Effect of hydrogen on SA-516-70

[Murec]

We seem to have a small leak on a pipe carrying syngas - 56% H2.
The line is made of SA-516-70 pressure containing shell with SA-240-T310 liner in contact with the gas and refractory between the two. A leak would mean that both liner and shell are cracked.
I would like to ask what could be the effects of the exposure to hydrogen on the shell material?
We are planning to repair by grinding and welding the crack on the shell. Is this enough? Should we replace a larger piece of the pipe around the shell?

Thanks
M

 

[metengr]

Murec;
What is the operating pressure and service temperature of the syngas?

 

[Murec]

About 3100 kPag (450 psig) and 1000C (1800F)- inside the liner.
The water jacket around the shell is around 80C (175F).

 

[metengr]

Murec;
Based on the above, at the stated temperature and pressure local weld repair is feasible. You don't mention the time interval for how long you operated with the shell leak. I would presume it was a short period of time. Being the base material is carbon steel you may need to evaluate the condition of the base metal once you remove the failed liner and refractory to get a better look see as to the condition of the shell ID surface.

You may need to have surface replication (field metallographic examination) performed of the shell ID surface to evaluate the condition of the base metal where the liner failed before attempting weld repair of the shell. I would also consider UT for wall thickness checks of the shell.

Finally, I would perform nondestructive testing (wet fluorescent MT) both before (to evaluate the condition of the SA 516 Grade 70 base material) and after the weld repair. Let the replication, UT and surface NDT results be your guide regarding extent of shell repair (local weld repair or flush patch).