×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Grade 9 vs Grade 91 chromoly

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







 

RE: Grade 9 vs Grade 91 chromoly

atomicbob;
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

Well the good news it was caught in time. Now , the question is , if they are not familiar with the difference between gr 9 and gr 91, doesn't it follow that they probably  would not fabricate the gr 91 vessels right the first time?

RE: Grade 9 vs Grade 91 chromoly

Yep.

RE: Grade 9 vs Grade 91 chromoly

(OP)
Thanks Metengr! I knew the stresses must be there. It didn't make any sense to me. We'll keep looking.

RE: Grade 9 vs Grade 91 chromoly

(OP)
Well, I seem to be back to where I started. Back in section II part D, Table 1A.

9Cr-1Mo isn't shown in plate form.

What am I missing?  

RE: Grade 9 vs Grade 91 chromoly

atomicbob;
Look at ASME SA 387 Grade 91.  For Grade 9, SA 336 forged plate.

RE: Grade 9 vs Grade 91 chromoly

(OP)
Thanks. I see that one, but my MTR's are for SA-387 Gr 9 Cl 2.

 

RE: Grade 9 vs Grade 91 chromoly

(OP)
Ah ha! Said the blind man.

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources