Outer Crack in P1 Steel

[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]

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