Pinch valves are divided into two types: support sleeve and unsupported sleeve. The picture shows a pinch valve without a support sleeve, which is a commonly used pinch valve. An elastic sleeve is installed in a split metal valve body so that the fluid only contacts the sleeve. The metal valve body is a pressure vessel made of cast iron or aluminum, and the operating air pressure should be greater than the fluid pressure. The diameter of the sleeve is the same as that of the pipe. When the pinch valve is fully opened, there is no pressure drop at both ends of the valve. The sleeve and the valve body are pressurized with compressed air, liquid or process fluid. When pressure squeezes the sleeve, the sleeve pipe restricts the fluid, forming a pressure drop, and adjusting the fluid flow. When the pressure disappears, the original shape is restored under the elastic force of the sleeve. This kind of pinch valve is suitable for DN25~DN1200mm, which can contain solid particles.
The pinch valve supporting the sleeve is supported by a pipe with slots of equal height, which is sealed in the pressure tank. The support pipe is divided into an inlet and an outlet by a formed plug. The plug is used to prevent fluid from directly entering the pipeline. The fluid entering the valve is forced to exit the pipe radially through the slot. In this way, the elastic sleeve is lifted away from the valve seat it surrounds, and the fluid must flow radially back to the pipe and exit the valve. The fluid pressure lifts the sleeve away from the support tube valve seat. The force of the fluid is offset by the pressure of the control fluid and the elastic force generated by the elastic sleeve. This kind of pinch valve is suitable for clean fluid with rated working pressure <10MPa and DN<300mm.
The sleeve should be made of thermoplastic, elastic materials with good wear resistance and chemical compatibility, such as chlorinated butyl rubber, ethylene propylene rubber, neoprene rubber, polyurethane, and fluoro rubber.
The characteristics of the pinch valve are as follows.
1. The adjustable is relatively small, generally 8~26 according to the structure of the sleeve.
2. There is no valve stem and packing, etc., with good sealing performance, which can meet the requirements of bubble sealing.
3. It can handle fluids with entrained solids.
4. For split pipe clamp valves, serious accidents such as leakage of the controlled fluid due to the failure of the sleeve will occur.
5. Due to the limitation of elastic materials, the temperature and pressure resistance are poor. Generally, the temperature for continuous application should not exceed 200″C.