Using ASME Section VIII div 2 to evaluate API650 Tank Nozzle

[manu1982]

I am trying to check a Nozzle for API650 Tank as per ASME Section VIII Div 2 using an FEA Software.
Now problem is that I can’t use the ASME allowable as nozzle will fail just because of pressure itself. This is because allowable stress in API650 is more than ASME Section II.
Appendix P.3 of latest API650 (Year 2013) states that stress calculations can be done as per ASME Section VIII Div 2 provided that acceptance criteria for stresses is as per P.3.3
I also have some doubts regarding criteria specified in P.3.3:
P.3.3.1 - It seems that criteria for general and local primary membrane stresses (+ Primary bending) are reversed.
Clause P.3.3.1 States " For membrane stress, limit stress to 1.5(Sd). Local primary membrane stress, including primary bending, shall be limited to 1.1(Sd)."
P.3.3.2 – Is surface stress same as primary+secondary stress range. If so, API650 seems to be even more conservative than ASME section VIII. It limits the surface stresses to less than UTS
Clause P.3.3.2 States " For surface stress, limit stress to the greater of 2(Fy) and 3(Sd), but shall not exceed the tensile (ultimate) strength.”
Would you think that these limits are mistaken.
I would be very thankful if someone would shed some light on this.

 

[TGS4]

The limits in P.3.3 don't make sense to me, either.