BS ISO 23978:2020 pdf free.Natural gas – Upstream area – Determination of composition by Laser Raman spectroscopy.
BS ISO 23978 Zero gas Pure argon or other monatomic gas is used to set the zero level of the Raman analyser. The purity
should not be less than 9999 %. Base span calibration gases.Base span calibration gas used to set software parameters shall be working standard pure gases or binary mixtures in accordance with ISO 6142-1, ISO 6144 or with ISO 6145. Binary gas mixtures
consisting of blending zero gas and a single gas component present in natural gas are preferred when their typical concentrations in natural gas are below 75 %. For typical natural gas upstream area samples, 1 % H2S/Ar, 5 % CO2/Ar, 3 % N2/Ar, 3 % C3H8/Ar, 2 % C2H6/Ar, are suggested. As base span calibration gases for all but CH4 which can be pure (100 %) or Ar diluted.  Working span calibration gases.Regular calibration shall perform using working standard gas mixtures in accordance with ISO 6142-1,ISO 6144 or with ISO 6145. The working standard gas mixtures shall contain appropriate concentrations and cover the analytic range of the analyser. All components in the reference standard shall be homogenous in the vapour state at the time of use. The concentration of a component in the reference standard gas shall be close to the actual sample gas concentration, shall be less than relatively 20 % of
the corresponding component in the test gas, the minimum concentration shall be greater than 0,02 %.Base span calibration Before sample measurement, base span calibration should be done to overcome the instrument drift caused by temperature, pressure and general electronic fluctuations, and the cross-interference caused by the multiple components in the gas could be maximum eliminated by calibrating the cross-interference factors. According to 7.2.2, connect base span calibration gas to the analyser, start
calibration, observe the signal values, adjust the cross-interference factors till the interference signal to a reasonable value (usually in a range of-1 to 3).Sampling and sample analysis.Connect gas sample, gas pressure regulator, filters, and analyser in sequence adjust pressure and flow to the experimental conditions, start sample analysis, the sample will be automatically measured.Sampling shall be in accordance with ISO 10715.Sulfur-containing sample should go through the absorption solution before it is vented.BS ISO 23978 pdf download.