Most valve types are either good at sealing or good at controlling flow, rarely both. A gate valve seals but destroys itself when throttled. A globe valve controls well but wears badly in abrasive service. A pneumatic pinch valve is unusual in doing both — and the reason lies in how it is actuated.

A pneumatically actuated pinch valve closes by admitting compressed air into a chamber surrounding a flexible sleeve. As pressure rises, the sleeve is squeezed progressively. There is no discrete open or closed position — increasing air pressure reduces the flow area continuously, and reducing it lets the sleeve recover.

That makes the valve inherently proportional. A regulator on the air supply becomes a flow control, which is why pinch valves are used for trimming flow on slurry lines where other valve types would be destroyed by throttling.

In a gate or ball valve, throttling means a metal edge sits in a high-velocity stream. In a pinch valve, throttling means an elastomer sleeve forms a smooth converging passage. The medium still touches only elastomer, and nothing slides across anything. The wear that occurs is distributed over the sleeve and appears as gradual thinning rather than localised erosion.

See the VMP pneumatic pinch valve for a standard air-operated design.

The relationship is not linear. Near the closed position, a small additional pressure produces a large reduction in area; near fully open, a large change in pressure produces little change in flow. Practical installations therefore use a positioner or a characterised regulator rather than assuming a straight line. The important property is repeatability — the same air pressure gives the same opening, cycle after cycle.

To close against line pressure, the actuator must develop enough force to overcome it. This is why a pinch valve needs a defined air pressure to suit a given line pressure, and it is worth confirming the available air supply before specifying the valve rather than after. A valve that cannot fully close will never seal reliably.

For heavy abrasion, the PVE heavy duty pinch valve is built for mining, cement and slurry duty.

Sleeves are available in natural rubber for abrasive duty and in food-grade EPDM for food and pharmaceutical contact. Tell us your line conditions and we will size the valve. See the pinch valve range or read the selection guide.