This document discusses different types of actuators. It defines an actuator as a transducer that converts one form of energy into motion. The main types discussed are pneumatic, electro-pneumatic, hydraulic, electro-hydraulic, and electric actuators. Pneumatic actuators are most commonly used in process control and work by using air pressure on a diaphragm to move a valve plug. Electro-pneumatic actuators combine a pressure transducer, positioner, and pneumatic actuator to handle signals from computer controllers. Hydraulic and electro-hydraulic actuators similarly use fluid pressure on pistons, while electric actuators can be motors or solenoids.

1. ACTUATORS
Ranjana N
6th sem

2. Introduction
• Actuator is a transducer that translates the control
signal from one form of energy into another form.
• During valve operation, the translational motion is
transformed into rotary motion.
• It produces an output position that is proportional to
its input signal.

3. Types of Actuators
Following are the types of Actuators classified based
on their functions:
• Pneumatic Actuators
• Electro pneumatic Actuators
• Hydraulic Actuators
• Electro hydraulic Actuators
• Electric Actuators

4. Pneumatic Actuators
OMost commonly used process control
actuators.
OIt is also called as a Spring Actuator.
OThe controlled input-air pressure
provides sufficient force on the
diaphragm to offset a portion of the
spring force.

5. Pneumatic Actuator
O Increase in controlled
input-air pressure
moves the valve plug in
downward direction,
reducing the flow
through the valve. This
action is termed as Air-
to-close. If the actuator
inlet port is below the
diaphragm then it is
termed as Air-to-open.

6. Electro pneumatic Actuators
• It is a combination of a
current to pressure
transducer, a feedback
positioner and a
pneumatic spring
diaphragm actuator.
• It is used to handle
pulse signals from a
digital computer
controller.

7. Hydraulic Actuators
 It is usually present in
the form of hydraulic
piston.
 The piston is moved by
applying pressurized
hydraulic fluid to either
side of the piston with
an opposing spring
providing for the
motion in the other
direction.

8. Electro Hydraulic Actuators
• It consists of an electric-
to-hydraulic transducer,
a feedback positioner
and a hydraulic piston.
• It is similar to that of
pneumatic piston
actuator; both need
some means of piston
position feedback.

9. Electric Actuators
• Two types: electric
motor and electrical
solenoid.
• Used for two-position
actuators provided with
a forward and reverse
winding.