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PS-G-03 Provisional Specifications for the Verification and Reverification of Mechanical Conversion Devices

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1. Scope
These specifications apply to any mechanical base pressure and/or base temperature conversion devices, with or without supercompressibility correction functions, submitted for verification or reverification under the Electricity and Gas Inspection Act.

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

3.  Performance Requirements
3.1  Base Pressure Conversion Function Accuracy Tests
3.1.1  Subject to clauses 3.1.3 and 3.1.4, where the device owner has provided the inspector with objective evidence regarding the yearly minimum and maximum operating pressures of the distribution system on which the device is to be installed, verification or reverification of the base pressure conversion function accuracy of the device shall be performed in accordance with the test points and tolerance limits for the relative error of the pressure multiplier specified in Table 1.

3.1.2  For the purposes of clause 3.1.1, the following information shall be considered as objective evidence for the determination of the yearly maximum or minimum operating pressures of a gas distribution system:

1. information supplied by the device owner's engineering department regarding the maximum and minimum design operating pressures of the distribution system;
2. the measured set point pressure of a regulator installed upstream of the conversion device as an indication of the system's maximum operating pressure; or
3. continuous measurement recordings of system pressure covering a period of at least one year and taken from a site located within 100 metres, measured along the pipe, upstream of the conversion device to be tested.

Note:  All measurements mentioned in this clause are to be made with measurement equipment of known accuracy.

 Table 1

3.1.3  Subject to clause 3.1.4, where no information has been provided regarding the characteristics of distribution system pressures to which the device will be subject, the test points for the base pressure conversion function accuracy of the device and the tolerance limits for the relative error of the pressure multiplier shall be as specified in Table 2.

Table 2

Note: p_max symbolizes the device's maximum operating pressure.

3.1.4  In addition to the requirements of clauses 3.1.1 and 3.1.3, where the verification or reverification is performed at the device's operational location, the device shall be tested at its operating pressure at the time of the test and the relative error of the pressure multiplier shall fall within the tolerance interval of -2.0% to +1.0%.

3.1.5  Where a device fails to meet the requirements for verification or reverification, any subsequent reverification shall require a complete retesting of the device in accordance with clause 3.1.1 or clause 3.1.3 and, if applicable, clause 3.1.4.

3.1.6  For any verification or reverification, the value of the atmospheric pressure marked on the device shall fall within the tolerance interval established by the expression:

where

1.  p_a is the mean atmospheric pressure at the device's intended or actual operational location, approximated by the calculation in accordance with subsection 37(1) of the Regulations or determined on the basis of historical data recorded by Environment Canada;
2.  p_g is the minimum operating gauge pressure of the device, which shall be taken as 30% of the device's maximum operating pressure in cases where the information specified in clause 3.1.1 has not been provided; and
3. k is a constant which is equal to

1. 0.621 when p_a and p_g are expressed in units of kilopascals, or
2. 0.090 when p_a and p_g are expressed in units of pounds per square inch.

3.2  Base Temperature Conversion Function Accuracy Tests
3.2.1  For initial verification at any location and reverification at a testing facility, the test points for the base temperature conversion function accuracy of the device and the tolerance limits for the relative error of the temperature multiplier shall be as specified in Table 3.

Table 3

3.2.2  Subject to clause 3.2.3, for reverification at the operational location, the test points for the base temperature conversion function accuracy of the device and the tolerance limits for the relative error of the temperature multiplier shall be as specified in Table 4.

Table 4

Reference value of temperature Error tolerance limits

±1.0% to ±1.0% ±1.0%

Note: t_o symbolizes the flowing gas temperature at the time of the test.

3.2.3  For modular-type base temperature conversion devices installed on rotary meters, where the test point temperatures of clause 3.2.2 cannot be achieved due to equipment or facility limitations, the device shall be tested at the flowing gas temperature and the relative error of the temperature multiplier shall not exceed ±0.5%.

3.2.4  Where a device fails to meet the requirements for verification or reverification, any subsequent reverification shall require a complete retesting of the device in accordance with clause 3.2.1 or clause 3.2.2, as applicable.

3.3  Combined Base Pressure and Base Temperature Conversion
Device Accuracy Tests
3.3.1  The requirements of section 3.1 and 3.2 shall apply to the base pressure and base temperature conversion functions of the combined conversion device respectively.

3.3.2  In addition, the algebraic sum of any pair of base pressure and base temperature conversion errors shall fall within the tolerance interval of:

1. for verification tests performed at any location or reverification tests performed at a location other than the device's operational location, ±1.3%; or
2. for reverification tests performed at the device's operational location, -2.0% to +1.3%.

3.4  Supercompressibility Correction Function Accuracy Tests
3.4.1  Where a conversion device includes a supercompressibility correcting function, the values of the gas relative density, carbon dioxide content, nitrogen content, and flowing temperature used for calibration of the device shall be marked on the device, shall be representative of the gas in the distribution system on which the device will be installed, and shall be objectively substantiated by the device owner with evidence obtained by measurement of the gas parameters.

3.4.2  Subject to clause 3.4.4, for a base pressure conversion device with a supercompressibility correction function, the device shall be verified or reverified in accordance with the requirements of clause 3.1 and the relative error of the supercompressibility-corrected pressure multiplier shall fall within the tolerance interval of:

1. for verification tests performed at any location or reverification tests performed at a location other than the device's operational location, ±1.3%; or
2. for reverification tests performed at the device's operational location, -2.0% to +1.3%.

3.4.3  Subject to clause 3.4.4, for a combination base pressure/base temperature conversion device with a supercompressibility correction function, the device shall be verified or reverified in accordance with the requirements of section 3.3 and the algebraic sum of any pair of the relative errors of the supercompressibility-corrected pressure multiplier and the temperature multiplier shall fall within the tolerance interval of:

1. for verification tests performed at any location or reverification tests performed at a location other than the device's operational location, ±1.6%; or
2. for reverification tests performed at the device's operational location, -2.0% to +1.6%.

3.4.4  For any reverification performed at the operational location, the flowing gas temperature at the time of the test and the marked values of the other gas parameters shall be used in the determination of the relative error of the supercompressibility-corrected pressure multiplier or the combined supercompressibility-corrected pressure and temperature multiplier, as the case may be.

3.5  Converted and Unconverted Register Accuracy Tests
3.5.1  Where all of the applicable accuracy tests for a particular verification or reverification of a conversion device have been conducted without reference to the device's base pressure and/or base temperature converted volume register, at least one test shall be conducted to ascertain that the ratio of the accumulated converted volume to the accumulated unconverted volume is equal to the pressure and/or temperature multiplier, as the case may be. No additional error shall be introduced by the registers.

4.  Other Requirements
4.1  Any conversion device which is discovered in service and is not approved and verified for operation over the full range of the gas distribution system's operating pressures shall be rejected and removed from service.

4.2   All other requirements for the verification and reverification of mechanical conversion devices not relating to the performance of the devices remain unchanged.

Alan E. Johnston
President
Measurement Canada