Let's say you have a 3"J4" PSV with a 10" discharge line to a collector system. And let's suppose that you are doing your back-pressure hydraulic calculations either with HYSYS or FlareNet. In order to accommodate the 4"to10" reducer, in the outlet, into your calcs, would you add a 4" line with an enlargement into your model or you will just consider that reducer in your 10" line (probably as enlargement or contraction)? because it makes a large difference: if you do consider a 4" line in your hydraulic calcs, in most cases, it would be your major pressure drop if you have a large flow.
I appreciate your help, but please answer ONLY my question and right to the point...thanks