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

Category: Gas
Issue date:
Effective date:
Revision number: 4
Supersedes: PS-G-06 (rev.3)



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 must be calculated as follows:

E r r o r   % =   v o l u m e   a t   t e s t   m e t e r - v o l u m e   a t   r e f e r e n c e   m e t e r v o l u m e   a t   r e f e r e n c e   m e t e r   ×   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 must be calculated as follows:

F i n a l   m e t e r   f a c t o r   =   100   /   ( 100   +   F W M E )

Flow weighted mean error
(erreur moyenne pondérée du débit)

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

F W M E   % =   i = 1 n Q i Q m a x   ×   D i   ×   W i   ÷   i = 1 n Q i   ×   W i Q m a x

Where Qi is the test flow rate

Di is the deviation at the tested flow rate Qi

When Qi ≥ 0.95 Qmax, then Wi = 0.4, otherwise Wi = 1.0

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 tube
(conduite du compteur)

Length 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

The following requirements apply:

  1. Meters must 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 must consist of at least three measurements, each measurement lasting a minimum of 100 seconds. The tested flow rates must be approximately equally spaced between 0.1 Qmax and Qmax, and must include, as a minimum, 0.1 Qmax, 0.25 Qmax, 0.5 Qmax, 0.75 Qmax and Qmax.

    Notes:

    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 with those media will be accepted. For ultrasonic domestic gas meters, the manufacturer must 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.
    2. Where test facilities are not available to perform tests over the entire operating pressure range of the meter, the applicant must provide test data demonstrating that the pattern to which the meter belongs is insensitive to operating pressure.
    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 must be sufficient to ensure an error resolution of 0.1% or better.
  2. The errors of the meter must not exceed the following tolerances:
    Table 1: Errors
    Error Ultrasonic meters Ultrasonic domestic meters
    Maximum permissible error ± 1.0% ± 1.0%
    Linearity ± 0.3% ± 0.5%
    Repeatability ± 0.2% ± 0.4%

    Notes

    1. The tolerance for the maximum permissible error applies after the application of the final meter factor, if any.
    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.
  3. At the time of approval, ultrasonic domestic meters must be tested for zero volume accumulation under no flow conditions. This test must 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 must 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 must not change by more than ± 0.1%.

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

5.1.3 Verification and reverification accuracy tests

The following requirements apply:

  1. Subject to clause 5.1.3 (b), tests must be conducted with a suitable test medium at a pressure representative of the meter's intended use. Each test point must consist of at least three measurements, each measurement lasting a minimum of 100 seconds. Ideally, the meter must 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 must be at least 0.4 Qmax and the meter must 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 must be tested as above in both directions.

    Note: 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 must not exceed the tolerances set out in clause 5.1.1 (b). Where the meter's maximum test flow rate cannot be achieved, the errors of the meter must not exceed the following tolerance limits:

    • Maximum permissible error: ± 1% x %Qmax attained / 100
    • Linearity: ± 0.3%
    • Repeatability: ± 0.2%

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

    Note:

    1. The tolerance for the maximum permissible error applies after the application of the final meter factor, if any.
    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.
  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 must be equal to (0.3 ± 0.05) Qmax and (0.95 ± 0.05) Qmax, using air as the test media. The test duration must be sufficient to ensure an error resolution of 0.1% or better.

    • Maximum permissible error: ± 1%

    Note: For ultrasonic domestic gas meters, the manufacturer must 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.

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

5.2 Verification requirements

5.2.1 Parameter programming

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

5.2.2 Final meter factor

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

5.2.3 Installation inspection

Metering installations must 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 must 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 General

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 must either be identical to those being replaced or must be approved by MC and recommended for use in the particular circumstances by the manufacturer of the meter. Upon completion of the exchange, components must be resealed after completion of the following checks.

5.4.2 Transducer exchange

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

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

5.4.3 Electronics exchange

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

  1. The new processing circuitry must be installed in accordance with the manufacturer's instructions.
  2. Serial numbers and firmware versions of the new and old circuitries must be recorded.
  3. Where necessary, calibration parameters must be programmed into the new processing circuitry in accordance with the manufacturer's instructions. Once programming is complete, it must be verified that the new parameters are identical to the old parameters.
  4. The velocity of sound measurement for each path must be determined. The obtained values must 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 must not exceed the errors set out in clause 5.1.1 (b) 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 must 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 General

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

6.1.2 Pressure tap

A pressure tap must 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 Outputs

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

6.1.4 Speed of sound

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

6.1.5 Transducer malfunction

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

6.1.6 Sealing provisions

Provisions for sealing must be made pursuant to subsection 7.2.

6.1.7 Communications

The meter must use the standard communication protocol set out in ANSI C12.18-1996 and IEEE P1377/ANSI C12.19-1996, or the manufacturer must provide, free of charge, software to interrogate, control and verify the meter. The executable software must be formatted for personal computers. Operating manuals and documentation must also be provided. The software must preclude the possibility of disruption of the meter's operation during the verification process. MC undertakes to ensure that the software will be used solely for the purpose of the 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 Transducer orientation

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

6.2.2 Low flow cut-off

The installation must 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 Tube length

Unless otherwise stated in the NOA, the upstream meter tube must have a length of at least 10 pipe diameters. The downstream meter tube must 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 must have lengths of 10 pipe diameters.

6.2.4 Interior finish

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

6.2.5 Gaskets

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

6.2.6 Flow conditioners

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

6.2.7 Inside diameter

The inside diameter of the meter tubes and the inside diameter of the meter body must not differ by more than ± 1% 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 Temperature sensing

The temperature of the flowing gas must be measured downstream of the metering element in the normal flow direction. There must be nothing between the metering element and the temperature sensor which could cause a change in pressure. This requirement applies 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 Thermowell characteristics

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

6.2.10 Ambient temperature

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

6.2.11 Throttling device

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 must be consulted and must conduct tests to demonstrate that the meter is not adversely affected by the device.

6.2.12 Ultrasonic source

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 must be consulted and must conduct tests to demonstrate that the meter is not adversely affected by the device.

6.2.13 Outputs

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

7.0 Administrative requirements

7.1 Markings

7.1.1 General

The following information must 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;
  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. Inspection number, which must 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 Transducer exchange

The following information must 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 Electronics exchange

The following information must 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 Remote component parts

Where portions of the meter are intended to be installed remotely from each other in a multi-meter installation, the component parts must 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 must have suitable provisions for sealing them to the meter body and must be so sealed. The processing circuitry must have suitable provisions for sealing circuit boards to the meter body and must 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

The purpose of revision 4 was to:

The purpose of revision 3 was to:

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

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 and inside diameter 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 (a) Test flow rates and pressures applicable
5.1.1 (b) Tolerances applicable
5.1.1 (c) Flow weighted mean error applicable
5.1.1 (d) Zero volume accumulation applicable
5.1.2 Component exchange applicable
5.1.3 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 (general) applicable
5.4.2 Transducer exchange applicable
5.4.3 Electronics exchange applicable
5.5.1 Influence and disturbance factors applicable
6.1.1 Design 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
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