Johnasian You are governed by piping code for PWHT for Carbon steel. (ASA B 31.3) Piping code for this thickness strictly may not require PWHT for 32" line. Since you have observed crack at the root weld, detected by RT, you have to repair from root. PWHT cannot be done in a compartmental way for only repaired area of the weld. This will generate undue stresses at some other locations. The entire weld has to be given PWHT for carbon steel. Piping code PWHT sequence of heating, holding, and cooling cycle will have to be followed after you repair the cracks and re-radiography is successful. For carbon steel, heat to 620 * or - 10 deg cent, hold for 1 hr and cool upto 350 deg cent at 100 per hr and still air cool the entire weld Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Feb 21, 2010 E-mail: nishi@vsnl.com >I would like to request some opinion regarding below; > >- We have 32" x 22mm thk CS Pipe. RT has been carried-out >after PWHT and crack indication was found in the root. We >will repair this defect and RT again. > >- My query is; >1. Do we need to re-PWHT the entire weld or only the >repaired area. >2. Is there any code that covers the re-PWHT conditions? >3. How many time can we re-PWHT a certain joint. > >Thanks!