What's the Difference Between a Hydraulic Actuator and a Pneumatic Linear Actuator?
Linear actuators (or cylinders) are responsible for converting energy from a power source (air, liquid, or electricity) into force, and depending on the size of your application, the energy source you use will differ. There's a variety of types of actuators available: hydraulic (fluid-based), pneumatic (air pressure-based), or even electric. You can read more about when it is appropriate to use electric actuators here. For now, we’re delving into the main differences between hydraulic and pneumatic actuators and their distinctive advantages/disadvantages:
- Hydraulic actuators use hydraulic fluid, meaning they can hold torque and force without continuous application of fluid pressure. However, they can leak–and the leaked fluid invites contamination.
- Pneumatic actuators are ideal for applications that require less power and more consistent, reliable, linear motion. They use compressed air, so they don’t require a hydraulic system.
Read on to learn more about the pros, cons, and differences between hydraulic and pneumatic actuators.
Hydraulic cylinders can produce tremendous force because hydraulic fluid can achieve much higher pressures consistently.. This is essential for operating heavy construction equipment, for example. They can produce as much as 25x the force that a pneumatic cylinder can generate, as well as higher horsepower per weight. One of their main advantages is their ability to hold torque and force without the continuous application of fluid pressure from the power source. Hydraulic fluids can more readily be used within a closed system. This is because fluids are not compressible like air.
On the downside, hydraulic actuators can leak, and the leaked fluid invites contamination that can cause damage to internal or external working parts. It also takes an assortment of other equipment to operate hydraulics – motors, pumps, fluid reservoirs, etc. Hydraulic systems can also be very noisy, even when outfitted with noise-reduction equipment. These factors, and the fact that they don’t do well in extreme weather due to their fluid-powered nature, can make hydraulic actuators too unwieldy and unrealistic for many environments.
Pneumatic cylinders are driven by air pressure rather than fluid. Pressurized air is less costly and more readily available than hydraulic systems; however, air can sometimes be less efficient as a power source because it can be compressed, causing the actuator to lose pressure. The air compressor that powers a pneumatic actuator must be located relatively close by, and it has to run continuously. It is also possible for the air to become contaminated by equipment lubricants, which increases the risk of damage. Luckily, there are preventative measures you can take to reduce the risk of damage.
The bottom line is that pneumatic actuators operate at lower pressures and speeds than hydraulic cylinders. For many applications, though, this is an advantage: pneumatic cylinders provide highly reliable, consistent linear motion, with accuracy tolerances within 0.1 inches and repeatability tolerances within .001 inches. They can also perform just as well in extremely high or low temperatures, which would cripple fluid-based hydraulic actuators. In addition, because pneumatic actuators have no motor and use no hazardous materials, they can easily meet mechanical safety requirements and are even approved for food processing applications.
In many industrial applications, moving machinery–and controlling that movement consistently–is what matters most. Pneumatic actuators, or cylinders, are often ideal for these applications. To achieve maximum efficiency, it is important to size pneumatic actuators accurately for the job at hand. W.C. Branham manufactures several different types of pneumatic actuators, each available in a variety of bore sizes.
As of 2022, W. C. Branham has been partnered with ARTEC as their sole distributor in the US and Canada of ISO & UNITOP Pneumatic Cylinders. Because they meet such strict international standards regarding size, materials, and durability, they are also interchangeable with a number of existing W. C. Branham product lines such as:
- OVLPRO™ - Low Profile Rod Air
While pneumatic cylinders may be the best choice for your industrial application, choosing the right one(s) for your project can be complex. No worries–if you need help spec’ing, W.C. Branham is happy to help.