PWHT for attachment welds (temporary support welds) [Discussion]

Hello, I would like to invite you join to discuss the topic.


  • Pressure vessel P-Number 1.
  • PWHT is required.


  1. Acc. to ASME VIII Div. 1, Do we apply PWHT for attachment welds (temporary welds)?
  2. In case of ASME B31.3 apply, Do we preheat at 95 deg. C alternative PWHT? or 100% MT for weldment?
  3. Where can we refer to answer both questions?

Bien ND

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If your weld exceeds the dimension given in UCS 56 table then definitely you have to Pwht the attachment weld unless you are good to go with out PWHT.

Assuming that the vessel is not in Lethal Service or subject to PWHT due to process service, per ASME VIII, Div. 1

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As per ASMe section 8 you can do a preheat of 95 C for a joints over 32 mm to 38 mm in order to avoid PWHT not sure about 31.3.

Thanks @Aravind_km,
This vessel required PWHT and comply with NACE MR 0103.
Do we apply PWHT for the attachmwnt weld? This weldment will be removed and ground.

Hi Bien,

  1. Acc. to AMSE Sec VIII Div 1, PWHT is required if the governing thickness met UW-40
  2. Acc to B31.3, Yes Preheat may be applied for all type of welds (table Table 331.1.3)

Remarks: Even the weld is not exposed to sour service fluid (considering the requirement of PWHT is due to service requirement), the HAZ has formed…PWHT is REQUIRED


Hi @zairil89,

The vessel contact with H2S, so PWHT is mandatory. Thanks for your joining the topic.