Valves

Mechanical devices used by Humankind to control especially water and air, to hold dominion over various fluids by controlling the fluids to pass or stop the flow rate, adjust the flow, block the return flow, secure the flow, change the flow direction and limit the flow pressure are called valves.

Another definition, the valves are devices which give way to fluid, stop them, mix and change the direction of the fluid and / or the amount, pressure or temperature.

Valves are used predominantly in plumbing systems. Today, wide ranges of valve types are used from easy opening, closing of the taps to control fluid of complicated servo systems. These can be very small valves used in aerospace applications as well valves which are expressed in meters and in tons used for pipe lines. Control of the fluid used for different purposes may be; known liquids, gases, steam and radioactive materials or even liquids containing solid particles and gases. Even solid powders such as cement and flour may be taken into consideration as fluids. Valves can be used from vacuum rate to 7000 bar pressure and above, from temperature -200 Celcius to metal melting temperature. Concerning the physical life, there are valves that can be opened and closed just once or as well valves that can be opened and closed many thousands of times without requiring maintenance and repair.