pinch valve
2008-08-25

Many fluids cannot be controlled through conventional valves because of heavy contaminants, high solid content or heavy viscosities. So many industries use specific valves, called pinch valves, to control fluids, wastewater, slurries, abrasives and corrosive chemicals. Pinch valves includes any valve with a flexible elastomer body that can be pinched closed, cutting off flow, using a mechanism or fluid pressure. Pinch valves are full bore, linear action valves so they can be used in both an off / on manner or in a variable position or throttling service. They can effectively control the flow of both abrasives and corrosives, as there is no contact between metal parts and the transport media. Major components of a pinch valve consists of body and a sleeve. The sleeve is crucial to the performance success of the valve. This sleeve enables a pinch valve to have a bi-directional, drop tight shut off with which to control flow. Most pinch valve sleeves are made of flexible elastomer compounds, many of which resemble rubber in composition and feel. Because a sleeve's composition is crucial to the success of the valve's application, valve manufacturers offer different elastomer options from which the sleeve can be constructed. Pinch valves may be closed either by manual means, or fluid actuation. Electromechanical closure is effected by actuating a solenoid, which then lowers a bar or gate onto the sleeve, cutting off the flow. With fluid actuated pinch valves, the pinching action is accomplished by air or hydraulic pressure placed directly on the elastomer sleeve. The valve body acts as a built-in actuator, eliminating costly hydraulic, pneumatic, or electric operators. Because pinch valves are useful in a wide range of industries, they are used widely in medical, pharmaceutical and other sanitary applications.

Wastewater treatment plants use pinch valves wherever sludge flows need to be controlled. Because pinch valves use the rubber body of the valve itself to control the rate of flow, they keep all working parts out of the sludge. Pinch valves are also ideal for controlling the flow of grit. Water treatment plants use pinch valves to control the flow of lime slurries and other thick-flowing fluids. Pinch valves are ideal for corrosive chemicals, because the only part of the valve in contact with the fluid is the rubber valve sleeve itself. Pinch valves are available in a wide range of materials, so there's a resilient option available for nearly every kind of chemical. Food processors use pinch valves for weighing, filling, and processing systems. Pinch valves are extraordinarily versatile, making them ideal for controlling liquid flows as well as solids that behave like fluids. Power plants find pinch valves useful for a wide range of applications, from flue gas desulfurization scrubbers to fly ash handling to controlling coal, coal oil, and ash slurries. Mining industries use pinch vlaves for lime control, dust collection, slurry controls for thickening clarifiers, and leaching processes. Chemical systems offer dozens of potential applications for pinch valves, including lime addition and pH control systems, control of dirty and viscous chemicals, pump isolation, and back-pressure systems. Pinch valves can also be used in pulp and paper mills. Pulp stock, coating and recycled paper lines are some of the most difficult applications for a valve. The flexible elastomer sleeve of a pinch valve are able to withstand these abrasive services. Pinch valves can also be a great asset in food and beverage plants, cement/sand/silica factories, refineries, pneumatic conveying, and scrubbing. While the design of pinch valves provides extensive advantages for use in sterile lines, and in situations where product purity is a high priority; these same design features do create some disadvantages. Due to their elastomeric bodies, pinch valves are not viable in situations where the transport media is of a high temperature. They are also contraindicated for services that require high-pressure flow, and for use with gases.