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Encyclopedia > Valves

A valve is a mechanical device that regulates the flow of fluids (either gases, fluidised solids, slurries or liquids) by opening, closing, or partially obstructing various passageways.

There are a number of names for particular types of valve:

  • Ball cock, often used as a water level controller (cistern)
  • Ball valve, which is good for on/off control.
  • Bibcock
  • Butterfly valve, particularly in large pipes
  • Cock, colloquial term for a small valve
  • Gate valve, mainly for on/off control
  • Globe valve, which is good for regulating flow.
  • Hydraulic valve (diaphragm valve)
  • check valve or Non-return valve, allows the fluid to pass in one direction only
  • Pilot valves regulate flow or pressure to other valves.
  • Plug Valve , for on/off control
  • Solenoid valve, an electrically controlled hydraulic or pneumatic valve
  • Tap (British English), Faucet (American English) is the common name for a valve used in homes to regulate water flow.
  • Rotary valves and piston valves are parts of brass instruments used to change their pitch.

Different valves may be used for a variety of purposes:

  • A flow control valve maintains a constant flowrate through the valve.
  • A heart valve regulates blood flow through the heart in many organisms.
  • A poppet valve is commonly used in piston engines to regulate the fuel mixture intake and exhaust. The sleeve valve is another valve type used for this purpose.
  • A pressure reducing valve reduces pressure to a preset level downstream of the valve.
  • A pressure sustaining valve maintains pressure at a preset level upstream of the valve.
  • A regulator is used in SCUBA diving equipment and in gas cooking equipment to reduce the high pressure gas supply to a lower working pressure
  • A safety valve or relief valve operates automatically at a set differential pressure to correct a potentially dangerous situation, typically over-pressure.
  • A three way valve routes fluid from one direction to another.

Other uses of the term

See also

  Results from FactBites:
Mitral Valve and Mitral Valve Prolapse (305 words)
The mitral (MI'tral) valve is between the heart's left atrium (upper, holding chamber) and left ventricle (lower, pumping chamber).
Mitral valve prolapse is also known as click-murmur syndrome, Barlow's syndrome, balloon mitral valve and floppy valve syndrome.
However, those who have leaky (regurgitant) prolapsing valves are at increased risk of developing an infection of the lining of the heart or heart valve known as endocarditis. In the past, some people with MVP have been given antibiotics before certain dental or surgical procedures to help prevent an infection called bacterial endocarditis (BE).
Aortic valve stenosis - CNN.com (2904 words)
Aortic valve stenosis — or aortic stenosis — is a condition in which the heart's aortic valve narrows.
Aortic valve stenosis is narrowing of the aortic valve.
Aortic valve stenosis also may be related to age and the buildup of calcium deposits on heart valves or a history of rheumatic fever.
  More results at FactBites »



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