basic understanding of control valves working principle of control valves flow characteristics of control valves

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Presented by:
Syed Waqas Haider
Process Engineer

2. Control Valves
control conditions (flow, pressure, temperature, and liquid level )
open or close in response to signals received from
controllers
Controller compare a "setpoint" to a "process variable"
(value provided by sensors)
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Control
Valves
Rotary
Motion
Butterfly
valves
Ball
vales
Plug
valves
Linear
Motion
Globe
Valves

4. Three main parts
Valve's actuator
Valve's positioner
Valve's body
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5. The purpose of the valve actuator is to accurately locate
the valve plug in a position dictated by the control signal
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6. Pneumatic Valve Actuators: Adjust the position of the valve
by converting air pressure into rotary motion or linear motion.
Piston and Diaphragm Actuators are examples of Pneumatic
Actuators
Electric Valve Actuators: An electric actuator is powered by
motor that converts electrical energy to mechanical torque
Hydraulic actuator: Consists of a cylinder or fluid motor that
uses hydraulic power to facilitate mechanical operation. The
mechanical motion gives an output in terms of linear, rotary or
oscillatory motion
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according to their supply

7. Multi-turn actuator
gives torque for at least one full
revolution
Part-turn actuator
gives torque for less than one full
revolution
Linear actuator
opens and closes valves that can be
operated via linear force--sometimes called rising stem
valves
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according to their movement

8. Positioners are instruments that help improve control by
accurately positioning a control valve actuator in response
to a control signal
Positioners receive an input signal either
pneumatically or electronically and provide output power
to an actuator
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9. Some of the mechanisms
i. Force Balance Positioners
ii. Motion balance Positioners
iii. Electronic Positioners
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Sensor to detect valve position
Micro-Processor Error = Position - Signal

13. Valve Bodies
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Quick Opening: Quick open plugs
are used for on-off applications
designed to produce maximum flow
quickly
Linear: produces equal changes in
flow per unit of valve stroke regardless
of plug position, used where valve
pressure drop is a major portion of the
total system pressure drop
Equal Percentage: change in flow
per unit of valve stroke is directly
proportional to the flow occurring just
before the change is made, generally
used for pressure control