ACTUATORS

Ranjana N6th sem

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.

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

Pneumatic Actuators

OMost commonly used process control actuators.

O It 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.

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.

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.

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.

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.

Electric Actuators

• Two types: electric motor and electrical solenoid.

• Used for two-position actuators provided with a forward and reverse winding.

Thank you