ASME Vessels and PWHT Requirements

If the vessel is NOT in lethal service, you are fillet welding a NON-PRESSURE part, and none of the other stipulations in UW-2 apply (because you didn't provide enough information) then PWHT is NOT mandatory for this case.

But you must ensure that you have a preheat of 200F (95C).

Thanks for your reply. In my case the non pressure part need to be welded with pressure part inside the column after PWHT and hydro test.

Non pressure part having thickness of 16mm with fillet size of 12mm both side and Pressure part is conical having thickness of 36mm.

Since it is a repair job. What rectification procedure need to adopt. As per the above clause UW-56 the PWHT can be avoidable and hydro test is required for whole column, which seems very difficult to apply at installed situation. Please suggest.

Ahhh!!! A repair job. Assuming that you are to follow the National Board NB-23 (as the ASME codes are for new construction) - you need to check with your inspector/jurisdiction as to which code edition to follow (I don't have the NB code with me, but I seem to recall you should check section 4.4 in the latest edition). They have changed the rules/guidelines over the years. In the latest edition, and particularly with a simple repair (which this sounds like), you should be allowed to perform additional NDE in lieu of hydrotesting - but you must check with your local inspector. Having said this, the PWHT requirements are almost always dicated by the original code of construction so the exemption to the post weld treatment will still apply.