Hi Experts, Please advise if Pre-he Hi Experts, Please advise if Pre-he WeldEngr2016 (Mechanical) (OP) 8 May 16 07:16 Hi Experts, Please advise if Pre-heat is must for a wall thickness of 37mm and plate grade is A387 gr22. What technique of pre-heat can be applied by a pipe mill. The final pipe is A691 cl-22. RE: Hi Experts, Please advise if Pre-he Duwe6 (Industrial) 9 May 16 00:20 Usually YES. What Code are you working to? That usually makes a difference. RE: Hi Experts, Please advise if Pre-he weldstan (Materials) 9 May 16 20:00 If A-691 does not address preheat, the pipe mills's preheat will be established by the welding procedure and its procedure qualification record. RE: Hi Experts, Please advise if Pre-he racookpe1978 (Nuclear) 11 May 16 14:04 If that pipe mill is actually "welding" pipe after it is rolled and axially welded and treated, and not just forming its pipe. The initial fabrication and metallurgy of the pipe itself is not addressed by the PWHT requirements of weld fabrication after it becomes "pipe" and is shipped. The post-fabrication metallurgy and crytal structure of "pipe" and its welds and its fittings are all intended to protect and preserve that initial metallurgy established by the mill before shipping.