I&C Valve Actuators

Card Set Information

Author:
ereim
ID:
31846
Filename:
I&C Valve Actuators
Updated:
2010-09-01 08:48:32
Tags:
Valve Actuators Position Indicators
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Description:
Valve Actuators and Position Indicators
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  1. A device to engage and disengage the valve stem from an electric motor or handwheel
    Declutch lever
  2. Refers to the overshoot and undershoot that occur as the receiving device tries to match the sending device
    Hunting
  3. A valve actuator that uses a piston to translate a signal into valve motion
    Hydraulic actuator
  4. A mechanical device attached to the valve stem to indicate valve position by way of remote and/or local indicating lights
    Limit switch
  5. An instrument transformer that provides accurate position indication throughout the range of a component’s travel
    Linear variable differential transformer (LVDT)
  6. A handwheel or lever that directly controls valve stem position
    Mechanical actuator
  7. A valve actuator that use pneumatic (air, nitrogen, etc.) pressure as the source of thrust to operate the valve stem
    Pneumatic actuator
  8. Switches constructed of flexible ferrous strips and are placed near the intended travel of the valve stem or control rod extension
    Reed switches
  9. A remote indication or control system. Consists of synchro units that electrically govern or follow the position of a mechanical indicator or device
    Synchro equipment
  10. A type of electrical valve actuator. The valve stem is attached to a magnetic core that is attracted by a magnetic force generated by a coil when energized
    Solenoid valve
  11. A device used to manipulate the position of the valve stem
    Valve Actuator
  12. DESCRIBE the four basic types of pneumatic actuators.
    Pneumatic actuators use air pressure on either one or both sides of a diaphragm or piston to provide the force to position the valve

    • Pneumatic diaphragm
    • Pneumatic piston
    • Pneumatic cylinder
    • Pneumatic vane
  13. Given a drawing, DESCRIBE how a pneumatic-operated valve with a solenoid pilot valve would reposition following a loss of pneumatics
  14. Given a drawing, DESCRIBE how a pneumatic-operated valve with a solenoid pilot valve would reposition following a loss of electrical power
  15. STATE the methods that can be used to determine or verify valve position locally or remotely
    • The simplest means of determining valve position is observing the position indicating light
    • Another method to determine valve position is by locally observing valve stem position
    • An additional method to determine valve position is by a locally mounted pointer
    • Some valves do not have any visual means to determine valve position. In these cases, system parameters such as flow, pressure, and temperature can be used, as well as attempting to operate the valve in the closed direction
  16. DESCRIBE the proper methods or techniques for operating and verifying the position of manual valves
    To physically check a valve position, turn the valve handwheel a short distance in the “shut” direction. If the handwheel turns, the valve is open. If the valve handwheel will not turn, the valve is already shut
  17. DESCRIBE the synchro position indicators to include the basic construction and theory of operation
    Remote indication or control may be obtained by the use of self-synchronizing motors, called synchro equipment. Synchro equipment consists of synchro units that electrically govern or follow the position of a mechanical indicator or device. An electrical synchro has two distinct advantages over mechanical indicators: (1) greater accuracy, and (2) simpler routing of remote indication.

    • There are five basic types of synchros that are designated according to their function. The basic types are:
    • Transmitters
    • Differential transmitters
    • Receivers
    • Differential receivers
    • Control transformers


  18. DESCRIBE limit switches and reed switches to include basic construction and theory of operation
    • A limit switch is a mechanical device that can be used to determine the physical position of equipment
    • Reed switches are more reliable than limit switches, due to their simplified construction
  19. Motor Operated Valve
  20. Solenoid Operated Valve
  21. Pneumatic Piston Valve
  22. DESCRIBE potentiometer position indicators to include basic construction and theory of operation
    Potentiometer valve position indicators provide an accurate indication of position throughout the travel of a valve or control rod. The valve stem extension is physically attached to a variable resistor, usually through a geared linkage

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