Hydraulic Actuators

What Are Hydraulic Actuators

Hydraulic actuators are devices that translate compressive hydraulic motion into either a mechanical linear or rotary motion. This conversion is necessitated by the piston and cylinder components that form part of its mechanism.

The mechanical output energy is in the form of motions that can either be in oscillatory form, linear form, or rotary form. You can use such actuators in running various machines such as agricultural tractors or even in automobiles.

Hydraulic Actuators Vs. Pneumatic Actuators

As we have already seen, hydraulic actuators use hydraulic oil or water as the compressible medium to transmit power. Pneumatic actuators rely on compressed air to do the same.

The air is taken from the atmosphere and passed through a compressor that stores it at very high pressure. They are usually very stable and you can operate them at pressures of between 80 to 100 psi.

These actuators operate using a compressor unit to generate the compressed air and a tank to store it. Additionally, they have delivery hoses attached to them to supply the compressed air.

Hydraulic Actuators Vs Electric Actuators

You will notice the difference between these two types of actuators still being the means of conveying the actuating energy. Unlike the hydraulic actuator that uses fluids, the electric ones rely on a motor to change electrical energy to mechanical energy.

This provides a form of torque that translates into motion. They are designed with a system of gears and various screws such as balls and rollers to translate rotational energy into linear energy.

Benefits of Hydraulic Actuators

Just like every other machine, hydraulic actuators lessen the workload for you among very many other benefits. We can have a general look at some of these advantages:

· Mobility

Hydraulic actuators are designed in such a way that they are compact and easily portable. This means that you can apply them in your mobile operations or heavy transportation equipment.

· Strength to Weight Ratio

Hydraulic oil can withstand very high compressive forces without compromising its credibility. When you compare the size of your actuator with the amount of work it can do, you get how efficient its relative force is.

Such high output forces are very important especially if you are dealing with construction or manufacturing applications.

· Safety

These actuators come equipped very many safety features such as rod locks that ensure your operational safety. Others such as bypass valves ensure that you don’t operate with high-pressure oil by closing it off or heat dissipating dump valves.

· High Speed

The response you can get when you apply hydraulic pressure on one part of the compressible fluid is instant. If your application heavily relies on speed for efficiency, then this rapid motion can be very beneficial to you.

· Excellent Control

You can fine-tune your hydraulic actuator to the settings that are precise to your application. This gives you more control that accords it with the accuracy required during its motion in moving loads.

· Maintenance

In addition to easily operating them, you will not require much when it comes to their maintenance. If you follow the proper maintenance guidelines, then you will carry out very minimal maintenance that will save you time and money.

Applications of Hydraulic Actuators

Manufacturing Industry
Manufacturing Industry

This industry heavily relies on hydraulic actuator applications.  You can find them as components in heavy machinery like cranes, excavators, and many other precision equipment. Because you can easily control them while achieving huge amounts of force density, you can safely use them to move heavy objects. The efficiency of your operations is greatly improved at the same time as the reduction of your manual labor costs.

Aerospace Industry

You may have noticed how the aircraft’s landing gear retracts during landing and taking off. They are designed in such a way that the safety of their operation is guaranteed given the delicate nature of this means of travelling. The opening and closing of private jet cabin doors is also another good example. The actuator’s motion control is usually very stable in all these critical operations.

Automotive Industry

Advancements in technology have necessitated the need for vehicles to have good fuel economy. You will not fail to find an electric vehicle with a steering powered by hydraulic actuators. Additionally, hybrid vehicles heavily rely on hydraulic actuators in the operations of their suspensions.

Agricultural Industry

The lifting of plows, irrigation, and many other farm tractor operations are made possible through hydraulic actuators. Such applications are high-power reliant with speed of application equally important.

Types of Hydraulic Actuators

Single-Action Hydraulic Actuators

We commonly refer to them as displacement cylinders and the pressure applied to them covers just one side of the piston. The piston has to return to its initial position and requires either gravity or some form of assistive component. That is why you will find a return spring in most of them for that purpose. The rest will rely on gravity to restore the piston to its initial position.

Double-Action Hydraulic Actuators
Double-Action Hydraulic Actuators

As the name suggests, the applicable hydraulic pressure can be on either side of your actuator’s pistons. The piston will move towards the side that has a lesser pressure on your actuator cylinder. This because the higher hydraulic side on the other side pushed it away due to the pressure difference between the two.

Linear Hydraulic Actuators

You can use these actuators when your application requires a force that is provided in a straight line. Hydraulic cylinders are a good example since their pistons provide a linear motion when actuating.

Rotary Hydraulic Actuators

As the name suggests, you can use this for applications that require a constant angular motion or a form of rotational motion. Hydraulic motors are a perfect example.

Semi Rotary Hydraulic Actuators

It is similar to the rotary hydraulic actuator although this assists you where your application requires just a partial angle of actuation. These angular motions can be several 360° revolutions or even any other angles below that.

Telescopic Actuators

These are hydraulic actuators that you can use when your application has very limited space but requires a long stroke length. They have sleeves that fit into each other and can increase the stroke in stages.

Working Principle of Hydraulic Actuator

The law that governs the reactions of fluids to force and pressure is Pascal’s Law. Hydraulic oil is a liquid that undergoes the same and therefore their operation will be based on this law.

This law states that any pressure you apply on any point in a contained fluid is equally transmitted in all directions within the fluid without any loss. You will find the working principles of the different hydraulic actuators to be varying but all operate under Pascal’s Laws.

Besides, the hydraulic oil supplying your actuator is usually stored in a reservoir tank. It is transmitted from there into your actuator using a hydraulic pump.

This normally takes place under very high pressure to ensure that enough hydraulic power is created. A control valve controls the motion and pressure of the hydraulic fluid into and out of the cylinder.

Hydraulic lines supply them with both inlet and outlet hydraulic oil that raises or lowers the piston. The hydraulic fluid is always under pressure therefore any form of leakage can impact the performance of the actuator.

Usually, the mechanical motion comes about when you exert some pressure at any point on the hydraulic oil. This mechanical energy is what lifts, rotates, or moves your load.

Components ofa Hydraulic Actuator

The design of a hydraulic actuator is in such a way that it contains several components working synchronously. We can have a look at these components with a brief description of their structure and functions.

· Barrel/Cylinder

This is the hydraulic oil’s entry and exit points on your hydraulic actuator. This component has to be made of a very strong material since oil enters it at a very high pressure.

· Hydraulic Seals

The work of the piston is to prevent hydraulic oil from passing from one side of the actuator to the other by blocking it. Incoming oil cannot reach the outlet port therefore it seals the oil where it has to be in the actuator.

· Stem

This component is made of a chrome bar and is responsible for transmitting the compressive force from the oil inlet of the cylinder.

· Piston

This is the component that is pushed by the inlet or outlet flow of hydraulic fluid inside a barrel. Also called the plunger, it is responsible for either expanding or contracting the rod when it moves within a cylinder.

· Hydraulic Pump

This is the component responsible for the conversion of mechanical power into hydraulic power. It gets the hydraulic fluid from a reservoir and directs it into the actuator’s output line under a certain pressure.

· Valve

When the hydraulic pump injects the hydraulic fluid into your actuator, this component regulates this flow. It can control its inflow and outflow in addition to determining the hydraulic fluid’s output pressure.

Design Options for Hydraulic Actuators

Various manufacturers have come up with different hydraulic actuator designs available in the market. They come in various designs with their components constructed with variations depending on the area of application.

Let us look at some of the design options you can choose from:

  • The barrel material is very important especially when it comes to withstanding pressure. Some of the materials we recommend are iron, aluminum, or stainless steel. These materials can also have different types of finishes
  • There are two options at play when you want to decide on the location of your cylinder cushioning. You can opt for just one side or go all out on both ends of your cylinder.
  • A flanged or tie rod design is among some of your options when picking your actuator’s end cap. You can also have them threaded or welded on the actuator
  • You can opt for bronze or steel as your piston material. You can also have them as aluminum or cast iron which are equally effective.
  • The ratios of the piston rod of your actuator can be in ratios of either 2:1, 7:6 or 4:3

Choosing the Right Hydraulic Actuator

When you’re sourcing the most appropriate actuator for your application, you have to consider several application demands. Here is a brief preview of the things you have to factor in before settling for the best hydraulic actuator:

· Application Load

Determining the mass that your hydraulic actuator will be handling is the most important factor you have to consider first. The force generated by your actuator must be sufficient enough to move your load and also allow some margin of error.

· Operating Pressure

Pressure is a very important parameter when it comes to exerting the power required by the hydraulic fluid. The pump you use must provide sufficient hydraulic pressure to your actuator to shoulder the desired load requirements.

· Space Requirements

The space that your hydraulic actuator will occupy in your application is also a crucial determinant factor. You should go for an actuator that has a collapsible height that can comfortably fit in your application space without straining.

· Accuracy and Control Requirements

The market has various types of actuators each with its degree of precision and level of operational control. Let’s take an example of a single-acting actuator that relies on hydraulic pressure for plunger extension and a return spring for retraction.

It will not give you more control compared to the double-acting one that lifts and lowers its plunger exclusively using hydraulic force.

· Stroke Requirements

We can define stroke as the difference in the length that your actuator can achieve when fully extended and fully retracted. This can easily tell you how far your load can be pushed or pulled by the hydraulic actuator.

· Hydraulic Actuator Material

When you are comparing your material options, keep in mind that they have a direct impact on your actuator’s weight and durability. Stainless steel actuators are stronger and may last you longer than the ones made from aluminum.

However, if your application can be affected by weight, then you should go for aluminum material. This is usually robust and light and you can easily reposition or even transfer it.

· Mounting Requirements

You need to establish where your hydraulic actuator will be located and how stable it has to be for precision. This means that you have to be clear on whether it will require mounting holes or collar threads to be mounted.

Troubleshooting and Maintaining Hydraulic Actuators

Breakdowns are common in every other machine you operate just like the hydraulic actuator. Various factors can lead to such errors which may adversely impact the performance of your actuator.

We are going to look at some of the common problems you are likely to encounter while using your hydraulic actuator and their detection. We will also outline some of the preventive practices you can apply to avert them.

· Leakages

Possible Causes:

The most likely cause is worn-out seals. However, if your hydraulic actuator return line is obstructed, it can also cause leakages.

Corrective Action

You can inspect your actuator seals and replace any worn-out ones. Ensure that the hoses have a free flow of hydraulic fluid and are free from tight bends and kinks

· Vibrations

Possible Cause

This can be brought about if the components of your actuator are misaligned

Corrective Action

You should service your actuator and ensure that components such as the spindle and piston are well-placed and properly aligned.

· Loss of Power

Possible Causes

The first possible cause is a faulty hydraulic pump. It can also be due to inadequate hydraulic oil in your actuator

Corrective Action

You should check whether your hydraulic pump supplies the oil with the right amount of pressure.

Confirm the Oil Levels in the Reservoir Tank

Besides these, you need to carry out regular maintenance practices on your actuator to prolong its efficiency and service life. Here are some of the basic maintenance practices that you can regularly perform on your hydraulic actuator:

· Oil Maintenance

You should have a consistent schedule for checking the oil you use in your hydraulic actuator. The best way you can ensure that it is contaminant-free and clean is by keeping all the entry point environments clean.

Also, check the manufacturer’s recommendation of how often you should get an oil change for your hydraulic actuator. Also, when topping up your hydraulic oil, ensure that it is of the same type as the one inside your actuator.

· Regular Filter Replacement

The function of the filter in your hydraulic actuator system is the removal of contaminants that may clog your actuator. When they filter such particles for a very long time, they become clogged.

This means that their efficiency will be greatly reduced and may interfere with the performance of your hydraulic filter. It is advisable that you do regular replacements and while at it, thoroughly clean the filter bowl.

· Piston Rod Inspections

The piston rod is prone to defects such as corrosion and pitting. This can result in contamination of the hydraulic fluid by moisture.

If accumulated, it can negatively impact the operations of your hydraulic actuator. You can make regular visual inspections of the piston before and after every operation to avoid this.

· Seal Replacements

The seals of your actuator are usually damaged by a corroded piston rod or excess pressure applied to them. A faulty seal may lead to hydraulic oil leakages in your actuator which is a serious safety concern.

Watch out for any leakages from your actuator. When replacing your seals, ensure you follow the manufacturer’s replacement procedures for efficient actuator operations.

· Hydraulic Line Inspection

Sometimes your actuator may exert excess pressure from the load it is sustaining on the hydraulic fluid lines. The lines may balloon meaning they will be letting in more hydraulic fluid under pressure than normal to pass to your actuator.

The damage will mostly be felt on the seals since they will begin to wear out.

The Future Of Hydraulic Actuators

Emerging trends have made the hydraulic actuator make huge strides in terms of technological advancements. Let us delve into how prospective the future of this type of actuator is.

· Digital Incorporation

You may have noticed that more and more hydraulic actuators have a digital control system that runs them. Imagine the precision you can derive from a dynamic combination of electronics and hydraulic actuators, next level.

You can achieve precise motions with sensors that use complex algorithms to run your actuator. You can easily optimize the energy consumed while at the same time monitoring your actuator in real-time.

· Miniaturization

It is now possible to get hydraulic actuator components that are compact and light in weight. This means that you can easily integrate your hydraulic actuator into devices that have space and weight constrictions.

This is very beneficial especially if your application involves robotics or even aerospace technology. They reduce the overall weight without compromising their strength and stability.

· Safety

There are advancements in the hydraulic actuator’s safety aspects such as pressure relief valves and other fail-safe methods. The availability of advanced monitoring systems ensures that you can carry out predictive maintenance and prevent potential accidents.


Hydraulic actuators can serve you in very many applications by enhancing performance while giving you many benefits. Such benefits include being powerful, durable, offering a rapid response, and requiring less when it comes to their maintenance.

You can easily control their motion by adjusting their settings to fit into your application requirements with precision. This can give you a competitive in your industry especially with this knowledge of their operation.

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