I know this is a bit out of point related to CAESAR, but i need some help.

Lateral Tee or 45 degree Tee is normally used for flare system.
However, there is no specific reason.
spec. is Just saying, stress, vibration, etc.

If anyone well knows this, please let me have your kind advice.
I want to know why lateral tee is used and what the benefit is.

As far as I know, it is to avoid the direct impingement of fluid on the header inside wall. Basically, to minimise the effect of kinetic energy 45° TEE is used.
Also, in case of relief valve discharge, to avoid the accumulation of liquid, such arrangement is used.

Somebody can correct me OR add if something is missed here.