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I am working in Hydrogen generation unit. In hydrogen export line one Low point drain flange caught fire due to minor leakage of hydrogen but no source of ignition was there. We could not find reason why auto ignition happens without source. If anybody know give some reason.
 
Answers
23/07/2015 A: J Sudeep, SATORP REFINERY, jsudeep81@gmail.com
Similar incidents occur in many industries: static electricity is the first suspect.
18/10/2014 A: JAGAN KHEDEKAR, IOCL, jagankhedekar@gmail.com
Energy required for ignition of hydrogen is only 0.02 MJ. High velocity leaking hydrogen can it self caught fire, due to friction in between gaskets and flanges. Also check if any high temperature steam lines passing near your H2 export line. Damaged insulation on steam lines needs to be replaced.
15/10/2014 A: Keng Chung, Well Resources Inc., kengchung@hotmail.com
Hydrogen is a negative Joule-Thompson gas. When release (leak), it will heat up. Also, you should check the auto ignition temperature of hydrogen mixture (with the surrounding gases), instead of hydrogen alone.
Good luck and be safe!
14/10/2014 A: Dhiren Rindani, Reliance Industries Ltd, dhiren.rindani@ril.com
All gasses when throttled cools down due to joules thompson effect, except for hydrogen and helium which has an inversion temperature lower than room temperature.
Due to reverse joule thompson effect hydrogen and Helium when throttled gets heated up. ( On expansion from higher to lower pressure) and auto ignites.
14/10/2014 A: Hubert Mueller, Bayernoil, guhumueller@web.de
Autoignition in hydrogen service is not so uncommon, especially if the hydrogenstream is very dry and the differential pressure via the leakage is high. The reason is the low conductivity of the hydrogen.