SA516-70 Properties over 750 deg F

[curlyjackme]

I am designing a knock out drum that has low internal pressure (64psi), but the internal design temperature is 775 deg F. My concern is for the repads that are required for nozzles to satisfy my replacement area. How will the repads be affected by the material properties of 516-70 at this temperature?

cj

 

[metengr]

Look up the allowable stress values in ASME Section II, Part D for this material at 775 deg F. You will need to interpolate between temperatures to arrive at the actual stress value.

 

[curlyjackme]

Thanks. One more question. Should I be concerned about creep at this temperature?

 

[TGS4]

The creep properties dominate the allowable stress starting @ 750°F, so @ 775°F, you would be in the creep regime. However, stay within the allowable stress values, and you'll be fine.

 

[jte]

cj-

Assuming ASME VIII Div. 1 here... As TGS pointed out, at 775°F you're in creep. I would expect that you have a bit of margin on your design temp vs operating temp, so chances are that the vessel will be operating out of the creep range or just barely in it. Either way, the allowable stresses already account for creep. They are governed by it - that's why the numbers are in italics in II-D.

jt

 

[MJCronin]

curly...

At a continuous operating temperature of 775F, you are at the threshold of a phenomena called "graphitization". This limit affects the usage of carbon steel materials.

The ASME BPV & Piping codes have for many years warned about the long term degradation of carbon steels at this temperature limit.

I do not believe that you should worry about only creep as graphitization is a much more well known threat to your material

-MJC

 

[MJCronin]

curly....

See:

http://www.eng-tips.com/viewthread.cfm?qid=120971&page=10

-MJC

 

[curlyjackme]

Thanks for all of the help.