# COMAR Title 20 — Public Service Commission

## Subtitle 55 — Service Supplied by Gas Companies

### Chapter 06 — Metering Test Facilities and Equipment

**Authority:** Public Utilities Article, §§2-121, 5-101, and 7-301, Annotated Code of Maryland

**Administrative History:** Effective date: July 1, 1964 (Order No. 55567)

**Administrative History:** Chapter revised effective October 21, 1974 (Order No. 60922)

**Administrative History:** Regulation .01C amended effective February 7, 2000 (27:2 Md. R. 146)

**Administrative History:** Regulation .02 amended effective May 5, 1986 (13:9 Md. R. 1032); February 7, 2000 (27:2 Md. R. 146)

**Administrative History:** Regulation .03A amended effective February 7, 2000 (27:2 Md. R. 146)

**Administrative History:** Regulation .04 amended effective February 7, 2000 (27:2 Md. R. 146)

#### Regulation .01 Meter Shop.

*COMAR 20.55.06.01*

A. Meter Shop. Each utility shall maintain or designate a meter shop for the purpose of inspecting, testing, and repairing meters. The shop shall be open for inspection by authorized representatives of the Commission at all reasonable times, and the facilities and equipment, as well as the methods of making the measurements and tests employed, shall be subject to the approval of the Commission.

B. Temperature Control. The area within the meter shop used for the testing of meters shall be designed so that the meters and meter testing equipment are protected from drafts and excessive changes of temperature. The meter shop shall be air-conditioned, if necessary, in order to achieve satisfactory temperature control.

C. Meter Storage. Unless the proving equipment corrects for temperature differences, the meters to be tested shall be stored in such manner that, at the time of the test, the temperature of the meters is substantially the same as the temperature of the prover.

#### Regulation .02 Provers and Attachments.

*COMAR 20.55.06.02*

A. Required. Each utility shall own and maintain, or have access to, one or more calibrated meter provers of appropriate size, and all other equipment necessary to test meters.

B. Temperature Control of Bell Provers. Means shall be provided to maintain the temperature of the liquid in the bell provers at substantially the same level as the air temperature in the prover room. The maximum difference in temperature should not be more than 2°F.

C. Accuracy.

  (1) Each meter prover shall be maintained in good condition, in correct adjustment, and accurate to within ±0.3 percent at each point used in testing meters.

  (2) A prover shall be calibrated at least once every 3 years and if moved or disassembled.

  (3) The accuracy of a bell prover shall be determined by one or more of the methods indicated below:

    (a) By comparison to a 1 cubic foot standard calibrated by the National Institute of Standards and Technology;

    (b) By comparison to an approved transfer standard for a bell prover in excess of 5 cubic feet; or

    (c) By strapping the bell prover with a calibrated tape whose accuracy is traceable to the National Institute of Standards and Technology.

  (4) The accuracy of any other type of prover shall be determined by appropriate standards traceable to the National Institute of Standards and Technology.

D. Attachments. A device used in conjunction with a prover is calibrated to the following accuracy standards:

  (1) If the accuracy of the attachment is determined independently of the system accuracy it shall be within ±0.2 percent; or

  (2) If the accuracy of the system includes the accuracy of the attachment the system accuracy shall be within ±0.3 percent at each point used in testing meters.

#### Regulation .03 Other Working Standards.

*COMAR 20.55.06.03*

A. Approved. Utilities may test meters by other methods approved by the Commission or by use of other working standards approved by the Commission.

B. Accuracy. The approved working standards shall be maintained in good condition and correct adjustment, shall have a high degree of repeatability, and shall be capable of determining the actual proof of the meter under test to within ±0.5 percent at rates of flow between 15 percent and 100 percent of rated capacity of the meter under test.

C. Test Period. The approved working standards shall be tested for accuracy by comparison with an acceptable standard at least once each 3 years.

#### Regulation .04 Pressure Test Equipment.

*COMAR 20.55.06.04*

Each utility which corrects meter readings to compensate for pressure shall have dead weight testers, test quality electronic pressure transducer gauges, test quality precision type bourdon tube spring gauges, mercury manometers, or field type dead weight pressure gauges as necessary for the proper testing of the pressure correcting devices.

#### Regulation .05 Temperature Test Equipment.

*COMAR 20.55.06.05*

Each utility which corrects meter readings to compensate for temperature shall have accurate thermometers and other equipment as necessary for the proper testing of the temperature correcting devices.

#### Regulation .06 Certificates.

*COMAR 20.55.06.06*

Each standard shall be accompanied at all times by a certificate or calibration card, duly signed and dated, on which are recorded the corrections required to compensate for errors found at the customary test points at the time of the last previous test.

#### Regulation .07 Care in Handling.

*COMAR 20.55.06.07*

Care shall be exercised in the use and handling of test equipment to assure that the accuracy is not impaired.