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Peja
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Join Date: Jun 2013
Posts: 14

PWHT and Stress Relieve

01/07/2014 2:19 AM

Dear All,

I have a vessel which is supposed do not required PWHT by code as the shell and head thickness is 25mm and 30mm respectively. However, the head right now requires stress relieve as per UCS-79(d). The head is formed using 2 pcs of plate, means there will be a welding on the head. Do i need to stamp "PHT" due to stress relieve on the head?

Let just say i have another vessels, and I have a nozzle neck with size 18" x 30mm thickness attached to that vessel. The neck need to do stress relieve due to the fiber elongation over than 5%. Do i have to stamp "PHT" on nameplate? If the answer is yes, how about if heat treated first the nozzle neck prior to welding activity, do i still need to stamp "PHT"?

I have heard someone said that if stress relieve, then heat treatment shall be performed after forming & before any welding on formed part, but i cannot find in the ASME code mentions that.

Appreciate if someone can assist me on this.

I found someone said that if stress rel
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Whitephone
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#1

Re: PWHT and Stress relieve

01/07/2014 2:27 AM

ASME VIII required PWHT over 19mm thickness
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Tornado
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#3
In reply to #1

Re: PWHT and Stress relieve

01/07/2014 3:31 AM

??

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Peja
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#2

Re: PWHT and Stress relieve

01/07/2014 3:07 AM

Forgot to mention that the material is SA 516 70 which is under ASME VIII Div. 1, Table UCS-56 (Note 2) and PWHT is mandatory when the thk over than 38mm.
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PWSlack
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#4

Re: PWHT and Stress Relieve

01/07/2014 12:49 PM

The simplest, quickest and easiest way to obtain advice is to discuss the problem with the Engineer/Surveyor from the company that provides burst/collapse indemnity insurance cover on the vessel. Just pick up the phone; that's what these people are there for.

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Peja
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Join Date: Jun 2013
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#5
In reply to #4

Re: PWHT and Stress Relieve

01/07/2014 8:53 PM

Yeah..may be after this, when people asking something in this forum, we can guide them by giving that answer. Quickest, smplest, and easiest...
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IRSHAD
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#6

Re: PWHT and Stress Relieve

01/07/2014 11:49 PM

Pl refer UF 32 of ASME section VIII point no 3.

(3) The finished weld shall be postweld heat treated or
given a further heat treatment as required by the applicable
material specification. The types of welding permitted in
UF-32(b) shall be performed prior to final heat treatment
except for seal welding of threaded openings which may

be performed either before or after final heat treatment.

So, PWHT is to be done after welding.
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Tornado
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#7
In reply to #6

Re: PWHT and Stress Relieve

01/08/2014 1:00 AM

Well, duh, the only time post-weld heat treatment can be performed is after the welding; otherwise it would be pre-weld heat treatment.

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rajan_bhiwandkar
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#8
In reply to #6

Re: PWHT and Stress Relieve

01/08/2014 1:11 AM

YES, I AGREE WITH IRSHAD.

YOU MAY GO FOR LOCAL STRESS RELIEVING BY ELECTRICAL HEATING COILS

FROM THE REPUTED AGENCY
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Peja
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#9
In reply to #8

Re: PWHT and Stress Relieve

01/08/2014 10:18 PM

For PWHT, yes i agreed that the activity should be done after welding because PWHT itself is done in order to remove residual stress left in the weld.

But how about stress relieve due to fiber elongation? Is it has to be done after complete weld, or just after formed the plate prior to start welding? We all know that stress relieve due to fiber elongation is to be done in order to remove residual stress left in the plate material instead of welding.

Can anyone give me an answer regarding "PHT" stamping as my first question? I already ask many people in my place regarding to this, but i also want to know answer from expert in here also.
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Tornado
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#10
In reply to #9

Re: PWHT and Stress Relieve

01/08/2014 10:31 PM

As for the forming stresses, heat treatment could be done at any time afterward. If the full vessel needs PWHT, that would also relieve the forming stresses in the nozzle; i.e., one treatment covering both goals. If the full vessel does not need PWHT, then the nozzle can be treated before welding, without needing to heat the whole vessel.

(At least that is the logic of the matter. There is no guarantee that your local code is entirely logical.)

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Peja
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#11
In reply to #10

Re: PWHT and Stress Relieve

01/08/2014 10:43 PM

Tq for your reply Mr. Tornado,

I do agreed with you. If my vessel right now is mandatory PWHT, then i don't have to think further, but just proceed with PWHT, so that both stresses in the material and weld can be removed.

But right now, it is just a matter of code stamping "PHT" as per my first question.
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Anonymous Poster #1
#12
In reply to #10

Re: PWHT and Stress Relieve

09/26/2014 2:11 AM

In this case, is there any disadvantage if we accidentally did two time of heat treatments? Because forming require stress relieve and Design require PWHT also. This mistake can be happen.If so, is there any defect on material or not? If yes, how to solve it? Thanks.
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Anonymous Poster (1); IRSHAD (1); Peja (4); PWSlack (1); rajan_bhiwandkar (1); Tornado (3); Whitephone (1)

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