800HT piping with no PWHT
800HT piping with no PWHT
(OP)
I need some help in regards to 800HT piping. Last year my company welded several joints in 800HT piping using Inco82 filler 14" SCH..312. Now about ½" from the weld toe in the HAZ the plant is experiencing t/w cracking. The system runs over 1000°f during service. My question is our PQR and WPS for P45 list no PWHT. I am aware of the requirements noted in SEC VIII Div. III for PWHT of 800HT however the code of construction for this job was B31.1 and B31.3. Are we wrong for not PWHT the joints?





RE: 800HT piping with no PWHT
With that said, you have followed the necessary code requirements for piping welds using B31.xx, as applicable. I am speculating that the cause of cracking could be from a fine grained region induced by welding. There are other possibilities - did you induce any cold strain in the piping system where the cracks are observed? This is critical because if so, the location of cold work in this material will result in premature failure from local creep damage.
Here is what I would do - contact Special Metals and consult with one of their materials folks that understands Incoloy 800, 800 HT. They should be able to provide you with technical guidance on this material.
RE: 800HT piping with no PWHT
In regards to cold strain, I am not sure of the conditions at this time. I do know that in the area of cracking the plant washes down the floor with a water hose!! And I can recall see the pipe in services last year glowing red. I trust the pipe didn't get wet at some point form the wash down causing this. The pipe is insulated but poorly.
RE: 800HT piping with no PWHT
Regardless, you still need to contact Special Metals and provide all information on how this pipe material was supplied and welded in the field.
RE: 800HT piping with no PWHT
RE: 800HT piping with no PWHT
I think you mean wall is 0.312" which , I guess is Sch 20 or 30.
RE: 800HT piping with no PWHT