Am working on a vessel which falls under lethal service (client’s requirement). As per the technical requirement, the vessel should be stress relieved after welding because of lethal service.

The MoC of the vessel is SA 240 TP 316L, Normally SS Vessel will not be PWHT.

Is there is any stipulation to overrule the PWHT requirement

Part UHA is applicable to your vessel. I assume the complete vessel is fabricated from UHA materials only. Since the vessel is in lethal service, so UW-2 does not mandate PWHT for UHA vessels. UW-2 mandates PWHT only for Carbon and Low Alloy Steel vessels.
According to Table UHA-32, PWHT for P-No-8 (as your case is), PWHT neither required not prohibited. You can exempt PWHT only in the case if PWHT is also exemt by UW-2 and UHA-51. UW-2 not requires PWHT for UHA materials due to lethal service. Now, all depends upon UHA-51.
What is calculated MDMT is your case?

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

ramse 24

Your vessel is exempt from PWHT. See Table UHA-32 Note 1.

leem817

Dear Leem,

Third sentence of paragraph UHA-32(a) reads out " Exmpetations for provided in the notes to Table UHA-32 are not permitted when PWHT is a Service requirement as set forth is UW-2 and UHA-51 ..................."
UW-2 does not require PWHT so UHA-51 needs to be checked.

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

No PWHT required for PNo 8 (Type 316)
Mauro