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Diaphragm valves (or membrane 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 diaphragm 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 diaphragm valves:
one type seals over a "weir" (saddle) and the other
(sometimes called a "straight-way" valve) seals over
a seat. The main difference is that a saddle-type
valve has its two ports in line with each other on
the opposite sides of the valve, whereas the
seat-type has the in/out ports located at a 90
degree angle from one another. 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
diaphragm valves usually come in two-port forms,
they can also come with three ports and even more.
When more than three ports are included, they
generally require more than one diaphragm; however,
special dual actuators can handle more ports with
one membrane.
Diaphragm 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
diaphragm valve, there are many other forms of the
diaphragm valve including: three way zero deadleg
valve, sterile access port, block and bleed, valbow
and tank bottom valve just to name a few.
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