S-G-03–Specifications for the approval of type of gas metering devices–Part 3

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


Part 3: Rotary meters

Table of contents


1.0 Scope

This part of the Specifications applies to all positive displacement rotary type gas meters.

Note: Rotary meter bodies and measurement modules are approved under one approval where the modules are not interchangeable; otherwise, they carry separate approvals.

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

Notes: The following requirements of Part 1, section 2.0 apply:

  • 2.1 Rated operating conditions
  • 2.2 Flow rate characteristics
  • 2.3 Maximum permissible errors
  • 2.4 Weighted mean error
  • 2.5 Repeatability
  • 2.6 Working pressure
  • 2.7 Temperature
  • 2.8 Durability
  • 2.9 Vibrations and shocks
  • 2.10 Orientation
  • 2.11 Flow direction

According to the meter characteristics, the following subsection of Part 1 may also apply:

  • 2.13 Drive shaft (torque)
  • 2.14 Different gases
  • 2.15 Influences from ancillary devices

3.1 Starting differential pressure

The starting differential pressure must not exceed 25 Pa (0.1 in. of water).

3.2 Maximum permissible errors

The error of the unconverted volume registration must not exceed the MPE indicated below in Table 1.

Part 3, Table 1: Rotary meter maximum permissible errors
Rotary meter type Test conditions MPE
With or without integral volume conversion module/function Reference ± 1.0%
"Other than reference" ± 1.5%
Rotary meter body with provision (i.e. sensing location or thermowell) to measure the flowing gas temperature for use by a volume conversion module/function "Other than reference" ± 2.0%

4.0 Technical requirements

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

  • 3.1 Design, composition and construction
  • 3.4 Case
  • 3.5 Zero flow
  • 3.6 Flow direction
  • 3.7 Indication
  • 3.12 Registration

According to the meter characteristics, the following requirements may also apply:

  • 3.2 Minimum temperature range
  • 3.3 Automatic volume conversion
  • 3.8 Output

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
    • (f) Pmin (where applicable) and Pmax
    • (g) Qmax
    • (h) Qmin
    • (j) Gas temperature range for which the errors ≤ MPE
  • 4.12 Inspection number
  • 4.13 Verification marks

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

  • 4.3 Bar codes or quick response codes
  • 4.4 Temperature converted volume
  • 4.5 Pressure converted volume
  • 4.6 Unidirectional flow measurement
  • 4.7 Bidirectional flow measurement
  • 4.8 Output drive shaft
  • 4.14 Operating information
  • 4.16 Modular design

5.1 Volume displacement

The volume displacement per cycle of the measurement chamber must be marked on the nameplate.

5.2 Overall gear ratio(s)

The overall gear ratio(s) of all gear assemblies between the primary measuring element and the shaft driving the uncorrected register and the output drive shaft, where provided, must be clearly and permanently marked, subject to the following conditions:

  • Where the rotary meter pressure body contains a gear assembly, the marking must be on the meter nameplate; and
  • Where a gear assembly is contained in an ancillary device, the marking must be on the ancillary device's nameplate.

6.0 Sealing requirements

Notes: The requirement of Part 1, subsection 5.1 applies.

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

  • 5.3 Modular design
  • 5.4 Output drive shaft

7.0 Administrative requirements

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

8.0 Performance test requirements

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

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