S-G-06—Specifications for the verification, reverification, installation and use of cone-shaped differential pressure meters

Category: Gas
Specification: S-G-06 (rev. 1)
Issue date:
Effective date:
Supersedes: S-G-06


Table of contents


1.0 Scope

These specifications apply to the verification, reverification, installation and use of cone-shaped differential pressure meters.

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 difference between the volume or flow rate measured by the meter under test and the volume or flow rate measured by a reference meter, calculated as follows:

(Deviation i %) = [[(Q i) – (Q ref i)] ÷ (Q ref i)] × 100%

where,

  • Q(i) = volumetric or mass flow rate or accumulated volume determined by the meter under test using its flow algorithm
  • Qref(i) = volumetric or mass flow rate or accumulated volume determined by the reference meter

Note: Corrections must be made in the calculations to account for the differences in gas pressure, temperature and compressibility between the two meters.

Flow algorithm (algorithme d'écoulement)

The mathematical relationship used to transform the measured pressure differential in the meter to a mass flow or volumetric flow rate at metering conditions.

Linearity (linéarité)

The maximum difference between the meter's mean deviations and any of the error deviations for test points between the maximum and minimum rated flow rates, calculated as follows:

(Linearity i %) = [(Deviation i %) ÷ (Mean Deviation %)] × 100%

Maximum flow rate (Qmax) (débit maximal)

The maximum flow rate of a meter, as listed in the meter's Notice of Approval.

Maximum permissible error (erreur maximale permise)

The largest allowable deviation within the specified operational range of the meter.

Mean deviation (écart moyen)

The mean error of the meter, calculated as follows:

(Mean Deviation %) = (1 ÷ n) × [(uppercase d1) + (uppercase d2) + … + (uppercase dn)]

where,

  • D(i) = percent deviation at test point (i)
Minimum flow rate (Qmin) (débit minimal)
The lowest flow rate at which the meter's deviation is less than the maximum permissible error and the linearity is less than the maximum prescribed values in clause 5.1.2, as listed in the meter's Notice of Approval.
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.
Reynolds number (Re) (nombre de Reynolds)
The dimensionless number equalling the ratio of inertial forces to viscous forces in closed pipe flow.
Specification limit (limite de spécifications)
The maximum error permitted for a meter's performance characteristic.
Test limit (limite d'essai)
The limit established when the specification limit is adjusted for the associated measurement uncertainty.

5.0 Metrological requirements

5.1 Accuracy tests

5.1.1 Subject to clause 5.1.3, initial verification tests shall be conducted with a suitable test mediumFootnote 1 at Reynolds numbers which are representative of the meter's intended use. Where Qmax cannot be achieved because of limitations of the test facility, the upper test flow rate shall be at least 0.4 Qmax and the meter shall be tested at least five flow rates approximately equally spaced between 0.1 Qmax and the maximum flow rate attainable by the test facility.

5.1.2 The maximum permissible error (MPE) of the meter shall not exceed the following:

where,

Where the meter's Qmax cannot be achieved, the errors of the meter shall not exceed the following tolerance limits:

Maximum permissible deviation = TL × Q attained ÷ Q max

5.2 Reverification interval

Meters shall be reverified in accordance with the applicable initial reverification period or subsequent reverification period prescribed in Measurement Canada bulletin G-18.

6.0 Technical requirements

6.1 Design, composition and construction

The meter shall conform in every technical respect to the approved type as documented in the NOA.

6.2 Installation and use

6.2.1 General

6.2.1.1 Unless otherwise stated in the NOA, the meter shall be installed either vertically or horizontally. In a vertically installed meter, the gas shall flow downward.

6.2.1.2 Where conditions of reverse flow may occur during meter usage, the installation shall incorporate features to prevent the reverse flow of gas through the meter.

6.2.1.3 The meter shall be installed in a manner designed to prevent the accumulation of contaminants.

6.2.1.4 Where a meter is subject to flow pulsations and it has been shown that the meter's accuracy is affected by such disturbances, appropriate provisions shall be made to reduce the intensity of the disturbance to a level that will not induce a measurement error greater than the MPE specified in clause 5.1.2.

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

6.2.2 Meter tubes

The meter shall be installed in a manner consistent with the manufacturer's installation requirements and any other special installation requirements set out in the NOA for the type of service that the meter is intended to be used.

6.2.3 Upstream meter tube length

Unless otherwise authorized by the NOA, a straight pipe equal in length to five times the nominal meter diameter shall be installed upstream of the meter.

6.2.4 Downstream meter tube length

Unless otherwise authorized by the NOA, a straight pipe equal in length to three times the nominal meter diameter shall be installed downstream of the meter. In cases where the thermowell is permanently installed in the downstream meter tube, the entire meter run (which includes the upstream and downstream straight pipes) must be calibrated as an integral system, unless otherwise authorized by the NOA.

6.2.5 Meter alignment

The meter shall be installed in a manner consistent with the manufacturer's maximum permissible meter / meter tube step change and maximum permissible meter non-axial alignment as specified in the NOA.

6.2.6 Thermometer well

Unless otherwise authorized by the NOA, the thermometer well used for measuring the flowing gas temperature shall be installed between two and five diameters downstream of the metering element.

6.2.7 Flow computer

The flow computer used to calculate the volumetric flow rate or mass flow through a meter shall be a model which has been type approved for use of the algorithms listed in the NOA.

7.0 Administrative requirements

7.1 Nameplate marking

The meter shall be marked in full accordance with the marking section of the NOA.

7.2 Verification marks

Upon verification or reverification, the meter body shall be marked with a verification mark. This may be done using a special steel punch designed to produce an imprint that uniquely identifies the meter verifier. Such marks may either be placed near the meter nameplate or placed on the outer edge of the meter's inlet connection flange. If the meter body has suitable provisions (e.g., drilled hole) for securely attaching a sealing wire, a conventional verification seal may be affixed.

8.0 Revisions

The purpose of revision 1 is to:

Date modified: