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- since 1996 -
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Technical Discussions
Aamir
Aamir
12:33 Jun-19-2009
HTHA

Dear All

Can some body please advise that if High Temperature Hydrogen Attack is found on the inside surface of alloy steel piping then how to assess further usability of the material. As fissures are found on the inside surface of piping in our case then we should use this line or just discard. But i tell you, exact thickness of line is about 50 mm and serious fissures along with decarburization is found upto max.10mm from the inside.

Waiting for your expert point of view on the captioned subject

    
 
 Reply 
 
Roger Duwe
NDT Inspector, API-510, 570, 653
MISTRAS, USA, Joined Jan 2009, 148

Roger Duwe

NDT Inspector, API-510, 570, 653
MISTRAS,
USA,
Joined Jan 2009
148
14:18 Jun-19-2009
Re: HTHA
In Reply to Aamir at 12:33 Jun-19-2009 (Opening).

Typically, the Fracture Mechanics of the material of the pipe at the temperature and pressure it is operating at are the criteria for the 'Run or Replace' decision.

Personnally, I would recommend immediate replacement unless the line was in low-pressure service, had very adequate supports at short spans, and located where a catastrophic failure wouldn't cause injury or much monetary damage. You are already at 20% of wall thickness, you probably havn't inspected 100% of the line, so being at 30-40% is possible, and HTHA may procede very rapidly from this point on.

I see continued usage as "too much risk, too little gain", because the line has to be replaced very soon. Why not now?

    
 
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