ASME B31 1

[eng741]

Hi all, my questions:

1) What's the difference between B31.1 and B31.3
2) Depending on B31.1, or B31.3 where can I find the allowable stress for a given material? Is there a formula, chart for the allowable stress? Also, where can I find the specs for any material?

Thanks in advance,

eng741

 

[metengr]

First read the scope section for each. Allowable stress values for permitted material is in an Appendix (A).

 

[eng741]

Thanks metengr, the only problem I am having now is that for material A-53 Gr. A at 650F there is no allowable stress. I am using ASME B31.3-2008 Appendix A like you said. It's on page 146-147 and the max temperature it goes up to is 400F. Would you, or anyone, happen to know the next step in finding the allowabe stress for 650F.

P.S. 650F will not be out on the field, I am analyzing it on CAESAR II.

Thanks in advance,

eng741

 

[metengr]

Look at ASME B31.1 Appendix A. The allowable stress goes to 800 deg F.

 

[eng741]

Thank you again metengr

Two more questions:
1) Is the allowable stress the limit for other stresses (bending stress, torsional stress, normal stress, etc.) that any of them should not exceed the allowable stress?
2) I found the allowable stress in B31.1 but out of curiosity the allowable stress does not match up to 400F with B31.3 (which is expected), but B31.1 has a smaller allowable stress throughout. Is there no way to get that high of temperature for that material in B31.3?

Thank you all in advance,

eng741

 

[TGS4]

To answer your questions
1) No. See the appropriate sections of B31.1 and B31.3. This issue is addressed rather extensively.

2) The design margins in B31.3 and B31.1 are different, and therefore the allowable stresses will be different. A53-A is simply not permitted in B31.3 above 400°F.

Why would you want to use such a poor carbon steel material in B31.3 service at higher temperatures, anyway? There are much better carbon steel pipes available, likely at a lower cost.

 

[eng741]

Thanks TGS4

They gave me a max operating condition to apply into CAESAR II. The software provided certain stresses on the pipe and I wanted to make sure (find out) if the allowable stress conformed with ASME B31.

The normal operating condition is in the 300F range. I'm new to reading codes and I want to learn as much as I can about stresses for certain material.

I still am unsure when to use B31.1 and B31.3 though.

Thanks,

eng741

 

[jte]

Since we're talking "scope"...

B31 questions are out of scope of the "Boiler and Pressure Vessel" forum.

They are within the scope of

http://www.eng-tips.com/threadminder.cfm?pid=378