Check valve into header

Hey Guys,
My brains mush. If I have a branch into a header of same pressure is a check valve req'd or just a block valve?
HC

4" branch from wellhead (Produced emulsion - oil) into a 8" header, then off to pipeline
2" steam startup circulation line in same production emulsion oil line 4".

Hopefully that helps

Why not ask process engineer on the same project? They are in better position to tell you also authorized to do that.

Generally speaking you place a check valve where it is not desirable to have backflow. This is common in some instances like pumps where we don't want negative impeller spin but also in branch lines. One common example is in your home where your floor drains have a backwater valve at the exit to outside drains. This prevents your basement from flooding should the sewers surcharge and the liquid level be higher than the outlet of your drains.
Ir depends on each situation, I have one example on my project where small bore pressure drains from a skid are routed to a flare. The idea is to flush the line like a blowdown however the drain only has a double block and bleed so operator error could occur and the drain valves left open. In this case a downstream check valve is required.