MOV (Motor Operated Valve), specification

MOVs are widely used primarily for isolation purposes in the process industries.

MOVs consists of two main parts, valve and electric actuator (including auxiliary gearbox). The valves to be actuated include gate, globe, butterfly, triple offset, ball and plug type valves.

Electric actuators can be defined into two (2) basic types:

1. Multi Turn 
A multi-turn actuator is an actuator which transmits torque to the valve for more than one complete revolution.

 2. Quarter Turn
 A quarter turn actuator is an actuator which transmits torque to the valve for only one quarter (45 degree) of a complete revolution. withstanding thrust.

Selection of Electric Actuators per valves type and requirement: 
-Wedge Gate (Rising, non-rotating threaded stem) Torque Seated.
-Parallel Disc Gate (Rising, non-rotating threaded stem) Position Seated.
-Knife Gate (Rising, non-rotating threaded stem) Position Seated.
-Globe Valve (Rising, non-rotating threaded stem) Torque Seated. 
-Stop Check Globes (Rising, non-rotating threaded stem) Torque Seated.
-Butterfly Valves Position Seated

Information required to properly size the actuators:
-Voltage and Voltage Variance (IE, Plus 10%, Minus 20%)
-Modulating or Open – Close Application.
-Torque Required (and Max. Thrust if applicable)
-Shaft Diameter (and Thread design if Applicable).
-Operating Time Required. -Enclosure Classification (NEMA 4X, 7, IP 68)
-Maximum Line Temperature. -Safety Factor to be applied if applicable.
-Detailed Actuator Specification for the Particular Project. -An Important Sizing / Selection Consideration Involves High Temperature, Rising Stem, Torque Seated Valves. When the Line Temp Exceeds 800 Degrees, a Thermal Compensating ‘Floating’ Stem Nut Design is Warranted.

Electric Actuator controls:
-motor starters
-control power supply or transformer
-pilot devices / local controls
-A positioner is required to accept an analog signal (i.e. 4-20mADC).
-A digital communications board is required to communicate via ‘fieldbus’ or ‘two-wire.’

Motor controls can be located:
-at the motor (actuator)
-at a remote location

Intrusive actuators motor controls (basic contorls):

-Reversing starters
-Power supply (115V of 24VDC)
-Auto phase correction -Monitor relay
-Loss of phase
-Thermal trip -Torque trip
-Pilot devices / local controls
-Standard interface board (24 VDC or 115 V)
-NEMA 4X/6 Weatherproof enclosure
-Torque and limit Switches enclosed within the Actuator housing

Intrusive actuators motor controls (optional contorls):
-Control interface boards
    -Positioner (accept analog signal)
    -Fieldbus Protocols (PROFIBUS-DP -Modbus RTU -DeviceNet)
    -Accept emergency signal
-Overload relays
-Solid state starters / Thyristors
-High temperature rating
-Low temperature rating
-Enhanced corrosion protection
-Submersible enclosure
-Explosion proof
-Lockable tamper
-proof protection cover
-Ability to remote mount the motor controls

  Non-intrusive actuators motor controls (basic contorls):
-Reversing starters
-Power supply (24VDC or 115VAC)
-Auto phase correction -Monitor relay / fault relay
-Standard interface (24 VDC or 115 V contact closure)
-Pulse time
-Pilot devices / local controls
-Enclosure: NEMA 4X/6 Weatherproof enclosure
-Electronic Control Unit
-Output signals (programmable output relays) for Position, Torque, Fault, Running Open, Running      Close etc
-Analog torque feedback
-Analog position feedback
-LCD display
-Electronic nameplate
-Wireless Communications via Bluetooth
-Ability to generate and store torque curves
-Interface boards which can include:
   -Adaptive positioner
   -Process controller PID
   -Digital communications interfaces (PROFIBUS-DP, Modbus RTU, DeviceNet, Foundation
    Fieldbus)                
   -Accept emergency input signal
-Optional reversing starters based on Actuator size
-Overload relays
-Solid state starters / Thyristors
-Additional programmable relays
-Voltage Tolerance (i.e. +/- 30% of nominal voltage)
-High temperature rating
-Low temperature rating
-Enhanced corrosion protection
-Submersible enclosure
-Explosion proof
-Lockable tamper
-proof protection cover
-Ability to remote mount the motor controls

  Key Take aways:
Electric Actuators serve a key role in process industries
-Specifying the proper actuator features is important
-What is the application? Multiturn, Part-turn or damper
-What are the valve characteristics? Torque or Thrust
-What type of Motor Controls are Req‘d? Non-Intrusive or Intrusive
-What is the Control Interface? Contact Closure, Analog or Fieldbus
-What is the environment? Nuclear, Weatherproof, Explosion Proof, High Temperature, Low    Temperature or Submersible
-What is the Primary and Control Voltage? Are voltage fluctuations of concern?