If I understand your question regarding installation of two threaded connnections in a cylinder (e.g., tube) one on each end, I believe you need to read UG-36 thru 39 of ASME Section VIII, Div 1 regarding openings. Multiple openings are treated differently than single openings, which I believe is your case. The ligament efficiency deals with multiple openings, thus it has to be factored in the vessel wall thickness formula.

 A single opening in a head or shell is treated in a different manner, as descibed in UG-36 thru 43. The issue concerning an opening in a pressure vessel is related to local reinforcement. An opening can be smooth bore or contain threads in UG-36 3) c).

Simply provide the minimum calculated thickness of shell plus corrosion allowance at the root of threads, add the additional wall thickness required by UG-31, add the thread depth and this is your minimum required thickness. Now add any minus tolerance on thickness to get the minimum nominal thickness.

prex

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