Full Text
REGD. No. D. L.-33004/99
The Gazette of India
EXTRAORDINARY
PART II—Section 3—Sub-section (i)
PUBLISHED BY AUTHORITY
No. 203] NEW DELHI, MONDAY, APRIL 21, 2025/VAISAKHA 01, 1947
CG-DL-E-25042025-262652
2642 GI/2025 (1)
MINISTRY OF CONSUMER AFFAIRS, FOOD AND PUBLIC DISTRIBUTION
(DEPARTMENT OF CONSUMER AFFAIRS)
NOTIFICATION
New Delhi, the 21st April, 2025
G.S.R. 242(E).— In exercise of the powers conferred by sub-section (1) read with clauses (c), (f), (h), (i)
and (s) of sub-section (2) of section 52 of the Legal Metrology Act 2009, (1 of 2010), the Central Government hereby
makes the following rules, further to amend the Legal Metrology (General) Rules, 2011, namely:-
1. Short title and commencement.- (1) These rules may be called the Legal Metrology (General) Second
Amendment Rules, 2025.
(2) They shall come into force on the 1st day of September, 2025.
2. In the Legal Metrology (General) Rules, 2011 (hereinafter referred to as the said rules), after rule 27, the
following rule shall be inserted, namely:-
“27A. Special provision for re-verification.-The re- verification of the following meters shall be carried out on the
completion of the period specified in the following Table below, namely:-
(a) for Volumetric Meters,-
Table 1.
| Serial No. | Type | Sub-type | Initial re-verification period | Subsequent re verification period |
| :--------- | :----------- | :----------- | :----------------------------- | :------------------------------- |
| (1) | (2) | (3) | (4) | (5) |
| 1. | Diaphragm | Meter | 7 years | 5 years |
| 2. | Rotary | Pressure body | 20 years | 17 years |
| 3. | Turbine | All types | 6 years | 4 years |
| 4. | Orifice | plate, fitting, tubes, and flow conditioner | 6 years | 4 years |
| 5. | Ultrasonic | Ultrasonic gas meter | 6 years | 4 years |
| 6. | Fluidic- oscillation | All types | 6 years | 4 years |
| 7. | Vortex | All types | 6 years | 4 years |
| 8. | Cone- shaped | All types | 6 years | 4 years |
differential pressure
(b) for Mass-flow Meters,-
Table 2.
| Serial No. | Type | Sub-type | Initial re-verification period | Subsequent re verification period |
| :--------- | :----------- | :----------- | :----------------------------- | :------------------------------- |
| (1) | (2) | (3) | (4) | (5) |
| 9. | Coriolis | NGV Dispenser System | 1 year | 1 year |
| | | All Other types | 6 years | 4 years |
| 10. | Thermal | All types | 6 years | 4 years |
(c) for Base Pressure and temperature conversion devices or Recording devices, -
Table 3.
| Serial No. | Type | Sub-type | Initial re-verification period | Subsequent re verification period |
| :--------- | :----------- | :----------- | :----------------------------- | :------------------------------- |
| (1) | (2) | (3) | (4) | (5) |
| 11. | Chart Recorder | All types | same as the host meter | same as the host meter |
| 12. | Mechanical- type Volume Conversion Device | Rotary meter modules | 7 years | 5 years |
| | | All other types | | |
| 13. | Electronic- type Volume Conversion Device | All types | 7 years | 5 years |
| 14. | Flow Computer | All types | 6 years | 4 years |
| 15. | Transducer or Transmitter | All types | 7 years | 5 years |
(d) for other Meters, devices, and installations,- Meter devices and installation not covered in
serial numbers 1 to 15 above.
Table 4.
| Serial No. | Type | Sub-type | Initial re-verification period | Subsequent re verification period |
| :--------- | :----------------------------- | :---------------------------------- | :----------------------------- | :------------------------------- |
| (1) | (2) | (3) | (4) | (5) |
| 16. | Gas Analyser or Chromatograph | All types | 1 year | 1 year |
| 17. | Energy Density | All types | 1 year | 1 year |
| 18. | Relative Density | All types | 1 year | 1 year |
| 19. | Flow Conditioner | Perforated plate | same as the host meter | same as the host meter |
| | | Tube bundle (straightening vanes) | same as the host meter | same as the host meter |
| 20. | Correction Device | All types (2) | same as the host meter | same as the host meter |
| 21. | Ticket printer | All types | same as the host meter | same as the host meter |
| 22. | Telemetering Device or System | All types | same as the host meter | same as the host meter |
| 23. | Metering Installations | Pressure factor metering (PFM) | same as the host meter | same as the host meter |
| | | All other types | same as the host meter | same as the host meter |
Note (1): Re-verification period shall be as stated above and the devices shall be inspected at their operational
location at the time of re-verification of meter.
Note (2): The “linearisation” function may either be incorporated into the circuit design of an electronic
volumetric meter or a flow computer, or in a separate correcting device.”
3. In the Eighth Schedule to the said rules, after PART X the following PART shall be inserted,
namely.-
“PART XI
GAS METERS
Part 1
Metrological and technical requirements
1. Scope.-
(1) This part applies to gas meters based on any measurement technology or principle that is used to measure the
quantity of gas that has passed through the meter at operating conditions. The quantity of gas can be expressed in
units of volume or mass.
(2) This part applies to gas meters intended to measure quantities of gaseous fuels or other gases. It does not cover
meters used for gases in the liquefied state, multi-phase steam and compressed natural gas used in compressed natural
gas dispensers.
(3) This part applies to built-in correction devices, devices for internal temperature compensation and includes any
other electronic device that may be attached to the gas meter.
2. Terminology.-
(1) Gas meter and its constituents,-
(i) gas meter,-
The instrument intended to measure, memorise and display the quantity of gas passing the flow
sensor;
(ii) measurand,-
The quantity intended to be measured;
(iii) sensor,-
An element of a measuring system that is directly affected by a phenomenon, body, or substance
carrying a quantity to be measured;
(iv) measuring transducer,-
The device used in measurement that provides an output quantity having a specified relation to the
input quantity;
(v) calculator,-
The part of the gas meter which receives the output signals from the measuring transducer and
associated measuring instruments, transforms them and stores the results in memory until they are used. In
addition, the calculator may be capable of communicating both ways with ancillary devices;
(vi) indicating or displaying device,-
The part of the gas meter which displays the measurement results, either continuously or on
demand;
Note: A printing device which provides an indication at the end of the measurement is not an indicating
device.
(vii) correction device,-
The device intended for correction of known errors in the function, for instance in the flow rate,
Reynolds number (curve linearisation), density, pressure or temperature or a combination thereof;
(viii) ancillary device,-
The device intended to perform a particular function, directly involved in elaborating, transmitting
or displaying measurement results. The main ancillary devices are,-
(a) repeating indicating device;
(b) printing device;
(c) memory device; and
(d) communication device.
Note 1: An ancillary device is not necessarily subject to metrological control.
Note 2: An ancillary device may be integrated in the gas meter.
(ix) associated measuring instrument,-
The instrument connected to the calculator or the correction device for measuring certain gas
properties for the purpose of making a correction;
(x) equipment under test (equipment under test),-
The part of the gas meter or associated devices or both which is exposed to one of the tests;
(xi) family of gas meters,-
The group of gas meters of different sizes or different flow rates or a combination thereof, in which
all the meters shall have the following characteristics; namely:-
(a) the same manufacturer;
(b) geometric similarity of the measuring part;
(c) the same metering principle;
(d) roughly the same ratios Qmax/Qmin and Qmax/Qt;
(e) the same accuracy class;
(f) the same electronic device [as specified in clause (ii) of sub-paragraph (5) of paragraph 2] for each
meter size and using the same metrological software routines (if applicable) for those components
that are critical to the performance of the meter;
(g) a similar standard of design and component assembly; and
(h) the same materials for those components that are critical to the performance of the meter.
(2) Metrological characteristics, -
(i) quantity of gas,-
The total quantity of gas obtained by integrating the flow passed through the gas meter over time,
which is expressed as volume ‘V’ or mass ‘m’, disregarding the time taken. The quantity of gas is the measurand
concerned [as defined in clause (ii) of sub-paragraph (1) of paragraph 2];
(ii) indicated value (of a quantity),-
The value Yi of a quantity as indicated by the meter;
(iii) cyclic volume of a gas meter (positive displacement gas meters only) ,-
The volume of gas corresponding to one full revolution of the moving parts inside the meter (working
cycle);
(iv) error,-
The measured quantity value minus a reference quantity value;
(v) weighted mean error (WME),-
The weighted mean error (WME) within this rule is defined as:
WME = ( ∑ (ki Ei) / ∑ ki ) with ki = Qi / Qmax for Qi ≤ 0.7 Qmax
ki = 1.4 - (Qi / Qmax) for 0.7 Qmax≤ Qi ≤ Qmax
where:
ki = weighting factor at the flow rate Qi;
Ei = the error at the flow rate Qi.
(vi) intrinsic error,-
The error determined under reference conditions;
(vii) fault,-
The difference between the error of indication and the intrinsic error of a measuring instrument.
Note 1: 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.
Note 2: “measuring instrument” is to be interpreted as a “gas meter”.
(viii) maximum permissible error (MPE) ,-
The 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;
(ix) accuracy class,-
The class of measuring instruments or measuring systems which meet the stated metrological
requirements that are intended to keep measurement errors or instrumental uncertainties within specified limits
under specified operating conditions;
(x) durability,-
It refers to the ability of a measuring instrument to maintain its performance characteristics over a
period of use;
(xi) measurement precision,-
The closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions;
(xii) repeatability,-
It refers to the measurement precision under a set of repeatability conditions of measurement;
(xiii) repeatability of error,-
It refers to the repeatability under reference conditions and not changing the flow rate between the
measurements;
(xiv) reproducibility,-
It refers to the measurement precision under reproducibility condition of measurement;
(xv) reproducibility of error,-
It refers to the reproducibility under reference conditions and changing the flow rate between the
measurements;
(xvi) operating conditions,-
The conditions of the gas (temperature, pressure and gas composition) at which the quantity of gas is
measured;
(xvii) rated operating conditions,-
The 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;
(xviii) reference conditions,-
The 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;
(xix) base conditions,-
The 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” which refer to influence quantities.
(xx) test element (of an indicating device),-
The device to enable precise reading of the measured gas quantity;
(xxi) resolution (of a displaying device),-
The smallest difference between displayed indications that can be meaningfully distinguished.
Note: For a digital device, if significant 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.
(xxii) instrumental drift,-
The continuous or incremental change over time in indication, due to changes in the metrological
properties of a measuring instrument.
(3) Operating conditions,-
The conditions of the gas (temperature, pressure and gas composition) at which the quantity of gas is measured;
(i) flow rate (Q),-
The 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;
(ii) maximum flow rate (Qmax),-
The highest flow rate at which a gas meter is required to operate within the limits of its maximum
permissible error whilst being operated within its rated operating conditions;
(iii) minimum flow rate (Qmin),-
The lowest flow rate at which a gas meter is required to operate within the limits of its maximum
permissible error whilst being operated within its rated operating conditions;
(iv) transitional flow rate (Qt),-
The rate which occurs between the maximum flow rate Qmax and the minimum flow rate Qmin that
divides the flow rate range into two zones, the “upper zone” and the “lower zone”, each characterised by its own
maximum permissible error;
(v) working temperature (tw),-
The temperature of the gas to be measured at the gas meter;
(vi) minimum working temperature (tmin)and maximum working temperature (tmax),-
The minimum and maximum gas temperature that a gas meter can withstand, within its rated operating
conditions, without unacceptable deterioration of its metrological performance;
(vii) specified temperature (tsp),-
The median temperature for gas meters with built-in conversion devices used as a reference for the
determination of the applicable operating temperature range.
Note: The difference between tsp and the gas temperature has an influence on the value of the maximum
permissible error.
(viii) working pressure (pw),-
The pressure of the gas to be measured at the gas meter;
(ix) minimum working pressure (pmin)and maximum working pressure (pmax),-
The minimum and maximum internal pressure that a gas meter can withstand, within its rated operating
conditions, without deterioration of its metrological performance;
(x) static pressure loss or pressure differential (Δp),-
The difference between the pressures at the inlet and outlet of the gas meter while the gas is flowing;
(xi ) working density (ρw),-
The density of the gas flowing through the gas meter, corresponding to ρw and tw.
(4) Test conditions,-
(i) influence quantity,-
The 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;
(ii) disturbance,-
The influence quantity having a value within the limits specified in this part 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.
(iii) overload conditions,-
The conditions outside the rated operating conditions (including flow rate, temperature, pressure,
humidity and electromagnetic interference) that a gas meter is required to withstand without deterioration of its
performance;
(iv) test,-
The series of operations intended to verify the compliance of the equipment under test (equipment
under test) with certain requirements;
(v) test procedure,-
The detailed description of the test operations;
(vi) test program,-
The description of a series of tests for a certain type of equipment;
(vii) performance test,-
The test intended to verify whether the equipment under test (equipment under test) is capable of
accomplishing its intended functions.
(5) Electronic equipment,-
(i) electronic gas meter,-
The gas meter equipped with electronic devices.
Note: For the purposes of this part ancillary equipment, as far as it is subject to metrological control, is
considered part of the gas meter, unless the ancillary equipment is approved and verified separately.
(ii) electronic device,-
The 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;
(iii) electronic component,-
The smallest physical entity in an electronic device used to affect electrons and/or their associated fields
in their movement through a medium or vacuum.
3. Units of measurement.-
(1) Measurement units,-
All quantities shall be expressed in SI units.
4. Metrological requirements.-
(1) Rated operating conditions,-
Table A.
| (1) | (2) | (3) |
| :-- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| (a) Ambient temperature (Temperature range chosen shall at least cover 50 K) | Low –40°C, –25°C, –10°C, 00C and +5°C (1) High +30°C,+40°C,+55°C, 650C and +70°C (1) |
| (b) Ambient relative humidity | As specified by the manufacturer; at least up to 93% |
| (c) Atmospheric pressure | As specified by the manufacturer; at least covering 86 kPa – 106 kPa |
| (d) Vibration less than | 10 Hz – 150 Hz, 1.6 ms-2, 0.05 m2s-3, -3dB/octave |
| (e) DC mains voltage (3) | As specified by the manufacturer |
| (f) AC mains voltage (3) | Unom – 15% to Unom + 10% |
| (g) AC mains frequency (3) | fnom – 2 % to fnom + 2% |
| (h) Flow rate range | Qmin to Qmax inclusive |
| (i) Type of gases | The family of natural gases, industrial gases, or supercritical gases; to be specified by the manufacturer (2), |
| (j) Working pressure range: | pmin to pmax inclusive |
(1) Different values of temperature are allowed depending on the different climatic conditions of the country.
(2) Supercritical refers to the situation where there is no distinction between the gaseous and liquefied state of the
fluid
(3) If applicable
(2) Values of Qmax, Qt and Qmin,-
The flow rate characteristics of a gas meter shall be defined by the values of Qmax, Qt and Qmin. Their
ratios and relations shall be within the ranges as specified in Table 1:
Table 1. Flow rate characteristics
| Qmax / Qmin | Qmax / Qt |
| :---------- | :--------- |
| (1) | (2) |
| ≥ 50 | ≥ 10 |
| ≥ 5 and <50 | ≥ 5 |
(3) Accuracy classes and maximum permissible errors (MPE),-
(i) General,-
A gas meter shall be designed and manufactured such that its errors do not exceed the applicable MPE
under rated operating conditions;
(ii) Accuracy classes,-
Gas meters may be divided in three accuracy classes 0.5, 1 and 1.5. A gas meter shall be classified
according to its accuracy in one of these classes. The value of the MPE is dependent on the applicable accuracy
class as specified in Table 2 below;
(iii) Correction for known errors,-
A gas meter may be equipped with a correction device, intended to reduce the errors as close as possible
to the zero value. Such a correction device shall not be used for the correction of a pre-estimated drift;
(iv) Maximum permissible errors (MPE),-
Table 2. Maximum permissible errors of gas meters
| Flow rate Q | During model approval and initial verification | During re-verification and in-service |
| :---------- | :------------------------------------------- | :-------------------------------- |
| | Accuracy class | Accuracy class |
| | 0.5 | 1 | 1.5 | 0.5 | 1 | 1.5 |
| (1) | (2) | (3) | (4) | (5) | (6) | (7) |
| Qmin ≤ Q <Qt | ± 1 % | ± 2 % | ± 3 % | ± 2 % | ± 4 % | ± 6 % |
| Qt ≤ Q ≤ Qmax | ± 0.5 % | ± 1 % | ± 1.5 % | ± 1 % | ± 2 % | ± 3 % |
(v) Gas meter with a built-in conversion device,-
For a gas meter with a built-in conversion device and displaying the volume at base conditions only, the
maximum permissible errors as specified in Table 2 are increased by 0.5 % in the temperature range of (tsp – 15) °C to
(tsp + 15) °C. Outside this temperature range an additional increase of 0.5 % per additional interval of 10 °C is
permitted to this extended MPE. The temperature tsp is specified by the manufacturer.
Note 1: The conversion may be based on temperature or pressure measurements or both.
Note 2: Gas meters indicating both actual volume and volume at base conditions are considered gas metering
systems.
(4) Weighted mean error (WME),-
The weighted mean error (WME) shall be within the values as specified in Table 3.
Table 3. Maximum permissible weighted mean error
| Flow rate Q | During model approval and initial verification | During re-verification and in-service |
| :---------- | :------------------------------------------- | :-------------------------------- |
| | Accuracy class | Accuracy class |
| | 0.5 | 1 | 1.5 | 0.5 | 1 | 1.5 |
| (1) | (2) | (3) | (4) | (5) | (6) | (7) |
| WME | ± 0.2 % | ± 0.4 % | ± 0.6 % | - | - | - |
(5) Repair and damage of seals,-
After repair of components of the gas meter which affect the metrological behavior or after damage to the
seals, the maximum permissible error shall comply with the errors on initial verification as specified in Table 2, as
well as the maximum permissible weighted mean error as specified in Table 3.
(6) Reproducibility,-
For flow rates equal to or greater than Qt, the reproducibility of error at the specific flow rate shall be less
than or equal to one third of the maximum permissible error.
(7) Repeatability,-
The repeatability of error of three consecutive measurements at the specific flow rate shall be less than or
equal to one third of the maximum permissible error.
(8) Working pressure,-
The requirements as mentioned in sub-paragraph (3) of paragraph 4 shall be fulfilled over the whole working
pressure range.
(9) Temperature,-
The requirements as mentioned in sub-paragraph (3) of paragraph 4 shall be fulfilled over the whole
temperature range, where the ambient temperature equals the gas temperature within 5°C.
For gas meters indicating the volume at base conditions only, the double maximum permissible error limits
for flow rates equal to or above Qt apply when the ambient temperature differs by 20 °C or more from the gas
temperature.
(10) Durability,-
A gas meter shall meet the following requirements after being subjected to a flow with rate between 0.8 Qmax
and Qmax comprising a quantity that is equivalent to a flow at Qmax during a period of 2000 hours, namely:-
(i) the maximum permissible errors as specified in Table 2 for re-verification and in use; and
(ii) for flow rates from Qt up to Qmax a fault of less than or equal to,-
- 1.0 times the maximum permissible error applicable during model approval for class 1.5 or
- 0.5 times the maximum permissible error applicable during model approval for other classes.
(11) Overload flow,-
A gas meter shall comply with the following requirements, after being exposed to an overload of 1.2 Qmax for a
period of 1 hour, -
(i) the maximum permissible errors as mentioned in sub-paragraph (3) of paragraph 4; and
(ii) a fault of less than or equal to one-third of the maximum permissible error.
(12) Vibrations and shocks,-
A gas meter shall withstand vibrations and shocks with the following specifications:
(i) vibrations,-
total frequency range: 10 Hz – 150 Hz
total RMS level: 7 m.s-2
ASD level 10 Hz – 20 Hz: 1 m2s-3
ASD level 20 Hz – 150 Hz: –3 dB/octave
(ii) shocks,-
height of fall: 50 mm
The fault after the application of vibrations and shocks shall be less than or equal to 0.5 times the
maximum permissible error.
(13) Metrological requirements specific to certain types of gas meters,-
(i) Orientation,-
If the manufacturer of the meter specifies that the meter will only operate correctly while installed in
certain orientations and if the meter is marked as such, the metrological requirements specified in sub-paragraph
(3) and (4) of paragraph 4 shall be fulfilled for these orientations only;
In the absence of such marks the meter shall fulfill these requirements for all orientations;
(ii) Flow direction,-
If the meter is marked as being able to measure the flow in both directions, the metrological requirements
specified in sub-paragraph (3) and (4) of paragraph 4 shall be fulfilled for each direction separately;
(iii) Flow disturbance,-
For types of gas meters of which the accuracy is affected by flow disturbances, the shift of the error due
to these disturbances shall not exceed one third of the maximum permissible error. In case such a gas meter is
specified to be installed in specific piping arrangements producing only mild flow disturbances, the meter shall be
marked as such and may only be installed in those specific piping configurations for which its accuracy has
proven to stay within this requirement;
(iv) Drive shaft (torque),-
For types of gas meters with one or more drive shafts, any fault which results from the application of the
maximum torque, as specified by the manufacturer, shall not be more than one third of the maximum permissible
error;
(v) Different gases,-
The types of gas meters which are intended to be used for different gases shall comply with the
metrological requirements as mentioned in sub-paragraph (3) of paragraph 4 over the whole range of gases for
which they are specified by the manufacturer;
(vi) Interchangeable components,-
For types of gas meters of which some components are intended to be interchangeable for operational
purposes (e.g. ultrasonic transducers or meter cartridges), the fault due to the interchange of such a component
shall not be more than one third of the maximum permissible error applicable during type evaluation, while the
error shall in no case exceed the maximum permissible error for that range;
(vii) Electronics,-
If a gas meter includes electronic components, the requirements as specified in Table 4 and Table 5 shall
apply;
(viii) Influences from ancillary devices,-
Gas meters provided with ancillary devices shall be designed such that all functions of the ancillary
devices (e.g. provisions for communication purposes) do not affect the metrological behavior.
Table 4. Requirements for gas meters containing electronic components
| Serial No. | Influence factor | Range | Error limit |
| :--------- | :--------------- | :----------------------------- | :---------- |
| (1) | (2) | (3) | (4) |
| (a) | Dry heat | Upper temperature specified | MPE |
| (b) | Cold heat | Upper temperature specified | MPE |
| (c) | Damp heat, steady state (non-condensing) | upper temperature specified, 93 % relative humidity | MPE |
| (d) | DC mains voltage variation (1) | As specified by the manufacturer | MPE |
| (e) | AC mains voltage variation (1) | 85 % & 110 % of the rated voltage | MPE |
| (f) | Low voltage of internal battery (1) | As specified by the manufacturer | MPE |
(1) If applicable
Table 5. Immunity requirements for gas meters containing electronic components:
| Serial No. | Disturbance | Required immunity | Fault limit / test condition (3) |
| :--------- | :----------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------ | :----------------------------- |
| (1) | (2) | (3) | (4) |
| (a) | Damp heat cyclic (condensing) | upper temperature, specified 93 % relative humidity | ½ MPE / NSFa |
| (b) | Vibrations (random) | total frequency range: 10 Hz – 150 Hz total RMS level: 7 m.s-2 ASD level 10 Hz–20 Hz: 1 m2.s-3 ASD level 20 Hz–150 Hz: –3dB/octave | ½ MPE / NSFa |
| (c) | Mechanical shock | 50 mm | ½ MPE / NSFa |
| (d) | Radiated radio frequency, electromagnetic fields | 10 V/m, up to 3 GHz | MPE / NSFd |
| (e) | Conducted (common mode) currents generated by radio frequency electro magnetic fields | 10 V (e.m.f.), up to 80MHz | MPE / NSFd |
| (f) | Electrostatic discharges | 6 kV contact discharge 8 kV air discharge | ½ MPE / NSFa+d |
| (g) | Bursts (transients) on signal, data and controllines | Amplitude 1 kV Repetition rate 5 kHz | ½ MPE / NSFd |
| (h) | Surges on signal, data and control lines | unsymmetrical lines: line to line 0.5 kV line to ground 1.0 kV symmetrical lines: line to line NA line to ground 1.0 kV shielded input/ output and communication lines: line to line NA line to ground 0.5 kV | ½ MPE / NSFd |
| :-- | :------------------------------ | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :----------------- |
| (i) | AC mains voltage dips and short interruptions (1) | ½ cycle 0 % 1 cycle 0 % 10/12(2) cycles 40 % 25/30(2) cycles 70 % 250/300 (2) cycles 80 % | ½ MPE / NSFd |
| (j) | DC mains voltage dips and short interruptions (1) | 40 % and 70 % of the rated voltage during 0.1 s and 0% of rated voltage during 0.01 s | ½ MPE / NSFd |
| (k) | Bursts (transients) on AC and DC mains | Amplitude 2 kV Repetition rate 5 kHz | ½ MPE / NSFd |
| (l) | Surges on AC and DC Mains | line to line 1.0 kV line to ground 2.0 kV | ½ MPE / NSFa+d |
| (m) | Ripple on DC mains power (1) | 2 % of nominal DC voltage | ½ MPE / NSFd |
(1) If applicable
(2) For 50 Hz/ 60 Hz respectively
(3)NSFa: No significant fault shall occur after the disturbance.
NSFd: No significant fault shall occur during the disturbance.
Tests specified in serial number (e) (g) and (h) are not applicable for non-mains connected gas meters.
Tests mentioned in serial number in (k) and (l) are not applicable, if meter is not connected by AC or DC mains.
5. Technical requirements.-
(1) Construction,-
(i) Materials,-
A gas meter shall be made of such materials and be so constructed to withstand the physical, chemical and
thermal conditions to which it is likely to be subjected and to correctly fulfill its intended purposes
throughout its life;
(ii) Soundness of cases,-
The case of a gas meter shall be gas-tight as specified according to national or international standards and
requirements concerning safety and at least up to 1.5 times of the maximum working pressure of the gas
meter. If a meter is to be installed in the open air it shall be impermeable to run-off water;
(iii) Condensation and climate provisions,-
The manufacturer may incorporate devices for the reduction of condensation, where condensation may
adversely affect the performance of the device;
(iv) Protection against external interference,-
A gas meter shall be constructed and installed in such a manner that mechanical interference capable of
affecting its accuracy is either prevented, or results in permanently visible damage to the gas meter or to the
verification marks or protection marks;
(v) Indicating device,-
The indicating device can be connected to the meter body physically or remotely. In the latter case the data to
be displayed shall be stored in the gas meter;
Note: There shall be provisions to access the data for customers and consumers.
(vi) Safety device,-
The gas meter shall be equipped with a safety device that shuts off the gas flow in the event of calamities,
such as an earthquake or a fire. A safety device shall be connected to the gas meter, provided that it does not
influence the metrological integrity of the meter.
A mechanical gas meter equipped with an earthquake sensor plus an electrical powered valve is not
considered to be an electronic gas meter;
(vii) Connections between electronic parts,-
Connections between electronic parts shall be reliable and durable;
(viii) Components,-
Components of the meter may only be exchanged without re-verification if the model approval establishes
that the metrological properties and especially the accuracy of the meter are not influenced by the exchange
of the components concerned [see clause (vi) of sub-paragraph (13) of paragraph 4]. Such components shall
be identified by the manufacturer by their own unique part numbers or identifiers.
Note: These components shall be marked with the model of the meter to which they may be attached and
may require exchange.
(ix) Zero flow,-
The gas meter totalisation shall not change when the flow rate is zero and the installation conditions are free
from flow pulsations.
Note: This requirement refers to stationary operating conditions. This condition does not refer to the
response of the gas meter to changed flow rates.
(2) Flow direction,-
(i) Direction of the gas flow,-
On a gas meter where the indicating device registers positively for only one direction of the gas flow, this
direction shall be indicated by a method which is clearly understood, e.g. an arrow. This indication is not
required if the direction of the gas flow is determined by the construction;
(ii) Plus and minus sign,-
The manufacturer shall specify whether or not the gas meter is designed to measure bi- directional flow. In
the case of bi-directional flow a double-headed arrow with a plus and minus sign shall be used to indicate
which flow direction is regarded as positive and negative respectively;
(iii) Recording of bi-directional flow,-
If a meter is designed for bi-directional use, the quantity of gas passed during reverse flow shall either be
subtracted from the indicated quantity or be recorded separately. The maximum permissible error shall be
met for both forward and reverse flow;
(iv) Reverse flow,-
If a meter is not designed to measure reverse flow, the meter shall either prevent reverse flow, or it shall
withstand incidental or accidental reverse flow without deterioration or change in its metrological properties
concerning forward flow measurements;
(v) Indicating device,-
A gas meter may be provided with a device to prevent the indicating device from functioning whenever gas
is flowing in an unauthorised direction.
(3) Indicating device,-
(i) General provisions,-
The indicating device associated with the gas meter shall indicate the quantity of gas measured in volume or
mass in the corresponding units. The reading shall be clear and unambiguous.
The indicating device may be,-
(a) a mechanical indicating device as specified in clause (iv) of sub-paragraph (3) of paragraph 5;
(b) an electromechanical or electronic indicating device as specified in clause (v) of sub-paragraph (3) of
paragraph 5;
(c) a combination of (a) and (b).
Indicating devices shall be non-resettable and non-volatile i.e. they shall be able to show the last stored
indication after the device has recovered from an intervening power failure.
Where the indicating device shows decimal submultiples of the quantity measured, this fraction shall be
separated from the integer value by a clear decimal sign.
It may be possible to use one display for other indications as well, as long as it is clear which quantity is
being displayed.
(ii) Indicating range,-
The indicating device shall be able to record and display the indicated quantity of gas corresponding to at
least 1000 hours of operation at the maximum flow rate Qmax, without returning to the original reading.
(iii) Resolution,-
The quantity corresponding to the least significant digit shall not exceed the quantity of gas passed during
one hour at Qmin.
If the least significant digit (e.g. last drum) shows a decimal multiple of the quantity measured, the face plate
or electronic display shall bear:
(a) either one or two, or three, etc. fixed zero after the last drum or digit; or
(b) the marking: "× 10" or "× 100", or "× 1000", etc.,
so that the reading is always in the units specified in sub-paragraph (1) of paragraph 3.
(iv) Mechanical indicating device,-
The minimum height of the numerals shall be 4.0 mm and their minimum width shall be 2.4 mm.
The last element (i.e. the decade with the least significant scale interval) of a mechanical indicating device
may deviate in manner of display from the other decades.
In the case of drum indicating devices, the advance by one unit of a figure of any order shall take place
completely while the figure of an order immediately below passes through the last tenth of its course;
(v) Electromechanical or electronic indicating device,-
The continuous display of the quantity of gas during the period of measurement is not mandatory.
The electronic indicating device shall be provided with a display test;
(vi) Remote indicating device,-
If an indicating device is used remotely, the associated gas meter shall be clearly identified.
The integrity of the communication between the instrument and the indicating device shall be checked.
Note: The serial number of the associated gas meter can be used for a clear identification.
(4) Test element,-
(i) General,-
A gas meter shall be designed and constructed incorporating the following, namely:-
(a) an integral test element; or
(b) a pulse generator; or
(c) arrangements permitting the connection of a portable test unit.
(ii) Integral test element,-
The integral test element may consist of the last element of the mechanical indicating device in one of the
following forms, namely:-
(a) a continuously moving drum bearing a scale, where each subdivision on the drum is regarded as an
increment of the test element;
(b) a pointer moving over a fixed dial with a scale, or a disk with a scale moving past a fixed reference
mark, where each sub-division on the dial or disk is regarded as an increment of the test element. On the
numbered scale of a test element the value of one complete revolution of the pointer shall be indicated in
the form: "1 revolution = m3 or kg or ……<unit>". The beginning of the scale shall be indicated by the
figure zero.
The scale spacing shall not be less than 1 mm and shall be constant throughout the whole scale.
The scale interval shall be in the form 1 × 10n, 2 × 10n, or 5 × 10n m3 or kg or ……<unit> (n being a
positive or negative whole number or zero).
The scale marks shall be fine and uniformly drawn.
With an electronic indicating device the last digit is used as the integral test element. Through either
physical or electronic means, a specific test mode may be entered in which the number of digits may be
increased or some alternative method may be applied for gaining resolution.
If applicable to the gas meter, the test element shall allow the experimental determination of the cyclic
volume. The difference between the measured value of the cyclic volume and its nominal value shall not
exceed 5 % of the latter at reference conditions;
(iii) Pulse generator,-
A pulse generator may be used as a test element if the value of one pulse, expressed in units of volume or
mass, is marked on the gas meter.
The gas meter shall be constructed in such a way that the pulse value can be checked experimentally. The
difference between the measured value of the pulse value and its value indicated on the gas meter shall not
exceed 0.05 % of the latter;
(iv) Attachable test device,-
An indicating device may include provisions for testing by inclusion of complementary elements (e.g. star
wheels or discs), which provide signals for an attachable test device.
The attachable test device may be used as a test element if the value of one pulse, expressed in units of
volume or mass, is marked on the gas meter;
(v) Increment of test element or pulse,-
The increment of the test element or pulse shall occur at least every 60 seconds at Qmin.
(5) Ancillary devices,-
(i) General,-
The gas meter may include ancillary devices, which may be permanently incorporated or added temporarily.
Examples of applications are,-
(a) flow detection before this is clearly visible on the indicating device;
(b) means for testing, verification and remote reading;
(c) prepayment;
Ancillary devices shall not affect the correct operation of the instrument. If an ancillary device is not subject
to legal metrology control this shall be clearly indicated;
(ii) Protection of drive shafts,-
When not connected to an attachable ancillary device, the exposed ends of the drive shaft shall be suitably
protected;
(iii) Torque overload,-
The connection between the measuring transducer and the intermediate gearing shall not break or alter if a
torque of three times the permissible torque as indicated in sub-clause (b) of clause (iii) of sub-paragraph (1)
of paragraph 6 and sub-clause (c) of clause (iii) of sub-paragraph (1) of paragraph 6 is applied.
(6) Power sources,-
(i) Types of power sources,-
Gas meters may be powered by the following, namely:-
(a) mains power sources;
(b) non-replaceable power sources; or
(c) replaceable power sources.
These three types of power source may be used alone or in combination.
Note: For the purpose of this part, rechargeable power sources are considered replaceable.
(ii) Mains power,-
An electronic gas meter shall be designed to ensure that in the event of a mains power failure (AC or DC),
the meter indication of the quantity of gas just before failure is not lost, and remains accessible for reading
after failure without any difficulty.
Any other properties or parameters of the meter shall not be affected by an interruption of the electrical
supply.
Note: Compliance with this requirement will ensure that the gas meter will continue to register the quantity
of gas that passed through the gas meter during a power failure (may be through a mechanical assembly).
The connection to the mains power source shall be secured from tampering.
(iii) Non-replaceable power source,-
The manufacturer shall ensure that the indicated lifetime of the power source guarantees that the meter
functions correctly for at least as long as the operational lifetime of the meter which shall be marked on the
meter or, alternatively, the remaining battery capacity in units of time can be presented on the electronic
indicating device.
(iv) Replaceable power source,-
If the instrument is powered by a replaceable power source, the manufacturer shall give detailed
specifications for the replacement thereof.
The date by which the power source is to be replaced shall be indicated on the meter. Alternatively, the
estimated remaining life of the power source shall be displayed or a warning shall be given when the
estimated remaining life of the power source is 10% or below.
The properties and parameters of the meter shall not be affected during replacement of the power source.
It shall be possible to replace the power source without breaking the metrological seal.
The compartment of the power source shall be capable of being secured from tampering.
(7) Checks, limits and alarms for electronic gas meters,-
(i) Checks,-
An electronic gas meter is required to check,-
(a) the presence and correct functioning of transducers and critical devices;
(b) the integrity of stored, transmitted and indicated data; and
(c) the pulse transmission (if applicable).
Note: Pulse transmission checks focus on missing pulses, or additional pulses due to interference.
Examples are double pulse systems, three-pulse systems or pulse timing systems.
(ii) Limits,-
The gas meter may also have the capability to detect and act upon:
(a) overload flow conditions;
(b) measurement results that are outside the maximum and minimum values of the transducers;
(c) measured quantities that are outside certain pre-programmed limits; and
(d) reverse flow.
If the gas meter is equipped with limit detection, the correct functioning shall be tested during the type
evaluation.
(iii) Alarms,-
If malfunctions are registered while checking the items as indicated in clause (i) of sub-paragraph (7) of
paragraph 5 or if the conditions as indicated in clause (ii) of sub-paragraph (7) of paragraph 5 are
detected, the following actions shall be performed, namely:-
(a) a visible or audible alarm or both, which remains present until the alarm is acknowledged and the
cause of the alarm is suppressed;
(b) continuation of the registration in specific alarm registers (if applicable) during the alarm, in which
case default values may be used for the pressure, temperature, compressibility, or density; and
(c) registration in a log (if applicable).
(8) Software,-
The requirements concerning the software applied in the gas meters are made in the mandatory Annexure I.
6. Inscriptions.-
(1) Markings and inscriptions,-
All markings shall be easily legible and indelible under rated conditions of use.
Any marking other than those prescribed in the model approval document shall not lead to confusion.
The following information shall be marked on the casing or on an identification plate. Alternatively, the markings
presented with an asterisk (*) shall be made visible via the electronic indicating device in a clear and unambiguous
manner.
(i) The following shall be the general applicable markings for gas meters, namely:-
(a) Model approval mark (according to Rules);
(b) Name or trade mark of the manufacturer;
(c) Model designation;
(d) Serial number of the gas meter and its year of manufacture;
(e) Accuracy class;
(f) Maximum flow rate Qmax= … <SI unit>;
(g) Minimum flow rate Qmin= … <SI unit>;
(h) Transition flow rate Qt = … <SI unit> (*);
(i) Gas temperature range and pressure range for which the errors of the gas meter shall be within the limits of
the maximum permissible error shall be expressed as:
tmin – tmax= … - … <SI unit> (*);
pmin– pmax= … - … <SI unit> (*);
(j) The density range within which the errors shall comply with the limits of the maximum permissible error
may be indicated and shall be expressed as:
ρ = … - … <SI unit> (*)
This marking may replace the range of working pressures unless the working pressure marking refers to a built-
in conversion device;
(k) Pulse values of HF and LF frequency outputs (imp/<SI unit>, pul/<SI unit>, <SI unit>/imp) (*);
Note: The pulse value is given to at least six significant figures, unless it is equal to an integer multiple or
decimal fraction of the used unit.
(l) Character V or H, as applicable, if the meter can be operated only in the vertical or horizontal position;
(m) Indication of the flow direction, e.g. an arrow (if applicable, see clause (i) of sub-paragraph (2) of paragraph
5 and clause (ii) of sub-paragraph (2) of paragraph 5;
(n) Character M, as applicable, if the meter is designed only to be installed in piping arrangements where only
mild flow disturbances may occur;
(o) Measurement point for the working pressure according to clause (iv) of sub-paragraph (1) of paragraph 9;
and
(p) Environmental temperatures, if they differ from the gas temperature as mentioned in sub-clause (i) of clause
(i) of sub-paragraph (1) of paragraph 6(*).
(ii) Additional markings for gas meters with a built-in conversion device having only one indicating device shall
include the following, namely:-
(a) Base temperature tb= … <SI unit> (*);
(b) Base pressure pb=.... <SI unit> (if applicable) (*);
(c) Temperature tsp= … <SI unit> specified by the manufacturer according to clause (v) of sub-paragraph (3) of
paragraph 4 (*).
(iii) Additional markings for gas meters with output drive shafts shall include the following, namely:-
(a) Gas meters fitted with output drive shafts or other facilities for operating detachable additional devices shall
have each drive shaft or other facility characterised by an indication of its constant (C) in the form “1 rev = …
<SI unit>” and the direction of rotation (“rev” means “revolution”);
(b) If there is only one drive shaft the maximum permissible torque shall be marked in the form “Mmax = …
N.mm”;
(c) If there are several drive shafts, each shaft shall be characterized by the letter M with a subscript in the form
“M1, M2, …Mn”;
(d) The following formula shall appear on the gas meter:
k1M1 + k2M2 + … + knMn≤ A N.mm;
where:
A is the numerical value of the maximum permissible torque applied to the drive shaft with the highest constant,
where the torque is applied only to this shaft; this shaft shall be characterized by the symbol M1,
ki (i= 1, 2, … n) is a numerical value determined as follows: ki = C1 / Ci,
Mi (i= 1, 2, … n) is the torque applied to the drive shaft characterized by the symbol Mi,
Ci (i= 1, 2, … n) represents the constant for the drive shaft characterized by the symbol Mi.
(iv) Additional markings for gas meters with electronic devices shall include the following, namely:-
(a) For an external power supply: the nominal voltage and nominal frequency;
(b) For a non-replaceable power source: the operational lifetime of the measuring device or, alternatively, the
remaining battery capacity in units of time can be specified on the electronic indicating device (*);
(c) For a replaceable battery: the latest date by which the battery is to be replaced or, alternatively, the remaining
battery capacity shall be specified on the electronic indicating device (*);
Note: In case an automatic alarm indicates when the battery life is below 10 %, the above markings are not
required.
(d) Software identification of the firmware (*).
7. Operating instructions.-
(1) Instruction manual,-
Unless the simplicity of the measuring instrument makes this unnecessary, each individual instrument shall be
accompanied by an instruction manual for the user.
However, groups of identical measuring instruments delivered to the same customer do not necessarily require
individual instruction manuals.
The instruction manual shall be in English language (in addition to English language, Hindi in Devanagri script or
other Indian regional languages may be used).
The manual shall include the following, namely:-
(a) an operating instructions;
(b) maximum and minimum storage temperatures;
(c) rated operating conditions;
(d) warm-up time after switching on the electrical power (if applicable);
(e) all other relevant mechanical and electromagnetic environmental conditions;
(f) a specification of the required voltage (-range) and frequency (-range) for instruments powered by an external
power source;
(g) any specific installation conditions, for instance a limitation of the length of signal, data and control lines;
(h) if applicable, the specifications of the battery;
(i) instructions for installation, maintenance, repair, storage, transport and permissible adjustments (this can be in a
separate document, not intended for the user or owner); and
(j) conditions for compatibility with interfaces, sub-assemblies (modules) or other measuring instruments.
(2) Installation conditions,-
The manufacturer shall specify the installation conditions (as applicable) with respect to the following, namely:-
(a) the position to measure the working temperature of the gas;
(b) filtering;
(c) leveling and orientation;
(d) flow disturbances (including minimum upstream and downstream pipe lengths);
(e) pulsations or acoustic interference;
(f) rapid pressure changes;
(g) absence of mechanical stress (due to torque and bending);
(h) mutual influences between gas meters;
(i) mounting instructions;
(j) maximum allowable diameter differences between the gas meter and connecting pipe work;
(k) other relevant installation conditions.
8. Sealing.-
(1) Verification marks and protection devices, -
(i) General provision,-
Protection of the metrological properties of the meter is accomplished via hardware (mechanical) sealing and via
electronic sealing wherever possible.
In any case, memorised quantities of gas measured (volume or mass) shall be sealed to prevent unauthorised
access.
(ii) Verification marks,-
Verification marks indicate that the