We have below mentioned query about WRC analysis.

“We refer to nozzle loads calculations as per WRC 107 in PV ELITE. Please note that as per Client job specification, pressure stress indices shall be considered as per ASME Sec. VIII Div.2 while calculating the stresses due to pressure for all nozzles irrespective of presence of cyclic service/fatigue requirement. These stress indices shall be considered for analysis at nozzle to shell junction and need not to be considered at edge of pad analysis.”

Please advise how to comply above CLIENT requirement with PV ELITE software (any option available to define PRESSURE STRESS INDICES)? How to take care of this PRESSURE STRESS INDICES in the design? Any guideline/ info, which you can provide on this subject?


As we have to perform/ design number of Vessels for the plant having this requirement, your positive response will help us.

Best Regards,
Sunil Agrawal
Chief Engr (Mech)

Tecnimont ICB Pvt Ltd
Mumbai

Dear Mr. Sunil
pl. note this is ASME SEC VIII Div-1 Forum. if you have any query regarding any software, pl. post the same in software / Calculation forum. However, pl. note following.
Theoretically pressure stress indices is applicable for fatigue loading only. whenever, equipment is in static loading condition, stress indices is not applicable at all. Also, note that , the way some software calculate the pressure Stress indices in it's Calculation & compare with Pm & Pm+Pb & Pm + Pb + Q is also not appropriate. As, you said you are using PVElite to calculate WRC, pl. check , there is tick for "Div-2 pressure stress indices" click that tick to add effect of pressure stress indices in WRC Calculation. However, pl. evaluate your result carefully as caution drawn above.

Thanking you.

Same client requirement we are facing in current project. In PvElite use "Div-2 pressure Indices" option is there, but when I applied it WRC-107 criteria fails. Actually PvElite is multiplying primary membrane stress (Pm) with Stress Indices which cause drastic increament in Pm where as its allowable value remains 'Sm' only, which means to make shell safe you have to increase its thickness almost 2 times, which I think not feasible.
As per my knowledge if we are considering pressure stress indices for local analysis of static loading condition then, we shall include it while calulating total stress as per WRC i.e Pm+Pl+Q which can be compare with allowable value 3Sm or 2Sy.
Please correct my understanding if I'm wrong.

npccmechanical:

I also feel the same but I would like to add we have to meet client requirement and AI requirement inspite of our own understanding or interpretation.

If client says that the stress indices have to be applied even for PL then we have to do so.

However FEA is one way out if acceptable to client (part 5 of Sec VIII Div.2)

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA