Pank143,

What do you think the sif is controlled by ? The overall shape or the connection detail ? Or both ?

There is no hole in the parent pipe where a trunnion is located.

A trunnion weld is commonly a fillet weld, whereas a tee will always be a full penetration weld.

Perhaps you have not noted the wide variation of sif's for differing types of tee. There is a clue here, that your statement is quite wrong.