The electro -pneumatic positioner is used in Control Valves with pneumatically operated actuators. The valve is operated by means of electrical controller or Control Systems With an control signal of 4 to 20 mA or split ranges of 4~12/ 12~20 mA. Electro-Pneumatic Positioner converts this control signal...
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June 2, 2016 admin
Control valve, Instrumentation
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Control valve selection is depend on below these points : Type of fluid to be controlled Temperature of fluid Viscosity of fluid Specific gravity of fluid Flow capacity required (maximum and minimum) Inlet pressure at valve (maximum and minimum) Outlet pressure...
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April 8, 2016 admin
Control valve, Instrumentation
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The root cause of the problem – a varying pressure drop caused by frictional losses in the piping and other factors – generally cannot be eliminated. This means there is no way to regain maximum flow capacity short of replacing the control valve with one having a...
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March 8, 2016 admin
Control valve, Instrumentation
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Hydraulic actuators use liquid pressure rather than gas pressure to move the valve mechanism. Nearly all hydraulic actuator designs use a piston rather than a diaphragm to convert fluid pressure into mechanical force. The high pressure rating of piston actuators lends itself well to typical hydraulic system pressures,...
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February 14, 2016 admin
Control valve, Instrumentation
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Pneumatic actuators use air pressure pushing against either a flexible diaphragm or a piston to move a valve mechanism. The following photograph shows a cut-away control valve, with a pneumatic diaphragm actuator mounted above the valve body. You can see the large coil spring providing default positioning of...
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February 14, 2016 admin
Control valve, Instrumentation
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Recall that the purpose of a valve positioner is to ensure the mechanical valve’s position matches the command signal at all times. Thus, a valve positioner is actually a closed-loop control system in its own right: applying as much or as little pressure to the actuator in...
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January 24, 2016 admin
Control valve, Instrumentation
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Motion-balance pneumatic valve positioner designs also exist, whereby the motion of the valve stem counteracts motion (not force) from another element. The following illustration shows how a simple motion-balance positioner would work: In this mechanism, an increasing signal pressure causes the beam to advance toward the nozzle, generating...
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January 24, 2016 admin
Control valve, Instrumentation
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Glob valve is so much used in current industries now a days. In glob valve flow is controling by movable plug and stationary seat. Glob valve design is one of the most popular design of sliding stem valve. Cut view of Glob valve photos are...
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December 16, 2015 admin
Control valve, Instrumentation
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