How do Diaphragm Valves Work?

In a majority of piping systems, valves serve as integral engineering devices. These mechanical/electromechanical devices have the ability to control the flow of various media. As such, there are many different types of valves, each of which suits a diverse set of applications. In this blog, we will be covering one specific type: diaphragm valves.

Diaphragm valves are a special type of shut-off valve that is bi-directional in nature. Structurally different from regular valves, these valves have a diaphragm in the opening and closing element. They are made of a soft, flexible material that is elastic, non-corrosive, and non-permeable, such as rubber and plastic. Furthermore, they are tasked with separating the fluid inside the valve from the cover cavity and the driving member, preventing contamination of the working medium and corrosion of operating components.      

In applications with low pressure, low temperature, and corrosive & suspended materials, diaphragms are particularly useful. They benefit from their simple construction, secure and durable sealing characteristics, increased resistance to corrosion, and more. More than that, as there is no leak path in the construction of these valves, they are considered leak-proof, making them ideal for operations that cannot risk any form of leakage.

These valves work like a pinch clamp valve. A resilient, elastic diaphragm is connected to the compressor via a diaphragm molded stud. When the operator wants to shut the valve, the actuator can be pressed or rotated, and the membrane is then forced into the edge of the firm dam, shutting the valve completely. Meanwhile, the compressor is moved up and down the valve stem. As the compressor is lifted, the diaphragm also lifts. Finally, the diaphragm is pushed into the curved bottom as the compressor is lowered.

Manufactured as two types, diaphragm valves are available in either weir or straight-through variations. Nonetheless, they all work the same way while their body form, diaphragm, and application vary. To customize a diaphragm for corrosive uses, the body interior and end flanges must be lined. There are a number of liner materials on the market, depending on the application requirements.

Weir-Type Diaphragm Valve

In weir-type diaphragm valves, the elevated lip/saddle configuration for limited flow control, the cover over the diaphragm, and the actuator provide a secure seal. This design makes it ideal for harmful or corrosive gasses and liquids as the cover maintains every breakdown of the membrane. The weir serves as the integrated element in the valve body and compresses the diaphragm to avoid a surge. The elevated weir also decreases the amount of strain and stress in the diaphragm. For smooth, fluid media, the weir-type valve is often utilized, but it is not compatible with viscous slurries and sediments that can build up on either side of the lip.

Straight-Through Diaphragm Valve

Straight-through diaphragm valves, on the other hand, are similar in appearance to their counterparts, but do not contain a lip/saddle and instead have a straight track. Their membranes are typically more compact in design and enable for a longer distance to pass, since the bottom of the valve must be touched. When the straight-through valve is open for optimal streamline flow in any direction, the diaphragm lifts high. Additionally, when closed with fibrous materials in the line, the diaphragm provides positive sealing.

Advantages and Disadvantages

In terms of advantages, diaphragm valves provide a strong chemical resistance dye for their lining. They are great options for the treatment of contamination-free corrosive oils, fibrous slurries, toxic fluids, and more. As such, fluids moving through the valve do not clog, erode, or spoil any operating parts.

With regard to disadvantages, diaphragm valves have limited operating temperatures and pressures. More than that, they may also decrease hydrostatic pressure, and they may suffer from corrosion if used in extreme throttling services containing impurities.


If you find yourself in need of diaphragm seals and valves, gaskets, flanges, and more, rely on Just NSN Parts. Just NSN Parts provides diaphragm valves for various military and civilian applications, all of which are subjected to varying levels of quality assurance testing and document verification processes. Initiate the procurement process with a competitive quote which can be accessed via our Instant RFQ service and see why customers choose Just NSN Parts for all of their operational needs. 


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