My vessel heads requires heat treatment, UG-79d state "shall be heat treated subsequently". If the vendor proposed the heat treatment after completion the whole vessel approx. 3 to 4 month, is this as per code requirement.

Thanks,
Gilbert

Gilbert,

Understand that you refer to UCS 79 (d).

"shall be Heat treated Subsequently" means heat treatment subsequent to forming operation and this can also be done along with the complete equipment.

This is infact advisable and economical to heat treat the heads along with the complete vessel in case equipment also require heat treatment due to process and/ or code requirements. You unnecessarily avoid two cycles of heat treatment for the heads in such cases.

You need to be however careful if normalizing is required for the heads as per user requirement. Since you are probably not going to normalize the complete equipment, heads to be normalized before welding the same to the shell.

Regards

Sanjeev

Gilbert,

Adding to Sanjeev's post..... the heat treatment called for in UCS-79 can should more accurately be termed as PFHT ("post forming heat tratment") This is strictly speaking different from PWHT refered by Code which may be mandated by process (example- in caustic service) or by Code requirements.

-jehan

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My stand is that one question should be answered prior to the post---what's the geometry of the formed head and what material? Whatever, in case the ratio of thx to diameter exceeds certain No., heat treatment for stress release should be followed "subsequentially", otherwise the probability of crack on the welding root or HAZ will be increased greatly, combined with "subsequential" welding stress the head. I have witnessed several corresponding crack cases in the past.