A check valve, clack valve, non-return
valve or one-way valve is a mechanical device, a valve, which
normally allows fluid (liquid or gas) to flow through it in only one
direction.Check valves are two-port valves, meaning they have two openings in
the body, one for fluid to enter and the other for fluid to leave. Check valves
work automatically and most are not controlled by a person or any external
control; accordingly, most do not have any valve handle or stem.
Frank
P. Cotter developed a "simple self sealing check valve, adapted to be
connected in the pipe connections without requiring special fittings and which
may be readily opened for inspection or repair" 1907 Nikola Tesla invented a deceptively simple one-way valve for fluids in 1916, called a Tesla valve. It was patented in 1920
Check valves are used in many fluid systems such as those in chemical and power plants, and in many other industrial processes.
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 nonflammable.
Domestic use
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.
Also used with most home made snowmakers.
Check valves used in domestic heating systems to prevent vertical convection, especially in combination with solar thermal installations, also are called gravity brake.
Rainwater harvesting
systems that are plumbed into the main water supply of a utility provider may
be required to have one or more check values fitted to prevent contamination of
the primary supply by rainwater.Pumps
Check valves are often used with some types of pumps. Piston-driven and diaphragm pumps such as metering pumps and pumps for chromatography commonly use inlet and outlet ball check valves. These valves often look like small cylinders attached to the pump head on the inlet and outlet lines. Many similar pump-like mechanisms for moving volumes of fluids around use check valves such as ball check valves. The feed pumps or injectors which supply water to steam boilers are fitted with check valves to prevent back-flow.Work
Check valves, or non-return
valves, allow water or other material to flow in only one direction, and stop
the material from flowing in the opposite direction. They are installed in pipe
lines and do not require any activation from outside. Instead, they sense when
the material in the pipes is beginning to move in the reverse direction and
plug up the pipe to prevent the material's movement.
This link is animation ball check valve:
