Pneumatic vs. Hydraulic Systems: What is the Difference?

Plenty of people use the terms pneumatic and hydraulic interchangeably. You might even think that they refer to the same technologies. Nothing could be further from the truth.

Pneumatic gear uses pressurized air or some other relatively inert gas to power devices. Hydraulics, on the other hand, employ a fluid in the liquid state to do work.

In spite of this very clear difference, there’s quite a bit of confusion between the two. Some of this might stem from the fact that gases are technically fluids, at least in terms of engineering parlance. There are also some other related technologies you might run into.

Regardless of what type of equipment you currently employ, you might quickly find that pneumatic gear outperforms hydraulic equipment in a number of use cases. Should you identify any specific tools that need to be replaced, SMC Pneumatics carries a full line that can potentially fit your needs quite nicely.

If you’re still a bit confused about the difference, then the list of pointers we’ve put together should help set the record straight.

How Pneumatic Equipment Works

Pressure provided by an external compressor or cylinder can move a physical piston mounted inside of a hollow cavity. This forms the basis for pneumatic linear actuator design. As air pressure increases, the cylinder will start to move along the axis of the piston. This in turn creates linear force.

Eventually, the piston reaches the other side of the chamber where a spring-back force or some sort of fluid forces it to move back in the other direction. The cycle will then begin all over again, which provides movement to power whatever tool the actuator is attached to.

While the reason for the flow of gas is fundamentally different from that of the pistons mounted inside of an internal combustion engine, the principle for their motion is quite similar. This provides an accessible way to easily visualize the motion of these components if you’re unfamiliar with pneumatic technology but have at least a working knowledge of how automobiles function.

Principles Behind Hydraulic Technology

Overall, hydraulic linear actuators operate similarly to pneumatic ones. However, they don’t have anything to do with compressed air or gases. Rather, these components are powered by the movement of an non-compressible liquid flowing through hoses. The liquid is pushed through the line by way of a pump, which is usually powered by electricity or some other external energy source.

On the surface these two technologies seem rather similar. However, there are several key differences that set them apart.

Comparing Pneumatic Equipment with Hydraulic

Hydraulic designs tend to rely on rather complicated engineering, which can make them somewhat difficult to maintain in many situations. Pneumatic actuators are usually quite simple. They come in standard bore sizes ranging from ½-8 in., which can translate into upwards of 7,500 lb. of force depending on how they’re deployed. Solid steel actuators can generate close to 40,000 lbf., which is more than enough for most jobs. Increasing the amount of effort doesn’t normally increase the mechanical complexity, however.

Advances in miniaturization and materials manufacturing has helped to increase the number of options available to end-users. It’s also helped to drop costs somewhat. Pneumatic actuators often weigh less than hydraulic ones and represent a smaller initial investment as a result.

Hardware vendors have been able to provide very powerful hydraulic tools for some time, which has made them a common fixture at construction sites. However, it’s not necessarily as useful for many applications that call for precise motion. Pneumatic equipment is so precise that some dental drills and other medical tools run on compressed air.

This makes it an attractive option for those that work in sensitive industries that require a delicate touch.

Holding Pneumatic Parts Against Other Technologies

Technically, pneumatic and hydraulic machinery often involves electrical power in some way. However, a third type of technology that’s purely electric is also sometimes confused for these two. Electrical linear actuators feature a mechanical motor that turns a lead screw.

A threaded ball nut that matches the screw is driven along corresponding threads. The nut moves in a direction against the rotation of the screw before returning the actuator to the original set position.

Even though you might think that this sort of equipment is more efficient since it turns electrical energy into torque without requiring an intermediate device like an air compressor, there are still many instances where pneumatic equipment can outperform it.

For instance, compressed air-driven machinery can work well on work sites that might experience high temperatures.

Safety Considerations when Picking Out Tools

No matter what source of power you select, you’ll have to put some thought into safety concerns. Hydraulic fluids can be potentially dangerous if they leak out. Air compressors deal only with the ambient atmosphere, so even if they leak there’s no real concern about anyone being poisoned.

Compressed air can certainly cause mechanical trauma if something goes wrong, but it doesn’t pose much of a fire risk and usually won’t combust. As a result, pneumatic tools have become quite popular in many industrial settings where strict guidelines have to be followed at all times.

Since pneumatic tools don’t use any conventional electric motors, they don’t generate measurable magnetic fields. This may be an important consideration around any kind of equipment that’s sensitive to interference. Considering how much gear these days somehow involves radio waves, this is a particularly important feature.

Ordering Custom Pneumatic Tools

There are many instances where hydraulic technology is well suited, but countless people have realized that pneumatic equipment is a better fit for their workshop or job site. Contact us today and speak with a member of our skilled customer service team if you’re ready to learn more about how compressed air-driven equipment can revolutionize the way your business does work. Many companies have very specific needs, but you don’t have to worry about making a particular request. Our engineers are always ready to develop new solutions that meet your firm’s needs.