Valves [3]

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

Valves are used in a variety of industrial, military, commercial, and residential applications.

Some valves are driven by pressure only, they are mainly used for safety purposes in Steam engines and domestic heating or cooking appliances. Others are used in a controlled way in Otto cycle engines driven by a camshaft, and they have a major part in engine cycle control.

Globe valve

Types of valves

• 4-stroke cycle engine valves,
• Ball cock, often used as a water level controller (cistern);
• Ball valve, which is good for on/off control;
• Bibcock;
• Blast valve, used to prevent rapid overpressures in a fallout shelter or bunker;
• 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 flow rate 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.
• Vacuum breaker valves prevent the back-siphonage of contaminated water into pressurized, potable water supplies.

Other uses of the term

• in electronics, a valve (British English) = vacuum tube (American English)
• in electrical engineering, a valve is a component of the static inverters of a high voltage direct current power transmission system

See also

• Valve Software
• Plumbing
• Backwater valves