Is there possibility for Hydrogen Embrittlement in this situation?

[Raulradin]

Dear members,
Hope you are all well

What would happen if a contractor uses hydraulic jacks for reducing out-of-roundness and fit up circumferential weld joints under the pressure of jacks (shell to shell & shell to head joints)?

- Longitudinal weld of shells has been welded after rolling
-Maximum out-of-roundness is limited to 0.3% according to spec. Currently, out-of-roundness of shell is over 1.2% and contractor uses hydraulic jacks to fit up joints.
- Working temp. and pressure are 50C and 34 bar respectively.
- Service environment is hydrogen gas.

Literally, my concern is that the pressure vessel will be under cyclic pressure during service. Could Hydrogen Embrittlement occur in service?

I would appreciate any reference in codes and standards related to this problem.

Appreciating your time and help,
Best regards

 

[3DDave]

What is the strain produced to remove the out-of-roundness? I presume you mean the shell is out of round and not the head.

The strain being introduced is just an offset to the cyclic strain - the cyclic strain is what produces fatigue.

I think an expert in hydrogen embrittlement, if there is a strain portion to the answer, will need those values and the alloy as well to get a suitable response.

 

[Raulradin]

Thanks for your respond.

Yes, the shell ovality is out of acceptable range and it doesn't fit with head.
The material is carbon steel SA 516 Gr. 70

 

[Dhurjati Sen]

Contractors / vendors do such things all the time.
Mostly, it is done in their shops out of sight of the client / client's inspection team.
During service, there could be cyclic stress as you have mentioned. Fair enough, still other service conditions are required to assess for possibility of hydrogen embrittlement.

DHURJATI SEN
Kolkata, India

 

[blacksmith37]

Hydrogen cracking would be very unusual for steel with hardness less than HRC 22. Be sure to consider the hardness of weld HAZ.

 

[weldstan]

What is the service environment? Is it capable of inducing hydrogen embrittlement? To be safe, you may wish to PWHT the shell to head weld.