The history of a bug in my professional life. Chapter I

I have sent this post to a forum for support about a pressure vessels design and calculation commercial software. The problem is a possible bug responsible of the miscalculation of the MAWP on the nozzles. I will continue the history when someone replies me, for confirmation. --------------------- Hi all, I'm trying to repeat the calculations for a cold separator. The first analysis was done with 2011 release and it seems to be impossible to repeat this calculation with the 2012 release. The problem are the nozzles, because those that were ok with 2011, now aren't ok with 2012. There are some differences in used formulas between both releases: The first difference is the "Area contributed by the nozzle outside the vessel wall (A2)": 2011 computes exactly the same formula as in ASME 2010 Section VIII Div 2 4.5.85 for A2 depending on LH value and taking A2a or A2b, while release 2012 computes the addition of both values A2a + A2b. Is this ok? The second difference is the "Force acting on the nozzle": while 2011 computes the same formula as in ASME 2010 Section VIII Div 2 4.5.95, 2012 changes the sign as follows: 2011: FN = P*Rxn (LH-t) 2012: FN = P*Rxn (LH+t) Can anyone explain me the reason of that? Thanks in advance