Modern manufacturing applications heavily rely on both hydraulic and pneumatic power cylinders. We are going to have a critical look at how the two cylinders compare and give you an insight of the best option for your application.
What are Pneumatic Cylinders
We can describe pneumatic cylinders as a system that requires huge amounts of compressed air to operate. These cylinders make use of air pressure and fluid dynamics to carry out the mechanical motion of the cylinder.
The air is supplied to the cylinder from a compressor that is linked to your cylinder through transition lines and hoses. The regulation of the compressed air is usually through solenoid valves that are either manual or automatic.
What Are Hydraulic Cylinders
Hydraulic cylinders is an actuator that useshydraulic oil to generate the force required to power your system. The hydraulic fluid moves within your cylinder under very high compressive pressure to generate a force.
They use pumps to move the hydraulic oil within your hydraulic cylinder with hydraulic valves that regulate the direction and force of the hydraulic fluid.
You will find a holding container that houses the hydraulic fluid used to run such cylinders. They have very large power and can move very heavy loads due to the incompressibility of the hydraulic oil.
Comparing Pneumatic Cylinders vs. hydraulic Cylinders
Let us discuss the features of the two types of cylinders individually:
- They use air as the power that moves the cylinder
- They have delayed movement since the air has to be compressed first
- They require a compressor to constantly supply it with compressed air
- They require hydraulic oil that is pressurized to operate
- They need a pump to move the hydraulic oil within the cylinder
- The hydraulic oil moves a piston or plunger within the cylinder
- They contain valves that control the flow of hydraulic oil and its direction
Although they work similarly, you will find different components in these two cylinders. Let us analyze the components of each of these cylinders:
- Air Compressor: this is the device that supplies your pneumatic cylinder with the medium that operates it. It gets it from atmospheric air, compresses it, and supplies your cylinder.
- Air Filter: it is responsible for getting rid of any form of contamination that is on the atmospheric air that needs to be compressed.
- Regulator: as the name suggests, it controls the pressure of the compressed air that goes onto your cylinder
- Control Valve: they basically control the movement of the compressed air into and out of your pneumatic cylinder
- Hydraulic Pump: this is what gives the hydraulic oil the pressure it requires to give cylinder its motion
- Fluid Reservoir: this is where the hydraulic oil that powers the cylinder is stored
- Hydraulic Fluid Filter: they clean your hydraulic oil by ensuring that it gets rid of any contaminants within it
- Control Valves: they control the movement and pressure of your hydraulic fluid within the cylinder
You need to supply pneumatic cylinders with compressed air from a compressor for them to work. The compressor gets pressure from atmospheric air and creates a high-pressure density within it.
The compressed air transmits the power through it that triggers the pneumatic actuator that converts it into mechanical energy. This mechanical energy is what initiates the motion of the pneumatic cylinder.
If your application requires a lot of strength, then a hydraulic cylinder is your best bet. Hydraulic oil is known to have an impressive mass density and can withstand very heavy pressure with its incompressibility.
This means that the oil can easily transmit the power required to run your application. Industrial applications can reach pressures of between 1000 to 5000 psi while mining equipment cab reach 10000 psi.
Pneumatic systems have an easily compressible air medium with a very low mass density. They have a low compressible pressure of about 80 to 100 psi.
They cannot handle the heavy forces that the hydraulic cylinders handle. The compressed air is also prone to fluctuations in pressure therefore making them unstable in some instances.
When it comes to safety, hydraulic cylinders are a better option compared to the pneumatic cylinders. In as much as pneumatic cylinders may not contaminate the air in the event of a leakage, it can cause physical injury.
However, hydraulic cylinders may be prone to some form of corrosion. Since they are also under pressure, they are also vulnerable to dangerous leaks.
When we compare the two hygienically, pneumatic cylinders take it hands down. This is because in the event of a leakage, the only thing that is expelled is air.
That air leakage is devoid of any contaminants such as metal particles. This is because these cylinders have filters that remove any foreign particles.
When you are carrying out maintenance practices, pneumatic cylinders are easier to work with compared to hydraulic ones. This is because the medium involved in their operation is just air.
You will only be required to check the seals and any form of leakages that may occur on the cylinders. You won’t need to clean the compressed air, just a change of your cylinder’s filters and regulators.
Hydraulic cylinders are highly susceptible to corrosion therefore you need to use non-corrosive pipes on them. The hydraulic oil may contain contaminants therefore requires that you change it regularly after some time.
The major advantage you will get when using pneumatic cylinders is their speed. Since you are using compressed air, its flow rate is usually very high therefore can move your cylinder pistons instantaneously.
The cycle speeds you can achieve with such cylinders is usually very high. This is very important especially with the small size of such cylinders.
The viscosity of hydraulic oil usually gives your hydraulic cylinder a slower response due to the high resistance. In as much as you will achieve higher forces with hydraulic cylinders, they won’t give you the rapid motion of pneumatic cylinders.
For you to drive both of these cylinders, you will require an electrical power input. As for the pneumatic cylinders, you will also need to have a running compressor that will supply your cylinder with compressed air.
You cannot recycle the supply of such air meaning that your compressor has to run continuously to replenish the air. You will encounter energy losses from the heat produced during the process of compression.
As for hydraulic cylinders, you can use the same hydraulic oil for a long time provided you have a good filter. If you carry out proper maintenance of your hydraulic cylinder, then you can have an energy-efficient cylinder.
You will require more energy to move a highly viscous fluid around your hydraulic cylinder. However, stronger pumps are finding their way into the market that can equally pump any hydraulic fluid despite its viscosity.
You will find very few movable parts in a hydraulic cylinder system. You can easily control such cylinders using simple levers or sets of push buttons. However, you will require complex systems to run your entire hydraulic system unit.
These will include hoses and valves in addition to the pump and a tank that stores your hydraulic oil. Pneumatic cylinders have a simple structure and can work under very low pressure.
The parts you will require for your pneumatic cylinders are usually not complicated and will cost you much less. The compressed air is neither corrosive nor combustible nor does corrosive therefore handling it not require a lot of precautions.
We can have a look at the merits of the two cylinders individually:
- You can easily control these cylinders by just using buttons and levers.
- They can achieve great force without necessarily using gears and levers
- The cylinder can give you a constant and consistent force and torque
- You can easily maintain them since they have fewer moving parts and are simple to operate
- The hydraulic liquid does not use up any energy that you supply to it
- They are relatively cheap when we compare them to hydraulic cylinders
- They are very efficient since they only require air that doesn’t contain moisture that damages the cylinder parts
- You require very little maintenance if well well-operated
- They can efficiently transmit power over long distances
Depending on your system requirements, you may require either a system that can sustain heavy loads or a small portable one. Whatever your option, both hydraulic and pneumatic cylinders can serve you quite well.
Now that you have a better understanding of the comparison between the two, you can make a very informed decision.