Diaphragm valve
A diaphragm valve opens or closes the flow path by flexing an elastomeric or polymer diaphragm. In a weir-type design, the diaphragm presses onto a raised section of the body to form the seal; full-bore designs use a different flow geometry. The diaphragm separates the process medium from the operating mechanism, which clearly distinguishes this valve from a needle valve with a stem tip moving into a seat. Selection depends on diaphragm and lining compatibility, temperature, cycling duty, solids content, and cleaning requirements.
Application and duty
Isolation or control duties where separating the operating mechanism from the process medium and diaphragm compatibility are important.