Regarding RT before or after PWHT

[Ajay]

Dear Sir,

As we all aware that PWHT and RT both are different in nature, in general we perform RT after PWHT(Where PWHT is required to be perform after welding). 

However it is not written anywhere that RT is to be performed after PWHT only.

My question now is , can we perform RT first and then go for PWHT? will it be acceptable ????.

I have seen many client inspectors asked contractors to perform PWHT first then RT whereas their specifications does not say anything in this regard.

All experts are requested to throw light on the subject. Documented proof/literature , if any, to support this will be higly appreciable.

regards,

Ajay 

[Raghuram Bathula]

depends on 

1. Project specific requirements

2. MOC

3. Code of Construction

Generally NDE after PWHT is a project specific requirements, and not by code of construction (except few materials, e.g. UHA 33(b) for ASME BPV div 1 vessels, or para 341.3.1.(a) for ASME B31.3 process piping welds)

[george....@gr.bureauveritas.com]

As a rule NDT has to be performed after all fabrication steps including PWHT. Some codes allow exceptions

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From: Ajay Sent: Τρίτη, 29 Σεπτεμβρίου 2015 - 07:37 To: material...@googlegroups.com Reply To: material...@googlegroups.com Subject: [MW:23575] Regarding RT before or after PWHT

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[Kannayeram Gnanapandithan]

For alloy steel greater than 3Cr, RTAfter PWHT.??

[Alan Denney]

NDT for final acceptance will be after PWHT. However it is relatively common to perform intermediate (in-house) NDT and perform any repairs prior to PWHT.

PWHT will relieve residual stress and can open up flaws which are otherwise closed by the residual stresses, and that is the reason why NDT for acceptance purposes is performed after PWHT.

 

Alan Denney

AKD Materials Consulting Ltd

 

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Ajay
Sent: 29 September 2015 05:03
To: material...@googlegroups.com
Subject: [MW:23575] Regarding RT before or after PWHT

 

Dear Sir,

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[Bala Murugan]

Dear Friends,,,

ASME Code VIII Div 1 is not specifying any NDE just because our vessel
must be subjected to the PWHT.

After completion of each weld unit, the required NDE must be done so
if the work was unsatisfactory then corrective steps can be taken to
improve the welding in the subsequent units.

So either our vessel is subjected to PWHT or not subjected, there is
no differences in the NDE technique and scope.

If our vessel is subjected in spot or full radiography and also PWHT
is mandatory. We must do radiography when welding completed and all
probable defects removed, repaired and reradiographed, then it is the
time to send the vessel to PWHT shop.

I have seen personally some vessel which had been cracked in weld or
even in base metal after PWHT and I understand why you are concern,
but ASME Code has not mandated radiography after PWHT.

So you may ask why code has not mandated this. It might because we
have another check point in hydrostatic testing so any crack which
developed in PWHT most probably will fail in the hydrostatic testing.

We do not must forget, based the ASME code the full responsibility for
pressure vessel is on the shoulder of manufacture not purchaser or
other parties.

You may note before start of the fabrication, the manufacture provided
his WPS and PQR, so if all welding controlled properly based WPS, this
cracking must not be happen.

I have seen some pressure vessel inspections and test plan which the
purchaser mandated RT before and after PWHT, so definitely the
manufacture will charge the purchaser because this is not code
requirement.

I have also seen some pressure vessel purchasers stated this
requirement in their purchase order and manufacture know from first
day of fabrication which has to do two times radiography.

I believe this practice is not correct in pressure vessel inspections,
the manufacture is responsible for quality on his own work and this
responsibility must not be transferred to the purchaser, engineering
companies and etc.

If the pressure vessel failed under hydrostatic test, then manufacture
must make repair or even rebuild the vessel.

So to prevent this bad incident, the manufacture will make all effort
to control the welding process precisely.

thanks,
Balamurugan M,

[Ajay]

Dear Sir,

I do agree with u completely,,,,,,,,,,,,But many contractors adament to do RT after PWHT.......if any documents to support the statement would be highly appreciated.

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[elias jarjoura]

Hey Guys ;

B31.1 and 31.3 have to do NDT after PWHT with P no. 3, 4 ,5A , 5B

It is quite common in some situations to perform a preliminary NDT, so to speak to establish the basic soundness of the weld especially on large bore or heavy thickness weldments but this would always be followed by an equally stringent NDT after any PWHT. 

RT or any other NDT does not alleviate the need for 'P'WHT as even a weld with no indications can develop delayed stress cracks .

For a joint and material so designated, it is smart to perform preliminary NDT before post weld heat treatment to assure you don't already have something that will require repair welding and further PWHT.

But I have never heard of a client accepting anything other than a post(!) PWHT NDT report, to do so would be an ultimate folly, as any amount of defects could arise due to the thermal stresses involved in PWHT.

Best Regards 

Elias 

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Date: Tue, 29 Sep 2015 13:04:04 +0530
Subject: Re: [MW:23585] Regarding RT before or after PWHT
From:.@gmail.com
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[george....@gr.bureauveritas.com]

Give me the applicable design an construction Code since the field is too large and I cannot give a general answer

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From: Ajay Sent: Τρίτη, 29 Σεπτεμβρίου 2015 - 11:18

To: material...@googlegroups.com Reply To: material...@googlegroups.com

Subject: Re: [MW:23594] RE: 23575] Regarding RT before or after PWHT

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[Kannayeram Gnanapandithan]

ref B31.1, 136.4, NDE of P3,4 &5A and 5B materials welds shall be performed after PWHT. For other materials , NDE may be before or after PWHT

THANKS & BEST REGARDS,

KG.PANDITHAN, IWE,  AWS-CWI, CSWIP 3.1,

CONSULTANT-WELDING & QUALITY

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[george....@gr.bureauveritas.com]

P-No 15E included. Example P91. For the other Pnos the Engineering has to agree for the PWHT timing. Check closer in B31.1

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From: Kannayeram Gnanapandithan Sent: Τρίτη, 29 Σεπτεμβρίου 2015 - 16:47 To: materials-welding Reply To: material...@googlegroups.com Subject: Re: [MW:23605] RE: 23575] Regarding RT before or after PWHT

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[george....@gr.bureauveritas.com]

P-No 15E included. Example P91

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From: Kannayeram Gnanapandithan Sent: Τρίτη, 29 Σεπτεμβρίου 2015 - 16:47 To: materials-welding Reply To: material...@googlegroups.com

Subject: Re: [MW:23605] RE: 23575] Regarding RT before or after PWHT

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[Kannayeram Gnanapandithan]

Yes P15E very much.

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[Himan Nikdin]

Hi Everybody

"For P-Nos. 3, 4, and 5 materials, examination shall be performed after completion of any heat treatment" this phrase is from ANSI B31.3 para 341.3(a)  Examination Requirements.

Regards,
H.Nikdin

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To: material...@googlegroups.com
Date: Tue, 29 Sep 2015 07:29:37 +0200
From: george....@gr.bureauveritas.com
Subject: Re: [MW:23580] Regarding RT before or after PWHT

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[alam]

Dear ,

Pwht is most important after welding but not for the all line .
Why because we have to identify the changes occur during welding and ...so on so many reasons.

pravez Alam
TP verifier
Air Energy
indonesia
+6289503908946

Expect the Unexpected.....

[salman cader]

The reason for pwht is to get rid of hydrogen cracking.......ask yourself.....is hydrogen cracking a planar defect or a volumner defect.....if its planar then you can do a rt before pwht but if the defects in hydrogen cracking is volumner too then you cant do a pwht.....

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[elias jarjoura]

The reason for PWHT is stress relief .

and occurrence of a defect if its volumetric planar or rounded has 100% nothing to do with pwht requirement .

Hydrogen Cracking (embrittlement) is the process by which metals such as steel become brittle and fracture due to the introduction and subsequent diffusion of hydrogen into the metal  This is often a result of accidental introduction of hydrogen during forming and finishing operations and totally not linked to the pwht process which will eliminate residual stresses caused by welding .

in case of occurrence of Hydrogen cracking or any sort of crack you do not proceed the joint is rejected , 

you never evaluate a crack all cracks in all codes and standards are rejected.

Last and final thing there is no such thing as ".......ask yourself....." should refer to design code and client specs or requirements and should meet those standards and follow a written procedure for pwht or any other requirement in a welding process.

Best Regards

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Date: Wed, 30 Sep 2015 13:17:07 +0900
Subject: RE: [MW:23621] Regarding RT before or after PWHT
From: salma...@gmail.com
To: material...@googlegroups.com

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[Ajay]

Dear Salman Sir,

please note that being working professionally there is no space for such things like """ ask yourself '"" . You, me and all works/follows written guidelines. 

sometimes its very difficult to make a contractor understand the statement without having any documented proof. So, I put the question in this forum for seeking expert comment. 

No doubt, I have received many valuable feedback from experts around the world.

I really thankful to you for your feedback as well.

regards,

Ajay Kumar Kadyan

EIL

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[Hareesh K V]

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Hareesh K V
+91-9447625012

[Hareesh K V]

Dear All,

Please go through the below.(Based on ASME B31.3)

I my opinion, based on these interpretations,For ASME B31.3 design requirements, NDT shall be performed after PWHT for P nos 3,4, and  materials and for P 1&2 materials NDT can be done before PWHT.

This is usually followed in the site.

Best Regards,

Hareesh K V

+91-8547859202