I mistakenly mentioned S.O. flanges when I intended to refere to lap joint flanges.
The specifications that I have for general flanged connection are:
1) Sch 40S A-312 SS pipe, stub ends, A-105 class 900# lap joint flanges.
2) Sch 10S A-312 SS pipe, stub ends, A-105 class 150# lap joint flanges.
These are for various process services.
I was wondering if it is good practice to install restriction orifices with this lap joint flanges or it is better to use welding neck flanges instead.