I'm running WRC on a standard vessel with deadweight and thermal loads. My corrosion allowance is .125" and the WRC program shows the nozzle to be overstressed. I now add the occasional loads into the appropriate column and all of a sudden my overstress is gone since the C.A. is no longer considered. Is this an error in the program?

Dear Mul211,

This is probably not an error. But, depending upon the sign of the occasional loads, the stresses they produce could counter act the stresses from other loads and reduce the stress in the Pm+Pl+Q category. So,

Re-run the analysis by switching the sign of occasional loads.

I think we should also add an extra check for Pm+Pl+Q (without occasional).

The stresses in Pm and Pm+Pl categories should be fine, as they are checked for occasional and sustained loads separately.