imported>Milton Beychok |
imported>Milton Beychok |
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| [[Image:Control Valve.gif|right|thumb|175px|{{#ifexist:Template:Control Valve.gif/credit|{{Control Valve.gif/credit}}<br/>|}} | | [[Image:Industrial piping.jpg|right|thumb|300px|{{#ifexist:Template:Industrial piping.jpg/credit|{{Industrial piping.jpg/credit}}<br/>|}}Large-scale industrial piping.]] |
| A typical control valve with pneumatic actuator and a positioner.]]
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| '''Control valves''' are [[valve]]s used within industrial plants and elsewhere to control operating conditions such as [[pressure]], [[temperature]], [[liquid level]] and [[flow rate]] by fully or partially opening or closing in response to signals received from controllers that compare a "setpoint" to a "process variable" whose value is provided by independent [[sensors]] that monitor changes in such conditions.<ref>{{cite book|author=Bela G. Liptak (Editor)|title=Instrument Engineers' Handbook|edition=4th Edition|publisher=CRC Press|year=2003|id=0-8493-1083-0}}</ref>
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| Control valves are an integral part of the hundreds (or even thousands) of control loops networked together in industrial plants to produce their various endproducts.
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| A control valve is part of an assembly that typically includes a valve body (and its internal parts), an actuator to provide the motive power for opening and closing the valve, and a variety of additional accessories such as positioners, transducers, manual operators and limit switches.<ref name=Fisher>[http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf Fisher Controls International] Control Valve Handbook</ref> The motive power provided by the actuators may be [[electrical]], [[hydraulic]] or [[pneumatic]].
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| ==Applications==
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| [[Image:Control Valve.png|right|thumb|219px|{{#ifexist:Template:Control Valve.png/credit|{{Control Valve.png/credit}}<br/>|}}Schematic diagram of conventional control valve with a pneumatic actuator.]]
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| Control valves are used in industries such as [[Petroleum refining processes|petroleum refining]], [[chemical]] and [[petrochemical]] manufacturing, [[nuclear power plant]]s and [[fossil fuel power plant]]s, [[natural gas processing]] and many others.
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| In such industries, control valves are an essential component of the systems used to control important operational parameters like pressure, temperature, liquid levels and flow rates.
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| Pressure control valves may be used to reduce [[liquid]] or [[gas]] pressures or they may be used to maintain a back-pressure (i.e., a pressure upstream of the valve). They may also be used to maintain a pressure difference between two points in a process.
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| Temperature control valves are used to maintain liquid or gas temperatures within process vessels or to control the heat transfer within heat exchangers and process heaters or furnaces.
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| Level control valves are used to maintain liquid levels within a desired range in process vessels or tanks. In some cases, they may also be used to maintain levels of solid particles.
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| Flow control valves are used to control the volumetric or mass flow rate of liquids and gases.
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| ==Types of control valve ==
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| The different types of control valve may be categorized as shown below:
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| *Conventional valve
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| *Severe service valve
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| *Pressure independent control valve
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| ==Types of control valve bodies==
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| The different types of control valve bodies include:<ref name=Fisher/>
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| *[[Angle valve]]s
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| **Cage-style valve bodies
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| *[[Angle seat piston valve]]s
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| *[[Globe valve]]s
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| **Single-port valve bodies
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| **Balanced-plug cage-style valve bodies
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| **High capacity, cage-guided valve bodies
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| **Port-guided single-port valve bodies
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| **Double-ported valve bodies
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| **Three-way valve bodies
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| *[[Rotary valve]]s
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| **[[Butterfly valve]] bodies
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| **V-Notch ball control valve bodies
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| **Eccentric-disk control valve bodies
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| **Eccentric-plug control valve bodies
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| ==References==
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| {{reflist}}
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| ==External links==
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| *''''[http://www.spiraxsarco.com/resources/steam-engineering-tutorials/control-hardware-el-pn-actuation.asp Control Valve Tutorials]''' A number of tutorials covering the sizing, capacity and characteristics of control valves. Actuators, positioners, controllers and sensors are also discussed - Spirax Sarco
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| *[http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf Control Valve Handbook (4th Edition)] A complete 297-page online book.
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| *[http://www.unisanet.unisa.edu.au/Information/100048info/IL8.doc Process Instrumentation (Lecture 8): Control valves] Excellent article from a University of South Australia website.
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| *[http://www.ccivalve.com Control Components Inc] Excellent website for reference to severe service control Valve. They are a leader in severe service control valve business.
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| *[http://www.flowcontrol.com/Animation/index.html Valve Animations] An informative series of Flash animations demonstrating conventional and pressure independent control valve operation.
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| ==See also==
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| *[[Control engineering]]
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| *[[Control system]]
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| *[[Instrumentation]]
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| *[[Instrumentation engineering]]
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| *[[Process control]]
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