PS-G-20—Provisional specification for the verification, reverification, installation and use of Coriolis mass flow meters

Category: Gas
Issue date: 2022-06-03
Effective date: 2022-06-03
Revision number: N/A
Supersedes: N/A

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Table of contents

• 1.0 Purpose
• 2.0 Scope
  • 2.1 Types of meters
  • 2.2 Inspection location
  • 2.3 Exclusions
• 3.0 Authority
• 4.0 References
• 5.0 Definitions
• 6.0 General
  • 6.1 Approved range of measurement
  • 6.2 Conforming meters
  • 6.3 Nonconforming meters
  • 6.4 Disposition of nonconforming meters
  • 6.5 Verification and reverification procedures
• 7.0 Administrative requirements
  • 7.1 Marking requirements
  • 7.2 Inspection certificate or record of inspection
  • 7.3 Reverification periods
• 8.0 Technical requirements
  • 8.1 General
  • 8.2 Meter zero stability
  • 8.3 Transmitter output verification
• 9.0 Metrological requirements
  • 9.1 Calibration target
  • 9.2 Device configuration
  • 9.3 Performance testing requirements
    • 9.3.1 Test medium
    • 9.3.2 Meter performance test points
    • 9.3.3 Repeatability error
    • 9.3.4 Weighted mean error
• 10.0 Sealing requirements
• 11.0 Installation requirements
• 12.0 Use requirements

1.0 Purpose

This provisional specification establishes requirements for the verification, reverification, installation and use of Coriolis mass flow meters that are approved by Measurement Canada (MC) for use in trade measurement and custody transfer applications.

2.0 Scope

2.1 Types of meters

This specification applies to mass flow meters that use Coriolis principles for gas flow measurement.

2.2 Inspection location

Inspection of a Coriolis mass flow meter must be conducted at:

• a test facility, for the purposes of initial verification and reverification,
• the operational location, for the purpose of an assessment of conformity with specified installation and use requirements.

2.3 Exclusions

This specification does not apply to initial verification or reverification of Coriolis mass flow meters used in natural gas dispensers or any other type of refuelling dispensers.

3.0 Authority

This specification is issued under the authority of subsection 12(2) and section 18 of the Electricity and Gas Inspection Regulations.

4.0 References

• Electricity and Gas Inspection Act
• Electricity and Gas Inspection Regulations
• PS-EG-02—Provisional Specifications for the Means and Methods of Physically Sealing Verified Electricity and Gas Meters
• S-G-03—Specifications for the Approval of Type of Gas Meters, Ancillary Devices and Associated Measuring Instruments
• G-18—Reverification Periods for Gas Meters, Ancillary Devices and Metering Installations
• AGA Report No. 11: Measurement of Natural Gas by Coriolis Meter — American Petroleum Institute MPMS, Chapter 14.9 (Second edition, 2013)
• OIML R 137-1 & 2: International Organization of Legal Metrology, International Recommendation, Gas meters — Part 1: Metrological and technical requirements — Part 2: Metrological controls and performance tests (2012)

5.0 Definitions

Coriolis mass flow meter
(débitmètre massique à effet de Coriolis)

A gas meter comprised of one or more oscillating tubes and electromagnetic components. All gas meter components are installed together in a metering assembly and measure the mass flow rate of the gas travelling through the system.

Maximum flow rate, Q_max
(débit maximal)

Highest mass flow rate at which a gas meter is approved to operate, as specified in the Notice of Approval.

Maximum operating flow rate, Q_max-of
(débit de fonctionnement maximal)

The highest operating mass flow rate representative of the gas at the intended installation site of the meter.

Maximum permissible error
(erreur maximale tolérée)

Extreme value of a measurement error, with respect to a known reference quantity value, that is permitted by specifications or regulations for a given measurement, gas metering device or measuring system.

Minimum flow rate, Q_min
(débit minimal)

Lowest mass flow rate at which a gas meter is approved to operate, as specified in the Notice of Approval.

Relative error
(erreur relative)

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

$E_r=\left(\frac{Q_m-Q_s}{Q_s}\right)\times 100\%=(\frac{Q_m}{Q_s}-1)\times 100\%$

Where,

• E_r is the relative error of the meter under test, expressed in percent (%)
• Q_m is the quantity indicated by the device under test
• Q_s is the quantity indicated by the reference standard, expressed in the same units as Q_m

Reverification
(revérification)

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

Transitional flow rate, Qt
(débit de transition)

Flow rate which occurs between the maximum operating flow rate Q_max-of and the minimum flow rate Q_min that divides the flow rate range into two zones, the "upper zone" and the "lower zone", each characterized by its own maximum permissible error.

Weighted mean error
(erreur moyenne pondérée)

The weighted mean error is defined as:

$$ \mathrm{WME}=\frac{{\Sigma }_{i=1}^n{k}_i{E}_i}{{\Sigma }_{i=1}^n{k}_i}$$

with

$k_i=\frac{Q_i}{Q_{max—\mathrm{of}}}$

for Q_i ≤ 0.7 Q_max-of

$k_i=1.4-\frac{Q_i}{Q_{max—\mathrm{of}}}$

for 0.7 Q_max-of < Q_i ≤ Q_max-of

Where,

• Q_i is the test flow rate
• k_i is the weighting factor at the flow rate Q_i
• E_i is the error at the flow rate Q_i

Verification
(vérification)

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

6.0 General

6.1 Approved range of measurement

Except where otherwise specified, any references in this specification to a Coriolis mass flow meter's measuring range are to be considered as references to its approved range as stated in its Notice of Approval (NOA).

6.2 Conforming meters

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

• the approved type as described in its NOA; and
• all applicable performance and non-performance requirements of this specification and any other applicable specification.

6.3 Nonconforming meters

A Coriolis mass flow meter that does not conform to any applicable requirements of this specification, or that possesses a defect that could affect its ability to satisfy normal usage requirements, is considered nonconforming and is not deemed accepted for the purposes of verification or reverification.

6.4 Disposition of nonconforming meters

A nonconforming or defective Coriolis mass flow meter can only be reinspected after its deficient quality characteristics have been corrected.

6.5 Verification and reverification procedures

Inspection of Coriolis mass flow meters for the purpose of verification or reverification is to be conducted in accordance with an inspection procedure developed by MC or authorized by MC for use by an accredited organization.

7.0 Administrative requirements

7.1 Marking requirements

A Coriolis mass flow meter must be marked clearly and legibly:

• with an inspection or meter number assigned by the contractor,
• with the NOA number (except for a type approved prior to July 1987),
• with the information indicated in the markings section of the NOA, and
• in accordance with the applicable requirements of specification S-G-03.

A Coriolis mass flow meter approved with an integrated or remote transmitter must be marked clearly and legibly with all the applicable information indicated in the marking section of its NOA and required by specification S-G-03 in respect to its transmitter.

7.2 Inspection certificate or record of inspection

An inspection certificate issued pursuant to section 14 of the Electricity and Gas Inspection Act for each verified or reverified Coriolis mass flow meter must include the information prescribed in section 21 of the Electricity and Gas Inspection Regulations, as well as the following additional information, where applicable:

• an indication of whether the flow meter is initially verified or reverified,
• the meter's mass flow rates: Q_max, Q_max-of, Q_min and Q_t,
• the expected maximum and minimum operating pressure range, average in-service operating pressure and calibration pressure,
• the mass flow calibration test points, and
• the transmitter's serial number, model, firmware version and pulse values of frequency outputs (i.e. K-factor and maximum frequency output of the device).

7.3 Reverification periods

The initial and subsequent reverification periods for Coriolis mass flow meters are as prescribed in bulletin G-18.

8.0 Technical requirements

8.1 General

A Coriolis mass flow meter must conform in every respect to the approved type described in its NOA and be free of any:

• physical damage or defect which could affect its ability to satisfy normal usage requirements, and
• dirt, debris or other foreign substance, both internally and externally, which could affect its ability to satisfy normal usage requirements.

8.2 Meter zero stability

The following requirements apply:

• Coriolis mass flow meters must be checked prior to conducting performance testing for meter zero stability. Mass flow registered under no flow conditions (i.e. flow at full rest) must not exceed the meter zero value, as specified in the NOA. Where no meter zero stability value has been specified in the NOA, refer to the manufacturer's specifications.
• Coriolis mass flow meters with a type approved bidirectional flow function must be checked for meter zero stability in both directions.

8.3 Transmitter output verification

Except where otherwise authorized by MC, the following requirements apply:

• Each activated pulse output associated with a legal unit of measure (LUM) (e.g. mass, mass flow rate) is subject to inspection.
• A deactivated pulse output is not subject to inspection if it can only be reactivated by breaking a physical seal.
• A deactivated pulse output is subject to inspection if the contractor or device owner intends to reactivate it following verification and sealing.

9.0 Metrological requirements

9.1 Calibration target

The calibration target of a Coriolis mass flow meter's measurement must be as close to the conventional true value (i.e. zero absolute error) as its adjustment will allow over the applicable measuring range.

Similarly, if a linearization function is enabled (optional), the adjustment applied by the curve that is configured in the meter must be as close to the average true value measured at each test flow rate.

Note: The tolerance for linearity applies after any corrections performed within the meter itself but prior to the application of linearization algorithms.

9.2 Device configuration

Prior to inspection, a Coriolis mass flow meter must be configured:

• for its intended use in service by the contractor,
• with approved LUMs for mass flow, as applicable,
• according to the flow direction for its intended use in service,
• according to its NOA provisions for the meter's intended use, and
• where equipped with a low-flow cut-off (LFCO) feature, the LFCO value is appropriately set as per the NOA.

9.3 Performance testing requirements

9.3.1 Test medium

Meter performance testing must be conducted using a suitable test medium at pressures which are representative of the meter's intended use.

Note: The test medium will normally be natural gas; however, if an applicant provides test data demonstrating that an alternative test medium is suitable for performing tests, tests on that medium will be accepted.

9.3.2 Meter performance test points

The following requirements apply:

Table 1—Performance testing

Test point designation	Mass flow rate (Q) (% of Qmax-of)	Flow pressure	MPE1
P12	Qmin or 10 ± 5%	Within ± 5% of average in-service pressure	Where Qmin ≤ Q ≤ Qt: ± 1.5% Where Qt < Q ≤ Qmax-of: ± 1.0%
P2	25 ± 5%
P3	50 ± 5%
P4	75 ± 5%
P5	95 ± 5%

1. Subject to paragraph (c), meter performance testing must be conducted at least at five flow rates, as specified in Table 1 of this specification, and meet the following conditions:
   • Each test point must consist of at least three measurements.
   • The meter's relative error at each test point must not exceed the maximum permissible error (MPE) specified in Table 1.
   • The duration of the tests must be sufficient to ensure that the uncertainty due to the meter resolution does not contribute more than 0.1% to the total test.
2. Where a Coriolis mass flow meter is approved for bidirectional flow and is intended to be used in bidirectional flow measurement applications, the meter must be tested in both flow directions (forward and reverse flows).

   Note: The tolerance for the MPE applicable to each test point as stated in Table 1 equally applies to bidirectional meters in both flow directions.

3. Where the test facility is not capable of achieving average in-service pressure due to the facility's pressure limitations, the test facility must provide test data to MC demonstrating that the performance testing can be done at an alternative pressure, without introducing a bias.

9.3.3 Repeatability error

The following requirements apply:

Where Q_min ≤ Q ≤ Q_t: ± 0.5%

Where Q_t < Q ≤ Q_max-of: ± 0.35%

• Each test point specified in table 1 must be evaluated for repeatability.
• At least three consecutive performance tests must be performed at each test point and the maximum error difference between three consecutive errors at each test point must not exceed the following tolerances:

9.3.4 Weighted mean error

The weighted mean error (WME) must not exceed ± 0.4%.

Note: The tolerance for the WME applies after the application of the final meter factor, if any.

10.0 Sealing requirements

Except where otherwise authorized by MC, a verified or reverified Coriolis mass flow meter is to be sealed in accordance with the provisions of its NOA and the requirements of provisional specifications PS‑EG‑02.

11.0 Installation requirements

Except where otherwise authorized by MC, a Coriolis mass flow meter must be installed:

• in accordance with any instructions or conditions included in the NOA, or as otherwise recommended by the manufacturer,
• in a manner designed to prevent accumulation of contaminants.

Where the Coriolis mass flow meter is equipped with a LFCO feature, the installation must also include provisions for the flow meter to be able to accumulate zero mass at flow rates of less than or equal to the LFCO value specified in its NOA. The LFCO value may be set to operate at flow rates higher than the value specified in the NOA, but not exceeding the meter's approved Q_min value. A higher value than Q_min may be set with the consent of the selling party.

12.0 Use requirements

Except where otherwise authorized by MC, the following requirements apply:

• Subject to subsection 9.3.2, Table 1, where the flow meter was verified or reverified at a Q_max-of flow rate of less than its approved rated capacity of Q_max, as specified in its NOA, it's essential that the Q_max-of value represents the expected in-service maximum mass flow rate. Where the in‑service maximum mass flow rate changes (exceeds) by more than 25% of Q_max-of after the verification or reverification of the flow meter, the flow meter will require reverification to this new higher operating flow rate. The flow meter's new higher operating flow rate must be within the approved range as per the NOA.


• The flow meter must not be used outside the range of ambient temperature for which it is approved. Where necessary, shelter and heaters or other arrangements must be provided to ensure that this requirement is met.


• Any adjustment, modification or exchange made to the flow meter or function's calibration or hardware components is deemed a verification triggering event.


• Only pulse outputs that have been inspected and verified and which are proportional to the mass of gas which has passed through the flow meter can be used for billing calculations.