Diaphragm - Flexible Rubber Design, Pressure Regulation For Fluid Dynamics & Shock Absorption

Diaphragm operated devices are essentially pistons operating within a cylinder. They transfer pressure from one sealed area to another. In the case of hydraulic and pneumatic cylinders, the moving piston is sealed off by a sealing device such as an o'ring, cup, vee packing, or a similar device. A diaphragm merely limits the stroke and provides a frictionless seal. Diaphragms generally cost less, have more tolerance range, and do not require hardened super finishes or lubrication.

The function of a diaphragm is the most important factor in its design and manufacture. Simple diaphragms move from one position to another, such as pressure switches and solenoid valves. There are only two positions. In the case of modulating devices, such as regulators, the diaphragm must respond to small changes in differential pressure and the diaphragm must return to the same corresponding position. Here, the concern is with flexibility, uniform spring rate, and a minimum change in effective area.

Diaphragms can also be used as shock absorbers as in a dash pot or as dampening devices in pulsating systems. In the latter the diaphragm reduces the high pressure spikes and smooths out the flow of fluid or gas to produce a more uniform flow. Diaphragms can also be used as barriers between fluids and gasses, such as in a pressure drop on the fluid side, the compressed gas expands against the diaphragm to maintain the fluid pressure.