Although it is largely true that actuators, be it a hydraulic, pneumatic or an electric linear actuator, are not universally suitable for every application, electrical linear actuators are becoming the primary choice in many applications where previously a pneumatic or hydraulic actuator was installed.
The need and application of linear actuators have grown exponentially. So much so that one of every three motion system is comprised of at least one linear actuator, with the variety of applications becoming endless. Once limited in applications where heavy duty work was required, often on shop floors, actuators have become more commonplace in everyday life.
With creative ways to help in many everyday endeavors, linear actuators have found applications in offices, to kitchen and garages. While there is very little likelihood that actuators that are built for specific applications are going away anytime soon, the changing needs in applications are giving way to one type of linear actuator being replaced by the other.
Both pneumatic and hydraulic linear actuators have been extensively used for rugged applications from farm to commercial, or home applications. However, those applications have become more nuanced and several factors such as accuracy, mid-stroke positioning, serviceability, and durability are becoming more desirable in these applications. Although linear actuators other than electrical are great for end-to-end application, their accuracy and predictability of operation for mid-stroke work is less desirable.
Let’s take a look at each type of linear actuator and how they are suitable for specific applications:
Hydraulic Linear Actuators:
Hydraulic linear actuators are highly suitable for application where an immense amount of power and force is needed with an acceptable amount of accuracy. Ideal applications for hydraulic actuators are in heavy machinery and trucks where a mobile power application is needed and high voltage is not readily available or suitable. Some of the pros and cons of hydraulic linear actuators are:
- Hydraulic linear actuators are suitable where high force and unlimited power is needed, such as in heavy machinery and trucks for lifting, pulling, hammering and towing heavy objects.
- More control and accuracy is desired using incompressible liquid to provide reasonably precise actions.
- Linear force can be created in the field where high voltage electricity is not available or feasible, such as fieldwork around flammable and combustible liquids and gases.
- A large footprint with various lines, pumps, and gaskets that allow the hydraulic fluid to move around the application. The larger the need for force the larger the lines and the pumps for it.
- One of the most expensive applications, both in the acquisition and future maintenance.
- One of the most tediously maintainable applications with filters, fluid lines, and pumps that need constant inspection and maintenance.
- Most hazardous in terms of safety and environment when a sudden leak or burst of supply lines or pumps occurs.
Pneumatic Linear Actuators:
Pneumatic linear actuators are useful where both the cost and availability of power are a factor. Being the cheapest of the three actuators, as far as the acquisition is concerned, pneumatic linear actuators are often used in places where both cleanliness and power free operations without the need for accuracy or extreme force is needed. Places such as kitchen and other food operations as well as shop floors use pneumatic actuators. Their pros and cons are:
- Pneumatic actuators provide relatively fast movement, as fast as 2 m/s
- Relatively inexpensive to acquire and operate.
- Simple to install and easier to troubleshoot.
- The run on compressed air so they are cleaner to operate.
- Because they run on air pressure, it is relatively difficult to achieve variable speed in pneumatic actuators.
- Along with variable speed, these actuators are also unsuitable where slow speed is required.
- Accuracy and mid-stroke positioning are also not easily achieved in pneumatic linear actuators and even when achieved tends to be very expensive and requires constant maintenance.
- Because of lack of high accuracy pneumatic actuators are not a good selection where you are seeking variable positioning with greater accuracy.
- The air compressors used for pneumatic linear actuators are not only wasteful converting very little of the electrical energy they consume, they also require regular maintenance.
- Various parts and pieces that supply the actuator with the compressed air such as lines and filter need maintenance and are likely points of failure of the system.
- Actuators themselves due to dry operations may need to be more frequently replaced.
Electrical Linear Actuators:
With its wide array of application, improvement in quality, cost reduction, and advancement in technology electrical linear actuators are fast becoming the only choice in a wide variety of situations. Especially with the advent of electromechanical actuators that do not need a constant supply of electricity to hold its position or can be operated with electricity and a hand crank, they are becoming more and more attractive for use in a variety of applications.
Here are the pros and cons of an electric linear actuator:
- Electrical linear actuators provide the fastest movement in linear actuators of up to 10 meters per second.
- Easily automated, electrical actuators can be programmed to predictably and accurately stop at any desired position along their linear length.
- High accuracy in movements, some actuators can provide an accuracy of +/- 0.003mm to +/- 0.015 mm.
- They are also capable of an accurately programmable speed at which they move along their length, a feature either unachievable or not accurate in other actuators.
- Can provide feedback in electrical impulses on motion and force applied to desired targets
- Can function with electrical control units of vehicles or machines to integrate multiple controls in a single switch, like a joystick.
- Electrical linear actuators need expert hands to install and integrate into existing systems.
- Need extensive training in troubleshooting and repairs.
- More costly to acquire, especially when compared with pneumatic linear actuators.
In conclusion, although pneumatic and hydraulic linear actuators were formerly attractive with their acquisition cost and their tolerance of changes in external factors such as extreme temperatures and dust. They were also favored in a shop environment where compressed air was in ample supply due to its being used to operate various shop tools and cleaning up. However, when it came to accurate operation and mid-stroke or variable height tasks, requiring a control valve and operator assistance, they have proven unreliable.