Gas quality is measured by the following standards:

  • ISO 6326 Natural gas - Determination of sulphur compounds;
  • ISO 6327 Gas analysis - Determination of the water dew point of natural gas;
  • ISO 6974 Natural gas - Determination of composition and associated uncertainty by gas chromatography;
  • ISO 6976 Natural gas – Calculation of calorific values, density, relative density and Wobbe index from composition;
  • ISO 12148 Natural gas – Calibration of chilled mirror type instruments for hydrocarbon dewpoint;
  • LVS EN ISO 11541 Natural gas – Determination of water content at high pressure.

Parameters of natural gas to be input into transmission and storage system:

No. Parameter Unit Standard, verification method
1

Heat of combustion (higher and lower)

at standard conditions P=101.325 kPa,
t=+25/0 0C (combustion/measurement)

 kWh/m3 LVS EN ISO 6976
2

Wobbe index at standard conditions

P=101.325 kPa,
t=+25/0 0C (combustion/measurement)

 kWh/m3 LVS EN ISO 6976
3 Hydrogen sulphide mass concentration mg/m3 ISO 6326
4 Mercaptan sulphur mass concentration mg/m3 ISO 6326
5 Mass of mechnical admixtures g/m3 LVS 459 
6

Density at standard conditions

P=101.325 kPa, t=0 0C

 kg/m3 LVS EN ISO 6976
7 Relative density   LVS EN ISO 6976
8 Composition, molar fraction mol % LVS EN ISO 6974
9 Methane mol % LVS EN ISO 6974
10 Ethane mol % LVS EN ISO 6974
11 Propane mol % LVS EN ISO 6974
12 Butane and higher hydrocarbons mol % LVS EN ISO 6974
13 Oxygen mol % LVS EN ISO 6974
14 Carbon dioxide mol % LVS EN ISO 6974
15 Nitrogen mol % LVS EN ISO 6974
16 Water dew point temperature at absolute pressure 3.92 Mpa  0C LVS EN ISO 11541:2003
17 Hydrocarbon dew point temperature at absolute pressure 2.5 to 7.5 Mpa  0C ISO 12148