Membrane Valves
Membrane Valves or Diaphragm Valves consists of a valve body with two or more ports, a diaphragm, and a saddle or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or steel.
Originally, the membrane valve was developed for use in non-hygienic applications. Later on the design was adapted for use in the bio-pharmaceutical industry by using compliant materials that can withstand sanitizing and sterilizing methods.
There are two main categories of membrane valves: one type seals over a weir (saddle) and the other sometimes called a straight-way valve seals over a seat. The saddle type is the most common in process applications and the seat-type is more commonly used as a tank bottom valve but exists also as a process valve. While membrane valves usually come in two-port forms , they can also come with three ports 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.
Membrane valves can be manual or automated. Their application is generally as Shut-Off Valves in process systems within the food and beverage, pharmaceutical and biotech industries. The older generation of these Valves is not suited for regulating and controlling process flows, however newer developments in this area have successfully tackled this problem.In addition to the well known, two way shut off membrane valve, other types include: three way zero deadleg valve, sterile access port, block and bleed, valbow and tank bottom valve just to name a few.
Actuators
Membrane valves can be controlled by various types of actuators e.g. manual, pneumatic, hydraulic, electric etc. The most common membrane valves use pneumatic actuators; in this type of valve, air pressure is applied through a Schrader valve which raises the diaphragm and opens the valve. This type of valve is extremely quick and as such is one of the more common valves used in operations where valve speed is a necessity. Hydraulic diaphragm valves also exist for higher pressure and lower speed operations. Some diaphragm valves are also controlled manually.