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Control valves


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

Published in: Education, Business
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Control valves

  1. 1. 1 Presented by: Syed Waqas Haider Process Engineer
  2. 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) 2
  3. 3. 3 Control Valves Rotary Motion Butterfly valves Ball vales Plug valves Linear Motion Globe Valves
  4. 4. Three main parts Valve's actuator Valve's positioner Valve's body 4
  5. 5. The purpose of the valve actuator is to accurately locate the valve plug in a position dictated by the control signal 5
  6. 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 6 according to their supply
  7. 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 7 according to their movement
  8. 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 8
  9. 9. Some of the mechanisms i. Force Balance Positioners ii. Motion balance Positioners iii. Electronic Positioners 9
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  12. 12. 12 Sensor to detect valve position Micro-Processor Error = Position - Signal
  13. 13. Valve Bodies 13
  14. 14. 14 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