To throttle before or after...That is the question ..:) 1

[offett]

We have an orifice plate to measure the flow and then a throttling globe valve to balance the flow in each branch in our system. Each branch has an orifice plate upstream of its throttling valve. I would like to know what are the advantages/disadvantages of throttling before the orifice plate vs throttling after the orifice plate? Thanks!

 

[LittleInch]

You don't say whether this is for liquid or gas, but similar issues apply. Three should be no real difference, but the main thing is to locate your plate where there is little turbulence. Clearly after a globe valve three will be a lot of swirl and disturbance so the orifice would need to be a long way downstream (20D) or you need to put in a flow straightener of some sort.

Other than that unless there is a big pressure loss in a gas system which means your size goes up, there's not a lot in it IMO.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

After causes less turbulence hitting the orifice plate.
Turbulence doesn't do much for accurate measurements.

Independent events are seldomly independent.

 

[Artisi]

Let's make it 3 in agreement, after is less trouble as it reduces the likelihood if turbulence.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Pumpsonly]

If you throttle before the OP, other than possible turbulence caused inaccuracy,you may not get a full flow at the piping down stream of the valve to the OP if high degree of throttling is required.

 

[offett]

Thank you all.. I will always instal my orifice before my throttling valve with appropriate distance between the two to negate turbulent effects in system.