Flow Meter Before or After Backpressure Valve
Flow Meter Before or After Backpressure Valve
(OP)
Hi,
I am going to install a Corolis Flow Meter From Emerson Products that is going to measure flow of about 0.8 GPH. I was going to place it before a backpressure valve having a pressure differential around 20 psig. The line after the backpressure valve is around 25 ft long. Will placing the meter before or after the valve hav any effect on its measured flow? I was going to put it before since having higher pressure at the flowmeter helps improves its accuracy.
Thanks.
I am going to install a Corolis Flow Meter From Emerson Products that is going to measure flow of about 0.8 GPH. I was going to place it before a backpressure valve having a pressure differential around 20 psig. The line after the backpressure valve is around 25 ft long. Will placing the meter before or after the valve hav any effect on its measured flow? I was going to put it before since having higher pressure at the flowmeter helps improves its accuracy.
Thanks.





RE: Flow Meter Before or After Backpressure Valve
Neither of these issues are show stoppers, both are pretty small impacts so if there is a compelling reason to put it downstream (e.g., equipment access) then you won't be doing a terrible thing. In other words, if all other things are equal, put it upstream, if not then put it where the other issues dictate.
David
RE: Flow Meter Before or After Backpressure Valve
RE: Flow Meter Before or After Backpressure Valve
When the Corolis meter first hit the market, they flogged it as a final solution to the age-old question of how to measure multi-phase flow. That marketing crap quickly went by the wayside. The meter is detecting the momentum of the flow stream and using that to infer a volume flow rate. If flow is constant then it "knows" density. If density is constant it "knows" mass flow rate and will infer a volume flow rate from the constant density.
Your controls guys have it right for a system that is intended to measure liquid. The introduction of a small amount of gas will introduce a significant error in density and therefore the momentum measured will result in the inference of the wrong volume.
On the other hand, there are a significant number of these gadgets working well in gas service. In gas service they are more forgiving of small water incursions, but a slug of liquid will still give you interesting answers.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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