ASME UCS-79 Heat Treatment

[victoredc]

Dear Friends;

I have a doubt with the requirements of heat treatment by UCS-79. When a toriespherical head need to be heat treated as per UCS-79 and the main vessel need postweld heat treatment because of the service* I understand that with the PWHT of the main vessel we already cover the treatment requirements of the head* so we can weld the head untreated and perform the heat treatment after welding. Please let me know if I am wrong.

Thanks in advance

Kind regards

[sharmilasu]

YES
You can consider the heat treatment to the vessel for compliance to UCS-79. Ensure the heat treatment time and temperature meets UCS-56

[techwarrior08]

Yes* overall PWHT of the vessel + head can be performed together even though the intent of doing PWHT is different.
Theoretically speaking* stress relieving is different from PWHT.
Stress relieving (UCS-79) is heat treatment for relieving of stresses due to cold working or excessive bending which causes fibre elongation whereas PWHT is basically done to reduce localised hardness for either service or welding reasons.
But Code treats them under the same case & hence PWHT can be done as per UCS-56.