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nadfourchon (Petroleum) (OP)
31 Jan 12 10:24
We are welding stainless steel pipe (316 to 316, 316L to 316L or Duplex to Duplex). Our normal sizes range from 3" to 4" OD and wall thickness ranging from .250" to .600" thick. During the welding of these pipes it has taken us up to 8 hours using GTAW process due to not exceeding our WPS maximum interpass temperature. Is there any acceptable means of slightly accelerated cooling once the max interpass temperature has been reached? I am only looking to maintain my WPS preheat to maximum interpass temperature without waiting for the weld to reach near preheat temperature, in normal still air, before the next pass.  Is cooling with forced air, between passes, by way of fan or air line acceptable?
My parameters for 316 & 316L are 146F Preheat to 285F Max Interpass and for Duplex 100F Preheat to 225F Max Interpass.   
metengr (Materials)
31 Jan 12 11:37

Quote:

Is there any acceptable means of slightly accelerated cooling once the max interpass temperature has been reached? I am only looking to maintain my WPS preheat to maximum interpass temperature without waiting for the weld to reach near preheat temperature, in normal still air, before the next pass.

Yes, using forced air to cool is permitted between passes.  
nadfourchon (Petroleum) (OP)
31 Jan 12 11:40
Is there any ASME or API document that I can reference when questioned by my customer representative or third party inspector?
metengr (Materials)
31 Jan 12 11:53
nadfourchon;
There is nothing in ASME Section IX to address your issue because this is a process detail. Keep in mind the austenitic stainless steel and duplex grades you are welding are not considered to be air hardenable steels. So, cooling rate during welding is not considered an essential variable. You need to convince your client that this material is not air hardenable, and forced cooling has little to no effect on welding and base metal performance.
 

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