PWHT
PWHT
(OP)
I am in the process of using localized Preheat on a non pressure attachment weld. I am using a manual log to record temp every 15 minutes, until weld is complete. The material is SA 335 P91 9 chrome. This is a pipe support weld, from dummy leg to base plate. I am pretty sure this is a non code weld. However I am wondering if the weld needs to be stress relieved.





RE: PWHT
What exactly is Grade 91, the pipe base material or the non-pressure part attachment? This is NOT a routine weld job because the Grade 91 material is considered an enhanced creep strength material. If and I mean if your pipe base material is Grade 91 you ABSOLUTELY need to PWHT this weld and follow exactly the requirements in ASME B31.1. The Grade 91 can be altered by the use of an improper filler metal and PWHT. Do you have a qualified welding procedure for this Grade of material????
RE: PWHT
RE: PWHT
The requirements for PWHT would be dictated by the pressure boundary base material. Since Grade 91 is a non pressure part attachment and you are welding to a carbon steel base plate (non-pressure part), I would butter the Grade 91 first, with an E9018 B3, PWHT the Grade 91 pressure part per Section I, and then weld the buttered part to the carbon steel header directly using E9018 B3.
However, why would you use Grade 91 in this application? It is not necessary.
RE: PWHT
RE: PWHT
RE: PWHT
RE: PWHT
That is what I was afraid would happen. I will pass this information on during my next quality meeting.
Thanks.
RE: PWHT
If you are using E9018B9 as the filler metal, which is what the procedure calls out, in that case you have to PWHT to avoid cracking in heat affected zone. If heat treatment is impracticable and your welding is in a non-pressure part, and fillet weld is not wider than 6mm, in that case you can use high nickel electrodes such as inconel 182 as filler metal without the need of posterior PWHT.
Hope it helps
Luis