Diaphragm Valves Use A Flexible Sheet

Diaphragm valves use a flexible sheet pressed close to the edge of a solid dam to narrow the flow path for fluid.

Their operation is not unlike controlling the flow of water through a flexible hose by pinching the hose. These valves are well suited for flows containing solid particulate matter such as slurries, although precise throttling may be difficult to achieve due to the elasticity of the diaphragm.

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 body may be constructed from plastic, metal, wood or other materials depending on the intended use.

There are two main categories of diaphragm valves: one type seals over a “weir” (saddle) and the other (sometimes called a “full bore or straight-way” valve) seals over a seat. The weir or saddle type is the most common in process applications and the seat-type is more commonly used in slurry applications to reduce blocking issues but exists also as a process valve.

While diaphragm valves usually come in two-port forms (2/2-way diaphragm valve), they can also come with three ports (3/2-way diaphragm valves also called T-valves) and more (so called block-valves). When more than three ports are included, they generally require more than one diaphragm seat; however, special dual actuators can handle more ports with one membrane.