PS-G-06 — Provisional Specifications for the Approval, Verification, Reverification, Installation and Use of Ultrasonic Meters

PS-G-06—Provisional Specifications for the Approval, Verification, Reverification, Installation and Use of Ultrasonic Meters (PDF, 129 KB, 16 pages)

Date: 2008-10-09
Bulletin: PS-G-06 (rev. 2)
Category: Gaz
Supersedes: PS-G-06 (rev. 1)

PS-G-06 (rev. 2): Summary of Amendments to PS-G-06 (rev. 1)
Section	Description
All	Reformatted to new formatting requirements.
5.1	Removed requirements identified under the Government of Canada paper burden reduction initiative. Added reference to applicable sections of LMB-EG-08.
6.1.1	Removed requirements identified under the Government of Canada paper burden reduction initiative.

1.0 Scope

These specifications apply to ultrasonic gas meters which operate by determining the difference in transit times of bursts of ultrasonic energy travelling in the upstream and downstream direction. All metering features or functions of an ultrasonic meter that are not explicitly addressed in this specification are also subject to any additional Measurement Canada requirement and specification that is applicable to the feature or function.

2.0 Authority

These specifications are issued under the authority of sections 12 and 18 of the Electricity and Gas Inspection Regulations.

3.0 Terminology

Deviation: The mean of the errors at a given flow rate.
Error: The difference between the volume measured by the meter under test and the volume measured by a reference meter. Corrections must be made for the differences of gas pressure, temperature, and compressibility between the two meters. The error shall be calculated according to clause 4.1.1.3.
Final Meter Factor: A factor which may be applied to a meter's output(s) which changes the output(s) by a constant percentage at all flow rates. The final meter factor shall be calculated according to clause 4.2.2.
FWME: The flow rate weighted mean error of a meter, calculated according to clause 4.1.1.4.
Linearity: The maximum difference between the FWME and any of the deviations.
Maximum Permissible Error: The largest allowable deviation within the specified operational range of the meter.
Meter Tubes: Lengths of straight pipe located upstream and downstream of the meter.
Multipath Meter: An ultrasonic meter with more than one velocity sensing path.
Processing Circuitry: Circuitry which provides for the generation, detection and timing of ultrasonic pulses and for the calculation of the meter's outputs.
Qmax: The maximum flow rate of the meter.
Reference Meter: A meter (or test facility) of known accuracy.
Relative Roughness: The dimensionless ratio (e) of the average pipe roughness (Ra) divided by the inside pipe diameter (D).
Repeatability: The largest spread of errors of a given meter when several successive measurements are performed at the same flow rate under the same operating conditions.
Transit Time: The time for an ultrasonic pulse to travel along a specified path.
Ultrasonic Gas Meter: A meter consisting of a meter body, one or more velocity sensing paths, and associated processing circuitry.
Ultrasonic Domestic Gas Meter: An ultrasonic gas meter which includes a battery powered register and associated processing circuitry, all enclosed within the same meter case and used to measure volumes of gas at working pressures up to a maximum of 200 kPa.
Ultrasonic Transducer: A device which transmits and receives ultrasonic pulses.
Velocity Sensing Path: A path travelled by ultrasonic pulses for the purpose of determining the velocity of gas in a meter.

4.0 Metrological Requirements

4.1 Maximum Permissible Errors

4.1.1 Pattern Approval Accuracy Tests

4.1.1.1

Meters shall be tested using a suitable test medium at flow rates over the range of 10% to 100% of Qmax at flowing gas pressures over the specified operating pressure range of the meter. Each test point shall consist of at least three measurements, each measurement lasting a minimum of 100 seconds. The tested flow rates shall be approximately equally spaced between 0.1Qmax and Qmax, and shall include, as a minimum, 0.1Qmax, 0.25Qmax, 0.5Qmax, 0.75Qmax and Qmax.

Note 1: The test medium will normally be natural gas. However, if an applicant provides data demonstrating that other media are suitable for performing tests, tests on those media will be accepted. For ultrasonic domestic gas meters, the manufacturer shall provide documentation demonstrating that the meter can be tested using an identified proving technology by comparison to natural gas of a specified composition and over the meter's intended operating conditions.

Note 2: Where test facilities are not available to perform tests over the entire operating pressure range of the meter, the applicant shall provide test data demonstrating that the pattern to which the meter belongs is insensitive to operating pressure.

Note 3: Where ultrasonic domestic meters are tested, this minimum measurement duration may not be applicable as a result of limitations associated with the proving technology employed. However, in all cases, the test duration shall be sufficient to ensure an error resolution of 0.1% or better.

4.1.1.2

The errors of the meter shall not exceed the following tolerances:

	Ultrasonic Meters	Ultrasonic Domestic Meters
Maximum permissible error:	±1.0%	±1.0%
Linearity:	±0.3%	±0.5%
Repeatability:	±0.2%	±0.4%

Note 1: The tolerance for maximum permissible error applies after the application of the final meter factor, if any.

Note 2: The tolerance for linearity applies after any corrections performed within the meter itself but prior to the application of linearization algorithms by equipment auxiliary to the meter.

4.1.1.3 Calculation of Error

Error (%) = [(volume at test meter − volume at reference meter) ÷ volume at reference meter] × 100

4.1.1.4 Calculation of Flow Weighted Mean Error (FWME)

The FWME shall be calculated as follows:

FWME (%) = ((Q1 / Qmax) × D1 × W1 + (Q2 / Qmax) × D2 × W2 + … + (Qn / Qmax) × Dn × Wn) ÷ ((Q1 × W1) / Qmax + (Q2 × W2) / Qmax + … + (Qn × Wn) / Qmax)

Where, Qi is the test flow rate

Di is the deviation at the tested flow rate Qi

When Qi≥ 0.95Qmax, then Wi = 0.4, otherwise Wi = 1.0

4.1.1.5 Zero Volume Accumulation

At the time of approval, ultrasonic domestic meters shall be tested for zero volume accumulation under no flow conditions. This test shall be carried out at the ambient temperature conditions of -30°C and +40°C or the extremes of the meter's ambient temperature range as declared by the manufacturer and set out in the notice of approval.

4.1.2 Transducer and Circuit Board Exchange

Applicants may provide test data demonstrating that transducers and circuit boards comprising the processing circuitry can be exchanged without necessitating reverification of the meter. Such data shall be obtained by performing accuracy tests on the meter at one flow rate first with the original component(s), and then with replacement component(s). The meter may be reprogrammed if necessary after the component(s) have been exchanged but before the second accuracy test is performed. The meter's performance as a result of any component exchange shall not change by more than ±0.1%.

Note 1: For the purpose of this specification, component exchange shall mean the exchange of one circuit board, or the exchange of one transducer or one set of transducers.

4.1.3 Verification and Reverification Accuracy Tests

4.1.3.1

Subject to clause 4.1.3.2, tests shall be conducted on a suitable test medium at a pressure which is representative of the meter's intended use. Each test point shall consist of at least three measurements, each measurement lasting a minimum of 100 seconds. Ideally, the meter shall be tested at a minimum of five flow rates approximately equally spaced between 0.1Qmax and Qmax. Where Qmax cannot be achieved because of limitations of the test facility, the upper test flow rate shall be at least 0.4Qmax and the meter shall be tested at at least five flow rates approximately equally spaced between 0.1Qmax and the maximum flow rate attainable by the test facility. Meters intended for bidirectional measurement applications shall be tested as above in both directions.

Note 1: The test medium will normally be natural gas. However, if an applicant provides test data demonstrating that other media are suitable for performing tests, tests on those media will be accepted.

The errors of the meter shall not exceed the tolerances set out in clause 4.1.1.2. Where the meter's maximum test flow rate cannot be achieved, the errors of the meter shall not exceed the following tolerance limits:

Maximum permissible error:: ±1.0% × %Qmax attained ÷ 100
Linearity:: ±0.3%
Repeatability:: ±0.2%

Where, %Qmax attained is the highest test flow rate attained

Note 2: The tolerance for maximum permissible error applies after the application of the final meter factor, if any.

Note 3: The tolerance for linearity applies after any corrections performed within the meter itself but prior to the application of linearization algorithms by equipment auxiliary to the meter.

4.1.3.2

Ultrasonic domestic gas meters may be verified or reverified at atmospheric pressure using appropriately certified gas meter proving technologies. Where ultrasonic domestic gas meters are verified using a measuring apparatus of the referenced type, the test points shall be equal to (0.3 + 0.05)Qmax and (0.95 + 0.05)Qmax, using air as the test media. The test duration shall be sufficient to ensure an error resolution of 0.1% or better.

Maximum permissible error: ±1.0%

Note 1: For ultrasonic domestic gas meters, the manufacturer shall provide documentation demonstrating that the meter can be calibrated using the identified proving technology by comparison to natural gas of a specified composition and over the meter's intended operating conditions.

4.1.3.3

The Notice of Approval of an ultrasonic domestic gas meter shall stipulate the fluids with which the meter can be calibrated, and any applicable conditions or restrictions.

4.2 Verification Requirements

4.2.1

The Notice of Approval shall be referred to for information regarding parameters in the processing circuitry which may need to be changed or programmed at the time of verification, and for sealing requirements.

4.2.2

Where provided, the final meter factor shall be set prior to sealing the meter as follows:

Final meter factor = 100 ÷ (100 + FWME)

Bidirectional meters may have different final meter factors for each direction of measurement.

4.2.3

Metering installations shall be inspected to assess compliance with the installation inspection requirements identified in Appendix "A". Ultrasonic domestic gas meters which are not subject to the piping requirements of clause 5.2.3, and which are installed where the average meter pressure does not exceed the atmospheric pressure by more than 3.45 kPa, are exempt from the requirements for installation inspection.

4.3 Reverification Requirements

Meters shall be submitted for reverification at least every six years. The requirements for reverification are the same as for verification.

4.4 Component Exchange

4.4.1

Where permitted by the notice of approval, seals on a meter in service may be broken by an inspector or by an accredited meter verifier to accommodate component exchange. New components shall either be identical to those being replaced or shall be approved by Measurement Canada and recommended for use in the particular circumstances by the manufacturer of the meter. Upon completion of the exchange, components shall be resealed after completion of the following checks:

4.4.1.1 Transducer Exchange

The following procedure shall be followed where a new transducer(s) are installed:

The new transducer(s) shall be installed in accordance with the manufacturer's instructions. If applicable, calibration parameters for the exchanged transducer(s) shall be entered into the processing circuitry.
Serial numbers of the new and old pairs of transducers shall be recorded.
The velocity of sound measurement for each path shall be determined with gas flowing through the meter. The velocity of sound measured on the path with the replaced transducer(s) shall be within 0.2% of the mean of the velocities of sound measured by the undisturbed paths.

4.4.1.2 Electronics Exchange

The following procedure shall be followed where new processing circuitry is installed:

The new processing circuitry shall be installed in accordance with the manufacturer's instructions.
Serial numbers and firmware versions of the new and old electronics package shall be recorded.
Where necessary, calibration parameters shall be programmed into the new processing circuitry in accordance with manufacturer's instructions. Once programming is complete, it shall be verified that the new parameters are identical to the old parameters.
The velocity of sound measurement for each path shall be determined. They shall agree with each other with a maximum spread of not greater than 0.2% of their mean.

4.5 Conditions for Metrological Characteristics

4.5.1 Influence and Disturbance Factors

For pattern approval purposes, the meter volumetric accuracy tests shall not exceed the errors set out in clause 4.1.1.2 over the following range of influence and disturbance factors:

Influence factors – As set out for "Class F" meters in section 9 and clause 11.5.3 of the OIML (International Organization of Legal Metrology) International Recommendation R-6, titled "General Provisions for Gas Volume Meters - 1989".
Swirl susceptibility – The inlet to the installation configuration recommended by the manufacturer shall be preceded in turn by a clockwise and a counter clockwise swirl generator, constructed of two ninety-degree elbows connected together orthogonally.

5.0 Technical Requirements

5.1 Design, Composition, and Construction

5.1.1

In addition to the approval requirements listed in this provisional specification, meters shall also be evaluated against the applicable requirements in sections 3, 4, 15, and 21 of LMB-EG-08, Specifications for Approval of Type of Gas Meters and Auxiliary Devices, 1987.

5.1.2

A pressure tap shall be located on the meter body. This requirement does not apply to meters with a maximum allowable operating pressure of 10 psig or less.

5.1.3

The meter shall provide one or more outputs proportional to the volume of gas which has passed through it, expressed at line conditions of pressure and temperature. This requirement does not apply to ultrasonic domestic gas meters. For bidirectional applications, a separate volume output shall be provided for each direction.

5.1.4

Multipath meters shall be capable of indicating the speed of sound in gas for each path.

5.1.5

The malfunction of any transducer pair in a multipath meter shall not cause the meter to cease functioning but shall cause an alarm to be generated.

5.1.6

Provisions for sealing shall be made pursuant to subsection 6.2.

5.1.7

The meter shall use the standard communication protocol set out in ANSI C12.18-1996 and IEEE P1377/ANSI C12.19-1996, or the manufacturer shall provide, free of charge, software which is executable on a recent release of the Microsoft disk operating system (MS-DOS) platform or Microsoft Windows, or compatible, to interrogate, control, and verify the meter. The executable software shall be provided formatted for IBM-compatible personal computers. If applicable, operating manuals and documentation may (by preference to printed material) be provided electronically in standard ASCII code on diskette(s) formatted for IBM-compatible personal computers. The software shall preclude the possibility of disruption of the meter's operation during the verification process. Measurement Canada hereby undertakes to ensure that the software will be used solely for the purpose of inspection of meters by government inspectors and not to disclose the contents of the software or its documentation to third parties.

5.2 Installation and Use

5.2.1

The meter shall be installed in a manner designed to prevent accumulation of contaminants in any transducer port.

5.2.2

The installation shall include provisions such that the meter can be made to accumulate zero volume at flow rates of less than 0.5% of Qmax. The low flow cut-off may be set to operate at a flow rate higher than 0.5% of Qmax, with the consent of the selling party.

5.2.3

Unless otherwise stated in the notice of approval, the upstream meter tube shall have a length of at least 10 pipe diameters. The downstream meter tube shall have a length of at least 3 pipe diameters unless the installation is intended for bidirectional measurement in which case both the upstream and downstream meter tubes shall have lengths of 10 pipe diameters.

5.2.4

The interior finish of the meter and the meter tubes shall not exceed a relative roughness of 0.0000625.

5.2.5

No gasket shall protrude past the interior surface of the meter tubes or the meter body.

5.2.6

If required by the Notice of Approval for the meter, a flow conditioner shall be located in the meter tube upstream of the meter body, and, in the case of bidirectional measurement, downstream as well.

5.2.7

The inside diameter of the meter tubes and the inside diameter of the meter body shall not differ by more than ±1.0% of the smaller of the two. Unless otherwise noted in the Notice of Approval, this requirement is also applicable to ultrasonic domestic gas meters.

5.2.8

The temperature of the flowing gas shall be measured downstream of the metering element in the normal flow direction. There shall be nothing between the metering element and the temperature sensor which could cause a change in pressure. This requirement shall apply in all cases except where a meter is approved, verified and operated with a built-in temperature sensor that is located within the meter body.

5.2.9

Where used, a thermowell shall project one third of the inside pipe diameter into the flowing gas stream and shall be oriented so as not to be aligned with any path.

5.2.10

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

5.2.11

Unless otherwise stated in the notice of approval, where a meter is to be installed within 100 pipe diameters of a throttling device such as a regulator or valve, or of a compressor or other device know to produce pulsations, the manufacturer shall be consulted and shall conduct tests to demonstrate that the meter is not adversely affected by the device.

5.2.12

Where a meter is installed within 1000 pipe diameters of a "Whisper Trim" valve or other device known to produce ultrasonic energy, the manufacturer shall be consulted and shall conduct tests to demonstrate that the meter is not adversely affected by the device.

5.2.13

The meter output(s) which is (are) proportional to the volume of gas which has passed through it shall be used for billing calculations.

6.0 Administrative Requirements

6.1 Markings

6.1.1

The following information shall be indelibly marked on, or be capable of being displayed, by the meter:

manufacturer's name
model number
body serial number (on the meter body)
meter serial number, if different from c)
direction of positive flow (or, for ultrasonic domestic gas meters, the inlet connection shall be identified)
maximum flow rate (at line conditions)
inside meter diameter (not applicable to ultrasonic domestic gas meters)
minimum(where applicable) and maximum operating pressure
approval notice reference number
space shall be provided for an inspection number (the number shall be marked on the meter body prior to verification of the meter)
type and range of output signal (for each output)
final meter factor (where used)
zero offset (where used)
density (where used)
viscosity (where used)
delay times for transducers (where used)
any other user-programmable factors used
firmware version (alternatively, may be displayed using manufacturer's meter interface software)
base temperature value (if the meter performs a volume conversion function using the flowing gas temperature).

6.1.2

The following information shall be marked, for meters with transducers which can be exchanged at the meter's operational location:

transducer model number (on each transducer)
transducer serial number (on each transducer)
pressure range of transducers (on each transducer)
identification of each transducer port (on the meter body)

6.1.3

The following information shall be provided, for meters with circuit boards which can be exchanged at the meter's operational location:

circuit board model number
circuit board serial number

6.1.4

Where portions of the meter are intended to be installed remotely from each other in a multi-meter installation, the component parts shall bear sufficient additional markings as are necessary to inform users which components of the system will operate with each other.

6.2 Sealing

Where a manufacturer can demonstrate through test results that transducers can be exchanged without requiring reprogramming of the processing circuitry and without affecting the meter performance, the transducers do not have to be sealed. Otherwise, individual transducers shall have suitable provisions for sealing them to the meter body and shall be so sealed. The processing circuitry shall have suitable provisions for sealing circuit boards to the meter body and shall be so sealed. Where access is not otherwise prevented by a seal, the electronics package may require a jumper with a sticker or seal applied to prevent unauthorized changing of calibration parameters.

7.0 Revision

The purpose of this revision is to remove requirements identified under the Government of Canada paper burden reduction initiative. The purpose of revision 1 was to add requirements for ultrasonic domestic gas meters, and to identify which of the existing requirements are not applicable to ultrasonic domestic gas meters. Some new definitions were also added, and the tolerances for relative roughness (clause 5.2.4) and inside diameter (clause 5.2.7) were amended.

Alan E. Johnston
President
Measurement Canada

Appendix A

Attricution of Characteristics
Section No.	Characteristics	Pattern Approval	Initial Verification	Subsequent Verification	Disputes	Installation Inspection
4.1.1.1	Test flow rates and pressures
4.1.1.2	Tolerances
4.1.1.3	Calculation of errors
4.1.1.4	FWME
4.1.1.5	Zero volume accumulation
4.1.2	Component exchange
4.1.3.1/.2	Verification and reverification tests
4.2.1	Parameter programming
4.2.2	Final meter factor
4.2.3	Installation inspection
4.3.1	Reverification
4.4.1	Component exchange
4.4.1.1	Transducer exchange
4.4.1.2	Electronics exchange
4.5.1	Influence and disturbance factors
5.1.1 /.2	Case
5.1.3	Construction, materials, finish
5.1.4	Connections
5.1.5	Pressure tap
5.1.6	Outputs
5.1.7	Speed of sound
5.1.8	Transducer malfunction
5.1.9	Sealing provisions
5.1.10	Communications
5.2.1	Transducer orientation
5.2.2	Low flow cut-off
5.2.3	Tube length
5.2.4	Interior finish
5.2.5	Gaskets
5.2.6	Flow conditioners
5.2.7	Inside diameter
5.2.8	Temperature sensing
5.2.9	Thermowell characteristics
5.2.10	Ambient temperature
5.2.11	Throttling device
5.2.12	Ultrasonic source
5.2.13	Outputs
6.1	Markings
6.2	Sealing