Repair of Crack in a pressure vessel head (in-service)

rajae312 · **Posted:** Mon Jul 18, 2011 5:36 pm

Hi!
Problem description:
Material of construction= SS304
Type of head= ellipsoidal
Size= ID800, t=6mm
Radiography of joint= 100%
Cracks developed in head at the location where temporary attachments were made during forming of head. Vessel was installed and in-service.
how this problem may be rectified within the code boundaries?
please help earliest.

Murtaza Zaidi · **Joined:** Wed Jul 13, 2011 9:59 am **Posts:** 4

If your vessel is coded one then requirements of NBIC nb-23 must be met as construction codes do not give the repair criteria.
As far as repair is concerned first gouge the crack portion upto the sound metal,perform DPT to ensure the soundness of base metal,then weld build up using qualified WPS and perform DPT again after completion of welding.You can also perform UT to check the lamination in base metal before and after repair.

rajae312 · **Posted:** Wed Jul 20, 2011 5:25 pm

Thanks Zaidi Sahib!
i wanna tell u that i m ignorant of NBIC NB-23. Kindly can u give me particular reference from this code?
Also one of the dish head leaked from that crack location, means total damage. what will be the solution of this problem.
Thanks again for your responce.

Murtaza Zaidi · **Joined:** Wed Jul 13, 2011 9:59 am **Posts:** 4

See section 3 of NBIC Part 3 for repairs.
For the Dishend with crack you can cut the complete portion with crack and insert a dollar plate(flush patch).see 3.3.4.6 for details.

rajae312 · **Posted:** Fri Jul 22, 2011 11:02 am

Thanks Zaidi sahib for the help

Repair of Crack in a pressure vessel head (in-service)

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