B31.3 PWHT & Preheat Exemption

[Nazeer]

Dear All,

Request Clarification on which thickness (Control thickness / Nominal thickness) to be applied in the B31.3 2014 -Table 331.1.3  for PWHT & Preheat exemption. Details furnished below.

Weld Joint Details:

Joint : Header Pipe to Weldolet

Weld Type: Integrally Reinforced Branch Connection (B31.3, Fig 3285.4)

Material: P.No 1

Header Pipe Size: NPS 16 , 12.7mm thick

Weldolet Size: NPS 16 x NPS 3 , sch 40

joint groove Thickness (At crotch of Header pipe & weldolet): 22mm

Nominal Thickness (Tm) As per B31.3, Fig 3285.4 : 22mm

Calculated Control Thickness (Tm+Tc):  28mm (22 + 6mm)

Based on above scenario, we had applied weldolet nominal material thickness Tm of 22mm (thicker member of the joint) on B31.3 Table 331.1.3  and not performed PWHT & preheat of 95 Deg C.

Whereas for PWHT exemption, Client is applying the control thickness  of 28mm on B31.3 Table 331.1.3 and insisting us to perform PWHT on the joint due to 95 Deg C preheat not applied.

In my opinion, nominal Thickness to be applied for PWHT exemption and control thickness to applied for calculating Minimum PWHT holding time.

Please advice and enlighten further, whether PWHT is mandatory for the above specified weld joint.

Thanks & Regards

Nazeer

[james gerald]

Yes your Client is correct. Please see the snap shot below.

Thanks & Regards

J.Gerald Jayakumar

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[atul khatri]

Hello Mr. Nazeer,

Yes, your understanding and interpretation is absolutely correct.

Control thickness is not to identify the PWHT requirement. It's to evaluate the holding time, holding temperature range and cooling range.

Whereas nominal thickness is the governing thickness for PWHT requirement , which in your case is lesser than 25mm , so PWHT is exempted.

Hope you are not dealing with Hydrogen , Amine , Oxygen or any Nace service while dealing with this case. 

Thanks and Regards

Atul Khatri

[Nazeer]

Dear Mr. Atul Khatri,

Thanks for you valuable reply.

Thanks & Regards

Nazeer

[Nazeer]

Dear Mr. Gerald Jayakumar

Thanks for your valuable reply,

Request your opinion on para 331.1.3(C) applicability.

Thanks & Regards

Nazeer

[james gerald]

Dear Mr. Nazeer,

Code always specify whether Nominal or Control Thickness is Applicable. Sorry for the Miss.

Thanks & Regards

J.Gerald Jayakumar

https://groups.google.com/d/msgid/materials-welding/3caad526-f3de-458f-aa6d-af169e3936d3n%40googlegroups.com

.

[George Dilintas]

Table 331.1.3 is granting an exemption for PNo1 BASED ON NOMINAL THICKNESS. Note 6 says that the nominal thickness is defined  in 331.1.(c). Looking in this para the nominal thickness is the thickness of the thicker parts.

So if it is below 25 mm you dont need preheat to get exemption

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Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

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

[Nazeer]

Dear Dr. Georgios Dilintas

Thanks for you valuable reply in perspective of preheat.

Thanks & Regards

Nazeer