Pressure equivalent allowable load under occasional B31.4

Hi there,

Please your help regarding pressure equivalent allowable load under occasional case B31.4.

During an evaluation of flange B16.5 ANSI 900 T1=15°C A105 table 2-1.1, results performed by CAESAR II indicates a factor of 1.15 between sustained and occasional of pressure equivalent allowable load.

I'm trying to find where this factor comes.

Thanks a lot.

I don't think it should be any factor. Maybe a bug?

We really need to see the job files. Can you open a Support Request on Smart Support and send in the files related to this issue?

Ok, I'll do that.

Meantime, attached pdf file contains an example of pressure equivalent allowable load, case sus vs case occ.

Best regards.

Now I remember...
Your pdf helped.
For load cases defined as occasional (OCC), the allowed pressure is increased by the occasional multiplier. A B31.1 analysis would default to an occasional load factor of 1.15.
See page 900 of the User Guide:

Thanks a lot Dave.

Considering your answer, I used help tool (F1) at CAESAR II Configuration Editor, SIFs and Stress, Code-Specific Settings, Occasional Load Factor, and I found the specific information that you mention.

I wonder if this is applicable to system under B31.4.

Can you share you opinion about it?

Best regards.

I can't say whether this bump in allowable pressure when evaluating occasional loads is right or wrong for any specific piping code. As I see it, there is no consensus on this issue.

This multiplier can be used by those who wish to do so. If you want to stick with the standard Peq values, you can duplicate your occasional load set and reset the occasional load case multiplier to 1.0 in the load case editor. (I say duplicate because you will probably be using the existing OCC case for stress evaluation.)

But the important thing is that you are aware of this multiplier. Congratulations on uncovering this in your review.

Aside - Some engineers will multiply the listed Peq times 1.5. These flanges are to remain leak tight during the hydrostatic leak test and this test is typically run at 1.5*Pdesign. This is one way to sidestep the very low load limit in this Kellogg method.

Thank you.