Grade 9 vs Grade 91 chromoly
Grade 9 vs Grade 91 chromoly
(OP)
We are fabricating ASME Code pressure vessels specified to be 9 chrome. We had used Gr 91 in our calculations and drawings for the plate materials, as it was the only grade of 9cr in our software (Advance Pressure Vessel).
The material we received is grade 9, and it was rejected as non-conforming by the client inspector. I believe the gr 9 should be acceptable, but we have been unable to find the stress curves for gr 9 plate in the ASME books, and can't run calculations.
Can anyone give me any direction here?
Thanks
The material we received is grade 9, and it was rejected as non-conforming by the client inspector. I believe the gr 9 should be acceptable, but we have been unable to find the stress curves for gr 9 plate in the ASME books, and can't run calculations.
Can anyone give me any direction here?
Thanks





RE: Grade 9 vs Grade 91 chromoly
The stress lines for Grade 9 are in Section II, Part D of the ASME B&PV Code. You assumption for using Grade 91 stress values as Grade 9 is incorrect, and should not have been used. You need to re-run the stress calcs using the correct stress values.
RE: Grade 9 vs Grade 91 chromoly
RE: Grade 9 vs Grade 91 chromoly
RE: Grade 9 vs Grade 91 chromoly
RE: Grade 9 vs Grade 91 chromoly
9Cr-1Mo isn't shown in plate form.
What am I missing?
RE: Grade 9 vs Grade 91 chromoly
Look at ASME SA 387 Grade 91. For Grade 9, SA 336 forged plate.
RE: Grade 9 vs Grade 91 chromoly
RE: Grade 9 vs Grade 91 chromoly
SA-387 Gr 9 is not recognized by Sect 8, Div. 1 as pressure vessel material per Table UCS-23.
Thanks for your help guys. I'll buy new shells and heads and then likely have some questions about welding and stress relieving Gr 9 to Gr 91 joints.