WPS for Furnace PWHT

[Prakash Kumar Bontra]

For furnace PWHT as per ASME B 31.3 all the joints in the spool (1" to 36") need PWHT approved WPS and where to refer?

Prakash Bontra

[Vishwas Keskar]

Pl elaborate your query 

Query is not clear 

Sent from my iPhone

On 27 Jan 2025, at 11:57 AM, Prakash Kumar Bontra <prakas...@gmail.com> wrote:



For furnace PWHT as per ASME B 31.3 all the joints in the spool (1" to 36") need PWHT approved WPS and where to refer?

Prakash Bontra

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[Raviraj Gohil]

For Furnace PWHT, All Joints under Heating and Cooling Cycle of Heat Treatment, How to ensure it's joint behaviour if not used WPS with PWHT!

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[Pipeline Welding]

I refer through other method as below, hope all agree:

Code Requirements for PWHT in ASME B31.3 Clause 331 - Heat Treatment

• 331.1.1: The code specifies that the heat treatment requirements shall apply to welds and heat-affected zones (HAZ) to ensure mechanical properties are achieved as per the base material and design requirements.
• 331.3 - Postweld Heat Treatment:
  • This clause mandates that PWHT is performed as per prescribed methods and conditions, including controlled heating and cooling cycles to relieve stresses and enhance the toughness and ductility of the welds and HAZ.

Importance of Using a WPS with PWHT  ASME B31.3  Clause 328.2.1 - Welding Procedure Qualification

• This clause explicitly requires that all welding procedures must be qualified as per Section IX of the ASME Boiler and Pressure Vessel Code (BPVC). A Welding Procedure Specification (WPS) is qualified using a Procedure Qualification Record (PQR), which includes:
  • The effect of PWHT on mechanical properties (e.g., tensile strength, hardness, impact toughness).
  • The behavior of the weld and base material under cyclic heating and cooling. 

Risks of Not Using a PWHT-Qualified WPS

• • When a WPS is not qualified for PWHT, the following risks emerge:

    • Mechanical Property Degradation: The welds may fail to meet design criteria (e.g., tensile strength, impact toughness, ductility) due to changes in microstructure caused by the heating and cooling cycles.

    • HAZ Cracking: Improper heat treatment can lead to brittle phases (e.g., martensite) or stress corrosion cracking, especially in materials like carbon steel or low-alloy steels.

    • Noncompliance with Code: Not using a WPS that accounts for PWHT violates the procedural qualification requirements under ASME Section IX (QW-407.1) and B31.3 Clause 328.2.1.

[kingslygeo vargheese]

The spools have 1" to 36" Piping joints.

The WPS with PWHT is available only for large diameter / high thickness.

can we do PWHT in the furnace if small size piping joints welded without PWHT WPS which is welding with higher size spools require PWHT?.

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[patni engineers]

WPS is required .You have to check size range and Qualification .

Pipe diameter , Thickness Range qualified and Required , Grade etc...

Regards

chandrakant

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[Hareesh K V]

Dear Sir,

I am not clear about the question.

Is the question is "The welding is done without following a WPS having  PWHT and actually the joints need the same" is it?

May I know the material ?

Also if it is of Carbon Steel material, is PWHT requirment is there based on design or based on ASME 31.3?

Regards,

Hareesh K V

On Mon, 27 Jan, 2025, 11:57 am Prakash Kumar Bontra, <prakas...@gmail.com> wrote:

For furnace PWHT as per ASME B 31.3 all the joints in the spool (1" to 36") need PWHT approved WPS and where to refer?

Prakash Bontra

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[Prakash Kumar Bontra]

As per ASME B31.3, Clause 331.1.6 (b):
Any required PWHT shall be carried out in accordance with the qualified WPS.

For furnace PWHT involving spools of different diameters and varying thicknesses, all weld joints subjected to PWHT must be welded using a WPS qualified with PWHT. This requirement remains applicable even when the individual joint thickness is less than 20 mm, despite the code-specified threshold of greater than 20 mm for P1 materials, as outlined in Table 331.1.1 of ASME B31.3 (2008).

Therefore, performing furnace PWHT on any joint that was welded using a WPS not approved for PWHT constitutes a non-conformance with the applicable quality requirements. Do you agree? If not please elaborate.

Prakash

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[Deerendra Karanth]

Yes, performing furnace PWHT on any joint that was welded using a WPS not qualified with PWHT violates Clause 331.1.6(b) of ASME B31.3. It constitutes a quality non-conformance, even if the individual weld is below the threshold thickness for mandatory PWHT.

BR, 

Deerendra 

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[Pipeline Welding]

Dear Mr Karanth,

I am in full agreement with your observation. The real challenge arises during local PWHT of shop and field weld joints. Weld joints located within the heating band—defined as 75 mm or three times the material thickness, whichever is greater—of a joint requiring PWHT, are themselves required to be welded using a PWHT-approved WPS, even if their individual thickness does not mandate PWHT.

Furthermore, even when the PWHT-required joint is welded and heat treated first, residual heat and stress from the subsequent welding of nearby joints (using a non-PWHT-approved WPS) can still affect the integrity of the previously treated weld.

In situations where weld joints are distributed between shop and field locations, ensuring proper traceability and compliance with PWHT process requirements becomes increasingly complex. Unfortunately, in many cases, PWHT estimation is not adequately considered during the initial planning phase.

In such cases, the code limitations are unclear and do not provide sufficient guidance to address this issue effectively. Additionally, when the weld thickness is less than 20 mm (for girth, branch, or wear pad welds) and is located close to a butt or O'let weld joint requiring PWHT, the application criteria remain undefined.

Any body can suggest guidance!!

Prakash