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OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 1 of 57 COMMITTEE DRAFT OIML WD1 Date:28 April 2009 Reference number:.Supersedes document:N/A OIML TC X/SC X Circulated to P-and O-members and liaison international bodies and external organisations for:Title:Gas meters discussion at(date and place of meeting):.Secretariat:The Netherlands comments by:.vote(P-members only)and comments by:.TITLE OF THE CD(English):OIML R 137-1 and-2 Gas meters Part 1:Metrological and Technical Requirements Part 2:Metrological controls and performance tests TITRLE DU CD(French):OIML R 137-1 et-2 Compteurs de gaz Partie 1:Exigences mtrologiques et techniques,Partie 2:Contrles mtrologiques et essais de performance Original version in:English OIML R 137-1:2006(E)K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 2 of 57 Explanatory note to the 1 WD(Temporary section to be removed after finalization of the Recommendation)After OIML R 137-1 Gas meters was approved by CIML in 2006 and effectively published in 2007,and the responsibility for this Recommendation was transferred to TC8/SC7,the secretary started the work drafting Part 2 Metrological controls and performance tests.But during this work,it was identified that a few minor changes in Part 1 would be necessary,although there is no formal project for the revision of Part 1.Nevertheless,expecting that the current project for part 2 will also lead to a revised Part 1,the secretary investigated what further changes would be advisable.This lead to the following proposed changes in Part 1(2006):Definitions changed in compliance with the new(2007)edition of the VIM.Not used definitions removed Separation in Parts 1 and 2 in better accordance with the general format for OIML Recommendations,presented during the OIML seminar in Douai(April 2008).In part 1 only the requirements are listed,due to the fact this part will be used for legislation and therefore paragraph 4.6 is introduced.Also the previous chapters 3 up to and including 6 are reshuffled to make the document in line with the general OIML format.Added requirements for the mains voltage to clause 4.1,rated operating conditions The reproducibility requirement is now only prescribed for gas meters with internal moving parts,while a repeatability requirement is introduced for gas meters without internal moving parts(4.6.1 and 4.6.2)The temperature test is now prescribed from Qmin up to and including Qmax,instead from Qt up to and including Qmax(paragraph 11.4.8).The temperature test with gas temperature unequal to ambient temperature is removed.The damp heat,steady state and damp heat cyclic test are performed at the upper temperature(Table 4).The test Orientation and flow direction is better separated into Orientation and flow direction(4.6.3 and 4.6.4).The requirements for the durability test is now from Qmin up to and including Qmax,instead from Qt up to and including Qmax(11.4.10 and 4.6.8).For flow disturbances the requirement is that the shift has to be 0.9Qmax a weighting factor of 0.4 shall be used instead of 1.2.2.6 Intrinsic error(OIML D 11,3.7)Error determined under reference conditions.2.2.7 Fault e(OIML D 11,3.9)Difference between the error of indication and the intrinsic error of a measuring system or of its constituent elements.Note:In practice this is the difference between the error of the meter observed during or after a test,and the error of the meter prior to this test,performed under reference conditions.2.2.8 Maximum permissible error(MPE)(VIM 4.26)extreme value of measurement error,with respect to a known reference quantity value,permitted by specifications or regulations for a given measurement,measuring instrument,or measuring system.2.2.9 Accuracy class(VIM 4.25)class of measuring instruments or measuring systems that meet stated metrological requirements that are intended to keep measurement errors or instrumental uncertainties within specified limits under specified operating conditions.2.2.10 Durability(OIML D 11,3.17)Ability of a measuring instrument to maintain its performance characteristics over a period of use.2.2.11 Operating conditions Conditions of the gas(temperature,pressure and gas composition)at which the quantity of gas is measured.2.2.12 Rated operating conditions Conditions of use giving the range of values of the measurand and the influence quantities,for which the errors of the gas meter are required to be within the limits of the maximum permissible error.2.2.13 Reference conditions OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 10 of 57 Set of reference values,or reference ranges of influence quantities,prescribed for testing the performance of a gas meter,or for the intercomparison of the results of measurements.2.2.14 Base conditions Conditions to which the measured volume of gas is converted(examples:base temperature and base pressure).Note:Operating and base conditions relate to the volume of gas to be measured or indicated only and should not be confused with“rated operating conditions”and“reference conditions”(VIM 5.05 and 5.07)which refer to influence quantities.2.2.15 Test element(of an indicating device)Device to enable precise reading of the measured gas quantity.2.2.16 Resolution(of an indicating device)(VIM 4.15)Smallest difference between displayed indications that can be meaningfully distinguished.Note:For a digital device,this is the change in the indication when the least significant digit changes by one step.For an analogue device,this is half the difference between subsequent scale marks.2.2.17 Drift(VIM 4.21)continuous or incremental change over time in indication,due to changes in metrological properties of a measuring instrument.2.3 OPERATING CONDITIONS Note:For the definition of operating conditions,see 2.2.11.2.3.1 Flowrate,Q Quotient of the actual quantity of gas passing through the gas meter and the time taken for this quantity to pass through the gas meter.2.3.2 Maximum flowrate,Qmax Highest flowrate at which a gas meter is required to operate within the limits of its maximum permissible error,whilst operated within its rated operating conditions.2.3.3 Minimum flowrate,Qmin Lowest flowrate at which a gas meter is required to operate within the limits of its maximum permissible error,whilst operated within its rated operating conditions.2.3.4 Transitional flowrate,Qt Flowrate which occurs between the maximum flowrate Qmax and the minimum flowrate Qmin that divides the flowrate range into two zones,the upper zone and the lower zone,each characterized by its own maximum permissible error.2.3.5 Working temperature,tw Temperature of the gas to be measured at the gas meter.2.3.6 Minimum and maximum working temperatures,tmin and tmax Minimum and maximum gas temperature that a gas meter can withstand,within its rated operating conditions,without deterioration of its metrological performance.2.3.7 Working pressure,pw Gauge pressure of the gas to be measured at the gas meter.The gauge pressure is the difference between the absolute pressure of the gas and the atmospheric pressure.2.3.8 Minimum and maximum working pressure,pmin and pmax Minimum and maximum internal gauge pressure that a gas meter can withstand,within its rated operating conditions,without deterioration of its metrological performance.OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 11 of 57 2.3.9 Static pressure loss or pressure differential,p Mean difference between the pressures at the inlet and outlet of the gas meter while the gas is flowing.2.3.10 Working density,w Density of the gas flowing through the gas meter,corresponding to pw and tw 2.4 TEST CONDITIONS 2.4.1 Influence quantity(VIM 2.52)quantity that,in a direct measurement,does not affect the quantity that is actually measured,but affects the relation between the indication and the measurement result.2.4.2 Disturbance(OIML D 11,3.13.2)Influence quantity having a value within the limits specified in this Recommendation,but outside the specified rated operating conditions of the gas meter.Note:An influence quantity is a disturbance if for that influence quantity the rated operating conditions are not specified.2.4.3 Overload conditions Extreme conditions,including flowrate,temperature,pressure,humidity and electromagnetic interference that a gas meter is required to withstand without damage.2.4.4 Test Series of operations intended to verify the compliance of the equipment under test(EUT)with certain requirements.2.4.5 Test procedure Detailed description of the test operations.2.4.6 Test program Description of a series of tests for a certain type of equipment.2.4.7 Performance test Test intended to verify whether the equipment under test(EUT)is capable of accomplishing its intended functions.2.5 ELECTRONIC EQUIPMENT 2.5.1 Electronic gas meter Gas meter equipped with electronic devices.Note:For the purposes of this Recommendation auxiliary equipment,as far as it is subject to metrological control,is considered part of the gas meter,unless the auxiliary equipment is approved and verified separately.2.5.2 Electronic device(D 11,3.2)Device employing electronic sub-assemblies and performing a specific function.Electronic devices are usually manufactured as separate units and are capable of being tested independently.2.5.3 Electronic component(D 11,3.4)Smallest physical entity,that uses electron or hole conduction in semi-conductors,gases or in a vacuum.OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 12 of 57 3 Units of measurement 3.1 MEASUREMENT UNITS All quantities shall be expressed in SI units 3 or as other legal units of measurement 4,unless a countrys legal units are different.In the next section the unit corresponding to the quantity indicated is expressed by.OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 13 of 57 4 Metrological requirements 4.1 RATED OPERATING CONDITIONS The rated operating conditions for a gas meter shall be as follows:Flowrate range:Qmin to Qmax inclusive Ambient temperature range:lower temperature to be chosen from 40 C,25 C,10 C and+5 C upper temperature to be chosen from+30 C,+40 C,+55 C and+70 C Ambient humidity range:93%Working pressure range:pmin to pmax inclusive Gases:the family of natural gases,industrial gases,or supercritical gases;to be specified by the manufacturer(Note 1)DC mains voltage:(Note 2)as specified by the manufacturer AC mains voltage:(Note 2)Unom 15%to Unom+10%Note 1:Supercritical refers to the situation where there is no distinction between the gaseous and liquefied state of the fluid.Note 2:Whatever is applicable.4.2 VALUES OF QMAX,QT AND QMIN The flowrate characteristics of a gas meter shall be defined by the values of Qmax,Qt and Qmin as stated in Table 1.Table 1 Flowrate characteristics Qmax/Qmin Qmax/Qt 50 10 5 and 50 5 4.3 ACCURACY CLASSES AND MAXIMUM PERMISSIBLE ERRORS 4.3.1 General Gas meters shall be designed and manufactured such that their errors do not exceed the limits of the applicable maximum permissible error under rated operating conditions,listed in 4.3.3.4.3.2 Correction for known errors Gas meters may be equipped with a correction device,which can be used to bring errors as close as possible to zero.A correction device can be used to improve the Accuracy Class specification.The correction device shall not be used for the correction of a pre-estimated drift.4.3.3 Accuracy Classes and maximum permissible errors(MPE)Gas meters shall be classified into the Accuracy Classes given in Table 2.The errors shall be within the applicable values given in Table 2.OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 14 of 57 Table 2 Maximum permissible errors of gas meters Flowrate Q On type approval and initial verification Accuracy Class In-service*Accuracy Class 0.5 1 1.5 0.5 1 1.5 Qmin Q Qt 1%2%3%2%4%6%Qt Q Qmax 0.5%1%1.5%1%2%3%*Note:National Authorities may decide whether they will implement in-service maximum permissible errors or not 4.3.4 Mechanical gas meter with a built-in mechanical temperature conversion device For a mechanical gas meter with a built-in mechanical temperature conversion device having only one indicating device displaying the volume at base conditions,the maximum permissible errors as indicated in Table 2 are increased by 0.5%in a range of 30 C extending symmetrically around the temperature tsp specified by the manufacturer.Outside this range an additional increase of 0.5%is permitted in each interval of 10 C.Compliance with these requirements shall be verified at temperatures deviating by not more than 2 C from the upper and lower limits of the specified intervals.4.4 WEIGHTED MEAN ERROR(WME)The weighted mean error(WME)shall be within the maximum permissible values given in Table 3.Table 3 Maximum permissible weighted mean error Flowrate Q On type approval and initial verification Accuracy Class In-service Accuracy Class 0.5 1 1.5 0.5 1 1.5 WME 0.2%0.4%0.6%-4.5 REPAIR AND DAMAGE OF SEALS After repair of the gas meter or damage to the seals,the maximum permissible error shall comply with the errors on initial verification as stated in Table 2,as well as the maximum permissible weighted mean error as stated in Table 3.OIML TC 8/SC 7 1WD OIML R 137-1&-2 Date:28 April 2009 K:AlgemeenOIMLOIML gasdraft R137-1-2-31WD R137-1+2 09-04-28.doc Page 15 of 57 4.6 OTHER METROLOGICAL REQUIREMENTS Gas meters shall fulfil also the following metrological requirements.4.6.1 Reproducibility Gas meters with internal moving parts shall have a reproducibility at which the experimental standard deviationi shall be less then or equal to 0.15 times the maximum permissible error,for flowrates equal to or greater than Qt.Note Gas meters with internal moving parts may have a hysteresis behaviour.4.6.2 Repeatability Gas meters without internal moving parts shall have a repeatability of less then or equal to 0.33 times the maximum permissible error.4.6.3 Orientation If the meter is marked as operating only in certain orientations,the requirements as mentioned in 4.3 and 4.4 shall be fulfilled in these orientations.In the absence of such marks the meter shall fulfil these requirements all orientations.4.6.4 Flow direction If the meter is marked as operating in more than one flow direction,the requirements as mentioned in 4.3 and 4.4 shall be fulfilled in both directions.4.6.5 Working pressure The requirements as mentioned in 4.3 shall be fulfilled for the whole working pressure range.The maximum difference between the error curves,obtained at different pressures,is limited to 0.5 times the maximum permissible error.4.6.6 Temperature The requirem