Hi Dears,
Recentley when i analyzed a case, a new problem accurred for me, but what is that?
"my case doesn't pass in OCC case when i use unreinforced pad according to branch table of Project's PMS,but when i changed the type of SIF to reinforced, the OCC stress lessen to half,but as you know I'm not allowed, so what do I do?"
Please note that I considered all supports location or design changes for get result.



Best Regards,
HoseinJahani

hi,

In occ case also the stress equation uses the SIF(i) and SIF(o) for finding the stresses.so you get less stress value when you switch on reinforced connection,because its having less SIF values.

so you have to reduce the stresses where you have failure.study the results carefully ,find which stress creating problem and solve by adding restraints or changing pipe routing according to your study.

if your stress lead agrees change the SIF factor multiplication value in configuration file.

That's right. Your stresses went way down because the SIF of a reinforced fitting is much smaller than that of an unreinforced one. Remember that the ASME stress intensification factors were produced from experimental data of cyclic bending tests. So it makes sense that an unreinforced branch would fail sooner than a reinforced one (thus the higher SIF).

What I would do is this: Confirm the SIFs called out in the project specifications are close to the SIFs called out in Appendix D of ASME B31.3 (assuming this is Process Piping). I would personally use the ASME ones but I don't know what piping code you are following. Also, if different from B31.3 and if you are going to stick to your spec's SIFs, then at least make a comparison of magnitude to make sure they are both ratio'ed properly. I bring this up because the ASME code adjusts its SIFs for reinforced branches based on pad thickness and such.

Also, if you are failing the OCC case a big reason could be the occasional loads being inputted wrong. Or, since you need to add SUS + OCC, your sustained stressed could be very high (meaning there are support issues).

Dear Ltorrado'
I use ASME B31.3 and I sure all my inputed occasional loads are true,follow as: 0.4g's GX 0.4g's GZ
Please help me about the project specification's SIF,I don't have any information about that?

While a reinforcing pad is not required for pressure design as per your branch table, you, as stress engineer, can ask for one if you deem it necessary for stress reason.

I was unable to understand why you are NOT allowed to use reinforced pad!!!!!

Take danb's advice and use reinforced pad AS IT IS REQUIRED TO MAKE THE SYSTEM SAFE!

Yes, sorry. I missed the part where you were not allowed to use a reinforced branch. That's strange. Just because the spec calls it out doesn't mean you are "not allowed".

danb is absolutely correct. If you deem it necessary, then it should be so. Whatever the stress engineer demands trumps anything else as long as it takes into consideration the work of other disciplines. In this scenario I don't see how it would be a problem. Hopefully the piping hasn't been IFC'ed yet.

Dear Ltorrado,

fortunately the peoject's PMS is IFR.

Thanx danb, Shahid Rafiq and specially you Ltoraddo for kindly guidance.