multiple small openings in pressure vessel

[blackegl]

I am trying to figure out how to put multiple small openings in a pressure vessel and I am having a hard time figuring out what sections of the code apply to what I am doing.
Design pressure - 500 PSIG
Design Max Temp - 200 Deg F
C.A. - 0.00"
MDMT - -20 Deg F
Carbon Steel Vessel: SA-516-70, 0.626" THK Shell 36" OD Horizontal

I am trying to put a 16" gas dome on top of the vessel without putting a 16" hole in the shell. So underneath the gas dome i want to pop in a couple 2" OD holes. 1 in the center along the center line of the vessel and then 6 equally spaced around the center hole. The pitch between the holes will be 4".

Per UG-36(c)(3)(-a)(-2) my opening would not require reinforcement other than inherent. So I have calculated the UG-40 Limits of Reinforcement UG-40(b)(1) as "d" the diameter of the finished opening only because i have no nozzle in the hole, just an open hole. So would it be correct to assume that if I place my holes such that I have 4" pitch, 2" OD hole - 2" gap - 2" OD hole, that I would not have a shared reinforcement situation and therefore I can stick with just UG-36(c)(3)(-a)(-2) and not need any additional reinforcement? Or am I completely missing something and need to take into consideration UG-53?

Thanks in advance.

 

[prex]

If the reinforcements of any two adjacent openings do not overlap, then you can treat them as being isolated, and if they don't need reinforcement, then you are OK. So you are correct.

prex
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