2015 EPO No. 24

Vehicle-Tank Meters, Gravity Discharge (Rev 09/14) DRAFT Page 1 of 7

NIST Examination Procedure Outline for

Vehicle-Tank Meters (VTMs)

Gravity-Discharge

It is recommended that this outline be followed as minimum criteria for examining all gravity-discharge vehicle-tank 

meters – analog or digital. Nonretroactive requirements are followed by the applicable date in parentheses. Do not use 

this outline for testing vehicle-tank metering systems measuring milk, LPG, cryogenics, or carbon dioxide or for testing 

power-operated vehicle tank meters. Nonretroactive requirements are followed by the applicable date in parentheses.

SAFETY NOTES

When excerpting this Examination Procedure Outline for duplication, the EPO Safety Annex (Safety 

Considerations and Glossary of Safety Key Phrases) should be duplicated and included with this outline.

Safety policies and regulations vary among jurisdictions. It is essential that inspectors or servicepersons be 

aware of all safety regulations and policies in place at the inspection site and to practice their employer’s safety 

policies. The safety reminders included in this EPO contain general guidelines useful in alerting inspectors and 

servicepersons to the importance of taking adequate precautions to avoid personal injury. These guidelines can 

only be effective in improving safety when coupled with training in hazard recognition and control.

Prior to beginning any inspection, the inspector should read and be familiar with the EPO Safety Annex - “Safety 

Considerations and Glossary of Safety Key Phrases." The terms and key phrases in each safety reminder of this 

outline are found in the glossary of the EPO Safety Annex. The inspector is reminded of the importance of 

evaluating potential safety hazards prior to an inspection and taking adequate precautions to avoid personal injury or 

damage to the device. As a minimum, the following safety precautions should be noted and followed during the 

inspection.

Clothing

Electrical Hazards

Emergency Procedures

Fire Extinguisher

First Aid Kit

Grounding

Ignition Sources

Lifting

Location

Nature of Product

Personal Protection Equipment

e.g., 

Safety Shoes, Safety Aprons, Gloves,

Eye Protection

Hard Hat, etc. if deemed necessary

Safety Cones/Warning Signs

Safety Data Sheets (SDS)

Static Discharge

Switch Loading

Traffic

Transportation of Equipment

also: Wet/Slick Conditions, Chemicals, Hazardous Materials, Petroleum Products, and 

Obstructions
2015 NIST EPO No. 24

Page 2 of 7 Vehicle-Tank Meters, Gravity Discharge (Rev 09/14) DRAFT

H-44 General Code and 

Vehicle-Tank Meter 

Code References

Inspection:

SAFETY REMINDER!!!

− Check the inspection site carefully for safety hazards and take appropriate precautions.

− Check to be certain that the ground surface of the inspection site is sufficiently strong and rigid to 

support the prover when it is filled with product - don’t forget to chock the wheels of the prover.

− Learn the nature of hazardous products used at or near the inspection site – obtain and read copies 

of MSDS’s.

− Know emergency procedures and location and operation of fire extinguisher and emergency 

shut-offs.

− Post safety cones/warning signs and be aware of vehicular and pedestrian traffic patterns.

− Use caution in moving in wet, slippery areas and climbing on prover, storage tanks, and vehicles.

− Use personal protection equipment and clothing appropriate for the inspection site.

− If leaks, spills, or exposed wiring cause hazardous testing conditions it is recommended that the 

testing be discontinued until the unsafe conditions are corrected.

− Be sure that a first aid kit is available and that it is appropriate for the type of inspection activity.

1. General considerations.

Selection ....................................................................................................................

Installation .................................................................................................................

Position of equipment................................................................................................

Accessibility ..............................................................................................................

Assistance ..................................................................................................................

Use and maintenance .................................................................................................

Use of ATC................................................................................................................

Invoices based on device readings with Automatic Temperature 

Compensator (ATC) ..........................................................................................

Period of use (ATC) ...........................................................................................

G-S.3., G-UR.1.1., 

G-UR.1.2., G-UR.1.3.

UR.3.3.

G-S.2., G-UR.2.1., 

G-UR.2.2., UR.1.1.

G-UR.3.3.

G-UR.2.3.

G-UR.4.4., G-UR.4.6.

G-UR.3.1., G-UR.4.1.,

G-UR.4.2., UR.2.3., 

UR.1.4

UR.2.5.1

UR.2.5.3.

UR.2.5.2.

Computing-capability ................................................................................................ UR.3.3.

2. Indicating and recording elements.

Design ........................................................................................................................ S.1.1.1.
2015 NIST EPO No. 24

Vehicle-Tank Meters Gravity Discharge (Rev 09/14) Page 3 of 7

H-44 General Code and 

Vehicle-Tank Meter 

Code References

Inspection (cont.):

Units .......................................................................................................................... S.1.1.2.(a) , S.1.1.3.(b) 

and (c)

Readability................................................................................................................. G-S.5., G-S.6. (1/1/77), 

G-S.7., S.1.2., S.1.3.

Values of intervals..................................................................................................... G-S.5.3.

Recorded representations.

General ............................................................................................................... G-S.5.6., S.1.4.2.

Required for vehicle-tank metering systems ...................................................... UR.2.2., UR.2.3.

Exceptions for aviation fuel................................................................................ UR.2.2.1.

Computing-type devices.

Display of unit price ........................................................................................... S.1.4.1, UR.1.2.

Money-value computations ................................................................................ S.1.4.3.

Gross and net indications for devices with ATC........................................................ S.2.5.3.

Advancement and return to zero................................................................................ S.1.1.4., S.1.1.5., UR.2.1.

Provision for sealing.................................................................................................. G-S.8. (1/1/90), 

G-UR.4.5., S.2.2., 

Table S.2.2.

Provision for sealing ATC Systems........................................................................... S.2.5.4.

3. Marking.

General.............................................................................................................................. G-S.1.

Location, Not-Built-For Purpose, Software-Based Devices............................................ G-S.1.1.(1/1/04)

Devices or Main Elements Remanufactured as of January 1, 2002................................. G-S.1.2.

Visibility of required markings after installation ............................................................. G-UR.2.1.1.

Money-Operated Devices, Responsibility........................................................................ G-UR.3.4.

Limitation on Use............................................................................................................. S.5.1.

Discharge Rates................................................................................................................ S.5.2.

Temperature Compensation for Refined Petroleum, if equipped with ATC................... S.5.6.

Meter Size......................................................................................................................... S.5.7.
2015 NIST EPO No. 24

Page 4 of 7 Vehicle-Tank Meters, Gravity Discharge (Rev 09/14) DRAFT

H-44 General Code and 

Vehicle-Tank Meter 

Code References

Inspection (cont.):

4. Measuring elements.

Vapor elimination ......................................................................................................

Security seal on adjusting mechanism.......................................................................

Provisions for thermometer well................................................................................

S.2.1.

G-UR.4.5., S.2.2.

S.2.6. (1/1/12)

5. Piping.

Directional flow valves and discharge line and valves..............................................

Leaks..........................................................................................................................

Facilitation of fraud ...................................................................................................

S.2.3., S.3.

G-UR.4.1.

G-S.2.

6. Devices Equipped with ATC. ................................................................................................

Provisions for deactivating ......................................................................................

Gross and net indications.........................................................................................

Provision for sealing ATC.......................................................................................

Temperature determination......................................................................................

S.2.5., S.2.5.1.

S.2.5.2.

S.2.5.3.

S.2.5.4.

S.2.5.5.

Pretest Determinations:

1. Test Equipment Set-up. Gravity discharge VTMs are designed to make deliveries to 

underground storage tanks; product is delivered to a tank that is entirely below the 

level of the truck tank. As such, when product is delivered from these systems the 

discharge end of the hose is approximately roadway level and the discharge hose is 

said to have a negative head to allow gravity to push product through the system.

To approximate commercial operating conditions in the testing operations of these 

devices, the prover height must simulate road level height so that the end of the 

delivery line from the VTM corresponds to its position when inserted in the fill pipe 

of an underground storage tank at a filling station.

2. Determine that the test fluid in the tank compartment is similar in character to the 

fluid to be measured....................................................................................................... .N.1.

3. Determine that a compartment or compartments have a sufficient amount of product 

to conduct “high head” and “low head” tests (also referred to as full compartment and 

near empty compartments tests since the head pressure acting on the meter decreases 

as the compartment is drained).

4. Test draft size. Determine if the prover size is adequate ................................................ N.3.

5. Ensure that the prover inlet is lower than the meter outlet.

6. Tolerances.

Applicable requirements............................................................................................

Tolerance values........................................................................................................

Repeatability..............................................................................................................

Devices equipped with ATC......................................................................................

G-T., T.1.

T.2., Table 1, Table 2

T.3.

T.2.1. (a), (b)

7. Note totalizer reading.
2015 NIST EPO No. 24

Vehicle-Tank Meters Gravity Discharge (Rev 09/14) Page 5 of 7

H-44 General Code and 

Vehicle-Tank Meter 

Code References

SAFETY REMINDER!!!

− Wear appropriate personal protection equipment such as petroleum-resistant, nonskid safety shoes 

(to prevent possible injury from spills or slipping on slick surfaces), protective clothing, eye 

protection (to prevent injury from splashed product), and a hard hat (to prevent injury from 

overhangs and projections).

− Use proper grounding procedures. Be sure that prover is equipped with an explosion proof motor.

− Carefully inspect electrical supply lines to test equipment for wear and damage; correct potentially 

hazardous conditions before use.

− Device operator should be present at all times during test - the operator (not the inspector) should 

operate the device under test.

− Never leave equipment unattended while it is in operation.

Test Notes:

1. Record totalizer (s) indication before and after each draft to determine proper 

operation.

2. If prover is dry, wet prover. Allow a 30-second drain period each time prover is 

emptied.

3. Level the test measure or prover. When the test measure or prover is full of liquid, recheck its level to ensure that the weight of the product has not affected the level 

condition.

4. Evaporation and volume change: exercise care so that the product temperature is the 

same in the prover as at the meter. ................................................................................ N.2

5. Temperature corrections are to be made for accuracy tests to account for any 

difference between the temperature of the liquid passing through the meter and the 

liquid in the prover. ....................................................................................................... N.5.

6. After each test draft:

a. Print a ticket (if so equipped). ................................................................................ G-S.5.2.2., G-S.5.6.

b. If computing type, check price computation on indicator and on recorded 

representations. ......................................................................................................

G-S.5.6., S.1.4.2., 

S.1.4.3., S.1.4.4.

c. Check for agreement between indicators................................................................ G-S.5.2.2.

7. Verify that any options for obtaining a recorded representation are appropriate. The 

customer may be given the option of not receiving the recorded representation. If 

the system is equipped with the capability, the customer may also be given the 

option of receiving the recorded representation electronically in lieu of or in addition 

to a hard copy. ............................................................................................................... G-S.5.6.

8. If the result of any test is at or near the tolerance limit, repeat that test. If necessary, 

conduct a repeatability test as outlined in Step 1 under “Tests: All Meters” below.
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Page 6 of 7 Vehicle-Tank Meters, Gravity Discharge (Rev 09/14) DRAFT

H-44 General Code and 

Vehicle-Tank Meter 

Code References

Tests:

SAFETY REMINDER!!!

− If supply or return lines are not coupled at their discharge ends, they must be held in place 

continuously while product flows through the line.

− Use proper lifting techniques to lift and move equipment.

− Be aware of and attempt to eliminate potential ignition sources in or near the inspection site.

− Be aware of vehicular and pedestrian traffic in the area.

Tests: Non-Temperature-Compensated Meters

1. Normal test - - full flow (high head/full compartment), basic tolerance. ...................... N.4.1., T.2.

2. Normal test - - full flow (medium head/one-half full compartment), basic tolerance. .. N.4.1., T.2.

3. Normal test - - full flow (low head/one and one-half times prover capacity in the

compartment), basic tolerance....................................................................................... N.4.1., T.2.

4. Proceed to “Tests – All Meters.”

Tests: Temperature-Compensated Meters

1. 1Normal test with temperature compensator activated - full flow, normal tolerance. 

(Do not deactivate the temperature compensator.)........................................................ N.4.1., N.4.1.3. T.2.1.

2. Deactivate temperature compensator and repeat normal test. Compare the 

compensated volume indicated or recorded to the actual delivered volume corrected 

to 15 °C (60 °F)............................................................................................................. N.4.1., N.4.1.3. T.2.1.

3. Proceed to “Tests – All Meters.”

Tests: All Meters

1. Repeatability Test............................................................................................................

If necessary, conduct a repeatability test. Test must include at least three consecutive 

test drafts. Test drafts must be conducted under approximately the same conditions 

(e.g., flow rate and temperature) and be of approximately the same draft size.

N.4.1.2., T.3.

2. RFI/EMI test (electronic equipment only) ......................................................................

This testing is typically done only if a problem is suspected or during the inspection 

of a new installation.

Radio Frequency Interference (RFI)

Electromagnetic Interference (EMI)

G-N.2., G-UR.1.2., 

G-UR.3.2., G-UR.4.2.

3. Check automatic stop mechanism. ..................................................................................

The device should stop the flow within one-half the minimum interval indicated.

G-UR.4.1.
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Vehicle-Tank Meters Gravity Discharge (Rev 09/14) Page 7 of 7

Post Test Tasks:

1. Security Means.

Check for the presence of security seals on the device. Document missing seals on 

the official report and apply new ones as needed. ......................................................... G-UR.4.5.

Adequate provision shall be made for applying a physical security seal or providing 

for other approved means of security. ...........................................................................

G-S.8, S.2.2., 

Table S.2.2.(1/1/95)

If system is equipped with an audit trail, note the event counter settings on the 

report form for future reference. If equipped with an event logger, print a copy of 

the event log and attach it to the report form for future reference. ................................

G-S.8., S.2.2., 

Table S.2.2. (1/1/95)

SAFETY REMINDER!!!

− Avoid switch loading!

− Test devices dispensing low-vapor pressure products (e.g., diesel fuel, kerosene) before testing 

devices dispensing high-vapor pressure products (e.g., gasoline).

− Take precautions to isolate equipment when transporting it to avoid exposure to hazardous 

fumes!

2. Record on the official report the number of gallons of product dispensed during test.

3. After all equipment at a location has been tested, review results to determine 

compliance with equipment maintenance and use of adjustments. ............................... G-UR.4.1., G-UR.4.3.

4. Record the compliance action and disposition of the device on the report and explain 

the results to the device owner.