Valve Actuators 2v
how doesthe force on the plunger increase?
the force on the plunger increases with the square of the number of turn times the coil current divided by the air gap.
Actuator Fail safe considerations of actuators.
Closed or open
Actuator positioners must be...
Compatible with control signal
When buying a Solenoid...
Consider if it is for Steam, Gas, or Liquid Size of the solenoid
Pros of a motor operated valves
Control Switches or push buttons can be located far away in a control room Process can be shutdown quickly without dispatching an operator Should leaks of dangerous chemicals or gases occur, motor operated valves can be used to isolate the process in areas dangerous to personnel
Two types of pneumatic actuators
Diaphragm Piston
An actuator must be.....
Mechanically compatible with the Bonnet and stem.
Motor operated valves are normally used as....
Remotely operated shut off valves
What is a 4-way solenoid valve used for?
Used to provide pressure and provide exhaust for a double acting cylinder.
3-way solenoid valve characteristics
flow from inlet to either outlet A or B
A solenoid actuator consists of....
A coil on a magnetic frame and a moveable magnetic plunger.
What is a positioner used for?
A positioner is used to position the valve to the exact position demanded by the control signal.
Pros of a solenoid valve
Fast Action Compact Size Relatively inexpensive Few Moving Parts
2 switches on a MOV
Limit Switch- Limits travel Torque Switch- limits amount of force.
Cons of a solenoid Valve
Limited to 3 to 4 inches Can only operate fully open or fully closed
Characteristics of a direct acting solenoid.
Plunger is connected to the valve stem Plunger moves to open and close the valve Limited to fairly low differential pressure application
2 types of Electric actuators
Solenoid Motor operated valve (MOV)
Motor operated Valves are normally used with...
Squirrel Cage motors
An actuator must have....
Stroke length and force sufficient to operate the valve. Stroke time appropriate to control transients
How does a solenoid actuator work?
The solenoid actuator works by having current pass through the coil, causing it to act like a magnet attracting the moveable plunger.
