Welding on ASME B31.3 PWHT Component Requirements

[blackegl]

We have a ASME U-Stamped vessel that has been PWHT. The Section VIII code boundary stops after the first nozzle weld. After that weld it is considered B31.3. After the nozzle to shell weld,(the Section VIII code boundary) there is a YALE closure welded to the end of the nozzle. This customer wants us to add an olet to this section pipe. It falls out side of the Section VIII code, so i was wondering what are the requirements for welding on ASME B31.3 pipe that has been PWHT. If it were within the code boundary, per the NBIC we would just preheat to 300 DEG F and maintain, however it is outside the code boundary. The thickness of the pipe is 1.125, P1 Materials. I would greatly appreciate any advice.

Thanks,

 

[weldstan]

The thickness of the weld governs. Under the new edition of the B31.3, PWHT is also not required.

 

[mk3223]

It may also depend on the process service the welds will see at the weld and the pipe section where added the Olet.
Is the preheat to 300F as the welding WPS, but not for PWHT? right?

 

[blackegl]

It is NOT lethal service. The weld size is small because it is for a 1/2" Thread-o-let. The preheat to 300F is the guideline in the NBIC for welding on a PHWT vessel so you don't have to complete local PWHT after the repair.

Thanks,

 

[TGS4]

Find out why the vessel and piping was PWHT. If it were for process reasons (H2S service, amine service, etc), that will dictate. Otherwise, follow the current B31.3, as recommended by weldstan.

 

[pdiculous963]

Double check your interpretation of the Code boundary, because the way I interpret your question is that you are considering the nozzle to shell weld the Sec. VIII-1 boundary. The nozzle to shell weld (corner joint) is not the Code boundary, but rather the boundary is the next weld or connection from the attached nozzle to another component. Per U-1(e) of Sec. VIII-1, the boundary is either:
[ul][li]the first welding end connection (i.e. for a butt weld or socket weld)[/li]
[li]the first threaded joint for screwed connections[/li]
[li]the face of the first flange for bolted, flanged connections[/li]
[li]the first sealing surface for proprietary connections or fittings[/li]
[/ul]

 

[DekDee]

pdiculous,
I saw that as well but wasn't sure what a YALE closure was so presumed the Olet was intended to be inserted in a spool attached to the nozzle (therefore past the ASME VIII code boundary).
However, if a YALE closure is just a fancy end cap welded to the end of the nozzle then an Olet in the nozzle itself would fall within ASME VIII jurisdiction - as you have noted