A valve can be operated both manually or with some external device.
When manually then the piston of the valve is rotated by means of a
hand liver attached to it and when it is automatic then the piston is
moved but by change in pressure or temperature of fluid inside.
Depending upon one's requirements there are majorly five types of
valves available in the market stated as:
Motor
Manual(Hand driver)
Pneumatic
Solenoid
Hydraulic
One common valve is a butterfly valve. Just like name it is a valve
which is used for regulating a system. It is a kind of rod on which a
disc is surmounted. Like any other valve when the pressure increases
or the valve is closed due to any reason then it turns around and
blocks the passageways thereby completely blocking the flow of fluid
through it. Otherwise when the valve is opened then the same disc gets rotated at another angle and allows the fluid to pass through it.
Thus, it behaves like a butterfly literally. Generally a Butterfly
valve is used when the pipe diameter through which the fluid is
flowing is long enough.
Pharmaceutical industries usually have plants installed of medicines
where liquid flows at high temperature and medicines are manufactured. They also need valves for regulating their system. The preferred valve used in such areas is Diaphragm valve. It is used in food industry
too. A diaphragm valve is made up of plastic or sometimes steel. For
the performance of this valve it is provided with actuators for
example, Pneumatic Actuator. A Diaphragm valve can be operated
manually or automatic.
One very interesting kind of valve is a flush bottom valve. These are
called bottom discharge valves too. They are called flush bottom
because they are used to flush tank and so are placed on the bottom of the tank to be flushed.
