Valves are safety instruments used to protect a system. They are placed at the entrance or exit of a passageway and open or close as per the system situation. In other words a valve to a mechanical system does almost the same thing as a valve in human heart does. In the human heart the function of a valve is to control the flow of blood in it. In technical words valve is a device which is installed on the passageways and regulate the flow of liquid, steam through it.A valve is an important device not only used in industrial but military, commercial, electrical applications also.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 ofvalves available in the market stated as:

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.