P-G-05—Procedure for the in situ verification and reverification of flow computers and transmitters pursuant to the requirements of S-G-05

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


Table of Contents


1.0 Scope

This inspection procedure provides instructions for the in situ verification and reverification of the following devices pursuant to the requirements of S-G-05 and intended for use in custody transfer metering applications:

Note: Where the verification and reverification due dates are within one year of each other, it is recommended that the flow computer and transmitters/RTDs be inspected when inspecting the devices currently due, to reduce the inspection cost, and improve the efficiency.

2.0 References

3.0 Safety

3.1 Measurement Canada's health and safety policy

The inspector should be aware of and fully conform to Measurement Canada's health and safety policy, including the provisions relating to personal protective equipment for the in situ inspection and testing of flow computers and transmitters/RTDs.

3.2 Contractor and third-party safety and security requirements

Subject to the policy established in bulletin GEN-16, the inspector should be aware of and conform to the contractor's and any third party's safety and security requirements that are applicable to the work site.

3.3 Potential hazards

The inspector should be aware of the following potential hazards which may occur during transport to and from the work site and while at the work site:

3.4 Contractor's responsibilities

The contractor's representative is responsible for the following:

Note: The inspector may provide advice, guidance and assistance to the contractor's representative as required.

4.0 Inspection apparatus

4.1 Measuring apparatus

The following measuring apparatus are required:

  1. Certified digital thermometer
  2. Certified digital pressure gauge(s)
  3. Voltage or current standard(s) (i.e. radian)

4.2 Additional equipment

The following additional equipment is required:

5.0 Inspection worksheet

The inspection worksheet referred to in this procedure may be obtained by contacting any Measurement Canada electricity and gas regional office.

6.0 Assessment of conformity with administrative requirements

6.1 General

Obtain and review the flow computer's and transmitters' notices of approval.

6.2 Nameplate information and markings

  1. Examine the flow computer and transmitters and assess their conformity with the marking requirements of S-G-05.
  2. Record the flow computer's and transmitters' required marking and any nonconformity with specified requirements on the inspection worksheet.

7.0 Assessment of conformity with technical requirements

7.1 Device construction and condition

  1. Examine the flow computer and transmitters and assess their conformity with the construction and condition requirements of S-G-05.
  2. Record any nonconformity on the inspection worksheet.

7.2 Firmware and software versions

7.2.1 Transmitters

  1. Confirm that each transmitter's installed firmware version is approved for use in trade, as indicated in the notice of approval.
  2. Record the installed firmware versions and any nonconformity on the inspection worksheet.

7.2.2 Flow computer

  1. Confirm that the flow computer's installed software version is approved for use in trade, as indicated in the notice of approval.
  2. Record the installed software version and any nonconformity on the inspection worksheet.

7.3 Features and operating ranges

  1. Confirm that the features of the flow computer and transmitters that are used have been approved by referring to the notices of approval.

    Examples of features:

    • Digital communication protocols;
    • Type of input and/or output signal;
    • Flow, supercompressibility and energy calculation method;
    • Linearization function.
  2. Confirm that the flow computer and transmitters are used within approved operating ranges by referring to the notices of approval.
  3. Record the features and operating ranges in use and any nonconformity on the inspection worksheet.

8.0 Assessment of conformity with metrological requirements

8.1 General

Where the flow computer and transmitters are due for inspection and the transmitter test method used requires a system test, the test should be conducted at one of the applicable test points for the transmitter, during the inspection of transmitters.

8.2 Transmitters

8.2.1 Temperature transmitters or resistance temperature detectors

  1. Install a certified digital thermometer in the temperature source and record its information (i.e. manufacturer, model, serial number, calibration certificate number) on the inspection worksheet.

    Note: Where the transmitter output is used to verify the transmitter, also connect a voltage or current standard to the output of the transmitter.

  2. Supply a temperature that corresponds to one of the test points prescribed in S-G-05.
  3. Allow the digital thermometer's reading to stabilize.
  4. Record the corresponding temperature values for the digital thermometer and the transmitter/RTD on the inspection worksheet.
  5. Calculate the absolute error of the transmitter's/RTD's indicated temperature value and record it on the inspection worksheet.

    Notes:

    1. Where the transmitter output or indicator reading is used to verify a transmitter, the flow computer reading for the transmitter input must be taken for at least one of the test points.
    2. Where the transmitter/RTD test is used for one of the flow computer system error test points, it continues for the duration of the system test for this test point.
  6. Compare the error to the applicable maximum permissible error (MPE) specified in S-G-05.
  7. Record the conformance status (i.e. accepted or rejected) of the transmitter's/RTD's temperature accuracy result on the inspection worksheet. An unacceptable accuracy result may indicate problems in the test equipment set-up or a deficiency in the device under test.
  8. Repeat the previous steps for all the temperature test points prescribed in S-G-05.
  9. Determine the overall conformance status of the transmitter/RTD in relation to all specified requirements and record the result on the inspection worksheet.
  10. Where the transmitter/RTD has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the device under test does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.2.2 Static pressure transmitters

  1. Connect a certified digital pressure gauge to the pressure source and record its information (i.e. manufacturer, model, serial number, calibration certificate number) on the inspection worksheet.

    Note: Where the transmitter output is used to verify the transmitter, also connect a voltage or current standard to the output of the transmitter.

  2. Supply a pressure that corresponds to one of the static pressure test points prescribed in S-G-05.
  3. Allow the digital pressure gauge's reading to stabilize.
  4. Record the corresponding static pressure values for the digital pressure gauge and the transmitter on the inspection worksheet.
  5. Calculate the relative error of the transmitter's indicated static pressure value and record it to the nearest 0.1% on the inspection worksheet.

    Notes:

    1. Where the transmitter output or indicator reading is used to verify a transmitter, the flow computer reading for the transmitter input must be taken for at least one of the test points.
    2. Where the transmitter test is used for one of the flow computer system error test points, it continues for the duration of the system test for this test point.
  6. Compare the error to the applicable MPE specified in S-G-05.
  7. Record the compliance status (i.e. accepted or rejected) of the transmitter's static pressure accuracy result on the inspection worksheet. An unacceptable accuracy result may indicate problems in the test equipment set-up or a deficiency in the device under test.
  8. Repeat the previous steps for all the static pressure test points prescribed in S-G-05.
  9. Determine the overall conformance status of the transmitter in relation to all specified requirements and record the result on the inspection worksheet.
  10. Where the transmitter has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the device under test does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.2.3 Differential pressure transmitters

  1. Open the downstream pressure sensor to atmosphere.
  2. Connect a certified digital pressure gauge and the pressure source to the upstream pressure sensor.

    Note: Where the transmitter output is used to verify the transmitter, also connect a measuring apparatus (i.e. voltage or current standard) to the output of the transmitter.

  3. Record the digital pressure gauge's information (i.e. manufacturer, model, serial number, calibration certificate number) on the inspection worksheet.
  4. Supply zero pressure to the upstream sensor.
  5. Allow the digital pressure gauge's reading to stabilize.
  6. Record the corresponding differential pressure values for the digital pressure gauge and the transmitter on the inspection worksheet.
  7. Calculate the relative error of the transmitter's indicated differential pressure value and record it to the nearest 0.1% on the inspection worksheet.

    Notes:

    1. Where the transmitter output or indicator reading is used to verify the transmitter, the flow computer reading for the transmitter input must be taken for at least one of the test points.
    2. Where the transmitter test is used for one of the flow computer system error test points, it continues for the duration of the system test for this test point.
  8. Compare the error to the applicable MPE specified in S-G-05.
  9. Record the compliance status (i.e. accepted or rejected) of the transmitter on the inspection worksheet. An unacceptable accuracy result may indicate problems in the test equipment set-up or a deficiency in the device under test.
  10. Apply the pressure corresponding to the next test point prescribed in S-G-05 and repeat the previous steps until the transmitter has been inspected at all test points.
  11. Determine the overall conformance status of the transmitter in relation to all specified requirements and record the result on the inspection worksheet.
  12. Where the transmitter has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the device under test does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3 Flow computer

8.3.1 Flow computer inputs

8.3.1.1 Transmitter inputs

Where the transmitters are inspected at the same time as the flow computer, the transmitter inputs are verified during the transmitter inspection (see section 8.2.1, 8.2.2 or 8.2.3, as applicable).

Where the transmitter's certificate is valid, the following steps may be completed at the test points for one of the system error tests described in section 8.3.3.

  1. Install the certified digital pressure gauge or certified digital thermometer at the source being measured by the transmitter.
  2. Record the corresponding values for the digital pressure gauge or thermometer and the flow computer on the inspection worksheet for the transmitter being verified.
  3. Calculate the absolute or relative error, as applicable, of the transmitter's indicated value and record it on the inspection worksheet.
  4. Compare the error to the applicable MPE specified in S-G-05.
  5. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet. An unacceptable accuracy result may indicate problems in the test equipment set-up or a deficiency in the device under test.
  6. Repeat the previous steps for each transmitter connected to the flow computer.
  7. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3.1.2 Gas composition input

Where the flow computer uses the composition values from an approved and certified gas analyzer to calculate the energy units, the transfer of the composition values is verified by completing the steps below.

  1. Obtain the gas analyzer's and the flow computer's gas composition values.
  2. Compare the values to ensure they are the same as the gas analyzer composition values used for the update.
  3. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet.
  4. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3.1.3 Meter inputs

Meter inputs are evaluated by completing the following steps during the system error tests as described in section 8.3.3:

  1. Compare the pulses generated, analogue output or digital data sent to the flow computer change in the meter input value to ensure the signal sent by the meter was received by the flow computer.
  2. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet.
  3. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3.2 Flow computer calculator function

Where there is access to the source coding of measurement software modules/subroutines, the converted volume and/or energy accumulation calculations are verified by completing the following steps.

Note: This applies to the initial inspection of these types of flow computers and reverification inspections where the seal is not intact or an updated load has been installed.

  1. Have the contractor's representative set the temperature, pressure and gas composition values to the middle of the expected range for the site.
  2. Set the flow rate to the middle of the range for the site.

    Notes:

    1. Where it is not possible or practical to set the flow rate frequency for pulse-based metering to the middle of the range for the site, connection of a device which simulates the meter output is required and the frequency must be set to the middle of the expected flow rate range for the site.
    2. For orifice metering, the flow rate is set by opening the downstream differential sensor to atmosphere and connecting a pressure source of 50% of the programmed differential pressure range to the upstream sensor. Where the pressure source is not certified, connection of a certified pressure gauge is required to obtain the true value of the differential pressure.
  3. Have the contractor's representative open a flow computer's window that displays the volume and/or energy flow rate units that will obtain an error resolution of at least 0.1%.
  4. Start the test, when the fixed and simulated inputs are stable, press the Print Screen key on the laptop and copy to a word-processing file for viewing.
  5. Record the volume and/or energy flow rate readings on the inspection worksheet.
  6. Set up the authorized test software for the type of metering, with the fixed or simulated values used for the test and the frequency used for the test for pulse-based metering.
  7. Set the applicable meter factor in the authorized test software (as applicable).

    Note: Where meter factors are expressed as a percentage, they need to be divided by 100 before being entered in the authorized test software.

  8. Calculate the volume and/or energy flow rate values using the authorized test software.
  9. Record the authorized test software results on the inspection worksheet.
  10. Calculate the relative errors of the flow computer's volume and/or energy flow rate values and record them to the nearest 0.1% on the inspection worksheet.

    Note: Where the pressure multiplier (Pm), temperature multiplier (Tm) and supercompressibility factor (Fpv) are accessible, verify them during one of the calculator function tests to ensure they are in agreement with the values calculated using the formula required under the Electricity and Gas Inspection Regulations.

  11. Compare the errors to the applicable MPE specified in S-G-05.
  12. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet. Unacceptable accuracy results may indicate problems in the test equipment set-up or a deficiency in the device under test.
  13. Repeat the previous steps for the remaining test points prescribed in S-G-05.
  14. Determine the overall conformance status of the flow computer in relation to all specified requirements and record the result on the inspection worksheet.
  15. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3.3 Flow computer system error

The following tests are completed to determine the total error of the measurement system. For each test, the billing units calculated by the flow computer using its inputs from the sources are compared to the authorized test software calculated billing units using the true values for the input sources.

8.3.3.1 Snapshot tests for system error
  1. Install the certified pressure gauges and certified digital thermometers at the applicable sources.

    Notes:

    1. Where it is not possible or practical to set the system to the pressure or temperature test points, install a controlled source at the applicable sensors.
    2. Where it is not possible or practical to set the flow rates required, an applicable source must be provided to the sensor. Pulse inputs must be disconnected from the flow computer and a frequency generator must be connected to the flow computer meter input. (Failure to disconnect meter inputs will result in frequency errors during the testing)
  2. Have the contractor's representative enter the gas composition required to obtain the heating value for the test.
  3. Have the contractor's representative open a flow computer's window that displays the pressure, temperature, meter factor (if applicable) and measurement units (or flow rates where the snapshot method is used) being evaluated and set the measurement units to the highest resolution available.
  4. Ensure that each source is set up for the applicable test points prescribed in S-G-05.
  5. Allow the system to stabilize and initiate the test.
  6. Where the snapshot test method is being used, have the operator press the Print Screen key on the laptop and copy the data to a word-processing file.
  7. Record the flow computer's volume and/or energy flow rate readings for snapshot method and also the meter factor (if applicable) on the inspection worksheet.

    Note: Where linearization is being applied, refer to the appropriate notice of approval for the exact modelling equation to calculate the meter factor to be entered in the authorized test software.

  8. Set up the authorized test software for the type of meter installed and the applicable meter factor for the flow rate, and enter the true values for each source, ensuring the units for both the source and final results are the same resolution as those used in the flow computer's display window.
  9. Calculate the volume and/or energy flow rate values using the authorized test software.
  10. Record the authorized test software results on the inspection worksheet.
  11. Calculate the relative error of the flow computer's volume and/or energy flow rate values and record it to the nearest 0.1% on the inspection worksheet.
  12. Compare the error to the applicable MPE specified in S-G-05.
  13. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet. Unacceptable accuracy results may indicate problems in the test equipment set-up or a deficiency in the device under test.
  14. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3.3.2 Test for system error at flowing conditions

The snapshot method is not permitted for the flowing condition system test point prescribed in S-G-05. Where applicable, the steps in section 8.3.4 should be completed during this test.

  1. Install the certified pressure gauges and certified digital thermometers at the applicable sources.

    Notes:

    1. Where it is not possible or practical to install a certified pressure gauge and certified digital thermometer to obtain the true units for the flowing gas pressure or temperature, install a controlled source at the applicable sensors.
    2. Where the meter output is in the form of pulses, install a pulse counter to count the pulses accumulated during the test.
    3. Where the meter output is analogue, connect the sensor to a controlled source with provisions to monitor the source with a certified standard.
  2. Have the contractor's representative return the gas composition to flowing conditions.
  3. Have the contractor's representative open the flow computer's window that displays the billing units, meter input (pulse count, differential pressure or digit reading), uncorrected volume flow rate, corrected volume and or energy flow rate(s) and set them to the highest resolution available.

    Note: Where applicable, the meter correction factor used is also to be included.

  4. Ensure that each source is set up for the applicable flowing conditions prescribed in S-G-05, then initiate the test and simultaneously press the Print Screen key to copy the start values for all variables required to complete the inspection.
  5. Record the start values for measurement units being evaluated on the inspection worksheet.
  6. Run the test for a period sufficient to obtain a 0.1% resolution for the test results.

    Note: For some flow computers, the test must be started at the top of the hour and run for a least one hour.

  7. Stop the pulse counter or remove the meter input supply source. Where the data continues to update simultaneously, have the operator press the Print Screen key on the laptop and copy the data to a word-processing file.
  8. Calculate the flow computer measurement unit values accumulated by the flow computer during the test and record them on the inspection worksheet.
  9. Set up the authorized test software for the type of meter installed and the applicable meter factor for the flow rate. Enter the true values for each source, ensuring the units for both the source and final results are the same resolution as those used in the flow computer's display window.
  10. For pulse-based metering, configure the authorized test software calculation based on pulses, enter the number of pulses received during the test, the pulses/unit (K factor), the test time (flow duration) and calculate the true measurement unit values.
  11. Record the authorized test software data on the inspection worksheet.
  12. Calculate the relative error of the flow computer's billing units registered and record it to the nearest 0.1% on the inspection worksheet.
  13. Compare the error to the applicable MPE specified in S-G-05.
  14. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet. Unacceptable accuracy results may indicate problems in the test equipment set-up or a deficiency in the device under test.
  15. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

8.3.4 Flow computer outputs

The flow computer outputs are verified by completing the following steps at the same time as the system error test at flowing conditions (section 8.3.3.2).

  1. Install a pulse counter at the flow computer output.
  2. Have the operator provide the measurement units corresponding to the output reported by the flow computer at the start of the test (with the certificate correction factor applied, if it is to be incorporated in the output) to the maximum resolution available on the screen, as mentioned in 8.3.3.2, step 3.
  3. Stop the pulse counter at the end of the test.
  4. Have the operator provide the measurement units corresponding to the output reported by the flow computer at the end of the test (with the certificate correction factor applied, if it is to be incorporated in the output) to the maximum resolution available on the screen, as mentioned in 8.3.3.2, step 2.
  5. Calculate the applicable measurement units accumulated by the flow computer during the test.
  6. Record the results on the inspection worksheet.
  7. Compare the calculated outputs to the units registered by the flow computer to ensure they are the same when taking into account the uncertainty of the pulse count due to start and stop errors.

    Note: Make sure the uncertainty of the start and stop errors does not cause an error exceeding 0.1%.

  8. Record the compliance status (i.e. accepted or rejected) of the flow computer on the inspection worksheet.
  9. Where the flow computer has failed to comply with the performance requirements of S-G-05, the contractor's representative may make any necessary adjustments. Repeat all required performance testing in accordance with this section and record all "As Left" results on the same inspection worksheet or a new one.

    Note: Where the flow computer does not comply with the specified performance requirements, it cannot be used for custody transfer or trade purposes until it has been corrected and reverified.

9.0 Sealing

Refer to S-G-05 and G-02 for the requirements pertaining to the sealing of conforming flow computers and transmitters/RTDs.

10.0 Inspection certificate

Complete and issue an inspection certificate in accordance with GEN-27 and section 21 of the Electricity and Gas Inspection Regulations.

Notes:

  1. Where a flow computer is approved with integral sensors, a single inspection certificate must be generated with the applicable seal period.
  2. Where a flow computer is used with approved non-integral pressure and temperature transmitters, distinct inspection certificates must be generated for the flow computer and transmitters with the applicable seal periods.

11.0 Fees

Charge the fee for the inspection of a flow computer and transmitters/RTDs at the operational location as established in Schedule 1, Part IV of the Electricity and Gas Inspection Regulations.

12.0 Nonconformity and defect reporting

Report details of any nonconformity or defects identified during the inspection to the regional gas specialist for review and follow-up.

13.0 Revision

The purpose of revision 1 was to:

Date modified: