What is a diaphragm valve? - Fluid Controls

In applications requiring some level of fluid control, there is likely to be a diaphragm valve involved as a major component. There are several types of diaphragm valves that each have their own properties and characteristics. Because of their many advantages, they&#;re hugely popular within the fluid control industry. Continue reading our helpful guide to discover more about what a diaphragm valve is.

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Diaphragm valves explained

Diaphragm valves make use of a flexible diaphragm to control, obstruct or isolate the flow of fluids. They can handle liquids, gaseous fluids and semi-solid media such as slurries, colloids, sludges, and brackish water. The diaphragm acts as the flow control element that flexes up or down to increase or decrease the fluid flow rate.

The sealing action of the valve is created as the diaphragm presses onto the solid dam inside the body. Diaphragm valves are classified as linear motion valves that require linear motion of the flow control element.

Diaphragm valves are ideal for handling liquids with solid particulate matter. They&#;re also widely used in the food and pharmaceutical manufacturing industries, as well as water treatment, sewage pipelines and treatment plants, electronics manufacturing and pulp and paper production. 

This is because, compared to other valves, diaphragm valves have a simple construction. Due to minimal contact made by their internal components, the build-up of sediments and biofilms is less likely to occur.

Advantages of a diaphragm valve

Diaphragm valves are available in a wide range of materials to suit various industrial applications. They&#;re also very popular because of their many benefits. Diaphragm valves are a small, yet crucial, part of process control and here is a selection of their main advantages:

• Applicable for a wide range of applications and environments.
• Various types and materials of diaphragm valves are available.
• Media flowing through the valve acts as a pilot and influences positioning of the diaphragm, placing the valve in its most suitable position.

Components of a diaphragm valve

There are several parts of a diaphragm valve that make up its composition. Each part has a vital role to play in the way the diaphragm valve works within its given application.

The full list of a diaphragm valve&#;s components are:

• Bonnet
• Valve body
• Diaphragm
• Compressor
• Stem
• Actuator
• Position indicators
• Connection

Bonnet

The bonnet serves as the top cover of the diaphragm valve and is bolted to the body. Its main function is to provide protection to the compressor, stem, diaphragm, and other non-wetted components.

Valve body

The valve body is directly connected to the pipeline where the fluid passes through. The flow area in the valve body depends on the type of diaphragm valve.

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Diaphragm

The diaphragm lifts if the fluid flow rate is increased or the valve is to be fully opened. The fluid then flows underneath the diaphragm. It isolates the non-wetted components (compressor, stem, actuator) from the flowing fluid. This means that solids and viscous fluids are less likely to interfere with the operating mechanism of the diaphragm valve.

Compressor

The compressor is a disc that lies between the valve stem and the diaphragm, supporting the valve and distributing the forces from the stem during linear movement.

Stem

The stem is a vertical shaft connected to the compressor that exerts linear motion to move both the compressor and diaphragm. Diaphragm valves can either have piston- or threaded-type stems. Piston-type valves are moved by a piston inside the bonnet with the valve stem acting as the piston rod. This requires linear force exerted by fluid pressure.

Threaded stem valves have a matching stem nut which requires torque to linearly move the stem, as well as lubrication for smooth operation.

Actuator

The actuator is used to move the stem, compressor and the diaphragm together. It provides the torque or linear force required by the diaphragm valve to rapidly control the flow rate. 

There are five types of actuators used in diaphragm valves:

• Manual actuators
• Electric actuators
• Pneumatic actuators
• Hydraulic actuators
• Thermal actuators

Position indicators

Position indicators are visual guides used to identify the position of the diaphragm valve, whether it is in an open or closed position. It can be a light, switch or stem. Position indicators are installed on some valves to indicate flow direction.

Connection

Diaphragm valves can be connected in a variety of ways. Threads, compression fittings, bolt flanges, clamp flanges, tube fittings, butt welds, socket welds, and metal face seals link diaphragm valves to the pipeline.

Diaphragm valves at Fluid Controls

For more information about high-purity diaphragm valves at Fluid Controls, contact us today on +44 (0) 118 970 or via at .

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