Check valve
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A check valve is a mechanical device, a valve, that normally allows fluid or gas to flow through it in only one direction. A double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines. A clapper valve is a type of check valve used in or with firefighting, and has a hinged gate (often with a spring urging it shut) that will only remain open in the outflowing direction. Check valves are also often used when multiple gases are mixed into one gas stream. A check valve is installed on each of the individual gas streams to prevent mixing of the gases in the original source. For example, if a fuel and an oxidizer are to be mixed, then check valves will normally be used on both the fuel and oxidizer sources to ensure that the original gas cylinders remain pure and therefore inflammable.
An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Typically the check valve is designed for and can therefore be specified for a specific cracking pressure.
Some types of irrigation sprinklers and drip irrigation emitters have small check valves built into them to keep the lines from draining when the system is shut off.
Nikola Tesla invented a deceptively simple one-way valve for fluids in 1920 (U.S. patent # 1,329,559).
In electronics, a diode functions in the same manner.
See also
External links
- [A picture of a microscopic checkvalve], a scaled down version of Tesla's original fluidic diode.
- [US Patent 1,329,559, Tesla's original fluidic diode] ([a test of a design showing very poor performance])
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