Trunnion stress comparison with ASME section VIII,Div-2 Allowable

[parijat10]

In trunnion stress check it is usually done as below:

1) SL + SA + SLP <= 1.5 * SH

2) SC + SA + SCP <= 1.5 *SH

Q1. In two Combined Local Stresses above how SA term is contributing because its direction is axial and not longitudinal or circumferential. All the terms above are calculated from Kellog’s formulae and the summation is compared with 1.5 times of allowable stress according to ASME pressure vessel code section VIII, Div-2: Pm+Pl+Pb<=1.5*SmH. Taking the first equation: SLP, general primary membrane stress in pipe wall due to internal pressure = Pm; SL local primary membrane stress in pipe wall due to loads in trunnion =Pl and Pb goes in Q near the vicinity of trunnion. Then how is SA contributing?

Q2. One more thing I want to confirm is: Kellog’s formulae only give membrane stress and not bending stress otherwise the allowable would have been 3 times of SH according to ASME pressure vessel code section VIII, Div-2.



3) Bending Stress in Trunnion, ST <= SH

4) Shear stress in fillet weld, SW <= 0.8 SH

Q3. Why the above two stresses are considered as Global and according to what basis the allowable are selected?

Q3. Different software like pipe mill use the above four conditions but they are unable to capture the local bending stress component due to trunnion load. Then only option is to do FEA. Is it right?

Find the .doc file for detailed calculation

Thanks and Regards
Parijat Bandyopadhyay

 

[DSB123]

parijat10,
I think you need to read the Kellog paper again as trunions always cause bending in the pipe whereas you apparently think differently. Also bear in mind the only accurate way is to perform a FEA.

 

[parijat10]

DSB123 Idon't have the papers. I got the formulae from here and there. If u can help me getting those i think my confusions will get solved.

Thanks and Regards
Parijat Bandyopadhyay

 

[DSB123]

parijat10,
I had a look at your attachment and the approach is incorrect. Google for the Kellog papers - they are on the net.

 

[parijat10]

DSB123,
I tried hard to find the Kellog papers but could not find those. If you can explain answer to my questions in brief it would solve my problem.

Thanks and Regards
Parijat Bandyopadhyay

 

[LSThill]

parijat10 (Mechanical)


I agree with DSB123 google search: Kellog Trunnion

Also: Trunnion support check calculation thread378-220232

http://www.eng-tips.com/viewthread.cfm?qid=220232