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 21: Conditioning orifice plates

Table of contents


1.0 Scope

This part of the Specifications applies to conditioning orifice plates and related meter run assembly components submitted for approval.

2.0 Definitions

Conditioning orifice plate (plaques à orifices tranquillisantes)

A multi-hole orifice plate designed to simultaneously function as a differential pressure element and as a flow conditioner. Conditioning orifice plates are designed for use with meter tubes that are shorter in length than those used with conventional orifice plates.

3.0 Metrological requirements

The requirements of Part 9, section 3.0 shall apply unless otherwise stated in this section.

3.1 Algorithm

3.1.1 Subject to 3.1.2, the algorithm used to translate the primary measurements of pressure and temperature into volumetric flow shall be the algorithm derived in Appendix D.

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

3.2 Disturbance factors

The difference between the meter accuracy established during meter error testing and the meter accuracy established during meter flow disturbance testing shall not exceed the errors specified in section 3.0.

4.0 Technical requirements

In addition to the applicable requirements of Part 1, section 8.0, the following shall apply.

4.1 The conditioning orifice plate shall be used in conjunction with an approved orifice fitting.

5.0 Marking requirements

The applicable requirements of Part 1, section 9.0 shall apply unless otherwise stated in this section.

5.1 In addition to the markings required in Part 1, 9.1(a), (b), (c), and (d), the following information shall be indelibly marked on the downstream face or on the flange of the conditioning orifice plate, without distorting it:

  1. Beta ratio;
  2. Inside diameter of the meter tube;
  3. Calibration factor (Fc).

6.0 Administrative requirements

The applicable requirements of Part 1, section 11.0 shall apply unless otherwise stated in this section.

6.1 Application for approval

6.1.1 The manufacturer shall provide supporting test data relating to the maximum permissible meter / meter tube step change and maximum permissible meter non-axial alignment.

6.1.2 Where a manufacturer intends to have a conditioning orifice plate reverified by means of dimensional inspection, the following conditions shall apply:

  1. Critical physical dimensions and their permitted deviations (tolerances) shall be provided by the manufacturer/applicant. Examples of which may include, but are not necessarily limited to:
    • Pipe inside diameter
    • Plate thickness
    • Number of bore holes
    • Average of bore diameters
    • Diameter of bore hole centres
    • Surface roughness
    • Bevel, if applicable
    • Overall plate diameter
  2. The manufacturer/applicant shall provide test data demonstrating that the dimensional tolerances do not introduce a deviation in performance that is greater than that specified in section 3.0.

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