Can I use a pneumatic cylinder in place of the hydraulic cylinder? Are they the same? What’s the difference? Which one is best for my application? All these are confusions wandering in people’s minds for years. But this article will wash out all the doubts related to pneumatic and hydraulic cylinders, their basics, how pneumatic cylinders work, applications, differences and most importantly use a pneumatic cylinder as a hydraulic one or not. So, keep learning!

Figure no 1 Pneumatic vs Hydraulic cylinder

1) Understanding Pneumatic and Hydraulic Systems

• Pneumatic Systems

Pneumatic systems employ the utilization of high-pressure air. They are popular for their fast work process, cleanliness and high maintenance. Common usages include some tools such as nail guns and machines in manufacturing which require high speed.

Figure no 2 Pneumatic cylinder

There are several types of pneumatic cylinders such as rotary actuators and both single- and double-acting cylinders. Each one has its purpose according to the application.

• Hydraulic Systems

More specifically concerned with hydraulic systems, these are systems which actually do work through the high pressure fluids. It usually in the form of liquid oil, glycol or other such work fluids which are fire resistant in nature.

 It shows the superiority of such systems in that they can cope with the needs of great power requirements. For example, in construction machines, and large industrial power presses.

Figure no 3 Hydraulic cylinder

• Key differences between Pneumatics and Hydraulics

• Medium used: Pneumatic systems use air medium while Liquids are core mediums in Hydraulic Systems.

• Pressure levels: Pneumatic Systems are commonly operated at lower pressures (normally less than 100 psi). While Hydraulics systems can operate in thousands of psi (1,500 up to 10,000 PSI).

• Force output: There is a higher force output in hydraulic systems than in pneumatic. Because a liquid is incompressible and thus can exert more pressure.

2) Pneumatic Cylinders:  Working and applications

• How do pneumatic cylinders work

Air cylinder working is so simple, that it is classified as a linear moving mechanism that utilizes strongly pressurized air. Generally, a cylinder, a piston, and a rod are the three main components comprising this device. In this device, once air is pumped into one side of the piston tube or cylinder. This air will push the piston which in turn causes the rod to move within the tube. This linear motion of the rod is inserted into machinery utilised to push, pull or lift objects. The air is then removed, which pushes a piston back to the home position. Yes! This is how the air cylinder works.

Figure no 4 Working mechanism of pneumatic cylinder

• Applications of pneumatic cylinders:

• Pneumatic actuators find application in such industries as machine automation, manufacturing and material handling systems.

• They serve as the actuators for production lines, packing machines and conveyor systems.

• Pneumatic cylinder working is applicable in automobiles, to open and close the doors and hoods. Moreover, in the movement of the arms of robots.

• Food and beverage companies employ pneumatic cylinder operations to operate filling and packaging machines.

• Their construction allows the handling of high-speed and high-precision movements. It makes them ideal for performing repetitive processes.

• Also, they are effective, reasonably priced, simple to service. They work in places with flammable or explosive situations where electric devices would be dangerous.

3) Hydraulic Cylinders: Working and applications

• Working mechanism: 

A hydraulic cylinder is a linear device that uses a rotary actuator. It consists of a hollow metal cylinder, an internal piston, and an extensible shaft called a rod. When hydraulic fluid at high pressure enters into one side of the cylinder, it pushes the piston forward thus pushing out the rod. This movement generates a force close to a ton that can either lift, push or pull an object weighing more than a ton. After a few minutes, it expells out or is directed to the other side of the piston, the rod returns to its resting position.

Figure no 5 Hydraulic cylinder internal structure

• Applications of hydraulic cylinders:

• The hydraulic model is employed in nearly every heavy machine and industrial appliance operating today. In construction machinery, such as excavators, cranes and bulldozers Hydraulic cylinders have application in lifting the arms and the boom.

• In agricultural practices, tractors and harvesters use these devices for up and down and orientation movement.

• Manufacturing is also dependent on hydraulic cylinders fitted in presses, plastic injection moulding systems and metal winders.

4) Pneumatic vs Hydraulic Cylinders

Pneumatic and hydraulic cylinders both serve a function of linear motion but the approach or the use varies a lot.

Figure no 6 Hydraulic cylinder for heavy tasks

Pneumatic cylinder	Hydraulic cylinder
Utilizing a pneumatic cylinder, the piston is propelled by compressing air.	As the term indicates, hydraulic cylinders use such liquids as hydraulic oil to apply pressure onto a piston in order to create movement.
The air cylinder operation does provide motion but the limitation is that air is compressible making them suitable for quick tasks.	Because the liquid is passively incompressible, a hydraulic cylinder can generate more pressure, unlike a pneumatic one making it best for heavy applications.
Pneumatic cylinders are made of less strong material like aluminium.	Hydraulic cylinders are made of heavy and strong materials that can withstand high pressure.
This is common in procedures where items are packages, high-speed food processing, or assembly lines where heavy lifting is not a priority but space and speed are.	But hydraulic cylinders work efficiently in harsh conditions. It can be more costly and difficult to service because of the fluids and seal systems used.

 

5) Can Pneumatic Cylinders be used as Hydraulic Cylinders?

Well, after delving into both types of cylinders in complete detail, we are able to discuss using pneumatic cylinders as hydraulic cylinders. To put it bluntly, the working principles of cylinders of either type are so disparate that it is not possible to substitute one for the other without some modification.

It would be rather unfeasible either to take any pneumatic cylinder ‘as is’ and apply it in a hydraulic cylinder system. Because, it is not a low-pressure application, as pneumatic cylinders are not constructed for hydraulic systems. Hydraulic liquid works with far greater pressures in comparison to air. Pneumatic Cylinders do not have such seals and strength materials to resist such high pressures and viscosity of hydraulic liquids. Doing so is likely to result in mechanical failure, damage of equipment and leakage.

Figure no 7 Pneumatic cylinders as hydraulic cylinder

But, wait a second, there is a slight chance, though very limited, of reengineering a pneumatic cylinder for use in the hydraulic system. But it involves more work and more adaptation like;

• The cylinder of the vessel needs to be strengthened.
• You can change the seal
• The entire structure is altered by changing the cylinder body material so as to handle the high pressures and possible leakages common to a hydraulic system.

Still, such a performance is very seldom achieved in a rodless pneumatic cylinder. But it is wise to say you should not change a pneumatic cylinder into a hydraulic one. In each type of system, you should use the respective type to enhance safety and efficiency.

6) Conclusion

To cut a long story short, both the pneumatic and hydraulic cylinders produce linear motion. However, they are rotationally oriented to different systems and serve different purposes. Pneumatic cylinders, which rely on pressurized air, are best in light and speedy operations whereas hydraulic cylinders which depend on liquid pressure are suitable for heavy-duty work.

You can’t use a pneumatic cylinder over a more hydraulic efficiently and safely without significant restructuring. There’s a reason for manufacturing each type of cylinder to address specific needs, and in order to avoid malfunction of systems or devices, you should use the right cylinder with regards to its working system.