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 3: Rotary meters

Table of contents


1.0 Scope

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

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

2.0 Definitions

Rotary meter (compteur à piston rotatifs)

Volume measuring gas meter (positive displacement type) in which the measurement of the gas flow is effected by rotating members set on timing gears to transfer and integrate the flowing gas to a register.

3.0 Units

The applicable requirements of Part 1, section 6.0 shall apply unless otherwise stated in this section.

3.1 Rotary meter pressure bodies designed to accept both metric and imperial modules shall be exempt from the requirement in 6.1.1 of Part 1.

4.0 Metrological requirements

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

4.1 Starting differential pressure

The starting differential pressure shall not exceed 25 Pa (0.1 inches of water).

4.2 Maximum permissible errors

4.2.1 The following MPEs shall apply to the unconverted volume registration at any flow rate within the flow rate range for which approval is sought regardless of the pressure of the flowing medium (see Part 3, Table 1).

Part 3, Table 1: Rotary meter maximum permissible errors
Rotary meter type Flow rate (Q) Working pressure (pw) Test conditions MPE
With or without integral volume conversion module/function QminQQmax PminpwPmax Reference ± 1%
"Other than reference" ± 1.5%

4.2.2 The MPE of the converted volume registration of a measuring system which comprises a rotary meter body with a built-in thermowell to measure the flowing gas temperature for use by a compatible volume conversion module/function shall not exceed ± 2% at "other than reference" test conditions, and at any flow rate within the flow rate range for which approval is sought, regardless of the pressure of the flowing medium.

5.0 Technical requirements

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

5.1 Provisions for proving

Where mechanical indicating devices are employed on meters with built-in correcting provisions, both the corrected and uncorrected indicating devices shall meet the requirements in subsection 3.3.3 of Part 13.

6.0 Marking requirements

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

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

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

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

7.0 Performance tests

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

7.1 Evaluation tests

7.1.1 Starting differential pressure test

At reference conditions, tests shall be performed to determine the differential pressure across the meter at the flow rate where the meter starts and continues to rotate.

7.1.2 Accuracy tests

7.1.2.1 At reference conditions, tests shall be performed at flow rates distributed over the measuring range (see Part 3, Table 2).

7.1.2.2 At "other than reference" conditions, tests shall be performed at 0.25 Qmax (see Part 3, Table 2).

Part 3, Table 2: Rotary meter accuracy testing (based on unconverted volume registration)
Flow rate (Q) Operating conditions Environmental conditions
QminQQmax Reference Reference
0.25 Qmax "Other than reference" "Other than reference"

7.1.2.3 Where a rotary meter body has a built-in thermowell to measure the temperature of the flowing gas, the rotary meter shall be tested with a compatible volume conversion module/function at flow rates distributed over the measuring range and at "other than reference" conditions (see Part 3, Table 3).

Part 3, Table 3: Rotary meter accuracy testing (based on converted volume registration)
Flow rate (Q) Operating conditions Environmental conditions
QminQQmax "Other than reference" "Other than reference"

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