How does a hydraulic cylinder work?

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The hydraulic cylinder is a device which is used and which equips various machines in many sectors of activity (agricultural, building, industrial…). However, do you know how the hydraulic cylinder works?

Operation of the hydraulic cylinder

The function of a cylinder is to transform energy into mechanical force. In the hydraulic cylinder, fluids under pressure are used, generally mineral oil and not water. Its operation is similar to pneumatic cylinders using pressurized air.

Thus, the hydraulic cylinder is a device which is made up of several important elements in order to ensure its proper functioning. There is a cylindrical tube, containing a movable piston which is itself attached to a rod allowing the transmission of energy to the machine which ensures the mechanical movement.

To complete the description, the fluid circulates inside the cylinder. By injecting it from one side of the tube, the piston will find itself pushed by the pressure to create the mechanical force, usable, for example, to lift heavy loads. This movement of the piston is then called the working stroke.

To determine the range of motion, however, it is necessary to refer to the length of the tube and the rod. The longer the cylinder and therefore the longer the piston stroke, the greater the mechanical force will be.

Finally, because we are talking about fluid, and to avoid leaks and therefore avoid loss of power from the jack, sealing is also an important concept. It is ensured on the hydraulic cylinder by seals which are located in the chambers where the fluids circulate, between the piston and the cylinder.

Seals are also one of the major causes of failures on a hydraulic cylinder as a result of wear that can cause significant leaks. A shock or a torsion of the cylinder can also cause a failure, the stroke of the piston not being able to be assured any more in a tube which is not perfectly cylindrical.

Different types of hydraulic cylinders

We cannot talk about the functioning of a hydraulic cylinder without mentioning the two types of existing cylinders: the single-acting hydraulic cylinder and the double-acting hydraulic cylinder.

Single acting hydraulic cylinder

With a single-acting hydraulic cylinder, the fluid is pressurized to one side of the pison. The jack therefore only performs a single working stroke, executed in one direction at a time. The return of the rod to the initial point is then effected by a spring, once the fluid has evacuated.

Double acting hydraulic cylinder

The double-acting hydraulic cylinder has two chambers. They allow the rod to enter or exit by pressurizing the fluid in one of the chambers. This model can therefore work in both directions. It is also possible to feed both chambers simultaneously to manage the force and speed of movement.

To recap and keep it simple, the single-acting hydraulic cylinder produces force in one direction only, while the double-acting hydraulic cylinder can be operated in two directions.

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