Crack in P1 Material from Outer side

[Engrshanas]

Hello,
I am facing an issue in our Hydrogen line. There is crack on base metal from the outer side. Inside the fluid is Hydrogen and there is no crack. Pipe thickness is 42mm, Process Temp and pressure is 180 oC and 290barg respectively. Plant commissioning date is 1992. In April 2015, I noted down these crack and it is many on the line. Also the line is fully insulated. I would appreciate if some one help me on this to what should be the reason?

Thanks

Regards
Muhammad

 

[metengr]

Muhammad;
First, do you have a picture or map of the location of the cracks on the OD of the pipe?

This is important because the orientation of the cracks relative to the pipe and location can aid in determining if the cracks were related to fabrication or in-service damage from thermal/mechanical bending stresses.

 

[weldstan]

Also, how often is this line cycled?

 

[Engrshanas]

Thanks very much for your concern. Cracks are not manufacturing or fabrication but it is in-service damage.Crack orientation is in all position like longitudinal or cross section etc.

 

[weldstan]

Are cracks in pipe or at welds or both?

 

[EdStainless]

Are they in a straight section of pipe or a bend?
How much indication is there of corrosion under the insulation?

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P.E. Metallurgy, Plymouth Tube

 

[Engrshanas]

Cracks are on the Pipe (Base Metal) only. Not in weld area. They can be found on straight section, but some bend area too. There is no indication for Corrosion under the insulation.

 

[EdStainless]

Really all directions, like spiderwebs?
And no leaks right?

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P.E. Metallurgy, Plymouth Tube

 

[SJones]

290 barg of H2, 180 deg C and nobody has investigated "the cracks" to demonstrate fitness for service? You need somebody on site performing a proper evaluation, not an internet forum.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[Engrshanas]

Yes in all direction with no leak

 

[Engrshanas]

Steve, yes we are working on it and perhaps we change the materials to P11 as it has good experience in tha US and Europe.

 

[EdStainless]

Yes Steve, it is one thing if they are only a few thou deep (then probably related to original manufacture) versus them being half way through the wall (just waiting to go boom).

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P.E. Metallurgy, Plymouth Tube

 

[weldstan]

You need to remove a section containing the cracks and perform a metallurgical investigation. You may be able to do an in situ surface replica to determine presence of martensite. This is a pretty heavy wall and you haven't indicated seamless manufacture or heat treatment.

Obviously as both Steve and Ed indicated, UT examination to determine crack depth is imperative.

 

[plantprowler]

Out of curiosity what is the pipe dia?

 

[GenB]

Interesting topic that needs high thnking. In my experience it could be insulation contamination, find the composition of the insulation and see if it has any Chlorides In it, at high temperature this will create the Web type hairlines. The cure, you may have to coat the pipe to avoid contamination.

 

[Engrshanas]

GenB, many thanks. This is what we missed. We shall do it and will check it there is possibility to control the crack....