Pinch valves are a type of non-contacting valve that control and stop the flow of fluids. They can be used in a wide range of applications and are commonly found in the chemical, sewage treatment, industrial, and food processing industries.
A pinch valve consists of three parts: a housing, an elastomeric rubber sleeve and end connections. The sleeve is placed in the housing from inlet to outlet, while the end connections are screwed or bolted at each end to provide support and connection to the valve.
The sleeve is made of rubber or other synthetic material. It resists wear from abrasion and corrosive media. It is typically reinforced with fiber to increase strength and durability. It is also lined with polyurethane to improve abrasion resistance.
Pinch Valves can be actuated using either pneumatic or manual methods. The pneumatic actuation method uses an air nipple on the valve body and is pressurized to crush the sleeve in a particular direction, which completely closes the valve.
Some pinch valves can be actuated by an electric motor actuator. These electric pinch valves permit manual, semi-automatic and automatic operation. The energized and non-energized time of an electric pinch valve is usually expressed as a duty cycle, which is calculated by the relationship between (ON time) and (ON +OFF time).
There are two primary types of pinch valves: external and internal. The type of evr valve you choose depends on the end-use application and the amount of maintenance you need to perform.
External pinch valves are better for medical or scientific instruments with frequent flow path replacement, including in-vivo diagnostic applications where blood and organic solvents may be present. These types of valves are rated to 5 million cycles or more before they need to be replaced, while internal pinch valves require less maintenance and can be rated to 200,000 to 500,000 cycles.
The sleeve for a pinch valve can be made of a variety of materials, including natural rubber and silicone. It should be resistant to abrasion from flowing media and must have good temperature resistance.
In addition, it should be lightweight to minimize weight and stress on the sleeve during cyclic operation. It should be able to handle low pressure differentials so that it can open and close with minimal control force.
Typical pinch sleeve materials include EPDM, NBR, natural rubber, silicone, GRS, Neoprene, Butyl, Buna-N, PTFE, FDA and Hypalon. They must have good abrasion resistance to prevent damage and must be able to withstand the minimum and maximum temperatures expected for your application.
These sleeve materials should be selected carefully and qualified. They must be compatible with the fluid being pumped through them and must meet all applicable regulatory requirements.
A pinch valve can be used in a wide variety of applications where flow path replacement is not a concern or cost-reduction is an important factor. For example, dialysis machines use external pinch valves to eliminate cross-contamination from patient blood samples. The same can be said of many other industrial applications, especially those where the pumped media is difficult to remove.