Pinch valves are a type of non-contacting control valve used for a variety of applications, including medical and pharmaceutical manufacturing, wastewater treatment, and sewage disposal. They are also used in pipelines handling corrosive fluids.
A pinch valve is a type of linear flow control valve that utilizes a single, non-contacting, rubber sleeve to isolate media from the rest of the system and provide a reliable shut off. This design prevents fouling of other parts of the valve and allows for easy maintenance, operation, and replacement of sleeve material.
These non-contacting valves are usually manufactured from aluminum or polyamide blends and stainless steel in washdown applications. Their sleeve material is usually a rubber elastomer or a synthetic material. The material should be able to withstand harsh conditions and resist corrosion, and the sleeve can be easily replaced when necessary.
The sleeve is the only wetted component of the valve and must be selected carefully to avoid damage from the media that it encounters. This is why the sleeve material should be lightweight and have good abrasion resistance. Common sleeve materials include natural or synthetic rubber, NBR, EPDM, GRS, Neoprene, butyl, Buna-N, PTFE, FDA, and Hypalon.
Body material is another consideration for pinch valves. Lightweight body material is ideal because it is easier to handle. This is important for applications where the sleeve needs to be removed or replaced frequently. The sleeve should be a natural or synthetic rubber that does not require the use of packing since the valves do not typically come into contact with the media.
Generally, these valves are closed by hydraulic pressure or air injected into the valve body. However, they can be operated manually by turning a hand wheel.
Pinch valves are available in a variety of sizes and types. The most popular designs include screw-operated pinch mechanisms, differential pinch mechanisms that pinch both sides of the tube, and mechanical pinch valves that use compressed bars to actuate the sleeve.
Some of these pinch valves are designed with conical sleeves that improve the linearity of the control curve. This reduces pressure differences during opening and closing, resulting in more uniform flow through the valve.
These pinch valves are not suited for high-pressure, pulsating or vacuum flow applications because the sleeve could collapse on these applications. They also cannot be fully open on high-pressure differentials.
A pinch valve can be controlled by air or hydraulic pressure applied to the sleeve and can close under 25 psi over line pressure. This is a cost-effective alternative to expensive hydraulic, pneumatic, or electric operators and eliminates the need for manual intervention.
The sleeve must be able to withstand high temperatures and the application’s minimum and maximum requirements. In addition, the sleeve must have enough rebound elasticity to be able to close freely when compressed.
The sleeve should be molded of natural or synthetic rubbers and plastics that have good abrasion resistance, as this will allow little damage to the sleeve if it is subjected to media impact. This will help the valve last longer and reduce maintenance costs.