A fire due to Pyrophoric FeS happened in H-Oil Vaccum Tower and the fire lasted for around 3 hours with maximum temperature attained at inside skin be 1021F with CS material and 887F with SS405 clad zones. w.r.t. this short period could there be any metallurgical impact so far as spheroidisation or intermatallics embrittlement in CS and SS405 respectively ? regards

Have you noticed any bulges or damages in the vessel shell where fire occured. If no sign of any damages then nothing to worry about it.As Mr.CVS suggested metallography at affected portion will gretaly help to assess the damage.In general the pyrophoric material will get accumulated in the packing zone. Kmno4 washing before after shutdown and before opening the manway will avoid such incident. regards,

Debasis Your question is addressed to Krish. Yet from the point of investigation and likely establishing cause i give my views. For in-situ metallography grit-blast is not required. Regular grinding and polishing will do. In fact, if any surface deformity and changes in structure had occurred, as it appears likely from your question, this has to be examined fully, i.e., as is where is for any surface deformity and micro-structural changes at the surface. Grit blasting may not help this. If top dome and walls are affected with bulging and definite surface damages. examine the reasons how internal pressure build up could have occurred for a pressure shell. Suggest to take a detailed diametral measurement and ascertain the diametral changes (profile mapping of diametral changes) and calculate how much internal pressure build-up that could have caused the bulging and surface damages. Metallography also should throw enough light on the structural changes. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India March 17, 2008 E-mail: nishi@vsnl.com >Dear Krish, >Top Dome and walls are most affected. Do U feel doing grit >blasting before n-situ metllography is a good practise as it >deforms a definite surface layer or u will prefer light >grinding/ buffing ? >regards