Pinch Valves Vs Slide Gate Valves: A Comparison
It may not be obvious which is the right valve type for your project. While most folks have an idea of which valve type is ideal--or even required--for their process system, this may not always be the case. This article is a primer of what to consider in the differences between slide gate/knife gate valves and pinch valves.
One of the first differences is shape. While this may seem self-evident, do you have enough space where you want to put your valve(s)? If space is tight, air operated pinch valves offer pretty compact in-line valve solutions. So placing them in crowded process areas is pretty easy, as long as you can manage the height of the valves. Slide/knife gate valves have admittedly shorter heights, but must have larger actuator bodies around them that protrude perpendicularly (at least on one side) from the direction of the pipe.
Laminar flow is the phenomenon of fluid particles flowing in smooth paths. This may not be visible when the material flows inside a pipe, however it may still be happening, or something close to this effect. Pinch valves offer a great advantage of basically being so smooth in their design, that they offer a completely smooth path of material flow when open. This can reduce resistance and wear inside a system and may be desirable. Slide/knife gates, in order to provide tight seals, have some turbulence-inducing design, where the gate actually meets the inner diameter of the valve body. It should be noted that for most applications, this is simply imperceptible and negligible, but for a few applications this may be important.
Pinch valves are, generally speaking, self-cleaning. As your product flows through the sleeve there is virtually no crevice for any to bury itself into. If you need to self clean a pinch valve, it is pretty much like cleaning a pot or pan in your kitchen. Pretty easy to access and clean. For slide and knife gate valves, these are not self-cleaning nor easy to clean. Slide / knife gate valves must be disassembled to access and clean all surfaces, which is very difficult. It is more compared to cleaning a toaster, not easy without disassembly.
Typically pinch valves are suitable up to 6 bar sealing pressure and since there are not working seals to maintain, pinch valves do not leak, even when operating with abrasive materials. A typical knife gate can be suitable for higher pressures, but does have more difficulty sealing the pressure, especially in abrasive applications where seal wear becomes an issue.
Both valve types are famously low maintenance when chosen for the correct applications. The choice of each valve should be evaluated with regard to the application they will be regulating. However, neither is wholly higher maintenance than the other. Pinch valves do find more popularity among those regulating the flow of abrasive applications where knife gate valves may not be ideal.