Dear Richard/Dave,

The main header size is 46" NB and branch line is 2" NB.

Query 1: Which connection is preferable weldolet connection or reinforced stub in for above mention header/ branch size as far as SIF is concern?

Query 2: How does Caesar calculate SIF value for Weldolet connection and Stub in RF type ? If it is appendix D , ASME B31.3 , as per which formula ?

Regards,
Maulik

This illustrates a good use of our Tee Scratchpad (below). A processor which is also accessible in the Piping Input Processor.
In terms of stress intensification, it's pretty much a toss-up. They are similar (using my assumptions).
You should be able to match the SIF formulae in Appx. D to what CAESAR II shows.
If you are calculating Code stress by hand, remember to consider the "effective section modulus" (Ze) for reduced outlet intersections.