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Pinch valves use a flexible sleeve to constrict or close the flow path, making them effective for controlling fluids with high concentrations of suspended solids. They can be operated mechanically or with compressed air and are suitable for flow control applications due to their wide operating ranges.
A pinch valve is a fluid control device that works on the principle of constricting the flow path to reduce or close the passage of material. Most pinch valve designs feature a highly elastic sleeve or insert in the valve body that is gradually constricted or closed by air pressure or mechanical intervention. This valve closing method is not only effective for controlling clean fluids, but also works well for slurries with high concentrations of suspended solids. This is because the flexible sleeve is able to form an effective seal around trapped particles that would otherwise jam or block the mechanism of other types of valves. Pinch valves are also particularly suitable for flow control applications due to their wide operating ranges.
Most valve designs rely on placing a solid barrier in the fluid flow path. It is usually a metal gate, ball, or wedge that is progressively pushed down to close an opening in the flow path, or snaps shut under spring pressure. These valves are suitable for controlling clean fluids but are unable to handle those with high concentrations of suspended solids due to the fact that particulate grains tend to jam the metal barriers. In these applications, the pinch valve proves to be one of the most effective solutions for both clean water and sludge suspensions.
Pinch valves generally consist of a metal casing equipped with a manual or electrically operated mechanical gate valve or a compressed air supply socket mounted on the top of the casing. Inside the casing is a highly flexible sleeve that forms the path for fluid flow through the valve. As the valve is actuated, the sleeve is gradually squeezed and closed in the center of its length to cut off the flow of fluid. This constriction can be achieved in two ways: mechanically or with compressed air.
The mechanical pinch valve is operated manually by turning a handle similar to those on gate valves or electric motors. In both cases, the handle or motor turns a machine screw which drives the valve mechanism. This mechanism typically consists of two flat metal bars, one above the sleeve and one below. As the lead screw rotates, it pulls both rods together simultaneously, thus tightening the sleeve as they do so.
Air operated valves have a contoured chamber that surrounds the sleeve. The compressed air is introduced into the chamber through a solenoid valve and a nipple; as pressure builds in the chamber, it tightens the sleeve until it is completely closed. When the valve needs to be opened, the cycle is reversed and the air is forced out, thus allowing the sleeve to return to its full port size. Due to the highly elastic nature of the sleeve and the gradual constriction exerted on it, pinch valve designs are well suited for flow control applications that require precise regulation over a wide range of flow rates.
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