The opening or closing of control valves is done by means of electrical, hydraulic or pneumatic systems. Positioners are used to control the opening or closing of the actuator based on electrical or pneumatic signals. These control signals were traditionally based on 3-15psi (0.2-1.0bar) but 4-20mA signals are now more commonly used for industry. With the introduction of “Smart” systems; HART, Fieldbus Foundation, & Profibus are the more common communication protocols available.
The primary function of a control valve is for throttling which is achieved by varying the restriction caused by the internal trim components. Various control valve trims are available in order to deal with certain process requirements such as characterisation, anti-cavitation and low noise.
Specifications
General design criteria
Standard pressure class ratings / end connections
Common materials of construction
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Material specifications
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Standard carbon steel
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ASTM A105A216 WCB WCC
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Low temperature carbon steel
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ASTM LF2 A352 LCC LCB
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Stainless steel
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ASTM A182 F316 ASTM A182 F316L ASTM A182 F304 ASTM A182 F304L ASTM A182 F321 ASTM A182 F347 ASTM A351 CF8M ASTM A351 CF3M
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Specials
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F44 SMO F51 Duplex Super Duplex Monel Hastelloy TitaniumInconel Bronze Alu. Bronze
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Other
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Available on request
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