The most common hydraulic cylinders in construction machines and agricultural machines

Cylinders are the parts in the hydraulic system that ensure that you can run your machine. The mechanical moving parts on an excavator, for example, cannot be set in motion other than by controlling them with a hydraulic cylinder. The reason hydraulics are used is that it is the most efficient way to apply a lot of force. The power of a cylinder is determined by the bore of the cylinder. The larger the surface area, the more work you can do with the cylinder. The length of the cylinder rod, and of course the cylinder tube, determines how far you can slide it in and out and therefore your reach.

In this blog we discuss the three most common cylinders in construction machinery and agricultural machinery.

The single-acting hydraulic cylinder

The hydraulic single-acting cylinder is the simplest form of cylinder. This type of cylinder has only one entry port for the hydraulic oil. When your hydraulic pump pushes the oil into the cylinder, the piston and rod can only go in one direction and that is to extend or retract. The latter form is less common, but ultimately the working principle is the same and the only difference is on which side of the piston the hydraulic oil is pumped in. Where pumping occurs, more pressure is created and that pressure pushes the piston and rod away.

With the single-acting cylinder, the retracting movement can only be achieved by lowering the pressure, so no more pumping. The final force that pushes the cylinder back in or out comes from the load resting on it, for example the gravity of the mechanical parts themselves, or a spring that pushes the piston and rod back and thus pushes the oil in the opposite direction to the pump. want to pump it in. A very simple mechanism.

What helps in this principle to achieve a controllable movement of the retreating cylinder is the check valve. This part ensures that the hydraulic oil flows back gradually and not harder under heavy load than under a light load.

The big advantage of this type of cylinder is that it is a simple cylinder and therefore also more favorably priced. Maintenance is also easier, because you have fewer moving parts. This cylinder is also more compact than more complex cylinders. This can be an advantage when installing when there is less space available.

The most common applications of the single-acting cylinder are machines in which the gravity of the load you lift also helps with the retroactive force, for example forklift trucks and scissor lifts, and applications where the loads are not too large and the machine is compact, for example small excavators and mini -shovels.

The double-acting hydraulic cylinder

The hydraulic double-acting cylinder are somewhat more complex than the single-acting one. The biggest difference is that you can operate this cylinder in both directions, because there is an entrance port for the hydraulic oil both before and behind the piston. So you can let your hydraulic pump do its work in both directions.

Because the cylinder can be pumped in two directions, the interior of the cylinder is often slightly more complex. In the double-acting cylinder you often see that there are more complex sealing rings and guides, because the oil must be stopped in both directions.

The big advantage of the double-acting cylinder compared to the single-acting is that you can work much more precisely. After all, you can precisely control the force of the cylinder in both directions. Because you have better control over the pressure, this cylinder is also more suitable for use in more complex machines, such as excavators. You can simply operate the mechanical parts of the machine, such as the excavator bucket, more precisely. Because you have better control, this type is also used more often in applications where the load is much higher. In a large crane or excavator you do not want to be dependent on the retreating movement based on the load. You want to be able to fully rely on precision control in both directions.

The telescopic hydraulic cylinder

This type of hydraulic cylinder consists of a cylinder rod that can slide together and apart. The principle is comparable to an old-fashioned stargazer or a fishing rod. The telescopic cylinder can be either double-acting or single-acting. So here again the principle where either the load, or a spring, or your hydraulic pump does the work in the retreating direction.

The major advantage of the telescopic hydraulic cylinder is obvious; the compact size compared to the reach of the cylinder. This means that these cylinders can be installed in a size in places where you cannot fit a non-telescopic cylinder. Because the entire cylinder can slide in and out of each other, you can still move enormous loads over a large distance with a compact cylinder size.

A good example of these are tipper trucks or the loading platform of your earth-moving trucks. To empty a container while it is loaded, with sand, for example, one side of the container has to be raised several meters, while perhaps 20 tons of load is pressing on the cylinder. With a non-telescopic cylinder, the cylinder rod would have to be meters long and the cylinder tube would also have to be enormous to be able to exert enough force. You would then end up with a cylinder size that you could not even fit. The telescopic hydraulic cylinder is ideal in these types of applications.

If you want to know how to best maintain your hydraulic cylinder, read our blog about it. In this blog we describe the most important things to keep your cylinder in top condition.