What is Pinch Valve? Working Principle & Function
The Pinch Valve is a solenoid-operated device that opens and closes tubes to control the flow of liquids and gases. In pinch valves, there are no dead zones or dead volumes where fluid can become trapped. Only the inside of the tubing comes into contact with the fluid. A pinch valve is a low-cost device that works in the same way as a tap. It has an on/off switch for turning off, allowing, or controlling the flow of any medium that passes through it. Pinch valves work well with slurries and granular materials, including sand, cement, gravel, textile fiber, charcoal, powder, pellets, chipping, glass fragments, and so on. These valves are cost-effective, dependable, and easy to use, making them excellent for a wide range of industrial applications. Using the proper pinch valves is an important component of working with industrial instruments. Pinch valves are air-operated devices that control liquid and gas flow by opening and closing tubes. There are, however, a variety of types with various prices that rely on diaphragm functions to function well.
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What is Pinch Valve?
A pinch valve is a full bore or fully ported control valve that obstructs fluid flow by pinching the valve.
Function and Application of Pinch Valves
A pinch valve is a flex-body valve with a flexible tube that may be mechanically pulled together or "pinched" by a mechanism or by fluid pressure to close the flow passage completely. These valves have a straight flow path with no fissures or moving elements. The pinch valves' soft bodies have the potential to close around the trapped materials. Pinch valves are ideal for managing slurries, foods, and medications because of this feature. Pinch valves are also used in the following industries:
- Cement industry
- Pneumatic Conveying industry
- Plastic industry
- Ceramic Industry
- Chemical industry
- Wastewater industry/Sewage treatment plants
- Dosing and weighing systems
- Environmental industry
- Commercial vehicle industry
- Mining industry
- Bulk and solid handling industry, etc.
Pinch valves, also known as clamp valves, are used to control or stop the flow of corrosive, abrasive, granular, fibrous, or abrasive media. Sludges, dust, emulsions, gaseous materials, powder, compressed air, granulates, pellets, and other materials can all benefit from the Pinch Valve as an isolating or controlling valve.
Working Principle of a Pinch Valve
A pinch valve is made up of three basic components: a housing, an elastomeric rubber sleeve, and end connectors. The elastomeric tube is the only component in contact with the flowing fluid and is placed into the housing with a pinch bar mechanism from inlet to exit. To provide support and connection, the end connections can be screwed, bolted, or threaded at each end.
Pinch mechanisms come in a variety of shapes and sizes. A basic screw-operated device that simply pinches one side of the tube, or a differential screw that pinches both sides of the tube. Mechanical mechanisms that squeeze the tube with air or hydraulic pressure can also be utilized.
The pinch valve is open in typical circumstances. When air or hydraulic pressure is applied to the valve, the elastomeric rubber sleeve is pushed down, pinching the valve. The flow is restricted, and the valve is closed when the sleeve is entirely pinched. A pinch valve's rubber sleeve has the potential to trap particles around it, resulting in an excellent shut-off.
The force of the flowing media and the rubber's rebounding property entirely open the valve when the external pressure is released. This fully opened valve allows the media to flow freely, preventing the valve from being clogged. The medium remains isolated because it only comes into contact with the rubber tube, ensuring that it is not contaminated.
Types of Pinch Valves
There are two types of pinch valves, depending on the body construction:
- Mechanically pinched valves are usually of the open kind, with no metal body casing. The open construction of pinch valves is used for visual and physical inspection of the valve body during operation. Although this is the simplest form, the liner is exposed to the elements.
- Enclosed pinch valves: From the outside, enclosed-body pinch valves resemble globe valves. The housing serves as a protective shell for the liner. Inside the metallic casing is the pinching mechanism.
Pinch valves can be one of the following sorts, depending on the pinching mechanism:
- Pinch Valve (Manual)
- Pinch Valve with Air Operation and
- Pinch valve controlled by hydraulic pressure.
Advantages and Disadvantages of Pinch Valves
A pinch valve's unusual design offers a number of benefits, including:
- It's safe to use with caustic and abrasive media.
- Low weight, small, simple, durable, and straight through design are all features of this product.
- There should be as little turbulence and friction as possible.
- The medium does not impede the flow path, resulting in a straight flow path.
- There is no pollution.
- Timely opening and shutting
- Low-cost maintenance
- Cleaning by itself
- Rubber sleeves can be easily replaced.
- Excellent sealing properties
- Low usage of energy
- Due to the streamline and laminar flow pattern, the sleeve will last longer.
Pinch valves, on the other hand, have several drawbacks, such as:
- Because elastomeric materials have temperature resistance limitations, the pinch valve is not suited for high-temperature applications.
- The rubber sleeve can collapse or deform on high-pressure differentials, and the valve may not be fully open.
- For vacuum applications, the pinch valve is ineffective.
- For pulsing flow, this is not the best option.
Selection of Pinch Valves
When choosing a pinch valve for a specific application, there are a number of crucial factors to consider. These are some of the parameters:
Body material for pinch valves: Lightweight body material is desirable. Because it comes into direct contact with the moving fluid, the elastomeric sleeve should be carefully chosen. EPDM, NBR, natural rubber, silicone, food-grade rubber, GRS, Neoprene, Butyl, Buna-N, PTFE, FDA, Hypalon, and other rubber compounds are common. To avoid damage, good abrasion resistance is essential.
Pressure Differences for Opening and Closing: The pressure differentials must be precisely considered for appropriate pinch valve operation.
Design temperature: The valve material should be able to tolerate the application's minimum and maximum temperatures.
The sleeve material is chosen from a variety of acceptable synthetic polymers based on the flow media's corrosiveness and abrasiveness. The operation temperature, which must be within the polymer's limit, is an important selection factor.
Pinch valves come in a variety of rubber qualities, including natural rubber, EPDM, nitrile, Viton, neoprene, and butyl. Housings and end covers/flanges are available in various materials, including aluminum, plastics, and stainless steel.
FAQs about Pinch Valves
- What is the purpose of the pinch valve?
A pinch valve is a low-cost piece of equipment that functions similarly to a tap. It contains an on/off switch that can be used to turn off, allow, or control the flow of any medium that passes through it.
- What is a pneumatic pinch valve?
The NPP Series 2-Way pneumatic pinch valves from Clippard are air-piloted devices that open and close tubes to control liquid and gas flow. There are no regions or dead volume in pinch valves where fluid can become trapped. The fluid only comes into contact with the inside of the tubing.
- How does a pinch valve stop flow?
Pinch valves are similar to diaphragm valves in that they have sleeves on the body that can be squeezed to control or halt the flow. Corrosion-resistant materials, such as rubber or PTFE, could be used for the sleeve. By squeezing and sealing a synthetic or natural rubber tube, these valves stop the flow.
- What do pinch valves and diaphragm valves have in common?
In terms of function and design, diaphragm valves are similar to pinch valves. In the valve housing of both, a soft seal rubber element performs the major role of preventing the flow of media.