Answer / rakesh barot

control valve opens or closes fully or partially by
receiving the signal from controller that compare set
point to process variable whose value is provided by the
sensors

Answer / srinivasansureshkumar

Control valve: Also called as final control element /
variable orifice (Restrictor) in a flow line.

Principle of operation : Motion Balance Principle.

Breif Description: The control valve consists of

1. Actuator (Provides power to drive the valve otion)
2. Range spring (Its the one dictates the operating range
of valve)
3. yoke (Supports the Actuator to valve boby)
4. Valve Body (where plug & Seat in there throttles the
flow according to the position between them)

** The signal provided to the actuator drives the actuator
stem which is coupled to the plug stem. this motion occurs
opposing the range spring until the resultant force
generated by the actuator and range spring nullifies.
The resultant is the travel position of the valve.

Answer / rabindra ojha

pneumatic control valve operated by air.to operate a cotrol
control valve requared accesories are (air, i/p,
positioner,regulator).i/p inlet air is 1.5 kg/sq.cm and
signal is 4 to 20 ma.i/p output is 0.2 to 1 kg/sq.cm.when
command is given corresponding output of i/p is gone to
positioner.its output go to control valve to operate the
control valve. positioner works on flaper nozzle principle.

Answer / vishok

The 4-20 ma signal is used to close-open the control valve.
the openning of the valve 0-100% is calibrated according to
the command signal. This adjustment is done inside control
valve while designing it. Pl go throught the manual for
internal diagrams of different valves.

Answer / ashok patel

Controller gives 4 to 20 mA signal to I-P converter & I-P
converter gives 0.2 to 1.0 Bar air pressure to control valve
for open or close operation against the balance force of
actuator spring.

Answer / gopal krishna

there are many control valves.but the most interesting control valve is pneumatic control valve as there will be i/p converter in control valve which takes the signal from plc i.e(4-20ma)and corresponding value of air will be used to operate the stem.now the stem position is taken feedback by positioner in control valve and checks it with the setpoint value.if matches its ok if not gives the compensating signal

Answer / zamir hussain shar qatar

is the electro pnuematic machine sued to control the flow
of process fluid

what u mean by speed control in turbin? how it was working?

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