[MW:12561] RE: 12548] defect on circ-seam of H2 service vessel

Hello Hrishi,

 

The attached picture is not very clear. However looking at the problem I would think there could be two scenarios:-

1. Devise a plan for smooth grinding and blending of the notch to the surrounding base metal.Ensure that minimum design metal thickness+required corrosion allowance is maintained, upon discussion with the design engineer.
2. If the above option is not acceptable then you may resort to controlled heat input weld deposition technique as per API-510, 8.1.6.4.2.3 Controlled-deposition Welding Method (Notch Toughness Testing Required). It would be advisable to  to qualify weld repair procedure as per Sec-IX, QW-290 with hardness control and preferably with impact test(if the original design specification calls for so).
3. The temper bead weld repair, is a substitute for PWHT if the above guidelines are followed.
4. Once the qualified welding procedure is used for weld repair, required NDE following weld repair shall be done.RT/UT  may be used in lieu of hydro test (as permitted by repair and alteration codes e.g API-510 and NBIC.

 

Thanks.

 

 

Pradip Goswami,P.Eng.IWE

Welding & Metallurgical Specialist & Consultant

Ontario,Canada.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

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From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of K.M Hrishikesan
Sent: Tuesday, September 27, 2011 2:14 AM
To: materials-welding
Subject: [MW:12548] defect on circ-seam of H2 service vessel

Dear Mr. Pradeep Goswami & other experts...

 

We have a newly fabricated Vessel having following details

 

 

Vessel:  1200 mm ID X 4550 mm TL-TL

MOC: SA 516 Gr 60

Code of constr: ASME section VIII div 1 2007 edn.

Thickness: shell-20mm; DE-24 mm

Design pr- 32.3 kg/sq.cm; Design temp - 80 deg.C

Service: LPG+Naphtha ; Vessel is designed for  Hydrogen service, 100%RT, Fully PWHT; hydrotested ,cleared by TPI, erected at site, yet to be commissioned

 

 

Imperfection (a notch or gouge out)of about 3-4 mm deep and 15 mm long observed on weld seam CS-1 (Top Dished end to shell circ. seam joint ) from inside of vessel. Please see the attached image of segment radiographed by us.

 

My queries...

 

What rectification shall I do on the defective segment on the service point of view?

What are the NDE's required?

Is a local PWHT mandatory at the repaired segment?

Any special precautions for H2 service...

 

appreciate your quick feedbacks..

 

Regards

Hrishi

 

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