Diaphragm Valves

Diaphragm Valves consists of a valve body with two or more ports, a diaphragm, and a "weir or saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or metal. Diaphragm valves can be manual or automated. Their application is generally as shut-off valves in process systems within the industrial, food and beverage, pharmaceutical and biotech industries.

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Detailed Description for Diaphragm Valves

Diapharam

A diaphragm valve is a control device that utilizes a flexible membrane to close, or shut, an opening. Pressure increase or decrease on either side of the diaphragm causes the valve to move its position. Often, these valves are used in industries like food processing, pharmaceutical manufacturing, mining, and pollution control, among others. They can be made from a variety of plastics and metals, depending on which application they will be used for.

The operating power for a diaphragm valve can come from a variety of sources. A pneumatic diaphragm valve uses air pressure to open or close it. Sometime a solenoid — a wire-wrapped metallic component that can produce a magnetic field in the presence of electricity — is employed to actuate the valve. Other times, it can be operated manually. In addition, hydraulic pressure is also commonly utilized.

There are two basic types of diaphragm valves — weir, or saddle type, and straight-way, or straight through, which seals over a seat. Weir valves typically have ports directly opposite each other on the valve. This kind is often used in pipes, through which gas, fluid, or slurry flow need to be regulated. Straight-way valves’ ports are generally at 90° angles to each other. These can often be found at the bottom of tanks. When they are used in this manner, they are referred to as tank valves and regulate outflow.

Some of these valves are employed as diaphragm control valves. These are automated and used to restrict flow. Others are used as diaphragm check valves. These are normally in a closed position, but when pressure builds from upstream of the valve, they open. They then close automatically when pressure drops.

Generally, a diaphragm valve uses an elastomeric, or stretchy rubber-like, substance for its membrane. Some common materials used are natural rubber, silicone rubber, and nitrile, among others. The body of the diaphragm valve can be made of metal or plastic. If the body is made of metal — either cast iron, ductile iron, stainless steel, or carbon steel are used. If it is made of plastic, many materials — such as polyvinyl chloride (PVC) or polypropylene (PP) — can be used.

In addition to being utilized in industrial and manufacturing processes, diaphragm valves of all kinds can be found in automatic sprinkler and irrigation systems, washing machines, and paintball guns. Many of these valves are often named for their uses. They include the two-way shut-off valve, sterile access ports, and three-way deadleg valves.

Diaphragm valves (or membrane valves) consists of a valve body with two or more ports, a diaphragm, and a "weir or saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or metal.

Diaphragm valves can be manual or automated. Their application is generally as shut-off valves in process systems within the industrial, food and beverage, pharmaceutical and biotech industries. The older generation of these valves is not suited for regulating and controlling process flows, however newer developments in this area have successfully tackled this problem. Diaphragm valves are used on shut-off and throttling service for liquids, slurries and vacuum/gas.

The seal is achieved by a flexible membrane, usually elastomer, and possibly reinforced with a metal part. The membrane is tensed by the effect of a stem/compressor with lineal movement until contact is made against the seal of the body.

The operating parts of the diaphragm valve are isolated from the flow. This makes this valve suitable for viscous flows and also hazardous, abrasive and corrosive flows as its sealing system avoids any contamination towards or from the environment.

Diaphragm valves are available in a wide variety of metals, solid plastics, plastic, rubber and glass linings. They are well suited to the handling of multiple chemical applications both clear fluids as well as slurries.

Advantages:

·         Diaphragm valves can also be used for throttling service. Its throttling characteristics are essentially those of a quick opening valve because of the large shutoff area along the seat.

·         A weir-type diaphragm valve is available to control small flows.

·         Diaphragm valves are particularly suited for the handling of corrosive fluids, fibrous slurries, radioactive fluids, or other fluids that must remain free from contamination.

·         The operating mechanism of a diaphragm valve is not exposed to the media within the pipeline. Sticky or viscous fluids cannot get into the bonnet to interfere with the operating mechanism.

·         Many fluids that would clog, corrode, or gum up the working parts of most other types of valves will pass through a diaphragm valve without causing problems. Conversely, lubricants used for the operating mechanism cannot be allowed to contaminate the fluid being handled.

·         There are no packing glands to maintain and no possibility of stem leakage in valves.

 

 


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