Minimum thickness calculations for hydrogen tubes

[deafcat]

I recently performed an inspection on a hydrogen vessel skid. The only documentation available from the client is from the vendor; it states that these vessels were built in 1943 and are "ASME certified." Shell material is listed as API-5A-J-55. I'm trying to run the minimum thickness calculations outlined in ASME VIII, and I cannot find the maximum allowable stress value for this material anywhere. I did find API 5L in ASME II, but nothing else. I believe the "55" indicates a stress of 55 kpsi. However, I ran across a post on this site that said API designated steel is not allowed for pressure vessel construction under ASME VIII. If anyone has any information on this, I would be extremely grateful, I'm kind of stuck on this one. Thank you