GS-ENG-09-01—Requirements for the certification by correlation of gas measuring apparatus—Working level bell provers

Table of contents


1.0 Scope

1.1 This document outlines the requirements for the certification, recertification, calibration and use of working level gas measuring apparatus using bell provers up to 10 cubic foot capacity. These measuring apparatus are used for the verification, reverification and/or compliance sampling of gas meters. Bell provers with a volumetric capacity greater than 10 cubic feet shall be processed for certification on an individual basis as determined by Measurement Canada.

1.2 This document is supported by procedures set out in GS-ENG-09-01.1: Procedures and Worksheets for Calibrating and Certifying Gas Measuring Apparatus - Working Level Bell Provers Pursuant to the Requirements of GS-ENG-09-01.

1.3 This certification document is considered as "interim" as it does not fully incorporate the requirements of S-S-02: Measurement Uncertainty and Meter Conformity Evaluation Specifications. However, the determination of measurement uncertainty is subject to the guidelines in GS-ENG-09-04: Guidelines for the Determination of Measurement Uncertainty in Working Level Bell Provers - Correlation Method.

2.0 Authority

This document is issued pursuant to sections Sections 7 and 8 of the Electricity and Gas Inspection Regulations . It has been produced under the delegated authority of the Senior Engineer - Gas Measurement, Measurement Canada for the purposes of setting out requirements for the calibration, certification and use of gas measuring apparatus.

3.0 Terminology

Calibration:
Comparison between two instruments, measuring apparatus or standards, one of which is of known accuracy. Tests are Performed to detect, correlate, report, or eliminate by adjustment any variation in accuracy of the instrument or measuring apparatus of unknown accuracy.
Cardinal point:
A major volume increment marking on the bell scale chosen as a point of reference for a selected test volume.
Certification:
A process which ensures that a measuring apparatus has been properly calibrated, properly installed for its intended use, and that an acceptable accuracy correlation exists between it and a reference standard.
Certification testing:
A specialized form of calibration performed according to fixed standards which must be met prior to the issuance of the certification certificate.
Designating authority:
Individual delegated the authority under the Electricity and Gas Inspection Act and associated Measurement Canada policies with the authority to certify a gas measuring apparatus.
Direct counting gas measuring apparatus:
A gas measuring apparatus which determines meter error using register revolutions of the meter under test.
High load rate:
The term used to describe the flowrate corresponding to the specified high load test flow rate, i.e. 145 ± 5% of a diaphragm meter's rated capacity of air at 0.5 inches differential pressure.
Inferential gas measuring apparatus:
A gas measuring apparatus which determines meter error by a method other than direct counting.
Initial certification:
Certification of gas measuring apparatus for the first time.
Local volumetric standard:
A master bell prover or certified transfer prover located at or near the site of the gas measuring apparatus.
Low load rate:
The term used to describe the flow rate corresponding to the specified low load test flow rate, i.e. 45 ± 5% of a diaphragm meter's rated capacity of air at 0.5 inches differential pressure.
Master bell prover:
The local volumetric standard which is traceable to a national volumetric reference standard.
Meter class:
A general grouping of meter types having varied manufacturers and model designations but having the same units of measure and similar rated capacities of air at 0.5 inches differential pressure. Class Designations (shown in ft3/hour): 100 class (<140), 200 class (140 to 200), 300 class (201 to 300), 400 class (301 to 350), 500 class (351 to 450), 600 class (451 to 500), 700 class (501 to 550), 800 class (551 to 650), 900 class (651 to 700), 1000 class (701 to 800). All other meters shall be formed into classes based on 99.0 ft3 intervals or S.I. equivalent.
Meter classification:
A grouping of meters having the same manufacturer, meter class, and units of measure formed from the listing of meters in the owner's statement of intended use.
Minimum range volume:
The nominal volume range over which a gas measuring apparatus is to be calibrated.
Monitor:
To observe, record or detect an operation or condition with instruments.
Non-converting meter:
A meter that does not correct the registered volumes for pressure and/or temperature.
Owner:
The owner of the gas measuring apparatus to be calibrated and certified or recertified.
Recertification:
Certification of a gas measuring apparatus subsequent to the initial certification.
Relative error:
The absolute error of measurement divided by the true (conventional) value of the measurand. The measurand is a quantity subjected to measurement.
Start point:
The fully raised position of the bell prior to commencement of the test sequence.
Technical Evaluator (Inspector):
Individual appointed by the Designating Authority and delegated under the Electricity and Gas Inspection Act and associated Measurement Canada policies to perform certification testing of a Gas Measuring Apparatus.
Transfer meter:
A non-converting meter supplied by the owner for the purposes of volume correlations on the gas measuring apparatus.
Volume correlation:
The process by which a specific volume registered by a transfer meter or measured by a gas measuring apparatus is related to or traceable to a local volumetric standard.
Working level gas measuring apparatus:
A gas measuring apparatus intended for use in the verification, reverification and/or compliance test of gas meters.
X-bar:
The arithmetic mean of the "n" results considered.

4.0 Administrative requirements

4.1 General

4.1.1 These requirements shall apply immediately upon issue to all gas measuring apparatus utilizing bell prover displacement technology.

4.2 Gas measuring apparatus requirements

4.2.1 For measuring apparatus to be certified all the requirements of this document shall be evaluated and the results shall meet the applicable requirements.

4.2.2 Gas measuring apparatus may be certified for testing any or all types of approved

gas meters at test flowrates within the flowrate capacity of the local volumetric standard and the gas measuring apparatus.

4.2.3 The certificate issued by the Designating Authority shall be valid for a period established by regulations for the gas measuring apparatus at the location where the calibration was completed. Any relocation, software, equipment, software or component replacements or modifications which affect the performance of the gas measuring apparatus shall require recertification of the gas measuring apparatus. The extent of the recertification shall be determined by the Designating Authority upon receipt of the notice referred to in clause 4.5.2(g), of this document.

4.3 Statistics

Gas measuring apparatus or accessories thereto intended to perform statistical calculations of average error and standard deviation of a sample of gas meters for the purposes of verification, reverification or compliance sampling shall do so pursuant to the requirements of a Measurement Canada approved statistical sampling plan for the verification or reverification of gas meters.

4.4 Certification testing

The method of certification testing shall be sufficient to ensure that the gas measuring apparatus will function accurately and reliably over the conditions to which it will be subjected. These conditions may include but are not limited to ambient air temperature, meter proving air temperature, model of meter, condition of meter, test flowrates, and modes of gas measuring apparatus operation. Where it has been determined analytically or empirically that the effect of a particular condition is not significant with respect to the accuracy of a specific type of gas measuring apparatus, the method of certification testing may, with the Senior Engineer's - Gas Measurement permission, be modified to take this evidence into account. If more than one method of meter proving is to be certified, sections 5.5.3, 5.5.4, and 5.5.5 must be performed using all meter proving methods requested.

4.5 Roles and responsibilities

4.5.1 Designating authority

The Designating Authority shall be responsible for:

  1. Any certification ensuing from the certification testing procedure.
  2. All calibration testing procedures and worksheet completion relevant to this requirements document.

4.5.2 Owner

The owner shall be responsible for:

  1. Providing a statement of intended use together with a full set of completed worksheets demonstrating that the gas measuring apparatus is fully compliant with all applicable requirements set out in these specifications prior to certification testing of the gas measuring apparatus by the Designating Authority.
  2. Making all adjustments and calibrations necessary to meet the requirements.
  3. Providing the transfer meters required by this document.
  4. Providing the leak test apparatus required to demonstrate the ability of the gas measuring apparatus to detect the specified operational leak.
  5. Using the gas measuring apparatus in the manner for which it was intended and in accordance with any conditions set out in the certificate.
  6. Ensuring that the gas measuring apparatus is maintained in good repair and in the required operational order.
  7. Giving the Designating Authority prior notification of proposed relocation, modification and/or need of repair to the certified gas measuring apparatus. The need for recertification will be determined by the Designating Authority upon receipt of this notification.
  8. Maintaining a log book or file which records the dates and details including the identification of the person or persons performing accuracy checks, adjustments, maintenance, repairs and modifications to the gas measuring apparatus. The log book for each gas measuring apparatus shall be made readily available to the Designating Authority upon request and shall be retained for a period of six years.
  9. Providing a stable temperature environment for the gas measuring apparatus. The prover room ambient air temperature, the meter outlet air temperature, the prover oil temperature and the gas measuring apparatus meter proving air temperature shall be continuously monitored. Records of these temperatures shall be maintained and reviewed prior to calibrating the gas measuring apparatus.
  10. Making available to the Designating Authority, operating instruction manuals which provide detailed information pertaining to the installation, maintenance, calibration and use of the gas measuring apparatus.

4.6 Statement of intended use of the gas measuring apparatus

4.6.1 Limitations

The owner shall provide to the Designating Authority a detailed statement of intended use of the gas measuring apparatus. The documentation provided shall be sufficient to determine the capabilities of the gas measuring apparatus, its intended uses and all installation requirements. The intended use of the gas measuring apparatus shall:

  1. be within the specifications and limitations of the gas measuring apparatus published by the manufacturer,
  2. be such that the gas measuring apparatus is capable of achieving and maintaining the required flow rates, and
  3. the minimum test volume shall be as specified in table 1 or the metric equivalent unless the owner or manufacturer can demonstrate that reducing the volume will not effect the performance of the apparatus.
Table 1 - Minimum test volumes for bell provers
Bell Capacity Direct Counting Type Inferential Type
Two Cubic Feet 2.0 Cubic Feet 0.5 Cubic Feet
Five Cubic Feet 2.0 Cubic Feet 0.5 Cubic Feet
Ten Cubic Feet 5.0 Cubic Feet 2.0 Cubic Feet

4.6.2 Statement of intended use - details

The statement of intended use of the gas measuring apparatus shall include:

  1. a full description of the gas measuring apparatus to be certified including the manufacturer(s), operating parameters, minimum and maximum test capacities, computer software and hardware revisions, model number(s) and serial number(s).
  2. a description of each class, type or design of meter to be tested on the gas measuring apparatus,
  3. a declaration of the categories of testing for which the gas measuring apparatus is to be utilized as set out in clause 5.5.3 and modes of operation as set out in clause 5.5.5, of this document.
  4. an identification of the minimum and maximum range of test capabilities (ie humidity, pressure temperature, flowrate) for which certification of the gas measuring apparatus is requested, and
  5. a declaration of the method(s) of meter proving, as set out in clauses 5.5.1 and 5.5.2.

5.0 Metrological requirements

5.1 Environment

5.1.1 Temperature

5.1.1.1 The prover room ambient air temperature shall be continuously maintained and monitored at ± 1.0°C of a temperature chosen by the owner. The chosen temperature may be changed by the owner at any time during the period of the certification but must fall within a range of 22°C ± 4.0°C and meet the requirement of section 5.1.1 3.

5.1.1.2 The prover room ambient air temperature, the meter outlet air, the gas measuring apparatus bell outlet air temperature and the prover oil temperature shall be within 0.5EC of each other during all testing procedures and during any subsequent verification, reverification or compliance sample testing during the certification period.

5.1.1.3 Prior to and during certification testing, the prover room ambient air temperature shall not vary by more than ± 1.0°C and ± 0.5°C over the previous twenty-four (24) hour and four (4) hour periods, respectively.

5.2 Prover oil

5.2.1 New prover oil, when acquired for use in bell provers shall have the following properties:

Viscosity, cST @ 40°C 3.0 - 7.5

Relative Density, kg/L @ 15°C 0.82 - 0.86

5.2.2 The owner shall ensure that specifications of oil purchased are met. The documentation supplied with regards to the prover oil shall clearly indicate the source, brand name and batch number of the oil being used.

5.2.3 Where more than one prover has been filled with new oil from the same batch, only one representative oil sample from one of the provers needs to be tested to ensure the oil meets the specifications.

5.2.4 Prover oil must be tested annually and at the time of certification, at an approved laboratory or by the use of authorized procedures. The sample is to be drawn from the top of the prover tank.

5.2.5 The following American Society for Testing Materials (ASTM) Test Method Specifications are applicable to testing oil for the stated properties:

Property ASTM Test method specifications

Viscosity D 445

Relative Density D 1298 or D 4052

5.3 Mechanical requirements

The gas measuring apparatus installation and operation shall be verified for compliance with the manufacturer's installation instructions and Measurement Canada requirements. Where auxiliary equipment is attached or is to be attached to the bell, the counterweight wheel or its shaft or any other movable component of the gas measuring apparatus installation not specifically mentioned, the bell balance calibrations shall be performed with these auxiliaries attached.

5.3.1 Bell Component installation

5.3.1.1 The components listed below shall be checked to ensure that they are vertical. Installation of the components shall be checked at least in two views spaced 90° from each other:

  1. prover tank
  2. support posts for the counterbalance wheel support frame
  3. counterbalance wheel support frame
  4. counterbalance wheel
  5. prover bell
  6. prover guide rods

5.3.1.2 The bell components shall be aligned such that all components will operate in the same plane of motion throughout the entire operating range of the bell.

5.3.2 Prover oil level

5.3.2.1 The prover oil level shall be checked at the start point and the maximum point of travel with the bell closed to atmosphere and the internal bell pressure adjusted to 2.00 ± 0.02 inches water column.

5.3.2.2 The sealant oil level shall be measured and recorded when the bell is lowered to its maximum travel and open to atmosphere.

5.3.2.3 The prover oil level shall be recorded and shall be shown on the certificate issued by the Designating Authority together with the reference point.

5.3.3 Bell balance

5.3.3.1 The bell balance testing shall commence at the start point used to start the proving operation and at points equal to 20, 40, 60 and 80 percent of the intended range of travel of the bell and end at the maximum point of travel.

5.3.3.2 The bell shall remain stationary at any and all points chosen for bell balance calibration.

5.3.4 Bell reference pressure

5.3.4.1 Upon completion of the procedure set out in clause 5.3.3, the bell pressure shall be adjusted, if required.

5.3.4.2 With the bell positioned within the range of bell travel, the main counter weight shall be adjusted to achieve a bell pressure of 2.00 ± 0.1 inches water column.

5.3.5 Bell static pressure

5.3.5.1 The bell static pressure calibrations shall commence at the

start point and at points equal to 20, 40, 60 and 80 percent of the intended range of bell travel and end at the maximum point of bell travel.

5.3.5.2 The bell static pressure at all calibrated points shall be equal to 2.00 ± 0.1 inches water column.

5.3.6 Bell dynamic pressure

5.3.6.1 The bell dynamic pressure calibrations shall commence at the start point and at points equal to 20, 40, 60 and 80 percent of the intended range of bell travel and end at the maximum point of bell travel.

5.3.6.2 The bell dynamic pressure at all calibrated points shall be equal to 2.00 ± 0.1 inches water column as the bell descends at a rate not exceeding 8.0 inches per minute.

5.3.7 Leak test

5.3.7.1 System leak test

5.3.7.1.1 A system leak test shall be conducted with all auxiliary equipment connected to the gas measuring apparatus. The piping of gas measuring apparatus shall include a meter in the system leak test.

5.3.7.1.2 The system leak test shall be conducted with the bell at a cardinal point near the bottom of the intended range of bell travel. The leak test time interval shall be a minimum of 10 minutes during which the bell position shall be monitored.

5.3.7.1.3 The position of the bell shall not change during the system test.

5.3.7.1.4 Gas measuring apparatus utilizing an outlet control valve, where the meter and associated piping up to the outlet control valve is pressurized; the entire system including the outlet control valve shall be part of the system leak test.

5.3.7.2 Operational leak test

5.3.7.2.1 The operational leak test procedure shall be incorporated into the use of the gas measuring apparatus process and shall be tested for both leak detection capability and repeatability.

5.3.7.2.2 Operational leak test procedures shall be capable of detecting a leak of 0.25 cubic foot per hour at 2.0 inches of water column or greater using a leak test duration and applied pressure/vacuum designated by the owner. The operational leak test shall be initiated three consecutive times to verify the reliability and repeatability of the process.

5.3.7.2.3 The owner shall provide the leak test apparatus, calibrated to the local volumetric standard or another certified reference standard, for the purpose of the operational leak test.

5.3.8 Flowrate tests

5.3.8.1 The flowrate setting mechanism of the gas measuring apparatus shall be tested at both the high and low load verification test points for each meter listed in the statement of intended use.

5.3.8.2 The flowrate mechanism shall be capable of setting the flowrates to within the specifications of the nominal high load and low load verification test points for each meter listed in the statement of intended use.

5.3.8.3 The flowrate setting mechanism shall be tested on the gas measuring apparatus using:

  1. transfer meters of known accuracy, and/or
  2. production meters of known accuracy,
  3. designated transfer meters representing flow rates between 10% to 150% of rated air capacity,
  4. selected meter(s) may represent both metric and imperial units of measurement with identical flow rates.

5.3.8.4 In the case of an adjustable flowrate mechanism, the flowrate mechanism calibration shall be repeated six times at the high load rate and six times at the low load rate for each meter. In the case of fixed flowrate caps, the flowrate tests shall be repeated three times at the high load rate and three times at the low load rate.

5.3.8.5 Each individual calculated flowrate shall be within ± 5% of the designated low and high load rates for the meter being tested.

5.3.9 Register verification

If the gas measuring apparatus is equipped with a register ratio verification option, it shall be verified. The register ratio option shall be verified by utilizing both a correct and an incorrect model of register representing a metric and imperial meter designated in the statement of intended use, to ensure that the system is capable of accurately detecting the correct register ratio.

Note: This optional equipment does not remove the dial test inspection requirement. Where inspection is done using direct counting method, the dial test is effectively addressed, since the proving is done directly off the test dial. Where inspection is done using an inferential method a dial test procedure shall be developed by the contractor, and evaluated and approved by the MC gas specialist.

5.4 Meter classifications and transfer meters

5.4.1 Meter classifications

Meters shown in the statement of intended use shall be grouped according to either meter class or meter classification, depending on the method of counting used by the gas measuring apparatus. A transfer meter is chosen to represent each meter class or meter classification.

5.4.2 Transfer meters

5.4.2.1 Transfer meters representative of meters in the various meter classes or meter classifications shall be used to determine the percent error of the gas measuring apparatus by comparison to the local volumetric standard.

5.4.2.2 Transfer meters shall be non-converting positive displacement gas meters.

5.4.2.3 Each transfer meter shall be calibrated to possess an error within the range of -2.0% and-3.0% at low and high load rates, and possess a maximum difference between the low load error and the high load error (spread) of 0.5 or less.

5.4.2.4 Transfer meters shall be acclimatized in the area of the gas measuring apparatus for a minimum period of four (4) hours.

5.4.2.5 It is the responsibility of the owner to ensure that selected transfer meters are proven repeatable prior to use as transfer meters. The suggested method is as follows:

  1. Potential transfer meters are exercised for a minimum of five minutes at a flowrate not exceeding 50% of the rated air capacity.
  2. The meter is then run six times at both the low and high load rates on the local volumetric standard to determine the meter error.
  3. The selected meter is considered acceptable for use as a transfer

meter provided that the percent error of each of the runs at the specified test flowrate is within ± 0.2 of the X-bar of percent errors for all six runs, (see table 3 for example).

Table 3 - Determination of meter repeatability
Run # 1 Run #2 Run #3 Run #4 Run #5 Run #6 x-bar 6 Runs Acceptable limits
0.5 0.6 0.4 0.6 0.5 0.5 0.52 0.52 ± 0.2

5.4.2.6 The flowrate of the local volumetric standard shall be set to within +/- 2.0% Qmax of the specified high and low load test points for the transfer meter to be tested. For example, the high load rate of a meter with a rated capacity of 180 cubic feet per hour would be within 257.4 cubic feet per hour to 264.6 cubic feet per hour and the low load rate would be 77.4 cubic feet per hour to 84.6 cubic feet per hour.

5.4.2.7 The flowrate of the gas measuring apparatus shall be set to 145 ± 5.0% and 45 ± 5.0% of the badged flowrate of the transfer meter to be tested. The flowrate of the gas measuring apparatus shall be set to within +/- 5.0% Qmax of the specified high and low load test points for the transfer meter to be tested. For example, the high load rate of a meter with a rated capacity of 180 cubic feet per hour would be within 252 cubic feet per hour to 270 cubic feet per hour and the low load rate would be 72 cubic feet per hour to 90 cubic feet per hour.

5.5 Volume correlations

5.5.1 Direct counting gas measuring apparatus

In order to test a direct counting gas measuring apparatus for the purpose of certification or recertification, a transfer meter shall be chosen from each meter class listed in the statement of intended use to act as representative of the class.

5.5.2 Inferential gas measuring apparatus

In order to test an inferential gas measuring apparatus for the purpose of certification, a transfer meter of each meter classification listed in the statement of intended use shall be tested. In the case of a scheduled recertification of an inferential gas measuring apparatus a transfer meter representative of each meter class listed in the statement of intended use is chosen.

5.5.3 Correlations

5.5.3.1 Volume correlation shall be made to the local volumetric standard to determine whether the gas measuring apparatus may be certified for:

  1. verification,
  2. reverification, and/or
  3. compliance sampling.

5.5.3.2 Volume correlations shall be conducted at the low and high load rates of each meter being tested.

5.5.3.3 Volume correlations shall be conducted with the gas measuring apparatus in the non-converting mode.

5.5.3.4 Testing of a gas measuring apparatus using a transfer meter shall be completed on the same day that the transfer meter acceptability and proof errors were established on the local volumetric standard.

5.5.3.5 Each transfer meter shall be proven six times on the gas measuring apparatus at both the low and high load rates of that transfer meter.

5.5.3.6 The percent error for each of the six runs shall be within ± 0.2 of the X-bar of the percent errors of that meter as determined on the local volumetric standard at each flowrate.

5.5.3.7 The requirements of sections 5.5.3, 5.5.4 and 5.5.5 shall be completed for each method of meter proving, as designated by the owner.

5.5.4 Maximum error detection

5.5.4.1 Volume correlations to determine the maximum detectable error shall be completed with non-converting transfer meters of any one meter class, type or design set out in the statement of intended use. Transfer meters shall be adjusted by the owner to register the following errors:

  1. for the purposes set out in clause 5.5.3.1 a) and/or b);
    1. + 2.5 ± 0.5%
  1. for the purposes set out in clause 5.5.3.1 c) only or in addition to 5.5.3.1 a) and/or b);
    1. + 9.0 ± 0.5% and - 9.0 ± 0.5%.

5.5.4.2 The transfer meters shall be run six times on the gas measuring apparatus at the high load rates. The X-bar of the errors of these six runs shall be used to determine compliance for maximum error detection. The gas measuring apparatus shall be placed in non-converting mode.

5.5.4.3 The percent error of each transfer meter test, as determined on the gas measuring apparatus, shall be within ± 0.2 of the X-bar of the percent errors as determined on the local volumetric standard.

5.5.5 Additional modes of operation

  1. Where the owner's statement of intended use includes the operation of the gas measuring apparatus in different modes of operation, each mode of operation shall be tested using one transfer meter.
  2. The transfer meter shall be proven six times on the gas measuring apparatus at the high load rate. The X-bar of the percent error of these six runs shall be used to determine compliance for each additional mode of operation.
  3. The percent error of each transfer meter test, as determined on the gas measuring apparatus, shall be within ± 0.2 of the X-bar of the percent errors determined on the local volumetric standard.
5.5.5.1 Temperature differential mode correlations
  1. The gas measuring apparatus shall be switched to and tested in the temperature differential mode. This mode is used for correlations and the verification/reverification of non-converting diaphragm gas meters. Temperature differential mode corrects for the difference in flowing air temperature between the bell outlet and meter outlet and applies a correction factor to determine the true meter relative error.
  2. During the test, the temperature sensors for the bell outlet air temperature and the meter outlet air temperature shall be made to differ by a temperature of 1.0 ° C ± 0.5 ° C by placing the meter outlet air temperature sensor in a temperature controlled bath.
  3. With the temperature difference maintained, test the transfer meter six times at high load rate and calculate the X-bar.
  4. The high load rate, as indicated on the gas measuring apparatus, shall be within ± 2.0% of the high flowrate as indicated on the local volumetric standard. Calibration will be required if the indicated errors are outside requirements.
  5. The resulting X-bar is adjusted by calculation to compensate for the artificial temperature difference. See procedures section for applicable formula.
  6. The calculated X-bar of the errors, as determined on the gas measuring apparatus, shall be within ± 0.3 of the X-bar of the percent errors of the transfer meter determined on the local volumetric standard.
5.5.5.2 Temperature converting mode correlations
  1. The gas measuring apparatus shall be switched to and tested in the temperature converting mode.
  2. The resulting meter errors are adjusted by calculation to compensate for the correction applied by the gas measuring apparatus.
  3. The X-bar of the errors, determined on the gas measuring apparatus, shall be within ± 0.3 of the X-bar of the percent errors of the transfer meter determined on the local volumetric standard.

6.0 Technical requirements

6.1 Use requirements

6.1.1 Weekly correlation - transfer meter / Local volumetric standard

6.1.1.1 Volume correlation of the transfer meters to the local volumetric standard shall be performed:

  1. each week prior to the use of the gas measuring apparatus,
  2. using a non-converting transfer meter having an error of - 2.5% ± 0.5% at a low and high load rates.
    1. using transfer meters which have been acclimatized for a minimum of four (4) hours.
    2. using transfer meters which have been constantly exercised at a rate equal to, or less than 15% of the badged flowrate.

6.1.1.2 The transfer meters used for the weekly volume correlation shall be representative of the metric or imperial meter classifications of those meters which are to be verified, reverified or compliance tested that week.

6.1.1.3 The transfer meter shall be run six times on the local volumetric standard at both the low and high load rates. The flowrate on the local volumetric standard shall be set to 145 ± 2.0% and 45 ± 2.0% of the badged air flowrate of the transfer meter to be tested. The X-bar of the percent errors of these runs shall be used to determine the average true errors. These values shall be utilized during correlation of the gas measuring apparatus during the next weekly period.

6.1.1.4 Transfer meter performance shall be tracked to ensure reliability and repeatability. Weekly errors which deviate by greater than ± 0.2 for either the high or low load rate from the previous correlation to the local volumetric standard, shall be investigated and noted in the designated prover log book.

6.1.2 Daily correlation - transfer meter / Gas measuring apparatus

6.1.2.1 Volume correlation of the gas measuring apparatus shall be performed:

  1. each day prior to the use of the gas measuring apparatus,
  2. using designated non-converting transfer meters from 6.1.1,
  3. using transfer meters which have been acclimatized for a minimum of four (4) hours.
  4. with the gas measuring apparatus in the;
    1. temperature differential mode if non-converting meters are to be verified or reverified, and/or
    2. temperature converting mode if temperature converting meters are to be verified or reverified.

6.1.2.2 For direct counting gas measuring apparatus, the transfer meters used shall be representative of the metric or imperial meter class of those meters which are to be verified or reverified that day. For inferential gas measuring apparatus, the transfer meters used shall be representative of the metric or imperial meter classification of those meters which are to be verified or reverified that day. Meters of any other classification shall not be processed until the transfer meter representing that meter classification has been subjected to the daily volume correlation process. Daily volume correlations need not be performed if gas meters are not to be verified or reverified during that day.

6.1.2.3 Transfer meters shall be run three times on the gas measuring apparatus at both the high load rate and low load rate. The low and high load rates of the gas measuring apparatus shall be set to within 145 ± 5.0% and 45 ± 5.0% of the badged air rate of the transfer meter to be tested. The X-bars of the percent errors of these three runs shall be used to determine the average true errors, and which shall be within ± 0.2 of the percent error as established against the local volumetric standard within the previous one week period.

6.1.2.4 Where the ± 0.2% allowable error tolerance has been exceeded, the below steps should be followed until the deficiency is resolved:

  1. repeat the correlation process shown in 6.1.2.3
  2. repeat the weekly correlation process, pursuant to clause 6.1.1;
  3. perform a complete diagnostic analysis/check to ensure the integrity of the gas measuring apparatus, and/or
  4. where the ± 0.2% allowable error tolerance is still being exceeded, the gas measuring apparatus shall be removed from service and a nonconformance initiated.

6.1.3 Operational leak detection

6.1.3.1 An operational leak detection sequence, shall be utilized prior to the final test sequence on all verification, reverification and compliance testing procedures.

6.1.3.2 The duration of the operational leak test shall be as determined by the owner and specified for the test shown in section 5.3.7.2.2.

6.1.4 Prover oil

The owner of the gas measuring apparatus shall have a sample of the prover oil tested annually and at the time of recertification for viscosity and relative density in accordance to the test methods requirement in section 5.2.5. Certificates of analysis shall be made available to the Designating Authority upon request.

6.1.5 Temperature

6.1.5.1 The prover room ambient air temperature shall be continuously maintained and monitored at ± 1.0°C of a temperature chosen by the owner. The chosen temperature may be changed by the owner at any time during the period of the certification but must fall within a range of 22EC ± 4.0°C and meet the requirement of section 5.1.1.3.

6.1.5.2 The prover room ambient air temperature, the meter outlet air, the gas measuring apparatus bell outlet air temperature and the prover oil temperature shall be within 0.5EC of each other during all testing procedures and during any subsequent verification, reverification or compliance sample testing during the certification period.

6.1.5.3 Prior to and during all verification, reverification or compliance sample testing, the prover room ambient air temperature shall not vary by more than ± 1.0°C and 0.5EC over the previous twenty-four (24) hour and four (4) hour periods, respectively.

6.1.5.4 Temperature records shall be retained for a time period of not less than three years.

6.1.6 Maintenance

6.1.6.1 The owner shall perform routine maintenance as specified in the manufacturer's and owner's manual. As a minimum, the maintenance and/or calibration of component and sensors shall be performed annually.

6.1.6.2 Calibration of pressure, temperature and other sensors shall be performed and referenced to a traceable standard.

6.1.6.3 Records of maintenance and calibrations shall be maintained as part of the prover log book as per section 4.5.2 (h).

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