Allowables B31.4

Dear All,

I am doing static analysis of a complete buried pipe, code B31.4.

If I run the analysis with 25 barg as P1, the output in Caesar give me allowables for operating load case, hence i have a certain value for the code stress ratio.

If I increase P1 from 25 barg to 27.3 barg, Caesar's output doesn't yield anymore allowables for operating case.

Why?

Thank you

No ideas?

It depends on whether the pipe is in tension or compression (restrained or unrestrained). Compression / restrained has an OPE condition. Tension / unrestrained does not. So the answer to your question is that the behavior depends on the specific. Loads

Thank you for your reply Richard.

I'll try to sum up my case, please tell me whether I am right or not.

Hoop stresses formula is as below:

sigma_h = (Pi - Pe) * (D-t)/(2*t)

By increasing Pi from 25 barg to 27.3 barg, Pi becomes higher than Pe, so the pipe is now in tension. Tension / Restrained doesn't have any OPE allowable.

You didn't mention such combination (Tension / Restrained), but I suppose that whenever we have tension, there are no OPE allowables.

Yes, exactly.