API 661 Airfin - PWHT needed for new header nozzle?

[MAKMWKL]

Good morning

I am working on a Revamp project in which we will be adding new nozzles to an existing airfin heat exchanger designed to API 661.

API 661, para 9.2.1 states "All carbon steel..headers shall be subjected to post weld heat treatment".

Tube-to-tubesheet joints are expanded with two grooves.

I would like to understand the intent of the PWHT requirement, and to understand if once the new nozzles are added to the header box if the header box must be PWHT'd.

Please note that the airfin in question is constructed from carbon steel (BS 1501 224 LT50 - norm) and that the service does not require PWHT. Also, the maximum thickness of plate is 30 mm, but the thickness of the area that the nozzles will be added is 19 mm.

Any help would be appreciated. Thanks.

AK

 

[gr2vessels]

No, the addition of the new nozzle(s) do not require PWHT. However, the welding procedure should take care to not induce excessive local stresses at the junction, like local preheating. Also, depending on nozzle size, I would avoid the oxy cut the holes. I would UT inspect the edge of these new holes for lamination.
Cheers,
gr2vessels

 

[Elise]

gr2vessels
please clarify how you confirm No PWHT required.
Where is this corroborated ?

 

[Duwe6]

Simple; a Fin-Fan header box is not a nozzle. API requires PWHT on all header box seams. It is silent on nozzles added to header boxes. If PWHT was needed, they would tell you, specifically.

Having said that, treat the new nozz like any addition to a PWHT'd item; use a high preheat for the material P-group, maintain that preheat through breaks and lunch, and put some kind of insulation on the welded area to allow it to cool off very slowly. Cheap 'insurance'.