Hydraulic cylinders are lineal hydraulic motors that are used to start the movement of a fluid or oil into an action so it can perform a working task. The principle of hydraulics states that if a force is applied at one point in a system using an incompressible fluid, then it will be transmitted to another point and multiplied in the process. This means you will get more force of energy coming out of the system than went into it.
Hydraulic cylinders are used in the actual process of exerting pressure on the hydraulic liquids which generates the force and motion. These types of cylinders are used in a variety of industrial applications. Because of the tremendous force that is exerted on them, they are normally made from sturdy materials such as cast iron, aluminum, bronze and stainless steel. The inside surface of the cylinder body needs to be smooth so it doesn’t wear out the packing and seals.
The rod end, front cover, and stem end of a cylinder refer to the cover that the piston rod moves in. The end opposite to the piston rod is known as the back cover and if there isn’t a cushion on the cylinder, there are usually no packings or bearings on this end. Cylinder covers can be round, square, or specially-designed shapes to fit the cylinder. They are attached to the body by screws, metal inserts, or threaded connections.
Cylinders come in various types with the most common ones being tie-rod, welded and ram. Tie-rod cylinders use one or more tie-rods. Welded cylinders use a heavy cylinder for better stability. Ram cylinders are primarily used as high pressure applications. Cylinders can be configured according to various specifications such as telescopic or simple. Most hydraulic cylinders have some common features such as integral sensors, double-end rods and adjustable strokes.
The two major kinds of hydraulic cylinders are single-action and double-action models. Single action cylinders can only create a forced action in one direction while double-action cylinders are able to create a forced action in two directions. Both types of cylinders can require a large amount of oil to do their tasks. A single piece of machinery that uses up to eight hydraulic cylinders can use as much as 100 gallons of oil to do its work.
Some important specifications to consider when choosing hydraulic cylinders are: the operating pressures that are applied on the cylinder, the diameters of the rod and the bore, the stroke, and the cylinder type.