S-G-03–Specifications for the approval of type of gas metering devices–Part 5

Category: Gas
Issue date:
Effective date:
Revision number: 3
Supersedes: S-G-03 (rev. 2)


Part 5: Orifice fittings

Table of contents


1.0 Scope

This part of the Specifications applies to orifice fittings being part of orifice meters used to measure natural gas.

2.0 Unit requirements

Note: The following requirements of Part 1, section 1.0 apply:

  • 1.1 Use of units
  • 1.2 Metric units of measure

3.0 Metrological requirements

Note: The requirements of Part 1, subsection 2.1 apply.

4.0 Technical requirements

Note: The following requirements of Part 1, section 3.0 apply:

  • 3.1 Design, composition and construction
  • 3.4 Case

4.1 Recognized standard

These specifications adopt the requirements set out in AGA Report No. 3, Part 2 (Fifth edition, 2016).

4.2 Dimensional measurements

Measurements must be made at reference environmental conditions to establish the dimensions of the orifice fitting as set out in AGA Report No. 3, Part 2 (Fifth edition, 2016).

4.3 Maximum permissible beta ratio

All orifice fittings must meet the tolerances for a maximum permissible beta ratio of 0.7.

5.0 Marking requirements

Notes: The following requirements of Part 1, section 4.0 apply:

  • 4.1 Permanency and legibility
  • 4.2
    • (a) Departmental approval number
    • (b) Manufacturer's name or registered trademark
    • (c) Model or type designation
    • (d) Serial number
    • (e) Ambient temperature range, where less than -30 °C to 40 °C
  • 4.12 Inspection number
  • 4.13 Verification marks

According to the characteristics of the device, the following requirements may also apply:

  • 4.3 Bar codes or quick response codes
  • 4.6 Unidirectional flow measurement
  • 4.7 Bidirectional flow measurement

5.1 Nameplate

The following information must be provided on a nameplate located on the orifice fitting:

  • Maximum permissible beta ratio (β);
  • Nominal thickness of the orifice plate to be used;
  • Seat gap width.

6.0 Administrative requirements

Note: The requirements of Part 1, section 6.0 apply.

7.0 Performance test requirements

Note: Test conditions and performance tests can be obtained by contacting MC.

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