Category: Gas
Issue date:
Effective date:
Revision number: 3
Supersedes: S-G-03 (rev. 2)
Part 2: Diaphragm meters
Table of contents
- 1.0 Scope
- 2.0 Unit requirements
- 3.0 Metrological requirements
- 4.0 Technical requirements
- 5.0 Marking requirements
- 6.0 Sealing requirements
- 7.0 Administrative requirements
- 8.0 Performance test requirements
1.0 Scope
This part of the specifications applies to positive displacement diaphragm type gas meters.
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 (except d, e, f and g)
- 2.3 Maximum permissible errors
- 2.4 Weighted mean error
- 2.5 Repeatability
- 2.7 Temperature
- 2.8 Durability
- 2.9 Vibrations and shocks
- 2.10 Orientation
- 2.14 Different gases
According to the characteristics of the meter, the following requirements may also apply:
- 2.13 Drive shaft (torque)
- 2.15 Influences from ancillary devices
3.1 True rated air capacity
Where the density of air1 used to establish the apparent rated air capacity (QA) differs from the density of dry air at standard conditions (i.e. 101.325 kPa or 14.73 psia, and 15 °C or 60 °F), the following formula must be used to convert the QA to the true rated air capacity of the meter (QT):
Where:
- QT is the true rated air capacity
- QA is the apparent rated air capacity
- ρt is the density of air at existing test conditions
- ρb is the density of dry air at standard conditions
3.2 Registration
3.2.1 Low load registration
With its inlet pressure at atmospheric pressure, the meter must start to register continuously at a flow rate not greater than 1% of its rated air capacity.
3.2.2 Maximum permissible errors
The error of volume registration must not exceed the maximum permissible errors (MPE) indicated below in Table 1.
Flow rates (Q) (% of the true rated air capacity) | Test conditions | MPE |
---|---|---|
5% ≤ Q ≤ 200% | Reference | ± 1.0% |
Other than reference | Temperature compensated meters: ± 2.0% |
3.2.3 Meter calibration
Meters selected for the evaluation of metrological requirements must be calibrated at reference test conditions by the manufacturer at 25% and 150% of the rated air capacity within an error not greater than ± 0.5% at these test points or a spread between the test points less than 0.5%.
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
- 3.6.2 Unidirectional flow measurement
- 3.7 Indication
- 3.12 Registration
According to the characteristics of the meter, the following requirements may also apply:
- 3.2 Minimum temperature range
- 3.8.1 Mechanical output
4.1 Mechanical registers
In addition to the applicable requirements mentioned in Part 15, subsection 3.1, the volume capacity of the proving dials or drums and test dial must correspond to an integral number of complete revolutions of the primary measuring mechanism of the meter.
4.2 Output drive shaft
Where a meter is equipped with an output drive shaft that can drive a stand-alone device intended for use as auxiliary attachment, the volume capacity per revolution of the shaft must correspond to an integral number of complete revolutions of the primary measuring mechanism of the meter.
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
- (j) Gas temperature range for which the errors ≤ MPE
- 4.6 Unidirectional flow measurement
- 4.12 Inspection number
- 4.13 Verification marks
According to the meter characteristics, the following requirements may also apply:
- 4.3 Bar codes or quick response codes
- 4.4 Temperature converted volume
- 4.8 Output drive shaft
5.1 Rated air capacity
The manufacturer's rated air capacity must be marked on the nameplate and must not exceed the true rated capacity as determined in subsection 3.1.
5.2 Diaphragm's manufacturer
The manufacturer of the diaphragm must be marked on the diaphragm in such a location that the marking is visible when the diaphragm assembly is in place.
5.3 Volume displacement
The cyclic volume must be marked on the nameplate.
6.0 Sealing requirements
Note: The following requirements of Part 1, section 5.0 apply:
- 5.1 General
- 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.
Footnotes
- Footnote 1
-
The density of dry air needs to be in accordance with standards and/or methods currently recognized by MC.