[MW:10993] RE: Stress Relieving

Abhishek,

 

You 're certainly familiar, that any PWHT operation consists of heating cycle, soaking/holding cycle and cooling cycle. Holding cycle, i.e temperature and time are  most important. Any prolonged exposure at this temperature range may harm materials properties(especially hardness and notch toughness).If the power is back within a short while, while the material is in the soaking/holding range, then it's not a major issue.

 

If the PWHT had to be called offor abandoned before the soaking cycle (i.e interruption happened during heating) it may not have major adverse effect on materials. However calling off PWHT within the soak cycle or in the cooling cycle (past soaking) and with multiple repeat should be carefully assessed. 

 

For a dissimilar material combination (P1=P4, P1= P5) , depending on the design code the recommended PWHT temperature would exceed the leaner one (P1).Hence multiple soaking at the PWHT temperature range could cause appreciable drop of mechanical properties of P1 material (especially toughness and hardness).

 

If there're any data available on simulated PWHT on these materials  this would help.

 

If you look in AWS D-10.10-1999, clause 12.6 addresses this issue, but the answer is subjective.

B-31.3, calls for thermocouples to be attached during PWHT:

Clause  331.1.6: Temperature Verification. Heat treatment temperature shall be checked by thermocouple pyrometers or other suitable methods to ensure that the WPS requirements are met. See para. 330.1.3(b) for attachment of thermocouples by the capacitor discharge method of welding

 

Hope this would clarify your query.

 

Thanks.

 

Pradip Goswami,P.Eng.IWE

Welding & Metallurgical Specialist & Consultant

Ontario,Canada.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

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From: ABHISHEK GHOSH [mailto:ghoshabhishekmech@gmail.com]
Sent: Friday, May 06, 2011 4:40 PM
To: materials-welding@googlegroups.com
Cc: pgoswami@sympatico.ca; pgoswami@quickclic.net
Subject: Stress Relieving

Dear All,

 

During PWHT ( SR ) at site , any time SR can be interrupted due to power failure, may be sometimes for rain, SR is stopped ..How many times we can make Re SR for A 106 Gr B?what to do with Sa 335 P5, P9 , P11 pipes???

 

In B 31.3 where no of thermocouples to be used is mentioned ??

 

Regards.

 

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ABHISHEK GHOSH
FAHAHEEL, KUWAIT
MOB: (00)965-60303798