Hydraulic and pneumatic systems are integral to the operation of cars, trucks, buses, aircraft, and other vehicles. These systems power everything from braking and steering to heating and air conditioning. However, there are some essential differences between hydraulics vs. pneumatics.

Hydraulic systems compress liquid, are used for industrial machinery, cost about $10,000, and produce around 6,500 PSI. Pneumatic systems compress gas or air, are used for smaller tools, cost approximately $1,500, and generate about 120 PSI. Overall, hydraulics are better for large jobs, while pneumatics can handle the small ones.

In this article, we’ll discuss the ins and outs of hydraulics and pneumatics, what each system is used for, and their pros and cons!

What Is a Hydraulic System?

The first type of system we’re going to dive into is hydraulics.

A hydraulic system, or hydraulic power system, uses pressurized fluid to power the moving parts of a machine. Hydraulics pumps relatively incompressible liquids at extremely high pressures using valves and actuators. The average operating pound-force per square inch of a hydraulic system is 6,500 PSI. 

Hydraulic systems are often paired with at least one other kind of power system. For example, some cars use hydraulics to power their steering and braking and use electric motors and gasoline to power the engine. Note that these systems are typically seen on heavy-duty vehicles like construction equipment, aircraft, or elevators.

Hydraulics use engineering and physics principles (think Pascal’s Law) to transfer force from one end to another- effectively, like a seesaw. If one end of the seesaw is pushed down, the other end moves up as a result. This allows for machinery to lift cumbersome pieces of equipment without much effort. 

Substance Used in a Hydraulic System

There are a few different substances that can be used in a hydraulic system to create force or motion.

The fluids hydraulics use include water, mineral oil, water emulsion, or ethylene glycol. In order to translate the fluid into power, you need a pump- this is usually a piston pump powered by a motor. 

Hydraulics also require a filter to remove particles from the hydraulic fluid before they clog any components of the system.

Parts of a Hydraulic System

Because hydraulics involves storing and pressurizing liquid material, hydraulic machines are usually incredibly large and intricate.

The main components in a hydraulic system are:

  • Hydraulic pump
  • Reservoir for hydraulic fluid
  • Filter
  • Actuator
  • Accumulator
  • Directional control valve
  • Flow control valve
  • Pressure relief valve
  • Other connecting pipes and wires

These parts work like a well-oiled machine (no pun intended) to ensure that your piece of equipment has adequate power.

What Are Hydraulics Used For?

Like I mentioned above, hydraulic machines are typically big and more complex and are used to power large industrial equipment.

Some areas where hydraulics are used include:

  • Jacks
  • Pumps
  • Lifts (fork, elevator, wheelchair, and car)
  • Cranes
  • Amusement parks
  • Gasoline pumps
  • Cars (braking and steering systems)
  • Snowplows
  • Hairdresser/office chairs
  • Airplanes
  • Boat rudders
  • Other industrial equipment (like on a construction site)

These are just a few of the places you might see a hydraulic system at work in your everyday life!

Pros of Hydraulics

There are a few advantages a hydraulic system has over a pneumatic one.

A hydraulic system is usually better at doing the heavy lifting- there are a variety of sizes to accommodate your industrial needs. This has led to hydraulic systems becoming the preferred choice in a wide range of commercial applications.

Other pros include:

  • Multitasking abilities (they cool, power, and grease a piece of machinery at any given time)
  • More power generated from comparatively smaller actuators
  • Constant torque and force regardless of speed
  • Durability
  • Longer operating time and more reliability due to the design
  • Fewer parts and less maintenance required

These are all critical benefits when deciding what system is suitable for your specific needs.

Cons of Hydraulics

While there are many advantages to using hydraulics, they do have some disadvantages.

A hydraulic system has the potential to leak fluid everywhere, which is why it’s imperative to make sure everything in your machine is adequately sealed and in good working order.

Other cons include:

  • The expense (the machines can be pricey and more energy is required to operate them).
  • Filtering oils, which can get messy
  • Being prone to leaks, which results in a lack of proper fluids rendering the entire machine nonfunctional
  • Fire hazard (created by oil leaks)
  • Loud operating sounds if air bubbles get into the system

The concept of hydraulics is also relatively complex and requires someone with a decent understanding of engineering to set up and use the machine properly. If you don’t know what you’re doing, the pressure in your machine can cause severe damage.  

Cost of a Hydraulic System

The overall cost of a hydraulic system can get pretty expensive.

It’s not uncommon for an industrial-sized hydraulic system to cost upwards of $10,000.

The reasons behind this are that the machine needs to be custom-built, with most parts and pieces assembled on site. Additionally, the oil or substance used can get pricey.

You must also consider what mammoth machines hydraulic systems are; the energy required to power them is unmatched.

What Is a Pneumatic System?

The second type of system is powered by pneumatics.

Pneumatic systems, also called compressed-air systems, use air or gas under pressure to provide mechanical energy for engines or other machines. Pneumatic systems power small, oscillating saws in the OR or medium-sized power tools in your garage. The average operating pound-force per square inch of a pneumatic system is 95 PSI. 

Pneumatics utilizes an air compressor to reduce the amount of air to increase its pressure. The compressed air is then pushed through a filter into the tubing. Here it is controlled by valves and an actuator, which converts it into power for your devices.

Overall, a pneumatic system is easier to operate, less expensive, and smaller in stature than a hydraulic system. That being said, it can’t handle as much weight or pressure. Because this system uses a compressed gas at lower pressures than hydraulics in order to operate, it’s best suited for smaller and lighter projects.

Substance Used in a Pneumatic System

Typically, there are 3 inert gases used in pneumatics.

The substances used in a pneumatic system include compressed air, nitrogen, and carbon dioxide.

Compressed air is usually used in commercial settings; it’s freely available and less combustible than regular oxygen. Nitrogen is the least reactive and most commonly used because it can be easily stored. Lastly, carbon dioxide is less popular because it quickly turns from gas to liquid and can cause suffocation in a closed space.

Parts of a Pneumatic System

Pneumatics is far less complicated than hydraulics; therefore, the parts are smaller and easier to learn.

The main components in a pneumatic system are:

  • Actuator
  • Air hoses
  • Accumulator
  • Gauges (or regulators)
  • Compressor
  • Check valve
  • Pressure relief valve

All of these parts work together to power your tools.

What Are Pneumatics Used For?

As described above, pneumatic systems are typically used for small tools and machinery because of their limited pressure capabilities.

Pneumatic systems are great for equipment actions that include gripping, positioning, clamping, or repetitive movements. They are also able to tension or press.

Some areas where pneumatics are used include:

  • Tire pressure gauges
  • Nail guns
  • Vacuum cleaners
  • The anti-slam feature on doors and drawers
  • Air compressors
  • AC systems
  • Drills and saws utilized by surgeons

Pneumatics can also be used as a direct-acting system on small loads that require exact precision, making them an attractive option across all industries.

Pros of Pneumatics

While pneumatic systems are usually smaller, there are some advantages they have over hydraulics.

Some pros include:

  • Lower PSIs reached, so safer to use (especially for novices)
  • More cost-effective (the machines and the energy used to power these machines are less expensive)
  • Smaller and can be portable (come in many sizes and pressure capabilities)
  • Utilizing compressed air results in less of a safety hazard
  • The power supply of compressed air or gas is much cleaner than oil (great for sterile environments like surgery)

Overall, if you’re looking for a reliable energy source that needs fewer than 120 PSI, choose a pneumatic system.

Cons of Pneumatics

For the many advantages, there are a few downsides to using pneumatics.

The first disadvantage is that a pneumatic system will not be able to supply the high pressure needed to power large machinery. Therefore, it’s unsuitable for heavy loads or large projects because pneumatic systems can’t handle them.

Other cons include:

  • Limited PSI capabilities
  • Sensitive to temperature change
  • Prone to air leaks if not secure (this can cause energy loss)
  • Hoses can corrode (if they’re not made of stainless steel) if they’re exposed to the outside conditions

Cost of a Pneumatic System

Because pneumatic systems are generally tiny in comparison to hydraulic systems, they are much less costly.

An average pneumatic system costs around $1,500.

For that small cost, you’ll be able to power your garage equipment and small machinery easily!

The Main Differences Between Hydraulics and Pneumatics

When you compare hydraulic vs. pneumatic, you’ll notice a few key differences between how they operate and what they’re capable of.

The main difference is that pneumatics use compressed air and gas for force, while hydraulics use relatively incompressible liquid. Hydraulic systems are much more substantial and have a capability of over 5,000 PSI, perfect for industrial settings. 

Pneumatic systems are used for smaller tools that require 100 PSI or less, ideal for sterile environments.

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In Conclusion

When considering hydraulic vs. pneumatic, it’s essential to consider the applications and advantages of each.

If you’re looking at larger tasks, like construction projects that require heavy-duty tools and equipment, then a hydraulic system may be the best option. Hydraulic systems are more expensive than pneumatics, but they can generate around 6500 PSI of pressure and cost $10,000. 

For smaller jobs with less demand on power generation capabilities (like saws or drills in home workshops), a pneumatic system might work better. Pneumatics are cheaper and produce less PSI.

So, which one is right for your job?