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

Category: Gas
Specification: S-G-02 (rev. 1)
Document(s): S-S-01, S-S-02, S-S-03, S-S-04, S-02
Issue Date: 2007-05-09
Effective Date: 2007-07-01
Supersedes: S-G-01


Table of contents


1.0 Scope

These specifications apply to the verification and reverification of diaphragm type gas meters of all sizes or capacity ratings, with or without attached telemetering devices, which are intended for use in the measurement of natural gas and manufactured hydrocarbon gases such as propane vapour.

2.0 Authority

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

3.0 Normative references

3.1 S-S-01, Specifications for the Generation of Pseudo-Random Samples

3.2 S-S-02, Measurement Uncertainty and Meter Conformity Evaluation Specifications

3.3 S-S-03, Prerequisites to the Use of Sampling Inspection

3.4 S-S-04, Sampling Plans for the Inspection of Isolated Lots and Short Series Lots

3.5 Electricity and Gas Inspection Act

3.6 Electricity and Gas Inspection Regulations

4.0 Terminology

Average Ambient Temperature

The arithmetic mean of the temperatures defined in the applicable specifications for the proving system being used, and the proving room.

Defect

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. (Note: Depending on the nature and severity of the defect, it may cause a nonconformity to occur immediately or at some time in the future.)

Dial Test

A comparative registration test performed on a diaphragm meter for the primary purpose of verifying that the installed index is functional and compatible with its host meter.

Direct-counting Mode

A selectable mode of operation on an automated prover that employs the use of a photo sensor to gate (trigger) the start and stop of a test run, using counted revolutions of the meter's test dial.

Diaphragm Meter

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.

Gas Measuring Apparatus

A term used in the Electricity and Gas Inspection Act and Regulations which, for purposes of application to this specification, can be interpreted to mean "prover" and/or "proving system".

High Load (H.L.) Test

A volumetric accuracy test conducted at the specified testpoint having the highest flowrate; sometimes also referred to as the "open cap" test.

Index

A mechanical-type register used on a gas meter for recording metered volume.

Large Diaphragm Meter

A diaphragm meter having a rated air flowrate capacity exceeding 500 standard cubic feet per hour (or metric equivalent), and which is primarily used for metering of commercial/industrial services.

Low Load (L.L.) Test

A volumetric accuracy test conducted at the specified testpoint having the lowest flowrate; sometimes also referred to as the "closed cap" test.

New Meter

A diaphragm meter which has never been used in service.

Nonconformity

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.

Non-TC Meter

A diaphragm meter fitted with a "standard tangent", which is not designed to provide a base temperature-converted volume registration.

Relative Error

The 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:

Er = ((Qm − Qs) ÷ Qs) × 100 % = ((Qm ÷ Qs) − 1) × 100 %

where,

Er is the relative error of the meter under test, expressed in percent
Qm is the quantity indicated by the meter under test
Qs is the quantity indicated by the prover or reference standard, expressed in the same units as Qm.

Remanufactured Diaphragm Meter

A diaphragm meter which has been manufactured using reconditioned castings from a previously used meter and rebuilt entirely with new O.E.M. parts, using the same manufacturing techniques, processes, and quality assurance criteria as are used in the manufacture of new meters; not to be confused with meters that have been rebuilt, repaired, or reconditioned.

Reverification

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

A diaphragm meter having a rated air flowrate capacity less than 500 standard cubic feet per hour (or metric equivalent), primarily used for metering of domestic/residential services.

Specification Limit

The maximum permissible error permitted for a meter's performance characteristic.

TC Meter

A temperature-converted diaphragm meter, more commonly referred to as a "temperature-compensated" meter (or TC meter). Diaphragm meters equipped with a TC tangent are designed to produce a volume registration which has been converted to a base temperature of either 15 °C (for cubic meters) or 60 °F (for cubic feet).

Telemetering

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 wire or wireless techniques for transmitting measurement data from the source meter.

Telemetering Device

A device used in a telemetering system to duplicate the register reading of the source meter, such as an automatic meter reading (AMR) device or a pulse generator/initiator.

Test Dial

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, designed for use in gating meter accuracy tests performed on a prover.

Test Value (ei)

The result of a measurement after correction for any known systematic or bias errors, at flowrate i.

Test Limit

The limit established when the specification limit is adjusted for the associated measurement uncertainty.

Verification

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

5.0 Symbols and abbreviated terms

k

multiplier calculated to provide specified coverage for the uncertainty of a measurement

ei

test value

ei´

bias corrected value of ei (Note: If no bias, then ei = ei´)

uci

combined standard uncertainty of ei

LSL

lower specification limit

USL

upper specification limit

MADT

median absolute deviation from target

UMADT

Upper MADT specification limit

TLL

lower test limit

TLU

upper test limit

T

target value for calibration (percent relative error)

Qmax

manufacturer's rated air capacity of the meter (maximum flowrate rating)

Qmin

manufacturer's rated minimum air capacity of the meter (minimum flowrate rating)

CSL1

compressed specification limits for type 1 marginal conformities (LQ = 3.15%)

CSL2

compressed specification limits for type 1 marginal conformities (LQ = 8.0%)

LCSL1

lower compressed specification limit (LQ = 3.15%)

LCSL2

lower compressed specification limit (LQ = 8.0%)

UCSL1

Upper compressed specification limit (LQ = 3.15%)

UCSL2

Upper compressed specification limit (LQ = 8.0%)

6.0 Metrological requirements

6.1 General

A meter shall meet all of the performance requirements and non-performance requirements specified in this specification and any related Measurement Canada (MC) bulletins, as well as conform fully with its approved pattern (design, features, functions, markings, etc.) described in the applicable Notice of Approval, in order to be verified or reverified.

6.1.1 Any meter that fails to meet a performance or non-performance requirement, or that possesses a defect which could affect its ability to meet specified requirements, shall be classified as nonconforming.

6.1.2 All meter conformity tests shall be performed in accordance with documented procedures that have been evaluated for technical adequacy by the relevant MC technical experts.

6.2 Conditions for testing

6.2.1 Test installation

6.2.1.1

The gas measuring apparatus used for final inspection of meters presented for verifications shall have a valid MC certificate of certification. Any conditions of use noted on the certificate shall be met.

6.2.1.2

Where required by the MC specifications and procedures applicable to the type of prover being used, correlation with the local volumetric standard (e.g. master bell prover) shall be established with the use of transfer meters.

6.2.1.3

Other conditions for testing, as prescribed in the MC specifications and procedures applicable to the type of prover being used, shall also be met. Such requirements may include:

  1. mitigation of the effects of pressure pulsations and resonance when using a rotary meter transfer prover
  2. target value and stability of the meter inlet pressure and meter outlet air temperature
  3. location and orientation of sensors for measuring pressures and temperatures
  4. maximum allowable difference between a bell prover's sealant temperature, supply air, and average ambient temperature
  5. maximum allowable rate of air leakage for the proving system
  6. stability of flowrate settings
  7. monitoring the pressure of the flowing gas (air) at the outlet of the meter under test, and applying a pressure conversion factor to the meter error calculation to compensate for the difference in pressure between the meter outlet and the gas measuring apparatus.

6.2.1.4

The temperature representative of the flowing gas (air) temperature to which the meter's temperature converting tangent is responding, shall be measured at a location approved by MC relative to the meter under test, to facilitate the calculation and application of a corresponding base temperature conversion factor/multiplier to the volume registered by the prover.

6.2.2 Ambient air temperature of test room

6.2.2.1

The ambient air temperature of the test room shall be continuously monitored and maintained within ±1.0 °C (±1.8 °F) of a temperature chosen by the meter verifier, unless otherwise specified in the MC specifications applicable to the type of gas measuring apparatus being used.

6.2.2.2

During meter testing, the temperatures of the test room ambient air and the gas measuring apparatus air supply temperature shall be maintained within 0.5 °C (0.9 °F) of each other, unless otherwise specified in the MC specifications applicable to the type of gas measuring apparatus being used.

6.2.3 Acclimation of meters in test room

6.2.3.1

Meters shall be acclimated inside the test room for a minimum of four (4) hours prior to the commencement of meter performance testing, unless otherwise authorized by Measurement Canada.

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

6.2.4 Relative humidity

If a sonic nozzle prover is to be used for meter testing, the relative humidity of the test room's ambient air shall be continuously monitored and maintained within the limits specified in the MC specifications applicable to this type of prover.

6.3 Meter performance tests

6.3.1 General

6.3.1.1

The requirements for reverification shall be the same as those for verification, with the exception that no bias may be applied to the calibration and test results for reverified meters.

6.3.1.2

Meters may be preconditioned (i.e. exercised) prior to testing, if desired.

6.3.1.3

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

6.3.1.4

Gating (i.e. starting and stopping) of a meter test run shall be triggered on the upswing of the test dial hand, when using either a non-automated prover or an automated prover operating in "direct-counting mode".

6.3.2 Meter leak test

Prior to commencing meter accuracy testing, and with the meter connected to the gas measuring apparatus (prover), a leak test shall be performed to detect any leaks in the meter and the proving system. The leak test shall be performed manually if it is not performed automatically as part of the prover's automated test cycle.

6.3.3 Testpoints

Meters shall be subjected to accuracy testing at the H.L. and L.L. testpoints specified in Table 1. The H.L. test shall be performed first, prior to performing the L.L. test.

Table 1
Testpoint Flowrate
High load (H.L.) (1.45 ± 0.05) Qmax
Low load (L.L.) (0.45 ± 0.05) Qmax

6.3.4 Test duration

6.3.4.1

The test duration, or the total volume measured during a meter accuracy test, shall be sufficient to permit the inspector to resolve the calculated test error to the nearest 0.1%, or better.

6.3.4.2

For tests gated off a meter's test dial, the test volume shall be equal to an integer multiple of the cyclic volume of the meter, or a volume of air that will produce one or more whole revolutions of the meter's tangent or output drive (wriggler or gear).

6.3.5 Index verification

6.3.5.1

A dial test shall be performed on all meters verified or reverified by the 100% inspection method, as well as those inspected by sampling, performed in accordance with applicable MC specifications. This requirement is also applicable to sample meters inspected under a MC-authorized compliance sampling plan, unless otherwise authorized by MC.

6.3.5.2

The dial test shall be performed with the index mounted on its host meter, unless otherwise authorized by MC.

6.3.5.3

Where a meter index is equipped with two test dials, the meter manufacturer's recommendations shall be followed concerning which test dial to use for the gating of tests performed in direct-counting mode on a prover.

6.3.5.4

If a meter is to be tested on an inferential-type prover using only the inferential test mode, the dial test may be performed using some other apparatus or method authorized by MC.

6.3.5.5

A visual examination shall be performed to verify that the correct model of index is installed, and that the meter reading dial hands of a clock-type index are properly aligned, or that the numerals of an odometer-type index are properly aligned.

6.3.5.6

If the index of a meter in service is to be replaced in situ with a new index for purposes of retrofitting the meter with an AMR, the replacement index shall be checked and installed in accordance with the requirements of the applicable MC bulletin.

6.3.6 Temperature compensation

6.3.6.1

When testing a TC meter, the test volume measured by the prover shall be converted to a volume expressed at the meter's base temperature. If this conversion is not being performed automatically by the prover, the value shall be manually calculated and applied to the "apparent test error" indicated by the prover.

Note: A correction for "delta-T" shall not be applied to a prover's indicated test error to compensate for the difference in temperature between the prover air and the TC meter's outlet air, as doing so would produce an incorrect test error result.

6.3.6.2

When testing a non-TC meter, a correction for "delta-T" shall be applied to the indicated test error to compensate for the difference in temperature between the prover air and the non-TC meter's outlet air.

6.3.7 Pulse generator

6.3.7.1

The temperature-converted volume output of a meter's pulse generator/initiator, if so equipped, is exempt from verification.

6.3.7.2

The non-converted volume output of a meter's pulse generator/initiator, if so equipped, shall be verified unless the pulse output has been permanently disabled. Unless otherwise authorized by MC, testing of a pulse output shall require a minimum of two complete consecutive increments of the test dial which drives the pulse generator. The test volume represented by the output pulses, shall match the corresponding volume registered by the host meter's box.

6.3.8 AMR device

An automatic meter reading (AMR) device is exempt from then need for verification or reverification. This dispensation does not apply to the index on which the AMR device is affixed.

6.3.9 Limits of error and conformity determination

6.3.9.1

The specification limit is ±1.60% and the minimum coverage criterion for the extended result is at least 99% coverage. For the purposes of 100% inspection, the test limit shall be as follows:

The lesser of TLu = 1.60 − k uci or TLu = 1.00%

The greater of TLL = −1.60 + k uci or TLL = −1.00%

where, k = 3.0000 and uci is determined in accordance to the requirements of MC Specification S-S-02 (reference 3.2).

6.3.9.2

Conformity shall exist if all of the following inequalities are satisfied:

ei ≤ TLu1 and ei ≥ TLL1where, TLu1 = (TLu + T) and TLL1 = (TLL + T)

median ( |e´i| ) ≤ 0.60

where, T is the target value established in section 6.3.9.4 and ei´ is the bias corrected value of ei´ determined in consideration of section 6.3.9.5.

Note 1: For large diaphragm meters the MADT limit value of 0.80 shall apply, subject to the implementation policy contained in MC bulletin S-02, "Implementation Schedule for the Application of Statistical Sampling Requirements." After the time period indicated in the implementation policy the MADT limit value shall be 0.60.

Note 2: The MADT is calculated from all observations. The calculation method is to first determine the absolute value of each error, e´i, then determine the median of those values.

6.3.9.3

Conformity shall be determined using a one-stage procedure in accordance to the requirements of MC specification S-S-02 (reference 3.2).

6.3.9.4

The target value (T) shall normally be zero, however meter owners may elect to have a bias applied to the H.L. and L.L. calibration of any given make/model of new or remanufactured diaphragm meter, provided that the applied bias value(s) are declared to MC by the meter owner prior to presentation of the meters for inspection. The chosen bias value(s) may be different for the H.L. and L.L. testpoints, but shall have a value which lies within the interval of −1.0% to 0.0%.

6.3.9.5

If the target value is not zero, then prior to calculating the MADT all errors shall first be transformed to zero using a MC-authorized procedure, in order to take into consideration the applied bias value(s) when determining the acceptability of a meter's calibration error.

6.3.9.6

Measurement results shall be reported in accordance with S-S-02 (reference 3.2).

6.4 Acceptance sampling inspection

6.4.1 Devices may have their conformity evaluated by 100% inspection or, where the prerequisites of MC Specification S-S-03 (reference 3.3) have been and continue to be met, by sampling inspection in accordance with the requirements of MC Specification S-S-04 (reference 3.4).

6.4.2 A lot of meters submitted for acceptance sampling shall not contain a mixture of TC and Non-TC meters, nor a mixture of imperial and metric meters. As well, meters in the lot shall meet all of the following additional requirements for lot homogeneity:

  1. Same manufacturer and model, unless otherwise authorized by MC in accordance with clause 6.4.3.
  2. Same measurement technology.
  3. Same units of measure.
  4. Same or similar capacity (within 10% of the rated flow capacity (air) of the other meters in the lot).
  5. Same model or type of telemetering device (if so equipped), unless otherwise authorized by MC in accordance with clause 6.4.3.
  6. Calibrated using the same quality and production processes.
  7. Permissible batch types:
    1. New and/or remanufactured meters; or,
    2. Previously-verified meters which have all been reconditioned (and/or repaired) and recalibrated within a six-month period.

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

6.4.4 For the purposes of sampling inspection, a conforming unit is as defined in these specifications, for performance and non-performance characteristics. A lot shall be sentenced based on the specification limit of ±1.60%. The criterion for the extended measurement result is at least 95% coverage. An accredited organization shall have the option to determine conformity using either a one-stage or two-stage procedure in accordance with the requirements of MC Specification S-S-02 (reference 3.2).

6.4.5 The compressed specification limit (CSL) values determined from the device's performance specification limits are defined as follows:

Table 2
Marginal conformity type Lower CSL Upper CSL
Type 1 (LQ of 3.15%) LCSL1 = 0.8350 (−1.60) + T UCSL1 = 0.8350 (1.60) + T
Type 1 (LQ of 8.0%) LCSL2 = 0.6797 (−1.60) + T UCSL2 = 0.6797 (1.60) + T
Type 2 (MADT, LQ 3.15%) ------- UMADT = 0.80
Type 2 (MADT, LQ 8.0%) ------- UMADT = 0.70

6.4.6 A device is classified as a marginally conforming unit if it has no nonconformity but exhibits performance falling outside the interval defined by the lower and upper CSL values (type 1 marginally conforming) or has an MADT value exceeding the MADT limit (type 2 marginally conforming). The type 2 limit of 0.80 shall apply if sampling is performed under the LQ 3.15% plan; otherwise the limit of 0.70 shall apply.

6.4.7 The conformity, marginal conformity, or nonconformity of the device's performance shall be determined in accordance with the requirements of S-S-02 (reference 3.2) and the following classification criteria based on the device's relative error (ei), 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 ei + k uci > UCSL1 or ei − k uci < LCSL1
  3. marginally conforming type 1 if ei + k uci > UCSL2 or ei − k uci < LCSL2 (optional under sampling inspection)
  4. marginally conforming type 2 if the median ( |e´i| ) > UMADT
  5. conforming otherwise

where, k = 1.6449, uci is determined in accordance to the requirements of MC Specification S-S-02 (reference 3.2), T is the target value established in section 6.3.9.4, and ei´ is determined in consideration of section 6.3.9.5.

6.4.8 For the purpose of sampling inspection, test results for the following quality characteristics shall be treated as non-performance observations (i.e. pass/fail):

  1. meter leak test
  2. index dial test
  3. pulse output test

6.4.9 Measurement results shall be reported in accordance with S-S-02 (reference 3.2).

6.5 Outgoing quality requirements

The outgoing quality standards for meter quality under both 100% inspection and sampling inspection are:

  1. No inspected meters shall be permitted to be placed in service with a result which is not contained within the 100% Inspection test limits specified in subsections 6.3.9.1 and 6.3.9.2.
  2. No meters shall be permitted to be placed in service with one or more nonconformities or defects. (Note: The accredited organization shall be responsible for deciding which types of quality characteristic deficiencies are to be identified as a defect.)
  3. Subject to a) and b) above, sample meters are considered acceptable regardless of the status of the lot.
  4. The outgoing quality requirements shall be met for the product of the associated limiting quality (LQ) value and the lot size, as specified in S-S-03 (reference 3.3) or S-S-04 (reference 3.4) for type 1 and type 2 marginal conformities.

6.6 Sampling plan for the inspection of isolated lots of meters in service

Meters in service may be reverified as a lot by compliance sampling with use of a MC-authorized compliance sampling plan.

7.0 Technical requirements

Refer to applicable MC specifications for approval-of-type requirements for the design, composition, and construction of diaphragm meters.

8.0 Administrative requirements

8.1 Markings

8.1.1 In order to qualify for verification and sealing, meters shall bear one or more nameplates or tags which are permanently fastened to the meter body, which bear indelible legible markings of the following items of information:

  1. contractor's assigned meter inspection number (company serial number).
  2. meter manufacturer's serial number.
  3. manufacturer's name or registered trademark.
  4. meter model (model number).
  5. ambient operating temperature range, if narrower than the range of −30 °C to +40 °C
  6. notice of approval (NOA) number (Note: Not applicable to meters approved prior to July, 1987).
  7. maximum allowable operating pressure (MAOP).
  8. manufacturer's rated capacity (air).
  9. base temperature to which the registered volume is being converted (15 °C or 60 °F), with a red-coloured background (Note: Applicable only to temperature-converting diaphragm meters).
  10. arrow to indicate the direction of forward gas flow, or the inlet connection identified with the word "inlet".
  11. direction of rotation of the meter's index drive shaft (applicable only to large diaphragm meters).
  12. capacity per revolution of the meter's index drive shaft marked in the vicinity of the shaft (Note: Applicable only to large diaphragm meters).

Note: Meters shall not be marked with a mixture of International System (SI) units of measure and Imperial System units of measure.

8.1.2 Temperature-converting (TC) meters presented for reverification which have a nameplate on which the red-coloured background of the base temperature markings has partially or totally faded, shall not be rejected or classed as a non-conformance, provided that all of the mandatory information markings (as listed in subsection 8.1.1) on the nameplate are still legible.

8.1.3 If any mandatory markings on a meter nameplate have become illegible due to damage, deterioration or fading, the nameplate shall either be replaced or a covered with a self-adhesive label which bears the same information. Such labels may have a cut-out window that exposes the original nameplate's serial number marking, if the serial number is still legible.

8.1.4 The use or application of new pre-printed self-adhesive verification labels is not permitted on meters which are being verified or reverified. Existing old verification labels shall either be removed or painted over, on meters being presented for reverification (excluding compliance sampling meters). A meter presented for compliance sampling which had been previously affixed with a self-adhesive verification label, shall not be considered non-conforming if the faded markings on the label are no longer legible, or if the label has fallen off.

8.1.5 Where a meter incorporates a pulse generator, the following information shall be marked on a nameplate mounted on the host meter:

  1. number of pulses corresponding to a unit of measured quantity or the number of measured units corresponding to one output pulse.
  2. type and amplitude of output signal, or contact rating (e.g. "form C" or "form A").

8.1.6 Where the information content of a meter's pulse output may vary with the meter model on which the pulse generator is installed, a nameplate, tag, sticker, or other suitable means for marking the required information shall be provided by the manufacturer.

8.1.7 Where a pulse generator is a separate entity which can be attached to an approved meter, the following information shall be marked on a nameplate attached to the pulse generator:

  1. number of pulses corresponding to one unit of input to the generator
  2. maximum frequency of input
  3. type and amplitude of output signal, or contact rating (e.g. "form C" or "form A")

8.2 Seals and sealing

Unless otherwise specified in the applicable Notice of Approval or other applicable MC specifications or policies, as to which components and sealing points require sealing (or the required sealing wire configuration), meters shall be sealed in accordance with the requirements in clauses 8.2.1 to 8.2.7 below.

8.2.1 Meters shall either be sealed using a MC-approved metal roll-up seal and metal sealing wire, and/or encasement seals consisting of a sealing cap and receptacle. The use of plastic mono-filament (or other material) is also permitted as an alternative to the use of metal sealing wire, provided that it has a diameter of at least 0.644 mm and durability characteristics which are at least equivalent to that of metal sealing wire.

8.2.2 At least one of the seals on each sealed component of a meter shall bear a verification marking which shows the year in which the meter was tested and verified, and the unique identity (name, initials, or logo) of the accredited organization which performed the verification or reverification.

8.2.3 On small diaphragm meters, at least one screw shall be sealed on each of the following components: index cover, top cover, and hand-hole cover (or calibration adjustment access hole plug/cover, if so designed). The front and back covers of the meter may be left unsealed.

8.2.4 On large diaphragm meters intended for operation on low pressure and/or Pressure Factor Metering (PFM) installations, at least one screw shall be sealed on each of the following components: index cover, top meter cover, undergear (intermediate gear) assembly cover, and calibration adjustment access hole plug/cover (if so designed). The front and back covers of the meter may be left unsealed.

8.2.5 On large diaphragm meters intended for operation on elevated pressure with use of an ancillary volume conversion device, at least one screw shall be sealed on each of the following components: top meter cover, undergear (intermediate gear) assembly cover, and calibration adjustment access hole plug/cover (if so designed). The front and back covers of the meter may be left unsealed.

8.2.6 If a meter is to be sealed using sealing wire and screws having drilled heads, the sealing wire shall be routed so as not to run in parallel between any two screws, nor with any excess slack, so as to minimize the possibility of those screws being removed (for purposes of tampering) and subsequently reinstalled without breaking the sealing wire.

8.2 If a verified meter is fitted with a pressure tap plug, the plug may be left unsealed or separately sealed so as to permit its removal without affecting the meter's verification seal or sealing wire.

8.3 Disposition of nonconforming meters

8.3.1 For small lots inspected by 100% inspection or larger lots inspected but not accepted by sampling, nonconforming meters and excessive marginally conforming meters shall be removed or repaired to ensure the outgoing quality standards of section 6.5 are met.

8.3.2 Individual non-conforming or defective meters may be resubmitted for inspection only after their deficient characteristics have been corrected.

8.3.3 Unacceptable lots may be resubmitted for inspection only after the meter owner or his agent has re-examined all meters and removed or corrected all non-conforming or defective meters. Re-inspection shall include evaluation of all quality characteristics where the non-acceptance is due to performance characteristics, or, for all other types of nonconformities and defects, evaluation of the characteristic(s) causing lot non-acceptance.

8.4 Reverification interval

The reverification interval (i.e. "seal period") for diaphragm meters is prescribed in the applicable MC bulletin.

9.0 Revisions

The purpose of revision 1 is to:

  1. amend the following MADT limit values, and amend the wording in the associated sections to reflect these changes:
    1. median ( |ei´| ) ≤ 0.60 conforming criteria for 100% inspection and sample meters;
    2. for large diaphragm gas meters, the above limit is 0.80, subject to the implementation policy in bulletin S-02;
    3. median ( |ei´| ) ≤ 0.80 conforming type 2 criteria for sampling under the LQ 3.15% plan;
    4. median ( |ei´| ) ≤ 0.70 conforming type 2 criteria for sampling under the LQ 8.0% plan.
  2. revise the requirements for index verification in section 6.3.5
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