Hi All

I have used CAESAR 2016 to calculate a transfer of piping section to pipeline in a pipeline station. The allowable stresses are from version 2006 of the code so different to the new version of the code that CAESAR 2017.

Not just the allowable but there is a difference in calculation the code stresses as well so it seems that the new version of the code is using Hoop stress in checking sustain.

Also looking at the allowable stresses for expansion in the CAESAR 2017 it seems to be less conservative and difference to what it has been claimed in the last 2016 version.

Would you please explain what is going on? And why is there a big change?

Many thanks
Pegah

What Piping Code are you referring to - B31.4?

Hi Richard

Yes my problem is with ASME B31.4 calculation.

Thanks
Pegah

There are significant changes between B31.4 2006 and B31.4 2016. The code stress equations have changed, a new one was added, and the allowable stress values changed.

Compare both Code books and you will see these changes. Running the same job in CAESAR II v.8.00 (which implemented B31.4 2006) and then again in CAESAR II v.9.00 (which implements B31.4 2016) will yield different results.

Dear Richard

You are correct, the values of the allowable stresses are changed and many other equations added.

But one thing which I don't understand is that when the bending stress in the unrestrained section of the pipeline for sustain case is less than the hoop stress, the value getting reported is hoop stress. Also the allowable stress gets set to hoop allowable of 0.72Sy.

Having said that if the bending stress is more than the hoop stress it gets calculated with the formula in section 402.6.2 and the allowable is 0.75Sy.

I haven't found a note yet in ASME B31.4-2016 to support this.

Thanks
Pegah

When there are multiple code checks, we print the one that governs. This is determined by taking the ratio of [code_stress / allowable_Stress] for each check. The stress values generating the largest ratio are printed in the report.

Hi Richard

Thanks for your reply. As the formula in section 402.6.2 for longitudinal stress, bending stress is an additional to half of hoop stress and it might give me a bigger ratio even for a very small no.

Are you saying this is a new code requirement to do multiple checks in sustain case?

Many thanks
Pegah