PS-G-06—Provisional specifications for the approval, verification, reverification, installation and use of ultrasonic meters

Category: Gas
Specification: PS-G-06 (rev. 3)
Issue date:
Effective date:
Supersedes: PS-G-06 (rev. 2)


Table of contents


1.0 Scope

These specifications apply to ultrasonic gas meters which operate by determining the difference in transit times of bursts of ultrasonic energy travelling in the upstream and downstream direction. All metering features and functions of an ultrasonic meter that are not explicitly addressed in these specifications are also subject to any additional Measurement Canada (MC) requirements and specifications that are applicable to the feature or function.

2.0 Authority

These specifications are issued under the authority of sections 12 and 18 of the Electricity and Gas Inspection Regulations.

3.0 References

4.0 Definitions

Deviation (écart)

The mean of the errors at a given flow rate.

Error (erreur)

The difference between the volume measured by the meter under test and the volume measured by a reference meter. Corrections must be made for the differences of gas pressure, temperature and compressibility between the two meters. The error shall be calculated as follows:

(Error %) = [(volume at test meter - volume at reference meter) ÷ volume at reference meter] × 100%

Final meter factor (facteur final du compteur)

A factor which applies to a meter's output(s) and changes the output(s) by a constant percentage at all flow rates. Bidirectional meters may have different final meter factors for each direction of measurement. The final meter factor shall be calculated as follows:

Final meter factor = 100 / (100 + FWME)

Flow weighted mean error (erreur moyenne pondérée du débit)

The flow weighted mean error (FWME) of a meter calculated as follows:

the long description is located below the image

Long description of the equation

(FWME %) = [(Q1 ÷ Qmax) × D1 × W1 + (Q2 ÷ Qmax) × D2 × W2 + … + (Qn ÷ Qmax) × Dn × Wn] ÷ [(Q1 × W1) ÷ Qmax + (Q2 × W2) ÷ Qmax + … + (Qn × Wn) ÷ Qmax]

Where,

  • Qi is the test flow rate
  • Di is the deviation at the tested flow rate Qi
Linearity (linéarité)

The maximum difference between the flow weighted mean error and any of the deviations.

Maximum flow rate, Qmax (débit maximal, Qmax)

The maximum flow rate of the meter.

Maximum permissible error (erreur maximale tolérée)

The largest allowable deviation within the specified operational range of the meter.

Meter tubes (conduites du compteur)

Lengths of straight pipe located upstream and downstream of the meter.

Multipath meter (compteur à trajets multiples)

An ultrasonic meter with more than one velocity sensing path.

Processing circuitry (circuit de traitement)

Circuitry which provides for the generation, detection and timing of ultrasonic pulses and for the calculation of the meter's outputs.

Reference meter (compteur de référence)

A meter of known accuracy.

Relative roughness (rugosité relative)

The dimensionless ratio (e) of the average pipe roughness (Ra) to the inside pipe diameter (D).

Repeatability (répétabilité)

The largest spread of errors of a given meter when several successive measurements are performed at the same flow rate under the same operating conditions.

Transit time (temps de transit)

The time for an ultrasonic pulse to travel along a specified path.

Ultrasonic gas meter (compteur de gaz à ultrasons)

A meter consisting of a body, one or more velocity sensing paths, and associated processing circuitry.

Ultrasonic domestic gas meter (compteur de gaz à ultrasons domestiques)

An ultrasonic gas meter which includes a battery powered register and associated processing circuitry, all enclosed within the same meter case and used to measure volumes of gas at working pressures up to a maximum of 200 kPa.

Ultrasonic transducer (transducteur à ultrasons)

A device which transmits and receives ultrasonic pulses.

Velocity sensing path (trajet de détection de vitesse)

A path travelled by ultrasonic pulses for the purpose of determining the velocity of gas in a meter.

5.0 Metrological requirements

5.1 Maximum permissible errors

5.1.1 Accuracy tests—Pattern approval

5.1.1.1 Meters shall be tested using a suitable test medium at flow rates over the range of 10% to 100% of Qmax at flowing gas pressures over the specified operating pressure range of the meter. Each test point shall consist of at least three measurements, each measurement lasting a minimum of 100 seconds. The tested flow rates shall be approximately equally spaced between 0.1 Qmax and Qmax, and shall include, as a minimum, 0.1 Qmax, 0.25 Qmax, 0.5 Qmax, 0.75 Qmax and Qmax.

Note 1: The test medium will normally be natural gas. However, if an applicant provides data demonstrating that other media are suitable for performing tests, tests on those media will be accepted. For ultrasonic domestic gas meters, the manufacturer shall provide documentation demonstrating that the meter can be tested using an identified proving technology by comparison to natural gas of a specified composition and over the meter's intended operating conditions.

Note 2: Where test facilities are not available to perform tests over the entire operating pressure range of the meter, the applicant shall provide test data demonstrating that the pattern to which the meter belongs is insensitive to operating pressure.

Note 3: Where ultrasonic domestic meters are tested, this minimum measurement duration may not be applicable as a result of limitations associated with the proving technology employed. However, in all cases, the test duration shall be sufficient to ensure an error resolution of 0.1% or better.

5.1.1.2 The errors of the meter shall not exceed the following tolerances:

Table 1: Errors
Ultrasonic meters Ultrasonic domestic meters
Maximum permissible error: ± 1.0% ± 1.0%
Linearity: ± 0.3% ± 0.5%
Repeatability: ± 0.2% ± 0.4%

Note 1: The tolerance for the maximum permissible error applies after the application of the final meter factor, if any.

Note 2: The tolerance for linearity applies after any corrections performed within the meter itself but prior to the application of linearization algorithms by equipment auxiliary to the meter.

5.1.1.3 The flow weighted mean error shall be within ± 0.4% at any flow rate greater than or equal to 0.95Qmax, otherwise it shall be within ± 1.0%.

5.1.1.4 At the time of approval, ultrasonic domestic meters shall be tested for zero volume accumulation under no flow conditions. This test shall be carried out at the ambient temperature conditions of −30 °C and +40 °C or the extremes of the meter's ambient temperature range as declared by the manufacturer and set out in the notice of approval (NOA).

5.1.2 Transducer and circuit board exchange

Applicants may provide test data demonstrating that transducers and circuit boards comprising the processing circuitry can be exchanged without necessitating reverification of the meter. Such data shall be obtained by testing the accuracy of the meter at one flow rate first with the original component(s), and then with replacement component(s). The meter may be reprogrammed if necessary after the component(s) have been exchanged, but before the second accuracy test is performed. The meter's performance as a result of any component exchange shall not change by more than ± 0.1%.

Note 1: For the purpose of these specifications, a component exchange shall mean the exchange of one circuit board, one transducer or one set of transducers.

5.1.3 Verification and reverification accuracy tests

5.1.3.1 Subject to clause 5.1.3.2, tests shall be conducted with a suitable test medium at a pressure representative of the meter's intended use. Each test point shall consist of at least three measurements, each measurement lasting a minimum of 100 seconds. Ideally, the meter shall be tested at a minimum of five flow rates approximately equally spaced between 0.1 Qmax and Qmax. Where Qmax cannot be achieved because of limitations of the test facility, the upper test flow rate shall be at least 0.4 Qmax and the meter shall be tested at least five flow rates approximately equally spaced between 0.1 Qmax and the maximum flow rate attainable by the test facility. Meters intended for bidirectional measurement applications shall be tested as above in both directions.

Note 1: The test medium will normally be natural gas. However, if an applicant provides test data demonstrating that other media are suitable for performing tests, tests on those media will be accepted.

The errors of the meter shall not exceed the tolerances set out in clause 5.1.1.2. Where the meter's maximum test flow rate cannot be achieved, the errors of the meter shall not exceed the following tolerance limits:

Where, %Qmax attained is the highest test flow rate attained.

Note 2: The tolerance for the maximum permissible error applies after the application of the final meter factor, if any.

Note 3: The tolerance for linearity applies after any corrections performed within the meter itself but prior to the application of linearization algorithms by equipment auxiliary to the meter.

5.1.3.2 Ultrasonic domestic gas meters may be verified or reverified at atmospheric pressure using appropriately certified gas meter proving technologies. Where ultrasonic domestic gas meters are verified using a measuring apparatus of the referenced type, the test points shall be equal to (0.3 ± 0.05) Qmax and (0.95 ± 0.05) Qmax, using air as the test media. The test duration shall be sufficient to ensure an error resolution of 0.1% or better.

Maximum permissible error: ± 1.0%

Note 1: For ultrasonic domestic gas meters, the manufacturer shall provide documentation demonstrating that the meter can be calibrated using the identified proving technology by comparison to natural gas of a specified composition and over the meter's intended operating conditions.

5.1.3.3 The NOA of an ultrasonic domestic gas meter shall stipulate the fluids with which the meter can be calibrated, and any applicable conditions or restrictions.

5.2 Verification requirements

5.2.1 The NOA shall be referred to for information regarding parameters in the processing circuitry which may need to be changed or programmed at the time of verification, and for sealing requirements.

5.2.2 Where provided, the final meter factor shall be set prior to sealing the meter.

5.2.3 Metering installations shall be inspected to assess compliance with the installation inspection requirements identified in Appendix A. Ultrasonic domestic gas meters which are not subject to the piping requirements of clause 6.2.3, and which are installed where the average meter pressure does not exceed the atmospheric pressure by more than 3.45 kPa, are exempt from the installation inspection requirements.

5.3 Reverification requirements

Meters shall be submitted for reverification at least every six years. The requirements for reverification are the same as for verification.

5.4 Component exchange

5.4.1 Transducer and electronics exchange

Where permitted by the NOA, seals on a meter in service may be broken by an inspector or by an accredited meter verifier to accommodate component exchange. New components shall either be identical to those being replaced or shall be approved by MC and recommended for use in the particular circumstances by the manufacturer of the meter. Upon completion of the exchange, components shall be resealed after completion of the following checks.

5.4.1.1 Transducer exchange

The following procedure shall be followed where one or more new transducers are installed:

  1. The new transducer(s) shall be installed in accordance with the manufacturer's instructions. If applicable, calibration parameters for the exchanged transducer(s) shall be entered into the processing circuitry.
  2. Serial numbers of the new and old pairs of transducers shall be recorded.
  3. The velocity of sound measured on each path shall be determined with gas flowing through the meter. The velocity of sound measured on the path with the replaced transducer(s) shall be within 0.2% of the mean of the velocities of sound measured on the undisturbed paths.
5.4.1.2 Electronics exchange

The following procedure shall be followed where new processing circuitry is installed:

  1. The new processing circuitry shall be installed in accordance with the manufacturer's instructions.
  2. Serial numbers and firmware versions of the new and old circuitries shall be recorded.
  3. Where necessary, calibration parameters shall be programmed into the new processing circuitry in accordance with the manufacturer's instructions. Once programming is complete, it shall be verified that the new parameters are identical to the old parameters.
  4. The velocity of sound measurement for each path shall be determined. The obtained values shall agree with each other with a maximum spread of not greater than 0.2% of their mean.

5.5 Conditions for metrological characteristics

5.5.1 Influence and disturbance factors

For pattern approval purposes, the meter volumetric accuracy tests shall not exceed the errors set out in clause 5.1.1.2 over the following range of influence and disturbance factors:

  1. Influence factors

    As set out for Class F meters in section 9 and clause 11.5.3 of OIML (International Organization of Legal Metrology) international recommendation R 6 — General Provisions for Gas Volume Meters.

  2. Swirl susceptibility

    The inlet to the installation configuration recommended by the manufacturer shall be preceded in turn by a clockwise and a counter-clockwise swirl generator, constructed of two ninety-degree elbows connected together orthogonally.

6.0 Technical requirements

6.1 Design, composition and construction

6.1.1 In addition to the approval requirements listed in these specifications, meters shall also be evaluated against the applicable requirements of S-G-03.

6.1.2 A pressure tap shall be located on the meter body. This requirement does not apply to meters with a maximum allowable operating pressure of 10 psig or less.

6.1.3 The meter shall provide one or more outputs proportional to the volume of gas which has passed through it, expressed at line conditions of pressure and temperature. This requirement does not apply to ultrasonic domestic gas meters. For bidirectional applications, a separate volume output shall be provided for each direction.

6.1.4 Multipath meters shall be capable of indicating the speed of sound in gas for each path.

6.1.5 The malfunction of any transducer pair in a multipath meter shall not cause the meter to cease functioning but shall cause an alarm to be generated.

6.1.6 Provisions for sealing shall be made pursuant to subsection 8.2.

6.1.7 The meter shall use the standard communication protocol set out in ANSI C12.18-1996 and IEEE P1377/ANSI C12.19-1996, or the manufacturer shall provide, free of charge, software to interrogate, control and verify the meter. The executable software shall be formatted for personal computers. Operating manuals and documentation shall also be provided. The software shall preclude the possibility of disruption of the meter's operation during the verification process. MC hereby undertakes to ensure that the software will be used solely for the purpose of inspection of meters by government inspectors and not to disclose the contents of the software or its documentation to third parties.

6.2 Installation and use

6.2.1 The meter shall be installed in a manner designed to prevent the accumulation of contaminants in any transducer port.

6.2.2 The installation shall include provisions such that the meter can be made to accumulate zero volume at flow rates of less than 0.5% of Qmax. The low flow cut-off may be set to operate at a flow rate higher than 0.5% of Qmax, with the consent of the selling party.

6.2.3 Unless otherwise stated in the NOA, the upstream meter tube shall have a length of at least 10 pipe diameters. The downstream meter tube shall have a length of at least 3 pipe diameters unless the installation is intended for bidirectional measurement, in which case both the upstream and downstream meter tubes shall have lengths of 10 pipe diameters.

6.2.4 The interior finish of the meter and the meter tubes shall not exceed a relative roughness of 0.0000625.

6.2.5 No gasket shall protrude past the interior surface of the meter tubes or the meter body.

6.2.6 If required by the NOA for the meter, a flow conditioner shall be located in the meter tube upstream of the meter body, and, in the case of bidirectional measurement, downstream as well.

6.2.7 The inside diameter of the meter tubes and the inside diameter of the meter body shall not differ by more than ± 1.0% of the smaller of the two. Unless otherwise noted in the NOA, this requirement is also applicable to ultrasonic domestic gas meters.

6.2.8 The temperature of the flowing gas shall be measured downstream of the metering element in the normal flow direction. There shall be nothing between the metering element and the temperature sensor which could cause a change in pressure. This requirement shall apply in all cases except where a meter is approved, verified and operated with a built-in temperature sensor that is located within the meter body.

6.2.9 Where used, a thermowell shall project one third of the inside pipe diameter into the flowing gas stream and shall be oriented so as not to be aligned with any path.

6.2.10 The meter shall not be used outside the range of ambient temperature for which it is approved. Where necessary, shelter and heaters or other arrangements shall be provided to ensure that this requirement is met.

6.2.11 Unless otherwise stated in the NOA, where a meter is to be installed within 100 pipe diameters of a throttling device such as a regulator or valve, or of a compressor or other device known to produce pulsations, the manufacturer shall be consulted and shall conduct tests to demonstrate that the meter is not adversely affected by the device.

6.2.12 Where a meter is installed within 1000 pipe diameters of a valve (with a Whisper Trim cage) or other device known to produce ultrasonic energy, the manufacturer shall be consulted and shall conduct tests to demonstrate that the meter is not adversely affected by the device.

6.2.13 The meter outputs which are proportional to the volume of gas which has passed through it shall be used for billing calculations.

7.0 Administrative requirements

7.1 Markings

7.1.1 The following information shall be indelibly marked on, or be capable of being displayed by, the meter:

  1. Manufacturer's name;
  2. Model number;
  3. Serial number (on the meter body);
  4. Meter serial number, if different from (c);
  5. Direction of positive flow or, for ultrasonic domestic gas meters, the inlet connection shall be identified;
  6. Maximum flow rate at line conditions;
  7. Inside meter diameter (not applicable to ultrasonic domestic gas meters);
  8. Minimum (where applicable) and maximum operating pressure;
  9. Notice of approval number;
  10. Space shall be provided for an inspection number, which shall be marked on the meter body prior to verification of the meter;
  11. type and range of output signal (for each output);
  12. Final meter factor, where used;
  13. Zero offset, where used;
  14. Density, where used;
  15. Viscosity, where used;
  16. Delay times for transducers, where used;
  17. any other user-programmable factors used;
  18. Firmware version (alternatively may be displayed using the manufacturer's meter interface software);
  19. Base temperature value (if the meter performs a volume conversion function using the flowing gas temperature).

7.1.2 The following information shall be marked for meters with transducers which can be exchanged at the meter's operational location:

  1. Transducer model number (on each transducer);
  2. Transducer serial number (on each transducer);
  3. Pressure range of transducers (on each transducer);
  4. Identification of each transducer port (on the meter body).

7.1.3 The following information shall be provided, for meters with circuit boards which can be exchanged at the meter's operational location:

  1. Circuit board model number;
  2. Circuit board serial number.

7.1.4 Where portions of the meter are intended to be installed remotely from each other in a multi-meter installation, the component parts shall bear sufficient additional markings as are necessary to inform users which components of the system will operate with each other.

7.2 Sealing

Where a manufacturer can demonstrate through test results that transducers can be exchanged without requiring reprogramming of the processing circuitry and without affecting the meter performance, the transducers do not have to be sealed. Otherwise, individual transducers shall have suitable provisions for sealing them to the meter body and shall be so sealed. The processing circuitry shall have suitable provisions for sealing circuit boards to the meter body and shall be so sealed. Where access is not otherwise prevented by a seal, the electronics package may require a jumper with a sticker or seal applied to prevent unauthorized changing of calibration parameters.

8.0 Revisions

8.1 The purpose of revision 3 was to:

8.2 The purpose of revision 2 was to remove requirements identified under the Government of Canada's paper burden reduction initiative.

8.3 The purpose of revision 1 was to add requirements for ultrasonic domestic gas meters, and to identify which of the existing requirements are not applicable to ultrasonic domestic gas meters. Some new definitions were also added, and the tolerances for relative roughness (clause 5.2.4) and inside diameter (clause 5.2.7) were amended.

Appendix A — Attribution of characteristics

Attribution of characteristics
Section no. Characteristic Pattern approval Initial verification Subsequent verification Dispute Installation inspection
5.1.1.1 Test flow rates and pressures applicable - - - -
5.1.1.2 Tolerances applicable - - - -
5.1.1.3 Flow weighted mean error applicable - - - -
5.1.1.4 Zero volume accumulation applicable - - - -
5.1.2 Component exchange applicable - - - -
5.1.3.1
5.1.3.1
Verification and reverification tests - applicable applicable - -
5.2.1 Parameter programming - applicable applicable applicable -
5.2.2 Final meter factor - applicable applicable - -
5.2.3 Installation inspection - - - - applicable
5.3 Reverification - - applicable - -
5.4.1 Component exchange - - - - applicable
5.4.1.1 Transducer exchange - - - - applicable
5.4.1.2 Electronics exchange - - - - applicable
5.5.1 Influence and disturbance factors applicable - - - -
6.1.1
6.1.2
Case applicable - - - -
6.1.2 Pressure tap applicable - - - applicable
6.1.3 Outputs applicable applicable applicable applicable applicable
6.1.4 Speed of sound applicable applicable applicable applicable applicable
6.1.5 Transducer malfunction applicable - - - -
6.1.6 Sealing provisions applicable applicable applicable - -
6.1.7 Communications applicable - - - -
6.2.1 Transducer orientation - - - - applicable
6.2.2 Low flow cut-off applicable - - - applicable
6.2.3 Tube length - - - - applicable
6.2.4 Interior finish applicable - - - applicable
6.2.5 Gaskets - - - - applicable
6.2.6 Flow conditioners applicable - - - applicable
6.2.7 Inside diameter - - - - applicable
6.2.8 Temperature sensing applicable - - - applicable
6.2.9 Thermowell characteristics - - - - applicable
6.2.10 Ambient temperature - - - - applicable
6.2.11 Throttling device - - - - applicable
6.2.12 Ultrasonic source - - - - applicable
6.2.13 Outputs applicable applicable applicable applicable applicable
7.1 Markings applicable applicable applicable - -
7.2 Sealing applicable applicable applicable applicable applicable
Date modified: