BS ISO 23978-2020 Natural gas – Upstream area – Determination of composition by Laser Raman spectroscopy.
7.2 Calibration
7.2.1 CalIbration frequency
Calibration should be carried out when experimental conditions were changed, And it should be recalibrated according to the needs of the user.
7.2.2 Calibration procedure
Connect the calibration gas with the analyser according to Figure 2. Adjust the input pressure and temperature to a stable condition. Sweep the analyser with the gas flow for at least 2 mm.
After the sulfur-containing calibration gas is injected, it should go through the absorption solution before it is vented
7.2.3 Zero calibration
According to 7.2.2. connect zero gas with the analyser, start calibration, update the background when
the signal values are stable.
7.2.4 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-i to 3).
7.2.5 Working span calibration
Using ISO 11095. the user shall choose the calibration method depending on the analytical accuracy that is required. The following are candidate methods and their requirements:
— bracketing calibration: the difference between calibration gas and analytical result should be less than relatively 20 %;
— response formula simulation: no less than three calibration gas should be used to cover the analytical range;
— one point calibration: the difference between calibration gas and analytical result should be less than relatively 20 %.
If the method is used to monitor fixed natural gas source, one point calibration or bracketing calibration should be applied, lithe method is used to analyse a non-constant natural gas source, response formula simulation should be applied.
7.3 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.