PWHT Thickness Requirements.

[Andrew Ubakwem]

Dear all

Pls what is the current thickness requirements for PWHT as per ASME B31.3? 

I came across old version of the code, it specifies that PWHT not required for all P1 materials, provided min preheat is maintained at 95deg'C.

We intend welding; 18" sch 80(23.83mm) to ASTM A 106, 24" sch 80(30.8mm), is PWHT required? Cite relevant Code sections Please.

Regards,

Andrew. 

[pgos...@rogers.com]

Hi ,

Which version of B31.3 code you’re following , 2018 or older?. You may still avoid PWHT, if the design code is of 2018 edition. See the exemption clauses from B31.3 -2018 as highlighted.

Note: If PWHT is mandated by design or process condition, e.g. sour service or other conditions, PWHT is mandatory irrespective of thickness. The  designer has to specify that in the drawing.

All appropriate clauses are highlighted for better understanding. Hope this would help you.

 

Thanks.

 

 

Pradip Goswami, P.Eng, IWE Consultant-Welding-Metallurgical Engineering
Cell & Whatsapp-905-9793232. Personal:pgos...@rogers.com

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[Sankaran Sp]

Dear Mr.Andrew,

irrespective of code, for P1 type material with 25mm and above thickness, after pre- heating & welding. PWHT is recommended one and it will reduce the HAZ hardness & eliminating the failure during service.  

Regards,

Sankaran.SP

Welding & Metallurgy expert

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[james gerald]

There are reasonable changes in ASME B31.3 2018 edition which exempts PWHT if applied a Preheat of 95degC for P1 materials. Please check.

Thanks & Regards

J.Gerald Jayakumar

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[atul khatri]

Hello Mr. Andrew,

ASME B31.3 states the general guidelines for PWHT requirements irrespective of fluid service.

Please follow the service specific standards like API RP 941 for Hydrogen service at elevated temperatures , NACE MR0103 etc.

Client requirements may also supersede the code requirement.

Feel free to discuss more.

Thanks & Regards 

Atul Khatri

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[Ghulam Mustafa]

Hello all members,

can we perform PWHT except P1 material.

(such as P8)

Best Regards

GMT

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[atul khatri]

Hello Mr. Ghulam,

Yes you can perform PWHT for any P No. even it's exempted as per B 31.3.

For P8 ,yes you can. We advise to perform the PWHT for stabilized SS grades of higher thickness (could be beyond 20 mm ) to avoid the Stress Relaxation cracking. 

But in general it's not required.

Br,

Atul 

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[George Dilintas]

As per table 331.1.3 for Pno. 1 material PWHT is not required when multilayered welding is used when the material thickness is larger than 5 mm and 95 deg C is applied when thickness is > 25 mm.

However, you should check if any specific service requirements apply

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Dr. Georgios Dilintas,

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Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis