Dear Experts,

Our client has special requirement to use structural members (H beam, Channel, Angle) as dummy supports, not Pipe to Pipe connections like normal projects. Also, Pad at elbow.

we had calculated equivalent pipe size to modal in CAESAR based on structural member's moment of inertia and allowable loads.

But while analyzing local stress junction i,e Elbow & trunion(H-beam), how to calculate SIF?

ASME B 31.3 Appendix D is for Pipe to Pipe connections, hence cant directly use that calculations into CAESAR, we need to put manually in CAESAR SIF values.

So, we need SIF value.

Please guide us to calculate SIF of structural members welded with PIPE.

Regards
Snehal Dave

Dear all,

Addition to above my query, we had calculated already SIFs from FEM (Nozzle Pro), but i.e with equivalent pipe which is equivalent to structure & Run Pipe.This value is very huge, looks impracticable to input into CAESAR.

Example :

Run Pipe = 3" Main pipe Elbow

Trunion = L - 75 X 75 X6 - Structural member (as per client requirement)

Equivalent Pipe = 2" (60.3) , 3.6 mm Thickness (Based on M.I. Formulas)

SIF from FEM = 16.8 (i) & 10.2 (O) (Nozzle PRO)

These SIFs are very high for 3" pipe, it is difficult to consider into calculations.

So, please guide us, if anyone had faced such case
Analysis -> Structural members welded with Elbow as trunion.

Thanks

Snehal Dave

Dear Friends, Richard & Dave,

I need your suggestion, please reply.

Regards
Snehal Dave

Normally for any welded attachment to the pipe such as trunnion and dummy pipe, we do not add any SIF's at that point, same thing we do with pipe shoes. We only used branch SIF's for branch connections where there is a cut hole in the parent pipe. Local stress check is needed for pipe with trunnion or dummy support attachment. In this separate calc, you must consider the geometry of your attached member (H beam or channel).

For elbow with dummy support, you can stiffened and lowered the SIF by selecting Single or Double flange in the bend description.

Dear Flex,

Thanks,

Are you not using any SIF where Dummy or Trunions are attaching at elbow???

Surprised..

I think SIFs shall be used to check the stresses at local junction even though there is no fluid inside dummy or trunions.

But it is one of like TEE junction.

May I correct??

Please share other friends here.

Regards
Snehal Dave

There is no need to consider SIFs for welded attachment on the pipe like trunnion or wedled shoe. However,you should consider stress concentration factor(SCF)when AIV calculation is conducted as a stress rasier.

For elbow with dummy pipe attachment, I will define my bend as Single Flange (in other projects, it's Double flange) to consider the stiffening effect of welded attachment on elbow, just like when there is a flange fitting makeup with the elbow. This will lower both the bend SIF and stiffness factor k. Both for elbow and pipe dummy attachments, local stress should be checked, instead, to qualify the piping integrity.

If you don't have access to an FEA program for examining local stresses at weld boundary, see post below for link to spreadsheet that uses Caesar output to qualify local stress at pipe wall for trunnion attachments. It is based on Section III, Div 1 Nonmandatory Appendix Y, and is modified for elbow attachments per results of EPRI TR-107453. (See EPRI link in spreadsheet for how to construct stress model at elbow.) Account for changes in stiffness in building your model. Fkx notes a common method.

http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=52480#Post52480