I imagine most people use the kellogs methods
for calculating the various local loads due to pipe attachments.
We had a 'Engineer' do work here to compile swl's for pipe supports at the start of a Project.
It was quickly evident that the tecniques used were complete rubbish and he left fairly quickly afterwards.
I believe that the kellog method is a simple addition of the axial,circumfrential, and longitudinal bending stresses, and are compared to simple allowables.
(i have though seen these three stresses added in umpteen different ways.)
Personally, simple FEA would be preferable
(i haver used this though)
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Best Regards