ASME B31.8

[marchieV]

I am analyzing a pipeline using ASME B31.8 of CAESAR II ver. 7 but I notice that some allowable are zero in the Output Report. How is that happened? I know about the par. 833.1 for the Restrained and Unrestrained but is that possible that the allowable will be zero?

 

[1503-44]

Some calculated stresses are zero?

Calculated stresses are not "allowables".

Can you post the output?

 

[LittleInch]

Which "allowables"??

Give us something to go on please

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[marchieV]

Please see attachment for the code stress report. You will see that most of the OPE cases has zero allowable stress.

Is it possible that if the system I am analyzing do not involve a very long pipeline, we can use ASME B31.3 instead of ASME B31.8? From scapper laucher until the underground only.

 

[1503-44]

It looks like there are several load cases that were not analysed.

 

[LittleInch]

The might be something wrong with the input.

What are those load cases?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[marchieV]

Most of the cases with zero allowable are Operating Conditions (OPE+Win/Occ etc). I read other forum/thread, it seems its not a wrong input and not new situation. I don't know what should I do.

 

[1503-44]

I guess somebody else did the analysis. Discuss anything you don't understand in the report with the author.

If those cases were not appropriate for the design conditions, or not critical, it's probably not wrong. You just need to agree that it's not wrong.

 

[EngrPaper]

I am not familiar with B31.8, but I'll presume its like B31.3 in this instance to maybe give you something to check.

B31.3 code stresses are in the sustained and expansion cases. Support loads are in the operating cases, generally speaking. So the code compliance report from CAESAR II does not show allowable stresses for operating cases because the code does not define an allowable stress for that case. See the below picture from a generic CAESAR II code compliance output for B31.3. Note that there are no allowable stresses in the operating case.

 

[1503-44]

OK that makes some sense. 8 is similar in that respect.
Calculated stresses also do not appear to be critical.