S-G-02—Specifications for the verification and reverification of diaphragm meters

Category: Gas
Issue date: 2019-01-18
Effective date: 2019-01-18
Revision number: 2
Supersedes: S-G-02 (rev.1)


Table of contents


1.0 Purpose

This specification establishes requirements for:

2.0 Scope

This specification applies to diaphragm meters approved by Measurement Canada (MC) for use in the trade measurement of natural gas, propane vapour or any other hydrocarbon gas. This includes diaphragm meters with a built-in telemetering function or retrofitted with an approved and compatible telemetering device prior to being inspected.

3.0 References

4.0 Authority

This specification is issued under the authority of section 18 of the Electricity and Gas Inspection Regulations.

5.0 Definitions

Biased calibration target (cible d’étalonnage biaisée)

A non-zero target value for the calibration of a meter’s performance accuracy that is established by the meter owner to account for a subsequent drift in a new or remanufactured meter’s performance due to the elasticity of its diaphragm material.

Defect (défaut)

A departure of a meter's quality characteristic from its intended level or state that occurs with a severity sufficient to cause the meter to not satisfy normal usage requirements. Depending on the nature and severity of the defect, it may cause nonconformity to occur immediately or at some time in the future.

Diaphragm meter (compteur à parois déformables)

A volume measuring gas meter (positive displacement type) in which the measurement of the gas flow is effected by means of measuring chambers with deformable walls.

Direct counting method of proving (méthode d’étalonnage par comptage direct)

A method of proving (i.e. performance testing) used by a gas measuring apparatus that employs a photo-type sensor to detect the rotation of the test dial on a meter’s index or a sensor that detects the rotation of a meter’s mechanical instrument drive output, as applicable. The sensor gates (i.e. starts and stops) the performance test and detects complete revolutions of the test dial or mechanical output.

Gas measuring apparatus (appareil de mesure du gaz)

For the purpose of this specification, a calibrated and certified volumetric prover intended for use in the inspection and testing of gas meters. Examples of such gas measuring apparatus include the bell prover, sonic nozzle prover, and rotary meter-based transfer prover.

Index (index)

A mechanical clock-type or odometer-type indicating device (i.e. register) used on a meter for recording and displaying metered volume.

Inferential method of proving (méthode d’étalonnage par déduction)

A method of proving (i.e. performance testing) used by a gas measuring apparatus that detects the operating cycle of a meter by some means other than the direct counting method. Examples include a proximity sensor that detects internal movement of a diaphragm meter’s bellows, or a pulse prover that detects pressure pulses produced by the operation of a diaphragm meter under flowing conditions. The sensor gates (i.e. starts and stops) the performance test and detects operational cycles of the meter.

Large diaphragm meter (compteur à parois déformables de grande capacité)

A diaphragm meter having a rated air capacity exceeding 500 ft³/h (or metric equivalent).

New meter (compteur neuf)

A newly manufactured meter that has never been used in service.

Nonconformity (non–conformité)

A departure of a meter's quality characteristic from its intended level or state that occurs with a severity sufficient to cause the meter to not satisfy one or more specification requirements

Rated air capacity (capacité nominale en air)

The volume flow rate of air through a diaphragm meter when the air entering its inlet is at standard pressure (101.325 kPa or 14.73 psi) and standard temperature (15 °C or 60 °F) and the differential pressure across it is 125 Pa (or 0.5 inches of water), as established and declared by the manufacturer.

Relative error (erreur relative)

Absolute error of measurement divided by the conventional true value of the measurand, and traditionally referred to as the true error. Expressed as a percentage, relative error is calculated as follows:

Er = ((Qm - Qs) / Qs) × 100 %

Where,

Er is the relative error of the meter under test, expressed in percent (%)
Qm is the quantity indicated by the device under test
Qs is the quantity indicated by the reference standard, expressed in the same units as Qm

Remanufactured diaphragm meter (compteur à parois déformables refabriqué)

A diaphragm meter which has been manufactured using reconditioned castings from a previously used meter and rebuilt entirely with new original equipment manufacturer parts, using the same manufacturing techniques, processes and quality assurance criteria as are used in the manufacture of new meters. Such meters of a particular make and model are generally type approved and marked with a modified model name (e.g. model name followed by the letter R) to ensure they are readily identifiable as having been remanufactured.

Renewed meter (compteur remis à neuf)

A previously used meter restored to the technical and metrological state of a new meter, as performed and attested to by the meter manufacturer. It can also mean a meter restored to the technical and metrological state of a new meter in accordance with the meter manufacturer’s specifications and procedures as concerns meter renewal, where these procedures form part of the quality management system of a Measurement Canada-accredited organization.

Reserviced meter (compteur remis à niveau)

A previously used meter subjected to calibration or light repair under the controlled conditions and documented procedures of an accredited organization’s quality management system recognized by Measurement Canada.

Reverification (revérification)

Any subsequent confirmation of a meter's conformance to legal requirements following its initial verification of conformance to those same requirements performed upon expiration of the meter's reverification period (i.e. seal period).

Small diaphragm meter (compteur à parois déformables de petite capacité)

A diaphragm meter having a rated air capacity up to and including 500 ft³/h (or metric equivalent).

Telemetering (télémesure)

The transmission of measurement information with the aid of intermediate means that permits the source meter information to be interpreted at a distance.

Note: The term "intermediate means" is broad enough to include wired or wireless techniques for transmitting measurement data from the source meter.

Telemetering device (dispositif de télémesure)

A device used in a telemetering system to duplicate the source meter’s indicated reading, such as an automatic meter reading device or a pulse generator.

Test dial (cadran d’essai)

The clock-style dial pointer(s) on the face of a meter's index, the circle of which has graduation marks that are not numbered. The test dial may be used for gating meter performance tests on a gas measuring apparatus using the direct counting method of proving.

Verification (vérification)

All of the operations carried out by an inspector or accredited organization to confirm that a meter entirely conforms to legal requirements.

6.0 Symbols and abbreviations

T
target value for calibration of a meter’s performance accuracy (expressed as a relative error)
ei
result of performance test number i (expressed as a relative error)
uci
combined standard uncertainty of performance test result
k
factor applied to combined standard uncertainty value to provide specified coverage for an extended performance test result
LQ
limiting quality
LSL
lower specification limit
USL
upper specification limit
LTL
lower test limit
UTL
upper test limit
MADT
measure of absolute deviation from target
LCSL1
lower compressed specification limit for type 1 marginal conformities (under LQ = 3.15% plan)
UCSL1
upper compressed specification limit for type 1 marginal conformities (under LQ = 3.15% plan)
LCSL2
lower compressed specification limit for type 1 marginal conformities (under LQ = 8.0% plan)
UCSL2
upper compressed specification limit for type 1 marginal conformities (under LQ = 8.0% plan)
UMADT
upper MADT specification limit
UMADT1
upper MADT specification limit for type 2 marginal conformities (under LQ = 3.15% plan)
UMADT2
upper MADT specification limit for type 2 marginal conformities (under LQ = 8.0% plan)

7.0 General

7.1 Conforming meters

A meter is considered as verified or reverified, as applicable, when it conforms to:

7.2 Nonconforming meters

A meter that fails to meet any applicable performance or non-performance requirement of this specification, or that possesses a defect which could affect its ability to meet specified requirements, is to be classified as nonconforming.

7.3 Verification and reverification procedures

The evaluation of a meter’s conformity with the requirements of this specification is to be conducted in accordance with documented verification and/or reverification procedures developed by MC or forming part of an accredited organization’s quality management system documentation.

8.0 Administrative requirements

8.1 Marking requirements

8.1.1 General

Subject to 8.1.2 and 8.1.3, a meter is to be clearly and legibly marked:

8.1.2 Notice of approval number

A meter of a type approved prior to July 1987 is not required to be marked with its notice of approval number.

8.1.3 Base temperature nameplate background colour

A new or remanufactured temperature converting (TC) meter of a type approved prior to October 8, 2008, must have its base temperature marked on a nameplate with a red background. However, a previously used TC meter presented for inspection with a base temperature nameplate having a partially or totally faded red background is not to be classified as nonconforming if the required markings remain legible.

8.1.4 Previously used meters with illegible markings

Where any or all of a previously used meter’s required nameplate markings are illegible, the nameplate is to be replaced or, where provided for by the meter’s notice of approval, an adhesive-backed nameplate with the required markings may be placed over the original nameplate prior to the meter being presented for inspection.

8.2 Previously used meters with pre-existing adhesive verification labels

Previously used meters presented for 100% inspection or acceptance sampling inspection must have any pre-existing adhesive verification labels removed or painted over. A sample meter from a lot subjected to compliance sampling inspection is not to be classified as nonconforming if the pre-existing adhesive verification label affixed to it has illegible markings or if it has fallen off.

8.3 Reverification periods

Diaphragm meters that have qualified to be granted a conditionally or unconditionally lengthened initial reverification period are identified in bulletin G-03.

The initial and subsequent reverification periods for diaphragm meters are established in bulletin G-18 and available extensions to reverification periods are established in specification S-S-06.

9.0 Technical requirements

9.1 General

Meters must be free of any physical damage, defects in workmanship or material deficiencies which could affect the meter's performance. Meters must also be free of dirt, debris and other foreign substances, both internally and externally.

9.2 Meter non-performance testing requirements

9.2.1 Meter leak test

A leak test is to be performed with the meter installed on the gas measuring apparatus prior to the commencement of performance testing in order to detect any leaks in the meter or the proving system. Where a leak is detected and attributed to the meter, the meter is to be classified as nonconforming.

9.2.2 Meter index—Visual examination

A visual examination of a meter’s index is required to confirm its conformity with the following requirements:

9.2.3 Meter index—Dial test

A dial test is to be conducted in accordance with the following requirements to confirm that an index is functional and compatible with its host meter:

9.2.4 Telemetering functions or devices

9.2.4.1 Built-in pulse generator

Except where otherwise authorized by MC or where a meter’s built-in pulse generator has been permanently disabled, a test consisting of a minimum of two complete consecutive increments of the test dial or odometer digit which drives the pulse output is required. The test volume represented by the output pulses must match the corresponding volume registered or indicated by the meter's index.

9.2.4.2 Automatic meter reading function or device

Where a meter having a built-in automatic meter reading (AMR) function or retrofitted with an AMR device is presented for inspection for the purpose of verification or reverification:

Requirements for the verification and reverification of AMR functions and devices are outside the scope of this specification.

10.0 Metrological requirements

10.1 Conditions for performance testing

10.1.1 Ambient air temperature of meter testing room

Except where otherwise specified in MC’s requirements for the certification and use of the type of gas measuring apparatus used for meter testing, the following requirements apply:

10.1.2 Ambient and proving air temperature differential

Except where otherwise specified in MC’s requirements for the certification and use of the gas measuring apparatus used for meter testing, the difference between the meter testing room’s ambient air temperature and the temperature of the air supplied to the gas measuring apparatus must not exceed 0.5 ºC (0.9 ºF) during meter performance testing.

10.1.3 Relative humidity

Where the gas measuring apparatus used for meter performance testing is a sonic nozzle prover, the relative humidity of the air passing through its nozzles must be within the limits established by the manufacturer, except where otherwise specified by MC.

10.2 Meter acclimation

Except where otherwise authorized by MC, meters are to be acclimated inside the meter testing room for a minimum of four hours prior to the commencement of performance testing.

Note: The actual time needed for complete acclimation of a meter varies depending on the difference in temperature between the ambient air of the test room and that of the room in which the meter was previously stored. In addition, acclimation time may vary for an individual meter depending on its relative position or degree of exposure to the ambient air flow within the test room.

10.3 Meter performance testing requirements

10.3.1 Meter calibration target value

Subject to 10.3.2, the target value for calibration of a meter’s performance accuracy is to be the midpoint of the range defined by the upper and lower specification limits (i.e. zero percent relative error).

10.3.2 Biased calibration target

Subject to the following conditions, the owner of a new or remanufactured meter is permitted to apply a biased calibration target for each of its flow rate test points (specified in Table 1):

10.3.3 Meter preconditioning

Meters may be preconditioned (i.e. exercised) prior to the commencement of performance testing.

10.3.4 Gating when using the direct counting method of proving

The gating of a meter’s performance test is to be triggered on the upswing of the test dial hand when using the direct counting method of proving. Where a meter’s index is equipped with two test dials, the meter manufacturer’s recommendations are to be followed concerning which test dial to use for the gating of tests.

10.3.5 Performance test duration

The following performance test duration requirements apply:

10.3.6 Performance tests

A meter’s performance is to be tested at the high load and low load flow rate test points specified in Table 1.

Table 1—Performance tests
Performance test Flow rate test point
High load 145 ± 5% of rated air capacity
Low load 45 ± 5% of rated air capacity

10.3.7 Order of performance tests

A meter’s performance must always be tested at the high load flow rate test point first.

10.3.8 Determination of meter’s measure of absolute deviation from target

A meter’s MADT is to be calculated as the median of the absolute value of all its performance test results (each adjusted for a biased calibration target, as applicable) as shown below:

MADT = median { | e_1 − T|, | e_2 − T|, | e_i −T| ... }

10.3.9 Reporting of performance test results

A meter’s performance test results are to be presented and recorded in accordance with the requirements of specification S-S-02.

10.4 Meter performance requirements—100% inspection

10.4.1 One-stage conformity test procedure

A meter’s conformity to the performance requirements for 100% inspection is to be evaluated using a one-stage conformity test procedure in accordance with the requirements of specification S-S-02.

10.4.2 Coverage criterion for extended performance test results

The minimum coverage criterion for a meter’s extended performance test results is at least 99% coverage, which is achieved by using a coverage factor of k = 3.0000.

10.4.3 Specification limits

The specification limits for a meter’s extended performance test results are ±1.60%.

10.4.4 Test limits

The test limits for a meter’s performance test results are to be established as follows:

Where k is the coverage factor specified in 10.4.2 and uci is the combined standard uncertainty determined in accordance with specification S-S-02.

10.4.5 Upper specification limit for measure of absolute deviation from target

The upper specification limit (UMADT) for a meter’s MADT result (calculated in accordance with 10.3.8) is 0.60.

Note: Effective January 1, 2016, the UMADT for large diaphragm meters was reduced from 0.80 to 0.60 in accordance with bulletin S-02.

10.4.6 Performance conformity criteria

A meter conforms to the performance requirements specified in 10.4.4 and 10.4.5 when the following criteria are all satisfied:

  1. ei ≤ (UTL + T) for all performance tests
  2. ei ≥ (LTL + T) for all performance tests
  3. MADT ≤ UMADT

11.0 Acceptance sampling inspection

11.1 Prerequisites to the use of acceptance sampling inspection

Where the prerequisite requirements of specification S-S-03 have been satisfied, homogeneous lots of meters may be verified or reverified using acceptance sampling inspection in accordance with specification S-S-04 and the applicable requirements of this specification.

11.2 Lot homogeneity requirements

11.2.1 Lot homogeneity criteria

A lot of meters submitted for verification or reverification by acceptance sampling inspection is not permitted to contain a mixture of TC and non-TC meters. In addition, all meters in a lot are required to satisfy the following homogeneity criteria:

11.2.2 Forming lots of mixed meters

If an accredited meter verifier wishes to combine in one lot various models or vintages of meters, and/or meters equipped with and without a telemetering device, they must submit a request to MC with accompanying documentation in support of their claim that the differing meters can be considered homogeneous for purposes of acceptance sampling inspection.

11.3 Non-performance quality characteristics

Each sample meter is subject to the following requirements and the conformity status for each is to be treated as a non-performance observation (i.e. conforming or nonconforming):

11.4 Meter performance testing requirements

Each sample meter is subject to the performance testing requirements specified in 10.3.

11.5 Meter performance requirements

11.5.1 One-stage or two-stage conformity test procedure

A sample meter’s conformity to performance requirements may be evaluated using either a one-stage or two-stage conformity test procedure in accordance with the requirements of specification S-S-02.

11.5.2 Coverage criterion for extended performance test results

The minimum coverage criterion for a sample meter’s extended performance test results is at least 95% coverage, which is achieved by using a coverage factor of k = 1.6449.

11.5.3 Specification limits

For the purposes of lot sentencing, the specification limits for a sample meter’s extended performance test results are ±1.60%.

11.5.4 Compressed specification limits and upper MADT specification limit

The compressed specification limits and upper MADT specification limits for a sample meter’s performance test results are as specified in Table 2.

Table 2—Compressed specification limits and upper MADT specification limit
Marginal conformity type Lower limit Upper limit
Type 1 (under LQ=3.15% plan) LCSL1 = 0.8350 (-1.60) + T UCSL1 = 0.8350 (1.60) + T
Type 1 (under LQ=8.0% plan) LCSL2 = 0.6797 (-1.60) + T UCSL2 = 0.6797 (1.60) + T
Type 2 (MADT, under LQ=3.15% plan) - UMADT1 = 0.80
Type 2 (MADT, under LQ=8.0% plan) - UMADT2 = 0.70

11.5.5 Performance conformity criteria

The conformity, marginal conformity or nonconformity of a sample meter’s performance is to be determined in accordance with the following classification criteria, which is to be applied in the order presented below:

  1. nonconforming if:
    • ei + k uci > (USL + T) or ei − k uci < (LSL + T)
  2. marginally conforming type 1 if:
    1. ei + k uci > UCSL1 or ei − k uci < LCSL1 (under LQ = 3.15% plan), or
    2. ei + k uci > UCSL2 or ei − k uci < LCSL2 (under LQ = 8.0% plan)
  3. marginally conforming type 2 if:
    1. MADT > UMADT1 (under LQ = 3.15% plan), or
    2. MADT > UMADT2 (under LQ = 8.0% plan)
  4. conforming otherwise

Where k is the coverage factor specified in 11.5.2, uci is the standard uncertainty determined in accordance with specification S-S-02, and MADT is determined in accordance with 10.3.8.

11.5.6 Marginally conforming performance

A sample meter’s performance is classified as marginally conforming type 1 if it has no nonconformity but exhibits performance falling outside the interval defined by the applicable lower and upper compressed specification limits. A sample meter’s performance is classified as marginally conforming type 2 if it has no nonconformity, is not classified as marginally conforming type 1, but has a MADT that exceeds the applicable UMADT limit.

12.0 Compliance sampling inspection of isolated lots of in-service meters

The reverification period of an isolated lot of in-service meters may be extended using compliance sampling inspection in accordance with the requirements of specification S-S-06 and the applicable requirements of this specification.

13.0 Outgoing quality requirements

The following outgoing quality requirements apply to meters subjected to 100% inspection and acceptance sampling inspection:

  1. Any inspected meter with a performance test result not satisfying the 100% inspection performance conformity criteria specified in 10.4.6 is not to be placed in service.
  2. Any meter with one or more nonconformities or defects is not to be placed in service. This includes any non-sample meter in a lot that may be observed with a nonconformity or defect. (Note: The accredited organization is responsible for deciding which types of quality characteristic deficiencies are to be identified as a defect.)
  3. Any sample meter from a non-accepted lot may be placed in service provided that it satisfies all applicable requirements for 100% inspection, in addition to a. and b. above.
  4. The numbers of type 1 and type 2 marginally conforming meters in a lot must not exceed the product of the lot size and the associated LQ value, as specified in S-S-03 or S-S-04 (as applicable).

Note: The outgoing quality requirement under d. is deemed to be satisfied for meters subjected to 100% inspection and accepted, and for lots of meters subjected to acceptance sampling inspection and accepted.

14.0 Disposition of nonconforming meters

14.1 Screening of non-accepted lot of meters

For lots of meters subjected to acceptance sampling inspection and not accepted, all nonconforming meters and a sufficient number of marginally conforming meters are to be removed, corrected or replaced to ensure the outgoing quality requirements of section 13.0 are satisfied.

14.2 Resubmission of individual nonconforming meters

Individual nonconforming or defective meters may be resubmitted for inspection only after their deficient quality characteristics have been corrected.

14.3 Resubmission of non-accepted lots of meters

Non-accepted lots of meters may be resubmitted for acceptance sampling inspection only after the meter owner or their agent has re-examined all meters and removed, corrected or replaced all nonconforming or defective meters. Where the non-acceptance was due to performance characteristics, re-inspection is to include the evaluation of all quality characteristics; where it is due to any other type of nonconformity or defect, it is to include the evaluation of the quality characteristic(s) that caused non-acceptance of the lot.

15.0 Sealing requirements

15.1 General

As applicable, a verified or reverified meter is to be sealed in accordance with its notice of approval, the requirements of specification PS-EG-02, and section 15.2.

15.2 Sealable components

15.2.1 Small diaphragm meters

Except where otherwise documented in a small diaphragm meter’s notice of approval, the following components are to be sealed:

15.2.2 Large diaphragm meters

Except where otherwise documented in a large diaphragm meter’s notice of approval, the following components are to be sealed:

15.3 Adhesive verification labels

The application of new adhesive verification labels to verified or reverified diaphragm meters as a primary verification marking is not permitted. Such labels may only be applied in accordance with the requirements of specification PS-EG-02.

16.0 Revisions

The purpose of revision 2 was to:

The purpose of revision 1 was to:

Date modified: