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12:07 May-06-2009
Acoustic emission testing of HIC affected pressure vessel

I would like to have the expert opinion about real time monitoring of Hydrogen Induced Cracking in a glass flake lined pressure vessel using Acoustic Emission Testing if condition favours to use the technique. Is it possible to detect step wise cracking & blister growth?


17:08 May-06-2009

bob sudharmin

Engineering, Reliability and Integrity Eng
Shell Malaysia Trading,
Joined Jan 2008
Re: Acoustic emission testing of HIC affected pressure vessel In Reply to krish at 12:07 May-06-2009 (Opening).

Interesting question. I am no expert in this field, but what I understand is that Acoustic Emission listens to corrosion activity and hence translates to possible loss of metal or even leaks.
Its also interesting to know about Hydrogen Induced Cracking which normally happens in a non coated pressure vessel and how this can happen in a glass flake lined vessel.
For step wise cracking & blister growth, Ultrasonics would still be the best detection and monitoring procedure, and surely I would also like to know more of whether AE is also capable of doing this

23:23 May-06-2009

Roger Duwe

NDT Inspector, API-510, 570, 653
Joined Jan 2009
Re: Acoustic emission testing of HIC affected pressure vessel In Reply to bob sudharmin at 17:08 May-06-2009 .

I'm a 'user', not a subject expert.

Blister growth = Maybe

Stepwise, or any other crack propagation = Absolutely! This assumes that it is possible to stress the vessel, by pressuring it up to a psi at least 10% about the highest it has seen in the last year or so.

20 or 40% above the last highest pressure used at will give much better results. What you are doing is listening for flaws to propagate under the increased stress. The more [safe] stress, the better, and the smaller defects that can be identified.

21:31 May-07-2009

John O'Brien

Consultant, -
Chevron ETC ,
Joined Jan 2000
Re: Acoustic emission testing of HIC affected pressure vessel In Reply to Roger Duwe at 23:23 May-06-2009 .

There was a report on work I think published by NACE a number of years ago that looked at the ability of AE to detect activity from HIC. Basically any propogation of the blister towards a step or the step cracks themselves will generate AE. Since then a number of people have monitored vessels with some success. A large amount of the hydrocarbon industry vessel population is made for SA 516 Grade 70 and this is a 'quiet' steel so density and placement of sensors can be crucial. Be aware that permenet moniroing may be more effective for results than 'intervention' testing by raising pressure.

Interetsing that this is an internally lined vessel and you still have HIC. Since you presumably have access to teh external surface I would still wonder why you are not AUT mapping the affected area or is your suspected hydrogen charging rate so high you fear rapid propogation.

10:13 May-08-2009
Re: Acoustic emission testing of HIC affected pressure vessel In Reply to John O'Brien at 21:31 May-07-2009 .

Thanks john and other for the expert comments.We did AUT scan and TOFD and found laminar type of indication at the mid wall of the plate close to the L-Seam/C-Seam welds.Originally the vesseal was coated with Coal Tar epoxy and latter it was upgraded with Glass flake vinyl ester.Thro AE we want to ensure whether the existing lamination/dense inclusion at the mid wall is growing or not in service.There is a possibility that it could be pre-existing manufacturing defect and hence it is operating under moderate H2S environment that we feels that the defective site will favor for hic to initiate.


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