It is unfortunate that you need to run a calc on a 1" nozzle, but nowadays many people want to see numbers especially from a "fancy" CII run. You may want to include an SIF for the threaded connection, but this will have NO effect on the nozzle loads. Just include any weights for threaded flanges etc. (modeled as rigids lik any other flange) and keep the calc small; not chase/model these small lines all over the plant.
It is sad we have to waste our time on plumbing.
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Bob Zimmerman, P.E.
Vice President of The Piping Stress International Association (The PSI)