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

Category: Gas
Issue date: 2022-06-06
Effective date: 2022-06-06
Revision number: 5
Supersedes: PS-G-06 (rev.4)

1.0 Scope

These specifications apply to ultrasonic gas meters approved by Measurement Canada (MC) for use in trade and custody transfer metering applications.

2.0 Purpose

These specifications establish requirements for the verification, reverification, installation and use of ultrasonic gas meters.

All metering features and functions of an ultrasonic meter that are not explicitly addressed in these specifications are also subject to any additional MC requirements and specifications that are applicable to the feature or function.

3.0 Authority

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

4.0 References

• Electricity and Gas Inspection Regulations, Part III
• G-18—Reverification Periods for Gas Meters, Ancillary Devices and Metering Installations
• PS-EG-02—Provisional Specifications for the Means and Methods of Sealing Verified Electricity and Gas Meters
• S-G-03—Specifications for the Approval of Type of Gas Metering Devices

5.0 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:

$\mathrm{Error}(\%)=\frac{\left(\mathrm{volume at test meter}-\mathrm{volume at reference meter}\right)}{\mathrm{volume at reference meter}}\times 100$

Final meter factor
(facteur final du compteur)

A factor which applies to a meter's outputs and changes the outputs 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:

$\mathrm{Final meter factor}=\times \raisebox{1ex}{$100$}\!\left/ \!\raisebox{-1ex}{$\left(100+\mathrm{FWME}\right)$}\right.$

Flow weighted mean error
(erreur moyenne pondérée du débit)

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

$\mathrm{FWME}(\%)=(\underset{i=1}{\overset{n}{\Sigma }}\frac{Q_i}{Q_{max}}\times D_i\times W_i)÷\underset{i=1}{\overset{n}{\Sigma }}\frac{Q_i\times W_i}{Q_{max}}$

• Where Q_i is the test flow rate
• D_i is the deviation at the tested flow rate Q_i
• When Q_i ≥ 0.95 Q_max, then W_i = 0.4, otherwise W_i = 1.0

Linearity
(linéarité)

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

Maximum flow rate, Q_max
(débit maximal, Q_max)

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.

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 of the average pipe roughness to the inside pipe diameter.

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.

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 domestique à ultrasons)

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.

6.0 General

6.1 Mandatory verification and reverification

Except where otherwise authorized, all ultrasonic gas meters used in trade or custody transfer applications are subject to mandatory verification and reverification.

6.2 Conforming meters

A meter is to be considered as verified or reverified, as applicable, when it conforms to:

• the approved type as described in its notice of approval (NOA), and
• all applicable performance and non-performance requirements of these specifications.

6.3 Non-conforming meters

A meter that fails to meet any applicable performance or non-performance requirement of these specifications, or that possesses a defect which could affect its ability to meet specified requirements, must be classified as non-conforming and not be accepted for use in trade.

Non‑conforming meters must be corrected and reinspected or removed from service.

7.0 Administrative requirements

7.1 Markings

7.1.1 General

A meter must be marked in full accordance with all applicable location, legibility and marking requirements of specification S-G-03 and with any additional marking requirements included in the NOA.

Where the markings section of the meter's NOA makes reference to particular sections of specification PS-G-06, these are superseded by the requirements of specification S-G-03.

7.1.2 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

The following requirements apply:

• A verified or reverified meter must be sealed in accordance with its NOA and the sealing requirements of specification PS-EG-02, as applicable.
• Where provided, the final meter factor must be set prior to sealing the meter.
• Where permitted by the NOA, transducers and circuit boards comprising the processing circuitry that can be exchanged without necessitating reverification of the meter do not have to be sealed to the meter body. Otherwise, they 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.

7.3 Reverification periods

The initial and subsequent reverification periods for ultrasonic meters are established in bulletin G-18.

8.0 Technical requirements

8.1 General

The ultrasonic gas meter is required to:

• conform in every material respect to the type approved and described in its NOA;
• be properly installed as required by its NOA or as recommended by the manufacturer, as applicable, and subject to applicable requirements of this specification;
• be free of any physical damage, defects in workmanship or material deficiencies which could affect the meter's performance; and
• be free of dirt, debris and other foreign substances, both internally and externally.

8.2 Installation and use

8.2.1 Installation inspection

Metering installations must be inspected to assess compliance with the installation inspection requirements identified in Appendix A.

Note: Ultrasonic domestic gas meters which are not subject to the piping requirements of section 8.2.4, and which are installed where the average meter pressure does not exceed the atmospheric pressure by more than 3.45 kPa (i.e. 0.5 psi in the Imperial system of units), are exempt from the installation inspection requirements.

8.2.2 Transducer orientation

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

8.2.3 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 Q_max. The low flow cut-off may be set to operate at a flow rate higher than 0.5% of Q_max, with the consent of the selling party.

8.2.4 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.

8.2.5 Interior finish

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

8.2.6 Gaskets

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

8.2.7 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.

8.2.8 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.

Note: Unless otherwise noted in the NOA, this requirement is also applicable to ultrasonic domestic gas meters.

8.2.9 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.

Note: 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.

8.2.10 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.

8.2.11 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.

8.2.12 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.

8.2.13 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.

8.2.14 Outputs

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

9.0 Metrological requirements

9.1 Maximum permissible errors

9.1.1 Accuracy tests - General

Subject to subsection 9.1.2, the following requirements apply:

• Tests must be conducted with a suitable test medium at a pressure representative of the meter's intended use.

  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.

• 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 Q_max and Q_max.

  Where Q_max cannot be achieved because of limitations of the test facility, the upper test flow rate must be at least 0.4 Q_max and the meter must be tested at least five flow rates approximately equally spaced between 0.1 Q_max and the maximum flow rate attainable by the test facility.

  Meters intended for bidirectional measurement applications must be tested as above in both directions.

• The errors of the meter must not exceed the tolerances specified in Table 1 below.

  Table 1: Ultrasonic gas meters errors

  Error	Tolerance	Tolerance where Qmax cannot be achieved
  Maximum permissible error	± 1.0%	± 1.0% × [%Qmax attained] ÷ 100
  Linearity	± 0.3%	± 0.3%
  Repeatability	± 0.2%	± 0.2%

  Notes:

  1. [%Q_max attained] is the highest test flow rate attained.
  2. The tolerance for the maximum permissible error applies after the application of the final meter factor, if any.
  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.

9.1.2 Accuracy tests - Ultrasonic domestic gas meters

The following requirements apply:

• Ultrasonic domestic gas meters may be verified or reverified at atmospheric pressure using appropriately certified gas meter proving technologies. 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.
• 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) Q_max and (0.95 ± 0.05) Q_max, using air as the test media.
• The test duration must be sufficient to ensure an error resolution of 0.1% or better.

• The error of the meter must not exceed the tolerances specified in Table 2 below.

  Table 2: Ultrasonic domestic gas meter errors

  Error	Tolerance
  Maximum permissible error	± 1.0%
  Linearity	± 0.5%
  Repeatability	± 0.4%

• The NOA of an ultrasonic domestic gas meter must be referred to for information regarding the fluids with which the meter can be calibrated, and any applicable conditions or restrictions.

9.2 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.

9.3 Component exchange

9.3.1 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.

9.3.2 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.

9.3.3 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.

10.0 Revisions

The purpose of revision 5 was to:

• move all approval requirements into S-G-03;
• make references to G-18 and PS-EG-02;
• reformat the document.

The purpose of revision 4 was to:

• delete section 5.1.1.3 and define W_i in the definition of flow weighted mean error as it used to be in revisions 1 and 2 of PS-G-06;
• reformat the document according to new formatting requirements.

The purpose of revision 3 was to:

• replace the reference to LMB-EG-08—Specifications for approval of type of gas meters and auxiliary devices with a reference to S-G-03 as the requirements of LMB‑EG-08 have been integrated into specifications S-G-03 (rev. 1), and therefore, LMB-EG-08 has become obsolete;
• reformat the document according to new formatting requirements.

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;
• add some new definitions;
• amend the tolerances for relative roughness and inside diameter.

Appendix A—Attribution of characteristics