Pinch valves are designed to control or stop the flow of corrosive, abrasive, fibrous and granular materials. These include sludges, dusts, emulsions, gaseous materials, compressed air, powder, pellets, and liquids containing solids among others.
Proportional pinch valves provide complete media isolation, eliminating a possible leak path and ensuring repeatable, consistent flow. These valves are ideal for pharmaceutical, bio-tech, semiconductor, life science and food & dairy applications.
Using air to operate pinch valve eliminates expensive mechanical parts, bearings, seals and packing that are required for other flow control valves. The only wetted part of the valve is a rubber sleeve, which acts as a built-in actuator to close or open the valve.
The sleeve can be made from a polymer that is suitable for the specific abrasion and corrosive characteristics of the flow media. A rubber sleeve is also more durable than many other types of valves due to its high rebound elasticity.
A sleeve can be manufactured in different thicknesses to suit the specific application. This allows a more consistent wear layer that increases the service life of the valve and reduces wear.
In comparison to traditional pneumatic valves, pinch valves are easy to install and operate, making them ideal for quick turnaround applications where there is limited access to power sources. They can also be used to prevent clogging and to isolate media in sanitary processes.
Air operated pinch valves work by introducing air or hydraulic pressure directly on the valve’s only wetted part, the flexible rubber sleeve. The sleeve is then compressed, causing it to open or close as desired.
Generally, a minimum air pressure of 25 psi is required for full closure. However, this pressure must be applied at least half way through the stroke. If a pinch valve is throttled too soon the smooth walls of the sleeve can be damaged or the resilient liner may tear, resulting in an ineffective throttling operation.
The effective throttling range of pinch valves is between 10% and 95% of the rated flow capacity. This is because the sleeve’s resilience and smooth walls take up most of the energy in the opening cycle before the media reaches a certain flow rate. This is why pinch valves can only be throttled at the last 50% of the stroke, rather than the entire open position.
This enables the pinch valve to be operated from a distance, without the need for a person to be present in the plant or to be located near the valve. It is therefore a safe and cost-effective solution for a wide variety of applications in the chemical, food, pharmaceutical and filtration industries where media are often contaminated with particles.
The sleeve is also self-cleaning, allowing the valve to be serviced without compromising product purity and safety. The sleeve is also easily replaceable, reducing downtime and maintenance costs.