S-G-03–Specifications for the approval of type of gas meters, ancillary devices and associated measuring instruments

Category: Gas
Issue date:
Effective date:
Revision number: 1
Supersedes: LMB-EG-08 and S-G-03


Part 9: Cone-shaped differential pressure meters

Table of contents


1.0 Scope

This part of the Specifications applies to cone-shaped differential pressure (CSDP) meters submitted for approval.

2.0 Definitions

Cone-shaped differential pressure meter (débitmètre à cône de type différentiel)

A meter consisting of a cone-shaped element placed at the centre of the pipe, leaving an annular space for the passage of fluid which causes the velocity of the flowing fluid to change. A change in velocity occurs whenever there is a change in flow cross-section (i.e., with a decrease in velocity, an increase in pressure). The differential pressure generated is used to calculate the flow rate.

3.0 Metrological requirements

The applicable requirements of Part 1, section 7.0 shall apply unless otherwise stated in this section.

3.1 Maximum permissible error

The MPE shall not exceed ± 1% at any flow rate within the flow rate range for which approval is sought.

3.2 Linearity

The linearity shall not exceed ± 0.5% at any flow rate within the flow rate range for which approval is sought.

3.3 Repeatability

The repeatability of errors shall not exceed ± 0.2% at any flow rate within the flow rate range for which approval is sought.

3.4 Algorithm

3.4.1 Subject to 3.4.2, the algorithm used to translate the primary measurements of pressure and temperature into volumetric flow shall be the algorithm derived in Appendix C.

3.4.2 Where the applicant can show sufficient evidence that an alternative algorithm is suitable, that algorithm shall be authorized for use in the NOA.

4.0 Technical requirements

The applicable requirements of Part 1, section 8.0 shall apply unless otherwise stated in this section.

4.1 A static pressure tap shall be located on the meter body.

5.0 Marking requirements

In addition to the applicable requirements of Part 1, section 9.0, the following shall apply.

5.1 The following information shall be indelibly marked on the meter or on a nameplate securely fastened to the meter:

  1. Beta ratio;
  2. Inside diameter of the meter tube.

6.0 Administrative requirements

In addition to the applicable requirements of Part 1, section 11.0, the following shall apply.

6.1 Application for approval

For inclusion in the NOA, the manufacturer shall provide supporting test data relating to the maximum permissible meter/meter tube step change and maximum permissible meter non-axial alignment.

7.0 Performance tests

The applicable requirements of Part 1, section 12.0 shall apply unless otherwise stated in this section.

7.1 Accuracy testing

7.1.1 Meters shall be tested to establish performance under fully developed ideal flowing gas conditions.

7.1.2 Tests shall be performed at flow ratesFootnote 9-1 distributed over the measuring range and at Reynolds numbers which are representative of the meter's intended use over the specified operating range of the meter.

7.2 Swirl susceptibility testing

The meter shall be tested according to subsection 7.1 and Part 1, subsection 12.3.7.

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