S-G-05—Specifications for the in-situ verification, reverification, installation and use of flow computers and transmitters

Category: Gas
Issue date:
Effective date:
Revision number: 1
Supersedes: S-G-05


Table of contents


1.0 Scope

These specifications apply to the in-situ verification, reverification, installation and use of the following devices used in natural gas custody transfer applications:

2.0 Authority

These specifications are listed under the authority of subsection 12(2) and section 18 of the Electricity and Gas Inspection Regulations.

3.0 References

4.0 Definitions

Authorized test software (logiciel d'essai autorisé)
Any program authorized by Measurement Canada to be used for verification purposes that computes the flow of hydrocarbon gases through meters using standard equations.
Calculator function (calculatrice)
Software coding installed in a flow computer that uses configurable fixed parameters and values from connected device live inputs to calculate legal units of measure for mass, volume and/or energy used in billing transactions.
Connected devices (dispositifs connectés)

Devices approved by Measurement Canada and connected to a flow computer to measure one or more gas stream parameters such as the following:

  • mass or volume flow,
  • static pressure,
  • differential pressure,
  • temperature,
  • gas composition,
  • relative density and heating value.

These devices provide input signals to the flow computer for use by its calculator function in the determination of the mass, volume and/or energy value used for billing transactions.

Flow computer (débimètre-ordinateur)

A microprocessor-based device that calculates and records volume consumption and/or time-stamped volume flow rates expressed at line conditions and base conditions. It may optionally also calculate energy consumption and energy flow rates. Calculations are performed by the calculator function. The device may be used with one or more associated gas meters of various types.

Inputs include volume weighted pulses and analogue or digital signals representing:

  • differential pressure,
  • static line pressure,
  • flowing gas temperature,
  • gas composition,
  • relative density, and
  • energy density (heating value).
Maximum permissible error (VIM 4.26) (erreur maximale tolérée)
The extreme value of measurement error, with respect to a known reference quantity value, permitted by specifications or regulations for a given measurement, measuring instrument or measuring system.
Measuring apparatus (instrument de mesure)
A device required for the inspection of gas meters which has been certified by tracing its accuracy at one or more points to reference standards kept by the National Research Council of Canada and/or Measurement Canada.
Resistance temperature detector (détecteur de température à résistance)
A temperature sensor that operates on the measurement principle that a material's electrical resistance changes with temperature.
Snapshot (instantané)

A manually triggered electronic memorization of a flow computer's instantaneously registered values of applicable measurement parameters and factors, such as:

  • volume pulse frequency;
  • pressure,
  • temperature,
  • volume and energy flow rates, and
  • other applicable measurement parameters and factors.
Transmitter (transmetteur)

A device that incorporates one or more transducers and may be equipped with telemetering capabilities. It converts one or more sensed inputs (e.g. gas temperature, static pressure, differential pressure) to one of the following output signals:

  • analogue (e.g. 4-20 mA, 1-5 VDC or resistance measurement),
  • digital (e.g. HART, Modbus, or Fieldbus).
Reverification (revérification)
The subsequent confirmation of a meter's conformance to legal requirements following the expiration of its initial or subsequent reverification period.
Verification (vérification)
The initial confirmation of a meter's conformance to legal requirements.

5.0 General

5.1 Mandatory verifications and reverifications

Unless otherwise authorized, all devices described in the scope of these specifications are subject to mandatory verifications and reverifications.

5.2 Non-conforming devices

Any device described in the scope of these specifications must be classified as nonconforming; and not be accepted for use in trade when it:

  1. does not comply with all applicable requirements of these specifications; or
  2. possesses a defect which could affect its ability to meet specified requirements.

Non-conforming devices must be corrected and reinspected or removed from service.

6.0 Administrative requirements

6.1 Transmitters

6.1.1 Registration of transmitters

Each transmitter must be registered with the local Measurement Canada (MC) district or regional office:

The following information must be provided to the local MC district or regional office:

  1. Name and contact information of the contractor or owner;
  2. Contractor's or owner's transmitter number and its serial number;
  3. Manufacturer's name or registered trademark;
  4. Model or type designation;
  5. Notice of approval number;
  6. Station name and location;
  7. Date of installation;
  8. In-service date;
  9. Firmware version;
  10. Hardware version; and
  11. One or more marked and configured operating ranges (where not the same).

6.1.2 Modifications to verified transmitters

The local MC district or regional office must be informed of any of the following significant changes to verified transmitters:

6.2 Flow computers

6.2.1 Registration of flow computers

Each flow computer must be registered with the local MC district or regional office:

The following information must be provided to the local MC district or regional office:

  1. Name and contact information of the contractor or owner;
  2. Contractor's or owner's flow computer number and its serial number;
  3. Manufacturer's name or registered trademark;
  4. Model designation;
  5. Notice of approval number;
  6. Station name and location;
  7. Date of installation;
  8. In-service date;
  9. Firmware and/or software version;
  10. Flow, supercompressibility and energy calculation method(s) used;
  11. Legal units of measurement used for billing; and
  12. Linearization function used and what it applies to (e.g. flow rate, pressure, temperature).

6.2.2 Modifications to verified flow computers

The local MC district or regional office must be informed of any of the following significant changes to verified flow computers:

6.3 Marking requirements

6.3.1 General

The flow computer and transmitters 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 applicable notice of approval. Where the markings section of the flow computer's or transmitter's notice of approval makes reference to particular clauses of specification LMB-EG-08, these are superseded by the requirements of specification S-G-03.

6.4 Sealing requirements

Unless otherwise authorized, verified and reverified flow computers and transmitters must be sealed in accordance with the provisions of their notices of approval and specification PS-EG-02, as applicable. Verification markings are to be applied to a visible location of the flow computer and transmitters where no sealing provisions are included in the notice of approval.

6.5 Reverification periods

The initial and subsequent reverification periods for flow computers and transmitters are as prescribed in bulletin G-18.

7.0 Technical requirements

7.1 General

The flow computer and transmitters are required to:

7.2 Transmitters

Transmitters are required to be used with or within the following approved features or operating ranges, as identified in the notice of approval:

7.3 Flow computers

The flow computer is required to be used with or within the following approved features or operating ranges, as identified in the notice of approval:

7.4 Software

7.4.1 Transmitters

The transmitter's firmware version must be approved, as identified in its notice of approval.

7.4.2 Flow computer

The flow computer must be installed with an approved software version, as identified in its notice of approval. All applicable programmable and configurable setup parameters must be validated when used by the calculator function in the determination of the measurement units.

8.0 Metrological requirements

8.1 Transmitters (including transducers)

8.1.1 General

A transmitter or RTD must be inspected when it does not hold a valid certificate. A measuring apparatus must be installed at the source of the transmitter/RTD to determine the error at the applicable test points as outlined in Table 1. The transmitter/RTD error must be within the maximum permissible errors (MPEs) listed in Table 1 for the type of device, at all points within its approved operating range.

Table 1: Transmitter and resistance temperature detector test points and maximum permissible errors
Device type Test point Maximum permissible errorsFootnote 2
Temperature transmitters and RTDs
  • 0 ± 1 °C
  • (flowing gas temperature)°CFootnote 3
  • ≥30 °C
± 2 °C
Static pressure transmitters
(% of line pressure)
0%, 50%, 100% ± 1.0%
(% of line pressure)
Differential pressure transmitters
(% of configured full scale)
0%, 20%, 40%, 60%, 80%, 100% ± 1.0%
(% of configured full scale)

8.1.2 Resistance temperature detectors

An RTD must be verified or reverified using the flow computer readings for the RTD input to determine the error relative to the measuring apparatus installed at the source, and must be within the MPE in table 1 for temperature transmitter/RTD.

8.1.3 Transmitters

Transmitters must be verified or reverified using readings from one of the following sources to determine the transmitter's calibration error relative to the measuring apparatus connected to that source:

A measuring apparatus must measure the transmitter output signal where it is used to determine the error. The reading or calculated reading must be compared to the uncorrected (non-linearized) flow computer reading or calculated reading for the process variable of the transmitter being evaluated at a minimum of one of the transmitter test points where the output signal at the transmitter or the transmitter indicator is used to determine the error. The error at the flow computer input must not exceed the applicable MPE specified in Table 1 and the difference must not exceed 20% of the allowable MPE for the transmitter.

8.2 Flow computer inputs

All flow computer inputs that are used in the determination of measurement units must be verified to ensure the flow computer receives the data being sent by the connected devices.

8.2.1 Pressure and temperature inputs

The pressure and temperature inputs must be verified as per section 8.1 when the transmitters/RTDs are also being verified or reverified during the inspection; otherwise, they must be verified at a minimum of one test point within the anticipated range for that metering site. The flow computer's uncorrected non-linearized reading for the process variable of the transmitter/RTD being verified must not exceed the applicable MPE listed in Table 1.

8.2.2 Gas composition input

Where the gas composition, heating value and any other quantity used to derive legal billing units (i.e. mass density, specific gravity) are provided by an approved and verified on-site gas analyzer, these values must be compared with the flow computer's registered values for the same sample of gas.

The values reported by the flow computer must be the same as those recorded on the gas analyzer report.

8.2.3 Meter inputs

Where the data received from the meter is in digital form, the flow computer's reading and the meter's output must be the same at the point in time when the flow computer's calculator function performs a calculation to update the readings on the flow computer. Where the signal received from a meter is in the form of pulses or an analogue signal, the flow computer's readings for pulse count, frequency, or interpreted analogue signal, must be within 0.2% of the source device.

The combination of the test duration and the resolution of the units used in the calculations must be sufficient to ensure an error resolution of 0.05% (1 part in 2000).

8.3 Flow computer calculator function

Note: This section is not applicable to flow computers that only permit access to configurable parameters (i.e. the user cannot change the source coding).

8.3.1 Verification of measurement units used in billing transactions

The converted volume and/or energy accumulation calculations must be verified over a combination of test points within the ranges of the connected devices where there is accessFootnote 4 to the source coding of the measurement software modules/subroutines.Footnote 5

The tests in Table 2 must be conducted to evaluate the overall converted volume/energy calculator function of the flow computer.

  1. The input values of these tests must be fixed to maintain the necessary stability to evaluate the functioning of the calculator.
  2. The flow rate reading(s) for snapshots or the test duration, and the units used in the accumulation tests must be sufficient to obtain a calculated error resolution of 0.1% (1 part in 1000).
  3. The test data indicated by the flow computer for the tests in Table 2 must be within ± 0.2% of that calculated using an MC-authorized test software. Linearization factors must be applied to the MC-authorized test software results in accordance with PS-G-14, where applicable.
Table 2: Tests to evaluate the overall converted volume or energy calculator function
Test no. Flow rate Temperature Flowing pressure ΔP (orifice) Gas compositionFootnote 6
1 Mid range Mid range Mid range Mid range Mid range
2 50% 15 ± 5 °C 25% 40% Low heating value (HV)
3 50% 0 ± 1 °C 100% 60% High HV
4 90% 30 ± 5 °C 50% 100% High HV

8.4 Flow computer outputs

Note: The converted (corrected) volume output of a flow computer's pulse generator/initiator, if so equipped, is exempt from verification.

The unconverted (uncorrected) volume output of a flow computer's pulse generator or initiator, if so equippedFootnote 7, must be verified unless the pulse output has been permanently disabled.

The start/stop test readings used for the test must be those with the maximum resolution available in the flow computer. The test duration must:

The test volume represented by the output pulses must match the corresponding volume registered by the flow computer.

8.5 System error

A volume/energy accumulation test must be completed at stable flowing conditions (see test 1 of Table 3 for test points).

Table 3: Volume or energy accumulation tests
Test no. Flow rate Temperature Flowing pressure (P) ΔP (orifice) Gas composition
1 ≥ 80% Flowing temperature ± 5 °C ≥ 80% ≥ 80% Flowing gas HV
2 ≥ 50% ≥ 25 °C 50% ≤ P ≤ 70% ≥ 50% Low HV
3 ≥ 50% 0 ± 5 °C 70% ≤ P ≤ 90% ≥ 50% High HV

The following test parameters must be sufficient to obtain test results having a resolution of 0.1%:

A separate certified sourceFootnote 9 must be used to simulate flowing conditions where the stability of the flowing gas pressure or temperature source does not provide the control necessary for test 1 of Table 3.

A volume/energy accumulation test must also be completed for tests 2 and 3 of Table 3.Footnote 10 A separate certified sourceFootnote 11 must be used to simulate test conditions where it is not possible or practical to obtain the pressure or temperature test points.

The overall converted volume and/or energy accumulation or flow rates for the snapshot method reported by the flow computer for each test must be compared to the overall converted volume and/or energy calculated, using an authorized test software. Linearization factors must be applied to the authorized test software results in accordance with the applicable section of PS-G-14 for the programmed linearization method, where applicable.

The error of the total overall converted volume and/or energy of a flow computer and its connected devices must not exceed ± 2.0% of the true values determined by the authorized test software.

9.0 Revisions

The purpose of revision 1 was to:

Date modified: