Good morning,
I have a jacketed pipe; the closure between jacket and process pipe is a reducer.
Reducer and process pipe have the same node number where they are welded together (after this point, process pipe runs without the jacket).
Can You tell me, please, if I have to apply SIF to this node?
If yes, what?
Thanks.
Best regards.

At a node with 2 SIFs ( welded and reducer) you must only 1 SIF set.
Take the max SIF (welded or reducer).

B31.3: reducer SIF = 1