Gas group as per IP 15 hazardous area classification

[ttv78]

thread238-103548
Dear all,

Can you please clarify me on the following on hazardous area classification :

1) I have a gas mixture with 90% methane and other hydrocarbons for the balance of % and a small portion of hydrogen sulphide.

If it is pure methane I can classify as gas group iia. However, as per ip 15, when there is a mixture, the most onerous one is to be considered for subgroup.

Please clarify if I should use II B classification instead of II A.

With best regards,

Vijay

 

[DRWeig]

Please clarify if I should use II B classification instead of II A

I have a gas mixture with 90% methane and other hydrocarbons

It depends on what those other hydrocarbons are, and what concentrations. We can't tell from here. Get a good assay and decide which mixture will be the first to explode in the presence of an ignition source as air is added to your mixture. Then decide which will be first to explode in the presence of an ignition source as your mixture is added to pure air. Some engineering judgement will be required to decide if either case is unlikely enough to warrant exclusion.

If it's common utility natural gas that comes in the pipeline to my house here in Georgia (US), it's group IIA. The heavy things have been scrubbed to the greatest extent economically possible.



Best to you,

Goober Dave

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[juleselec]

It'll most likely depend on the concentration of H2S, which is a IIB T3 material and probably more onerous than the long chain hydrocarbons in your gas mixture (e.g. C7+, C9+, etc). If you are talking trace elements, then it's probably not worth taking it into account.