ASME PWHT

WTH are you talking about!!!

Please refrain from the uise of Jargon in your posts to CR4.

This is a general use site - not a secret society where only those in the know get to participate in your discussion. It's okay to use it provided that you have spelt out the meaning of the acronyms at least once in your initial post - otherwise nobody is going to bother replying to you. (how many posts have you had so far??)

Thanks,

Pete.

I think he's refering to PWHT - Post Weld Heat Treatment.

However, not my area of expertise so I can't comment on it :p

If I were in his situation (asking a specific question to a scientific community), I know I wouldn't want just anyone answering my question.

If you don't know about PWHT on vessels, then I don't think you could give him a specifc correct answer. If you do know about PWHT on vessels, then you will probably know the jargon too.

FYI (for your information), PWHT means Post Weld Heat Treatment. ASME is the American Society of Mechanical Engineers.

Sorry,it is my bad.

Here is the definition of the acronyms i used in post# 10

ASME= american societe mecanical engineer(code by witch pressur vessels must be built ).

PWHT= post weld heating treatement.

AI= authorise inspector (a certifie inspector,that the duty is to make shure that any pressur vessel is built according to the appropriate ASME code,he also make shure that any repair or alteration are made according to the national board inspection codes,and he also verifie the qualification of the welders.

WPS= welding procedur specification

PQR= procedur qualification report.

NDE= non destructive examination

RBQ= regie du batiment du quebec (this the authorise inspection agency,if you google www.rbq.ca there is numerous info about the subjet.

I hope this can be helpful

It is normal practice that after welding of all weld attachements, vessels are post weld heat treated in one go. Bolted attachements are attached later on. It is mendatory to perform PWHT if any weld of full thickness of vessel has been carried out at any stage of repair however standards permit exceptional weld where heat affected zone (HAZ) created by such weld is not determinantal to the strength of the vessel. Such welds are performed using low heat input methods etc.

PWHT and stress relieving are misnomers. PWHT is done after performing welding job and it may require, post weld heating of job upto 250°C for one hour or so just after fininshing the welding to librate any hydrogen absorbed during welding. After cooling and NDT full weld stress reliving is performed.

However if we use term "Stress Reliving" that may required to be performed after cold working or any other hot work other then welding.

No,what is normal practice is:when we repair a pressur vessel the first thing to do is to read the deta-report of the pressur vessel and it is that document that will tell us if a PWHT is nessery.

When we repair a pressur vessel,what we do is we restor the vessel to it's original state.

In another word we bring the pressur vessel to the same state as it was when it left the factorie when it was bilt,the day it was borne,and before it left the factorie an authorise inspector,inspected the vessel and filled up the deta-report for that vessel,that is why sometime we will refer to the deta-report as the birth certificate of the vessel,also on that document we will fiend other info like what kind of metal was use to bilt the vessel,and what kind of NDEwe used to prouve the integrety of the vessel.Also please note that a vessel is approuve for a MAWP and max temperature of operation.

So if anything,i hope that you will understend that you should never perform any welding before at less having consult the deta-report of the vessel.

Also you need a WPS with is supported by a PQR and the work must be done by a welder olding a welding calification for that WPS,the work must be done in accordence with the section and addenta of the ASME that was use when they bilt the vessel.The proposition of repair must be submit to the juridiction in with the vessel is install for approuval befor the work is perform.

And finaly the job must be inspected by an authorise inspector,at less this is the way it must be done whenever the vessel is in the part of the province in witch i have the responsability of approuving such a job.

I hope this can be helpful,if not i sugess that you go on the site of the RBQ that way evreybody can sleep tight tonight.

Please see if the case is of repair or new built.

• Through UCS-56 of ASME VIII-1 "Requirements for Postweld Heat Treatment", there are some exemptions for PWHT. And you are kindly requested to read the full paragraph where you will find that:

Except as otherwise specifically provided in the notes to Table UCS-56 and Table UCS-56.1, all welds in pressure vessels or pressure vessel parts shall be given a postweld heat treatment at a temperature not less than specified in those Tables when the nominal thickness, as defined in UW-40(f), including corrosion allowance, exceeds the limits in those Tables.

The exemptions provided in Table UCS-56 or Table UCS-56.1 are not permitted when postweld heat treatment is a service requirement as set forth in UCS-68, when welding ferritic materials greater than 1⁄8 in. (3 mm) thick with the electron beam welding process, or when welding P-No. 3, P-No. 4, P-Nos. 5A, 5B, and 5C, P-No. 10, and P-No. 15E materials of any thickness using the inertia and continuous drive friction welding processes.

• My point of view is looking for an AI to investigate your case, may be there is a way for an exemption or at least carrying out a localized (partial) PWHT, which is permitted and accepted in such cases as per the code.

For a repair work in the vessel, if one has to do some welding it is allowed provided you have a localized PWHT done after the work and before you put the vesel in service. Please correct me in I am wrong.

Regards;

Nadeem

Yes, for such a repair work in a pressure vessel, you can doing a localized PWHT under the supervision of an authorized inspector AI if the vessel hold an ASME code certification, and you can do that whatever the vessel is a new or already in service.

It is true that most post weld heat treatments are done for stress relieve and also viceversa, most used method for the stress relief on metals is PWHT. However the terms are not identical.

There are heat treatment methods that are not done for stress relieve i.e quenching ( not usual for welded materials ) and also there are methods for stresss relief without using heat, i.e peening.

My question was really professional one to almost people who are not working in same field as mechanical engineer.

Thanks all, in particular, kind information can help me to better understand PWHT.

What is main purpose to be post weld heat treated after welding? I mean, PWHT can guarantee the part of welding effected on welding heat, so almost vessel required PWHT..

I am wondering if exceptional welding is to be post weld heat treated? Either local or whole PWHT is okey, but after PWHT, exceptional weld can be done provided that customer does not say restriction of weld after PWHT ?