Hello.

The entries in brackets belwo, are my comments. Please comment on them.

UCS-79 states that heat treatment (PWHT) is required for vessel shell sections, heads and other pressure parts of carbon and alloy steel, provided
- they are cold formed,
- they are constructed from plates,
- when the resulting extreme fibre elongation is more than 5% from the as-rolled condition and any of the following conditions is met

1. The vessel will contain lethal substances.
2. The material required impact testing as per ASME code.
3.The thickness of the part before cold forming exceeds 16 mm.
4. The reduction by cold forming from the as-rolled thckness is more than 10%. (this condition can only be found out after rolling of plates has taken place, the designer cannot anticipate)
5. The temperature of the material during forming is in the range of 121 to 482 deg C. (Why would the temperature be at this range)

So that means that even if a formed part exceeds 5% fibre elongation, but any of the conditions, from 1 to 5 are not fulfilled, PWHT is not required.

Thanks a lot. It is a long question. Thanks for patiently going through it.

Sharjeel

The exemption of fibre elongation more than 5% without requirement of heat treatment (in case none of the conditions as listed in code exist) is applicable only for P No 1, group 1 & 2 materials.

UCS 79 talks about heat treatment which may be different than PWHT.

Regards