Saver2008
Mechanical
- Oct 14, 2008
- 112
Hi!
I have the following problem:
1.- I have an horizontal cylindrical vessel with following thicknesses in body and heads and nozzles: 3/4", 1-1/2", 2". Material: SA-516-70 Killed. This equipment will be PWHT performed. The vessel is completely welded (circumferential and longitudinal welds are already done...like 1 month ago).
Client´s specification indicates me the following:
" A) Welded joints greater than 1 1/2 inches (38 mm) in thickness that require PWHT shall be heat treated immediately upon completion of welding. The joint shall not be allowed to cool below 300ºF (150ºC) prior to PWHT. A the weld and adjacent metal may be heated to 600ºF (315ºC), wrapped with insulation, and allowed to cool. PWHT may then be performed later.
B) For welded joints less than or equal to 1½ inches (38 mm) in thickness that require PWHT, the requirements of Paragraph A) are preferred. Alternatively, the joint may be permitted to cool prior to PWHT if the joint is 100 percent radiographed after completion of PWHT. "
Reason to meet paragraph A) and/or B) is due to dehydrogenation process, I mean, to perform a dehydrogenation heat treatment (eliminate residual hydrogen in the weld)
The situation here is when we welded body courses and nozzles, we did not performed the A) and B) paragraphs. We expect that during PWHT on complete body (PWHT will be performed within a furnace), residual hydrogen in the weld dissapears or be eliminated; but we are not sure.
Can you help me if our idea of PWHT can work for an non-realized DHT? What other option do I have?
Thank you very much
Roland
I have the following problem:
1.- I have an horizontal cylindrical vessel with following thicknesses in body and heads and nozzles: 3/4", 1-1/2", 2". Material: SA-516-70 Killed. This equipment will be PWHT performed. The vessel is completely welded (circumferential and longitudinal welds are already done...like 1 month ago).
Client´s specification indicates me the following:
" A) Welded joints greater than 1 1/2 inches (38 mm) in thickness that require PWHT shall be heat treated immediately upon completion of welding. The joint shall not be allowed to cool below 300ºF (150ºC) prior to PWHT. A the weld and adjacent metal may be heated to 600ºF (315ºC), wrapped with insulation, and allowed to cool. PWHT may then be performed later.
B) For welded joints less than or equal to 1½ inches (38 mm) in thickness that require PWHT, the requirements of Paragraph A) are preferred. Alternatively, the joint may be permitted to cool prior to PWHT if the joint is 100 percent radiographed after completion of PWHT. "
Reason to meet paragraph A) and/or B) is due to dehydrogenation process, I mean, to perform a dehydrogenation heat treatment (eliminate residual hydrogen in the weld)
The situation here is when we welded body courses and nozzles, we did not performed the A) and B) paragraphs. We expect that during PWHT on complete body (PWHT will be performed within a furnace), residual hydrogen in the weld dissapears or be eliminated; but we are not sure.
Can you help me if our idea of PWHT can work for an non-realized DHT? What other option do I have?
Thank you very much
Roland