Pinch Valves vs. Diaphragm Valves

[lowdere]

Looking at using pinch or diaphragm valve for a control valve application on dirty water containing abrasive material. I have found products using both technologies, but I am *told* pinch valves do not have good controlability. Can anyone offer advice for this application?

Thanks,
Eric

 

[Ashereng]

I guess that would also depend on the definition of "good controlability".

We have used pinch valves by Sur-Flo:

http://www.sur-flo.net/

for our service (oil with particulates) and it seems to work.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[JimCasey]

Sut-Flo and Red valve seem to be the names in pinch valves.

"Good Controllability" is a relative term. If the valve gives you the results you need, then the controllability is good. You will have, I assume, a low-pressure application with limited velocity. That makes it easier to apply a pinch valve. If the fluid is whistling along at 15 M/sec at 50 bars, your valve choice would be different.

Good control is provided by the valve control surfaces going where they are supposed to be in response to a control signal. Pinch valves have huge unbalanced areas, and the flexible tube can flutter just like the neck of a whoopie cushion. But if you apply the valve at 2-3 meters/sec, it is both much less likely to flutter and much less likely to be consumed by erosion than if the velocity is higher. Spend some extra bucks and go a size larger on the actuator, and use a precision positioner.