Sir,
There is no harm in using SIF of these ASME B 31.3 unlisted components like elbow stanchion or 90 deg trunions; better the SIFs come from some FEA analysis using FEPIPE.
If we have only CAESAR II, we can multiply/divide B 31.3 App D SIF/flexibility factor by some safety factor ( say 1.5 or 2), by first getting larger of unreinforced/reinforced tee & bend SIF/flexibility factor from CAESAR II.
Perhaps you are discussing about 90 deg trunions, where Coade directive of using WRC-107 for cylindrical shell/nozzle attachment is okay. But, I have seen people using 2.1(max value for fillet weld joint,socket weld flange or fitting SIF in B 31.3 App-D) as SIF in this application, the source of which some experienced forum member may be able to explain to us.
regards,
sam
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