Pneumatic Diaphragm Valve

Pneumatic Diaphragm Valve

Pneumatic diaphragm valve is a special type of cut off valve. Its opening and closing part is a diaphragm made of soft material, which separates the inner cavity of the valve body from the inner cavity of the valve cover and the driving parts, so it is called pneumatic diaphragm valve. 

Pneumatic Diaphragm Valve Types

  • Pnuematic Diaphragm Valve can be classified into three types
  • Normally closed pneumatic diaphragm valve, 
  • normally open pneumatic diaphragm valve and 
  • reciprocating pneumatic diaphragm valve

How Does Pneumatic Diaphragm Valve Work

The structural feature of pneumatic diaphragm valve is that a group of thin hemispherical metal films are clamped in the valve body as a barrier between the stem and the fluid. Valve sealing is achieved by pressing the valve disc on the valve seat through the stem head and metal film. The valve is opened by an internal spring. When the stem rises and comes out of contact with the membrane, the disc rises. Because the valve stroke is equal to the film stroke, so the characteristics of this valve lift is much smaller than the general valve.

In order to overcome the flow loss caused by low travel, the valve seat and flow area are larger than the general valve, in order to achieve greater flow. Because the valve seat is larger, its force is much greater than the usual valve, so as to get enough sealing force on the disc, because there is no direct contact between the stem and disc. The disc will not leave the seat through the stem, so the valve is suitable for one-way flow with pressure difference, and the medium usually comes from “under the seat”. But in use should avoid a lot of backflow, so as not to affect the closure of the valve. Generally speaking, it is economical and effective to select metal diaphragm valve under high temperature and high pressure. The valve can also be used in low temperature and low pressure occasions where the synthetic rubber diaphragm valve is not expected to be used.

Pneumatic Diaphragm Valve Features

The diaphragm separates the inner cavity of the lower valve body from the inner cavity of the upper valve cover, so that the valve stem, valve disc and other parts above the diaphragm are not corroded by the medium, and the packing sealing structure is omitted, and the medium leakage will not occur.

  • The diaphragm made of rubber or plastic has good sealing performance. As the diaphragm is a vulnerable part, it should be replaced regularly according to the characteristics of the medium.
  • Limited by diaphragm material, diaphragm valve is suitable for low pressure and relatively low temperature.
  • Generally, it is not suitable to be used in pipelines with temperature higher than 60 ℃ and conveying organic solvent and strong oxidizing medium, and it is not suitable to use pneumatic diaphragm valve in pipelines with higher pressure

Advantages of Pneumatic Diaphragm Valve

Pneumatic diaphragm valve is a kind of clamping valve, which is mainly used for opening and closing in pipeline.
Generally, the diaphragm valve is recommended for the medium require strict sealing performance, mud medium, abrasion, light structure, low pressure cut-off (small pressure difference) leakage to the atmosphere and abrasiveness. Diaphragm valve can be used in double position regulation, throttling, channel necking, low noise, cavitation and vaporization, and small operating torque. Under the conditions of high temperature medium, high pressure medium, high pressure cut-off (large pressure difference), fast opening and closing action and short structure length, diaphragm valve is not selected in daytime, except metal diaphragm valve