doing PWHT on material not requiring it by code

[AndyVictor]

Hi, greetings!
Is there any problem if WPS requiring PWHT (say 2hrs @720degC) is used for metal of lesser thickness(say 8mm -not rquiring PWHT)for P4 material. Is there any requirement of minimum value of hardness -will long pwht on small thckness affect its UTS or any other property.

Thanks

 

[unclesyd]

The only problem I see is your temperature of 720°C. Can you comeback with your material and the reason for the high temperature is called out if not a code requirement for your MOC..

Normally there is no problem with PWHT on thinner sections and you can call it a stress relief treatment. A PWHT is done on equipment that will see service in an environment that can cause SCC regardless of thickness.a

 

[AndyVictor]

Thanks, Unclesyd.

The material is A335P11(P No 4). I think the PWHT temp 720 is OK as per code.Also, is there any minimum hardness and max pwht time specified any where after PWHT? Only minimum soaking time and max hardness are seen specified.

 

[Duwe6]

Minimum hardness is not a problem and is figured into the Code-allowable material stress, and can be ignored. Maximum 'soak' time should be 12-hrs or so. 'Creep' is likely at that temp, so extremely long durations are a bad idea. Due to the cost of PWHT time, soak time is usually one chart division beyond the minumum soak time -- typically 1-hr per inch of thickness.

 

[metengr]

If the PWHT is subcritical as in your case at your stated temperature, there will be no harm to the P-No4 base material of lesser thickness (8 mm). The time duration of 2 hours will cause no harm.

 

[AndyVictor]

Thank you all.

It clears my doubt which I was pondering for some time.