Diaphragm Valves: Working Principle & Function | Linquip
Diaphragm Valve

What is a Diaphragm Valve? Working Principle & Function

Diaphragm Valves (also known as membrane valves) have a valve body with several ports, an elastomeric diaphragm, and a "weir or saddle" that serves as the diaphragm's seat. The valve body can be composed of plastic, wood, metal, or other materials, depending on the use. They're bidirectional throttle valves with an on/off switch. They're industrial tools that control the amount of fluid that can flow in and out of a valve, changing the fluid's speed and velocity. Weir-type valves are used for throttling and control, while straight-through diaphragm valves are utilized for on-off and control. It can be difficult to identify the proper diaphragm valve for your application because there are no industry standards for diaphragm valves. Before you look at your supplier's inventory, think about these factors. Valve size, pressure drop and range, kind of valve and actuator, connection type, material, and features, and applications are all items that, while not exhaustive, will at least put you on the right path.

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Basics of Diaphragm Valve | Linquip

A schematic diagram of a diaphragm valve (Reference: en.wikipedia.org)

What Is Diaphragm Valve?

In a diaphragm valve (or membrane valve), there are two or more ports in the valve body, an elastomeric diaphragm, and a saddle or seat on which the diaphragm closes. According to the intended use, the valve body may be made from plastic, metal, wood, or another material.

Basics of Diaphragm Valve

A diaphragm valve is an on-off, bi-directional throttle valve. Fluid flow is controlled by these valves by regulating the area that media can enter and exit, effectively affecting its velocity and speed. A thin, flexible membrane controls the opening and closing of the valve, which is why they are called "diaphragm" valves. They are made from materials such as stainless steel, plastic, or single-use materials.

Diaphragm valves are similar to pinch valves but use a linear compressor that presses the thin diaphragm into contact with the valve body. The devices can be actuated both manually and automatically and provide discrete and variable pressure control. Clean, leakproof, easy to maintain, safe, and effective, diaphragm valves are well suited for moderate pressure and temperature applications, which require stop/start control of fluid flow.

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Working Principle of a Diaphragm Valve

This flexible diaphragm is attached to a support member. The compressor represents the closure member. In the case of an open valve, the diaphragm will be lifted out of the flow path, resulting in streamlined fluid flow. During the closure of the valve, the diaphragm is tightly seated on the seat within the body, which is known as the weir. When the diaphragm is forced downward, the valve will close completely.

As there is no valve stem in the flow path, there is no need for stem packing in this valve. This valve requires less maintenance than conventional valves. Diaphragms are constructed from rubberized materials so that these valves can be used in highly corrosive environments.

The diaphragm of the valve is operated by opening air from the pilot. There are valves with direct-acting diaphragms, and there are also valves that have reverse-acting diaphragms. The control pilot's operating air pressure is applied directly to the valve diaphragm when the structure is direct-acting. Whenever the structure is reverse acting, air pressure is applied to the valve diaphragm on the underside. It is easiest to describe this as the movement of the diaphragm control valve being reverse-acting or direct-acting. In addition, it may be upward-seated or downward-seated.

The placement of the diaphragm control valve and its air-operated control pilot is determined by these factors as well as the purpose of installation.

Components of a Diaphragm Valve

A diaphragm valve comprises the following parts:

  • Valve body
  • Bonnet
  • Weir-seat
  • Diaphragm-disc
  • Stud
  • Plunger
  • Stem
  • Actuator

Function of a Diaphragm Valve

Function of a Diaphragm Valve | Linquip

Diaphragm valve function (Reference: www.instrumentationtools.com)

The operation and construction of diaphragm valves are simple. During an open valve position, the actuator is in contact with the diaphragm (or inner membrane) of the valve. In order to close the valve, the actuator must be pressed or turned, and the membrane must be pushed into the solid dam edge, thus closing the valve. A diaphragm valve can also have a half-open position where the membrane is partially closed, which throttles flow through the valve.

There is no direct exposure to the media within a pipeline for the operating mechanism of a diaphragm valve. Neither sticky nor viscous fluids can get into the bonnet to cause problems. Diaphragm valves allow fluids that usually clog, corrode, and gum up working parts of other valves to pass through. Conversely, the fluid being handled cannot be contaminated by the lubricant used in the operation mechanism. It is not necessary to maintain packing glands or worry about stem leaks.

A variety of diaphragm materials are available. The amount of time a diaphragm can last depends on the type of material handled, the temperature, the pressure, and the frequency of use. The excellent chemical resistance of some elastomeric diaphragm materials at high temperatures may make them noteworthy.

Nevertheless, any elastomeric material will lose its mechanical properties at higher temperatures, resulting in possible diaphragm rupture at high pressure. Consequently, when used in applications involving elevated temperatures, this should be considered by the manufacturer.

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Usage of Diaphragm Valves

The diaphragm valve can be used with corrosive liquids at low temperatures and pressures. These valves can be used for potable water, air, sludge, chemicals, as well as low-velocity slurries and effluents. They can be installed near pumps and bends, as well as vertical pipelines.

Common Applications of Diaphragm Valves

Diaphragm valves are widely used in many industries due to their affordability, effectiveness, and variety. There are a host of possible applications for diaphragm valves, but here are some of the most common:

  • Water treatment facilities
  • Pharmaceutical systems
  • Food and chemical processing plants
  • Power plants
  • Vacuum systems
  • Breweries
  • Corrosive applications.

Advantages of Diaphragm Valves

Diaphragm valves have the following advantages:

  • This valve has the best corrosion resistance or abrasion resistance that we could find.
  • There is no steam leakage.
  • They are suitable for use with hazardous chemicals and radioactive fluids.
  • Food and pharmaceutical processing use these valves since they won't allow contamination of the flow medium.
  • The valves are simple in construction and easy to operate.

Disadvantages of Diaphragm Valves

The following are the drawbacks of diaphragm valves:

  • They may not allow full drainage.
  • The diaphragm material restricts the working temperature and pressure, so it cannot be used for high temperatures or pressures.
  • The diaphragm limits hydrostatic pressure.

FAQ about Diaphragm Valve

  1. How Does a Diaphragm Valve Work?

With a diaphragm valve, a flexible diaphragm is attached to an air compressor by a stud that is molded into the diaphragm. To shut off the valve, instead of pinching the liner closed, the diaphragm is pressed into contact with the bottom of the valve body.

  1. What Does a Diaphragm Valve?

The diaphragm valve is a bidirectional, on-off throttle valve. By regulating the area through which media can enter and exit the valve, fluid flow can be controlled by changing its speed and velocity.