Pinch valves are similar to diaphragm valves in that the body has sleeves that can be squeezed to control or halt the flow.
A pinch valve is a flex-body valve with a flexible tube that may be mechanically pulled together or “pinched” to close the flow passage completely through a mechanism or fluid pressure. The flow passages of these valves are straight, with no splits or moving parts. The pinch valves’ soft bodies can seal around the trapped solids. Pinch valves are hence useful for handling slurries, foodstuffs, and pharmaceuticals. Pinch valves are less expensive and have a simple design.
What is Valve and what are the major types of Valves?
Operating Principle
Pinch valves make use of an elastic tubing (sleeve/hose) and a device that makes direct contact with the tubing (body). Forcing the tubing together will result in a seal with the same permeability as the tubing.
An elasticized reinforced rubber hose, a type of housing, and two-socket end caps comprise air-operated pinch valves (or flanges). The rubber hoses in air-operated pinch valves are normally press-fitted and centered into the housing ends by the socket covers.
There is no additional actuator; the valve closes as soon as pressured air enters the body. The elastic rubber hose begins to open due to the force of the process flow when the air supply is terminated and the volume of air exhausts.
How does a pinch valve work?
A pinch valve is made up of three main parts: a housing, an internal rubber sleeve, and end connectors. The only component that comes into touch with the media and is installed into the housing from input to output is the rubber sleeve. To give stability and connection to the valve, the end connectors are fastened, screwed, or threaded at either end. In its natural state, the valve is open (un-pressurized). When compressed air is delivered to the valve, it forces the rubber sleeve downward, causing a pinching action. The flow is blocked and the valve closes when the rubber sleeve is fully compressed. Unlike traditional valves such as a ball or gate valves, which can trap particles around the ball or discs, the rubber sleeve of a pinch valve can trap particles surrounding it, providing a good shut-off. When the external air pressure is removed from the rubber sleeve, the elastic rebounding property of the rubber sleeve, combined with the force of the flowing media, fully opens the valve. The fully opened valve allows unrestricted flow access to the media, preventing clogging or blockage. The media is also solely in touch with the rubber sleeve, allowing the media to be isolated with no contamination or harm to other components.
When abrasive media strikes the rubber sleeve, the impact is absorbed and deflected back to the medium. This robust feature allows the rubber sleeve to wear significantly slower and last longer than metal surfaces.
What are the types of Pinch Valves?
- Clamp Valve
- Air Operated Pinch Valves
Clamp Valve
This type of pinch valve features a flexible tube or clamp with a heat-shrunk reinforcement jacket made of fluorocarbon resin. A compressor moves down a stem with the rotation of a hand-wheel or power operator, and a yoke travels up the steam at the same time.
Air Operated Pinch Valves
We were able to achieve complete and genuine full bore by using an air-actuated pinch valve, and they are also capable of performing tight shut-off even on solids such as granules, pellets, and any type of slurries. Because the kinetic energy of the solids is absorbed through the extraordinarily high elasticity of the rubber, air-powered pinch valves work without causing any damage to the elastic rubber hose.
What are the selection criteria while choosing pinch valves?
When choosing a pinch valve for your application, keep the following criteria in mind:
- Material
- Maintenance
- Carryover Volume
- Temperature
Material
The materials used in the flow path are an important factor to consider when choosing pinch valves. The pinch tube is the only wetted material in external pinch valves. Tubing alternatives vary greatly; tubing selection is determined on compatibility with biological fluids and organic solvents. As a result, it is critical to run tests for each application. Tubing connectors must be chosen and qualified independently. Internal pinch valves often feature more than one wetted substance and incorporated tubing connectors such as hose barbs or threaded fittings. Because they are far more difficult to alter, these materials are chosen for their compatibility with a wide range of applications. As a result, compatibility difficulties are uncommon.
Maintenance
Don’t forget about continuing maintenance. Any valve selection should take into account maintenance requirements. This is critical for valve dependability as well as application stability.
Ball valves are a nice example of this. They are not clogged, jammed, or faulty. However, they are ineffective for regulating flow. When used to control flow, they might cause leaking or premature failure.
The type of valve connection influences the ease and speed of repair or replacement. Each connection type (threaded, barbed, push-in, and so on) has advantages and disadvantages.
Carryover Volume
Carryover volume is the amount of fluid volume that remains after a valve changes states. This is normally not a problem with 2-way “on-off” pinch valves; but, with 3-way pinch valves, the volume carried over can mix with other fluids and is wasted when flushed out. As a result, reducing this volume is critical. When carryover capacity is a factor, internal pinch valves provide a significant advantage since the volume between the pinch point and the Y-shaped combination point is minimised.
Temperature
Check that the valve materials can resist the application’s lowest and maximum operating temperatures.
Applications of Pinch Valves
Pinch valves are commonly employed in applications where the media must be totally isolated from any internal valve components. The sleeve will keep the flow media contained and isolate it from the environment, reducing contamination. They are commonly used in medical devices, clinical or chemical analyzers, and a variety of laboratory equipment.
Because the flexible rubber sleeve shuts drop tight around solids, pinch valves are also employed for slurries or processes with entrained materials. This prevents entrapment by the seat or in crevices, which could occur if a globe, diaphragm, butterfly, gate, or ball valve was used.
- Food and beverage industries
- Pharmaceutical industry
- Chemical industry
- Cement industry
- Bulk and solid handling industry
- Ceramic industry
- Plastic industry
- Wastewater industry
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Advantages and Disadvantages of Pinch Valves
Advantages of Pinch Valves
- Low maintenance cost
- Self-cleaning
- Useful with abrasive and corrosive media.
- Low turbulence and friction
- There is no pollution.
- Timely opening and shutting
- Rubber sleeves can be easily replaced.
- Excellent sealing properties
- Low energy consumption
- Low sleeve wear due to streamlining and laminar flow pattern
Disadvantages of Pinch Valves
- The valve is not appropriate for high temperature applications due to the elastomeric feature of the sleeve.
- Due to the high-pressure differential, the rubber sleeve may collapse or distort, causing the valve to not fully open.
- Suction inside the valve may cause the sleeve to collapse, making the valve unsuitable for vacuum applications.