Re: [MW:24705] Carbon/Manganese pressure vessel ASME VIII, Crack after PWHT

Centre of weld is not due to Hydrogen. Improper cleaning & impurities which was relaxed after PWHT

On 07-Apr-2016 8:18 am, "Zakaria ghrab" <zakaria.ghrab@gmail.com> wrote:

Dear Experts,

 Need your support for one issue :

Construction code : ASME VIII Div 1

Pressure vessel fabrication.

Material: A516 Gr 70N

Thickness : 48 mm

Welding process : SAW/FCAW;

Joint design: X

For one of Circulaire joints, UT & TOFD performed before PWHT and result was conform.

After PWHT, One crack around 40mm lenght, detected centerline of the weld surface in the internal side of vessel.

In my assessment, 

• crack may be hydrogen crack dur to no control of interpass temperature and heat input or due to Carbon picked up from parent metal to weld zone and due to lower manganese concentration, Crack occurs.
  
• May be Crack taked time to occurs (it's possible that crack present after 03 days of weldment, please confirm to us) and in this case may be NDE performed before crack that's why NDE reports before PWHT present conform result.

Please your support & Feedback experience and what you propose as corrective / Preventive actions.

--

Thanks and Regards, ?

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زكرياء غراب
GHRAB Zakaria 

EA2C Tunisia.

Tunisia : +216 96 635 805

Morocco : +212 6 06 58 88 56

Bénin : +229 97 128 387


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