PWHT

By jon20013 (*****)

Date 05-13-2008 19:35

I've responded (Code book NOT in front of me) that in general terms, ASME usually considers the thickness of the thinner material in an unequal thickness joint, therefore if this is true, a 16mm to 20mm joint would not require PWHT (Forum Members: please correct me if I mis-state as I don't have the code book at this moment). Also, PWHT could be avoided by applying a 200F preheat.

By gwg

Date 05-14-2008 18:00

It depends on the actual location of the weld. If the weld is not a pressure boundary weld, this is outside the requirements of ASME B&PV Code. What this means is that you are on your own regarding welding requirements. However, you can still follow Code PWHT requirements for non-pressure boundary welds.

By ekis

Date 05-15-2008 18:40

Thanks for the reply, but I have little bit confusion to you answer. What did you mean if outside pressure boundary? you meant that ASME B&PV Code should not be applied any more in welding, like welding circumferential seam weld of skirt which not directly welded to pressure parts body of vessel? So if not what specifc PWHT code?

By new tito (***)

Date 05-15-2008 20:07

You are going to have to do some investigating.

First, there is not a PWHT code. There is a code (quite a few actually) that has PWHT requirements. For example, ASME sec VIII for pressure vessels has requirements for PWHT. B31.3 for process piping has requirements for PWHT. AWS D1.1 for structural welding has requirements for PWHT. See what I'm getting at? You are dealing with a pressure vessel, that supposedly is built to ASME sec VIII, so this is the code that would govern if PWHT is required. No other code applies - not B31.3, not D1.1, not API 1104, not ASME sec I, II, III, IV, V, etc., not any of them other than the code to which it was built.

By presure boundary, the post above is referring to any componant that is containg pressure, i.e. the shell, the head, the nozzle, the flange, the re-pad, etc.

By ekis

Date 05-15-2008 20:56

Yes, Im agree with you Tito, Once an item referred to Specific code all Provisions to that item shall be applied as per that code, unless stipulated to refered to other code by that specific code, For example other code requires acceptance standard for RT results of UW 51. In ASME VIII Div 1.

By jon20013 (*****)

Date 05-15-2008 21:26

new tito, in a rare instance, I am at disagreement with one statement in your post; to the best of my knowledge, unless recently changed, D1.1 does not have any PWHT requirements. Has this changed in the last couple of years?

By hogan

Date 05-15-2008 21:36

there are a few references in d1.1, but c3.14 explains more

By new tito (***)

Date 05-16-2008 13:21

Honestly, I was simply hoping I was right and not shooting myself in the foot. It's been a really, really long time since I have dealt with D1.1, but I was just pointing out that each code has it's own PWHT requirements.

By gwg

Date 05-19-2008 16:07

There appears to be some confusion here. My original statement regarding location of the weld was meant to illustrate that ASME Boiler and Pressure Vessel Code has boundary limitations. This means that if the weld is structural, like a support structure for the vessel, this weld is technically outside the scope of ASME Section VIII, Div 1. Understand?

If this is the case, one can still use the PWHT rules in ASME Section VIII, Div 1 for the structural weld or one can use AWS D1.1, it depends on the designer and owner.

By ekis

Date 05-21-2008 07:20

I appreciate your sensible reply, but if you can just take a glance on my follow up question, I had mentioned specifically circumferential seam weld of vessel skirts, hence, its means to say that skirt was not structural in nature, perhaps you can just figure out what I am telling.
So, sensible to say that ASME Sec VIII DIV.1 still code to be apply for PWHT.
I would appreciate any more comments for better understanding of all concern.

Ekis

By cryogenicshaun (**)

Date 07-02-2008 20:28

Is the weld on the skirt welded directly to the shell? The requirements for the skirt (assuming that isn't welded to the shell) will probably be found on the fabrication drawings. I may be mistaken, it's happened before. I don't recall ever reading anything in Section VIII that addresses skirts.