What is a Hydraulic Actuator?

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  • Written By: M. Rosario
  • Edited By: C. Wilborn
  • Last Modified Date: 12 November 2019
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A hydraulic actuator is a mechanical device that uses hydraulics to convert energy into a linear movement. The mechanical energy produced is generally used to lift or press things that require a great deal of energy. Heavy equipment usually relies on several hydraulic actuators to function. A bulldozer, for example, is able to lift several tons of rubble through the actuators found in its lifting arm.

Hydraulic fluid is the main source of power in a hydraulic actuator. The movement of the actuator can be controlled by changing the amount of the hydraulic fluid inside it. During the ancient times, people used water as a hydraulic fluid. Innovations in chemical engineering however, created oils specifically designed for this purpose.

The basic mechanism for a hydraulic actuator is the conversion of the power of hydraulics. A pressurized hydraulic oil is a fluid that cannot be further compressed. When one end of the hydraulic actuator receives pressure, the hydraulic fluid multiplies that pressure and converts it to a mechanical movement. This is why hydraulic actuators are able to generate great power.

Common designs for hydraulic actuators consists of the cylinder, piston, hydraulic fluid, and the supply and return line. Majority of the mechanism's process happens inside the cylinder. It contains the piston and hydraulic fluid. An opening inside the cylinder attaches to the supply and return line.


One main advantage of the hydraulic actuator is the high amount of force it generates. Construction and engineering professions frequently employ hydraulic machines to serve various purposes. While lifting is commonly its main purpose, a hydraulic actuator can also push, crush, and stomp.

Accuracy and agility are two additional advantages of hydraulic machines. The piston is mostly controlled by altering the amount of hydraulic fluids inside it. There are machines that take advantage of this by mimicking the way an arm works. Several hydraulic actuators act as muscles that push and pull the machine arm to give it flexibility of movement.

Without the line, it is not possible to control the actuator movement. The line controls the amount of fluid inside the cylinder. By increasing and decreasing the fluid, the operator can control the piston movement. The piston is then attached to an external component.

Car brakes can operate with a hydraulic system. When the driver steps on the brake, a master cylinder moves. This activates the hydraulic brake actuator, which presses the brake pad against the wheel, which in turn slows the car down.

Rotary hydraulic actuators contain motors and a gear box to control a rotary force. The design of this type of actuator enables it to function without needing too much volume and energy. The motor in the rotary hydraulic actuator achieves this by attaching to two pistons at the same time. When the motor turns, is causes both pistons to move.


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