 stainless steel .000028

7.2. Correction for Difference in Temperature

If the temperature of the water in the standard

differs from that of the water in the measure being

calibrated, a correction must be applied to bring

the volumes of water to the same temperature

basis. A table for this purpose has been incorporated

(table I) in API Standard 1101 [1]. Lacking

such a table, factors for the adjustment of water

volimies to a common temperature may be derived from the density values. Water density

tables are available from several sources including

physics and chemistry handbooks.

Any correction to the water volume is partly

offset by the volimie change in the metal measures. (The temperature of a measure is assumed to be

the same as that of the water contained.) To

adjust the capacity of one measure to the capacity

it would have at the temperature of the other, a modification of formula (1) may be used.

Correction = Va{t—ti) (2)

where

y=measured volume

a =coefficient of cubical expansion of the measure whose volume is being adjusted.

^—^1 =temperature difference between measures.

As an example of the correction for a difference

in temperature, let us assume that the average

temperature of the water in a standard graduated

to deliver 100 gallons at 60 °F was 74 °F, but

after being emptied into the prover it was measured at 76 °F. Both measures are of mUd (low

carbon) steel. The change in the volume of water from 74 to 76° may be computed from the formula

density of water at 74°

(3) density of water at 76°

inn 1 s. 0-99748

=100

0:99721 = 100.027 gal.

The change is 100.027-100.000, or 0.027 gal.

WhUe the volume of water was increasing, the

capacity of the prover also increased by an amount

represented by formula (2), or

100X0.000018X2 =0.0036 gal.

The net correction for the temperature differ- ence, therefore, is 0.027 —0.0036 or 0.0234 gal.

Because the water in the prover is warmer than

when in the standard, the level in the gage will be

higher than it would be if the temperatures had

remained the same, and must be lowered by 0.0234

gal before adjusting the scale to the water level.

If the two measures are made of materials

having the same thermal expansion coefficient, no further correction is necessary, since the

standard is correct at 60 °F.

7.3. Correction for Difference in Thermal Expansion of Measures

If a standard is being used to calibrate a measure made of material having a different thermal ex- pansion coefficient, and the temperature is other

than the standard temperature (usually 60 °F) a correction must be applied to account for the

difference in volume change of the two instruments. The correction may be represented by

the following equation

C=Vit-m){ai-a2) (4) where

C=con'ection

1^= measured volume

f= temperature of observations (°F)

ai =cubical coefficient of thermal expansion

of metal in standard

a2= cubical coefficient of thermal expansion

of metal in measure being calibrated.

For example, suppose that a 100-gal prover

made of low-carbon steel is being calibrated with

a 50-gal standard made of 18-8 stainless steel. The average temperature (measured in the water

when the instruments are full) is 75 °F. The

correction would be:

C=100(75-60) (0.000028-0.000018)

=0.015 gal or 3.465 in.^ The standard, having a larger expansion coeffi- cient, will, when filled and emptied twice into the

prover, ffil the prover to a higher level by 3.465

in.' than it would if both measures were at the

standard temperature of 60 °F. If the water

level in the prover were lowered by 3.465 in.' and

the zero line on the scale adjusted to that level,

the prover would be correct at 60 °F. When working at a temperature below 60 °F,

the scale should be adjusted upward when other

conditions are as in the preceding example. At

50 °F the correction would be 100X10X0.00001

or 0.010 gal (2.31 in.'). If 2.31 in.' of water were added to the prover and the zero line on the scale

adjusted to that level, the prover would be correct

at 60 °F.

12 U.S. GOVERNMENT PRINTING OFFICE: 1963 O—674651
U.S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and Boulder,

Colorado, is suggested in the following listing of the divisions and sections engaged in technical work. In general, each

section carries out specialized research, development, and engineering in the field indicated by its title. A brief description of the activities, and of the resultant publications, appears on the inside of the front cover. WASHINGTON, D.C.

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lil BOULDER, COLO.

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