Re: [MW:23593] Regarding RT before or after PWHT

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,



On 9/29/15, Ajay <donsaab3@gmail.com> wrote:
> 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
>
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