Flow control valve

Flow control valve
Globe control valve with the pneumatic actuator and smart positioner

A flow control valve regulates the flow or pressure of a fluid. Control valves normally respond to signals generated by independent devices such as flow meters or temperature gauges.

Control valves are normally fitted with actuators and positioners. Pneumatically-actuated globe valves and Diaphragm Valves are widely used for control purposes in many industries, although quarter-turn types such as (modified) ball, gate and butterfly valves are also used.

Control valves can also work with hydraulic actuators (also known as hydraulic pilots). These types of valves are also known as Automatic Control Valves. The hydraulic actuators will respond to changes of pressure or flow and will open/close the valve. Automatic Control Valves do not require an external power source, meaning that the fluid pressure is enough to open and close the valve. Automatic control valves include: pressure reducing valves, flow control valves, back-pressure sustaining valves, altitude valves, and relief valves. An altitude valve controls the level of a tank. The altitude valve will remain open while the tank is not full and it will close when the tanks reaches its maximum level. The opening and closing of the valve requires no external power source (electric, pneumatic, or man power), it is done automatically, hence its name.

Process plants consist of hundreds, or even thousands, of control loops all networked together to produce a product to be offered for sale. Each of these control loops is designed to keep some important process variable such as pressure, flow, level, temperature, etc. within a required operating range to ensure the quality of the end product. Each of these loops receives and internally creates disturbances that detrimentally affect the process variable, and interaction from other loops in the network provides distur- bances that influence the process variable. [1]

To reduce the effect of these load disturbances, sensors and transmitters collect information about the process variable and its relationship to some desired set point. A controller then processes this information and decides what must be done to get the process variable back to where it should be after a load disturbance occurs. When all the measuring, comparing, and calculating are done, some type of final control element must implement the strategy selected by the controller. The most common final control element in the process control industries is the control valve. The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point.[1]

Images

See also

References

  1. ^ a b Fisher - Control Valve Handbook, Fourth Edition, Fisher Controls International, 2005

Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • flow-control valve — A fluid powered valve that controls the volume or the direction of fluid flow. Flow control valves, like check valve and selector valves, are normally used along with pressure control valves in fluid power systems. See flapper valve …   Aviation dictionary

  • pressure balance flow control valve — proporcingasis srauto reguliavimo vožtuvas statusas T sritis automatika atitikmenys: angl. pressure balance flow control valve; pressure proportional flow control valve vok. Druckwaage, f; Proportionalstromregelventil, n rus. пропорциональный… …   Automatikos terminų žodynas

  • pressure proportional flow control valve — proporcingasis srauto reguliavimo vožtuvas statusas T sritis automatika atitikmenys: angl. pressure balance flow control valve; pressure proportional flow control valve vok. Druckwaage, f; Proportionalstromregelventil, n rus. пропорциональный… …   Automatikos terminų žodynas

  • 2-way flow control valve — dvikanalis debito reguliatorius statusas T sritis automatika atitikmenys: angl. 2 way flow control valve vok. 2 Wege Stromregelventil, n rus. двухканальный регулятор дебита, m pranc. régulateur de débit à 2 voies, m …   Automatikos terminų žodynas

  • 3-way flow control valve — trikanalis debito reguliatorius statusas T sritis automatika atitikmenys: angl. 3 way flow control valve vok. 3 Wege Stromregelventil, n rus. трехканальный регулятор дебита, m pranc. régulateur de débit à 3 voies, m …   Automatikos terminų žodynas

  • one-way flow control valve — vienkryptis srauto reguliavimo vožtuvas statusas T sritis automatika atitikmenys: angl. one way flow control valve vok. Drosselrückschlagventil, n rus. регулятор расхода одностороннего действия, m pranc. clapet de non retour avec étranglement, m; …   Automatikos terminų žodynas

  • control valve — [1] A valve which regulates or operates a system, especially a hydraulic or vacuum control system. [2] Valve which regulates the flow or pressure of a medium which affects a controlled process. Control valves are operated by remote signals from… …   Dictionary of automotive terms

  • Pneumatic flow control — is the use of air as a control medium, or as the controlled medium, in which one medium controls the flow of another.Pneumatic flow control taxonomyThere are two possible pneumatic flow controls: those that are controlled by pneumatics, and those …   Wikipedia

  • Directional control valve — Directional control valves are one of the most fundamental parts in hydraulic machinery. They allow fluid flow into different paths from one or more sources. They usually consist of a piston inside a cylinder which is mechanically or electrically …   Wikipedia

  • control valve — mechanical device controlling the flow of a substance (liquid, gas, etc.) …   English contemporary dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”