GC - natural gas- calibration

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Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Thursday, October 7, 1999 - 07:29 am:

would like to consult you about the actual meaning of comparing the rates between
two concentrations of a natural gas standard and the areas obtained with the
GC for the corresponding compounds. I suppose it must both results be almost the same if the
calibration of my GC is going OK.
The thing is that I want to know how good is this criteria (assuming that my standard is good)
Are there any other recomendation about the way of doing the calibration.
Thank you very much.
PD: sorry for my english, I need more practise.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By BJenko on Thursday, October 7, 1999 - 09:51 pm:

The most commonly used analytical standard method for the natural gas industry is GPA 2261, available from the Gas Processors Association at their web site http://gasprocessors.com

The precision and accuracy of natural gas composition data and higher heating values calculated from GC data is very good. From my own experience, we routinely got BTU measurements on the same sample better than +/- 2 BTU in the lab. Process GC analyzers for BTU measurements do even better. Try contacting the GPA, and ask if any of their studies of repeatability and reproducibility for their methods is available as a report.

Obviously, the precision and accuracy of the individual components varies somewhat with concentration. If your measurements of Methane in the range of 80-100% on the same sample vary by more than +/- 0.5% on normalized data, your GC may have a problem, a leak at the sample valve for example.

I hope this answers your question, and gives you a good source for more info.

Bill Jenko
Sr. Chemist
Siemens Applied Automation


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