Valves check valve , clack valve , non-return valve , reflux valve , retention valve or one way valve is a valve that normally allows liquid (liquid or gas) to flow through it in only one direction.
The check valve is a two-port valve, which means they have two openings inside the body, one for the incoming fluid and the other for the liquid to go. There are different types of check valves used in various applications. Check valves are often part of ordinary household goods. Although they are available in different sizes and costs, check valves are generally very small, simple, or inexpensive. Check valves work automatically and most are not controlled by someone or external controls; therefore, most do not have a handle or valve stem. Bodies (external shells) of most check valves are made of plastic or metal.
An important concept in the check valve is the crack pressure which is the minimum upstream pressure at which the valve will operate. Normally the valve is designed for and therefore can be specified for a specific cracking pressure.
Heart valves are basically the inlet and outlet valves for the cardiac ventricle, because the ventricles act as pumps.
Video Check valve
Terminologi teknis
Crack pressure - inlet pressure where the first indication of flow occurs (stable bubble flow). Crack pressure is also known as unattractive head (pressure).
Reseal Pressure - pressure where there is no flow indication. Reseal pressure is also known as sealing pressure or seat head (pressure).
Back Pressure - differential pressure between incoming and outgoing pressure
Maps Check valve
Check valve type
A ball valve is a valve where the closing member, the moveable part to block the flow, is a sphere. In some check valves, the ball has a spring to help close it. For a design without spring, a backflow is required to move the ball toward the seat and make a seal. The interior surface of the main seat check valve is more or less spiked to guide the ball into the seat and form a positive seal when stopping the reverse flow.
Ball check valves are often very small, simple, and inexpensive. They are commonly used in spigots of liquid dispensers or minipump gels, spray devices, some rubber bulbs for air pumping, etc., manual air pumps and some other pumps, and refill syringes. Although the ball is most often made of metal, they can be made of other materials; in some special cases of highly durable or inert materials, such as sapphires. High pressure HPLC pumps and similar applications generally use inlet check valves and small ball outlets with artificial ruby ​​and sapphire chairs or both balls and ruby ​​seats, both for hardness and chemical resistance. After long-term use, such check valves can eventually wear out or the seat can develop a gap, which requires replacement. Therefore, the valve is made to be replaced, sometimes placed in a small plastic body mounted tightly inside a metal fitting that can withstand high pressure and which is screwed onto the pump head.
There is a similar check valve in which the disc is not a sphere, but some other form, such as a popet that is flooded by a spring. The ball check valve should not be confused with the ball valve, which is a different type of valve in which the ball acts as a controllable rotor to stop or direct the flow.
A diaphragm check valve uses a flexible rubber diaphragm positioned to create a normally closed valve. The upstream pressure must be greater than the pressure on the downstream side of a certain amount, known as the pressure differential, for the check valve to open the allowable flow. After the positive pressure stops, the diaphragm automatically returns to its original position.
swing check valve or tilting disc check valve is the valve where the disc, the movable part to block flow, swing on the hinges or trunnion, either to the seat to block backflow or out of the chair to allow forward flow. The cross-sectional section opening the seat can be perpendicular to the center line between two ports or at an angle. Although swing check valves can come in a variety of sizes, the large check valves often check valve swings. A common problem caused by a swing check valve is known as a water hammer. This can happen when the swing check closes and the flow abruptly stops, causing a spike in pressure that generates high-speed shock waves that work against piping and valves, putting enormous pressure on the metal and vibrations in the system. Undetectable, a water hammer can break down pumps, valves, and pipes inside the system.
The flapper valve in the flush-toilet mechanism is an example of this type of valve. The tank pressure holding it closed is overcome by manual flapper lifts. Then stay open until the tank flows and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve , which is used in fire and fire system security applications. The hinged gate just stays open toward the inrush. Clapper valve often also has a spring that keeps the gate closed when there is no forward pressure. Another example is the backwater valve (for sanitary drainage systems) that protects against flooding caused by the backflow of waste water. The risk is most common in sanitary drainage systems connected to the combined waste disposal system and in the rainwater drainage system. This may be caused by intense rain, melting or flooding.
A valve stop-check is a check valve with override control to stop flow regardless of direction or flow pressure. In addition to closing in response to inadequate backflow or forward pressure (normal valve behavior), it can also be intentionally closed by an external mechanism, preventing any flow from being released from forward pressure.
A valve lift-check is a valve where the disc, sometimes called the elevator, can be lifted from its seat by a higher pressure of the inlet or upstream fluid to allow it to flow into the outlet or downstream side. The guides keep the disk movement on vertical lines, so that the valve can later rearrange properly. When the pressure is no longer high, gravity or higher downstream pressure will cause the disk to descend to its seat, closing the valve to stop the flow back.
An in-line check valve is a valve similar to a lift check valve. However, this valve generally has a spring that will be 'lifted' when there is pressure on the upstream side of the valve. The required pressure on the upstream side of the valve to overcome the spring stress is called 'crack pressure'. When the pressure passes through the valve drops below the crack pressure, the spring will close the valve to prevent backflow in the process.
A duckbill valve is a valve in which the flow takes place through a soft tube jutting downstream. The back pressure paralyzes the tube, cutting the flow.
A non-return pneumatic valve .
Some check valves can be connected in series. For example, double check valves are often used as a backflow prevention tool to keep the contaminated water from sucking back into the city's water supply line. There is also a double ball check valve in which there are two consecutive balls/chair combinations in the same body to ensure a positive leak closure when blocking backflow; and piston check valves, wafer check valves, and ball-and-cone check valves.
Apps
Pump
Check valves are often used with some types of pumps. Piston-driven and pump diaphragms such as metering pumps and pumps for chromatography generally use inlet check valves and spherical outlets. These valves often look like small cylinders attached to the pump heads on the inlet and outlet paths. Many pump-like mechanisms to move the fluid volume around using check valves such as ball check valves. Feed pumps or injectors that supply water to the boiler are equipped with check valves to prevent backflow.
Check valves are also used in pumps that supply water to the water slides. Water to the slide flows through a double pipe as a tower that holds the steps to the slide. When a facility with a slide is closed for the night, the check valve stops the flow of water through the pipe; when the facility is reopened for the next day, the valve is opened and the flow restarts, making the slide ready for use again.
Industrial process
Check valves are used in many fluid systems such as those in chemical plants and power plants, and in many other industrial processes.
Common applications in the nuclear industry are feedwater control systems, sewers, make-up water, other process systems, N2 systems, and monitoring and sampling systems. In airplanes and aerospace, check valves are used where high vibrations, extreme temperatures and corrosive liquids are present. For example, spacecraft and propellant propellant propellant propellant launches for reaction control systems (RCS) and Attitude Control Systems (ACS) and aircraft hydraulic systems.
Check valves are also often used when some gas is mixed into one gas stream. A valve is installed in each individual gas stream to prevent gas mixing at the original source. For example, if fuel and oxidizers are mixed, check valves will normally be used on fuel sources and oxidizers to ensure that the original gas tube remains pure and hence non-flammable.
In 2010, NASA's Jet Propulsion Laboratory slightly modified the design of a simple check valve with the intent to store a sample of fluid that shows life on Mars in a separate reservoir of the device without fear of cross-contamination.
Domestic use
Some types of irrigation sprinklers and droplet emitters have small check valves installed in them to keep the channels from flowing when the system is turned off.
Check the valves used in domestic heating systems to prevent vertical convection, especially in combination with solar thermal installations, also called gravity brakes.
Rainwater harvesting systems incorporated into the main water supply from utility providers may be required to have one or more check valves installed to prevent contamination of main supplies by rainwater.
Hydraulic jack uses ball check valve to build pressure on the jack lifter side.
Check valves are usually used in inflatables, such as toys, mattresses, and boats. This allows the object to be pumped without continuous or uninterrupted air pressure.
History
Frank P. Cotter developed a simple "self-sealing valve, adjustable for plugging in pipe joints without the need for special fittings and which may be readily available for inspection or repair" 1907 (US patent # 865.631).
Nikola Tesla invented a simple one-way valve for fluid in 1916, called the Tesla valve. It was patented in 1920 (US patent 1,329,559).
Images
See also
- Diode, electrical analog of check valve
- Top feed
- The vacuum solver
- Reed valve
- Ball valve
- Butterfly valve
- Control valve
- Gate valve
- Globe Valves
- Diaphragm valve
- Needle valve
References
External links
- Working Principles Spring Check Valves
- Check out the different Operations Tutorial Valves, benefits, applications, and design selections, including lift valves, disks, swings, and wafers described in this tutorial
- A microscopic examination image, a small-scale version of the original Tesla fluid diode.
- US Patent 1,329,559 , the original Tesla fluid diode (a design test that shows very poor performance - n.b. the test protocol does not match the conditions described in the patent)
- Check Installation and Valve Advantages
Source of the article : Wikipedia
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