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Choosing the correct hydraulic cylinder size

When it comes to hydraulic cylinders, size does matter. The size of the cylinder comes down to the following important parameters including mass, bore diameter, rod diameter and even the way that it will move within the hydraulic system.

One of the first things you need to consider is what load mass you are going to be moving. Once this is known, the next consideration is the effect that this mass will have on the force required to move it. The force required to move the same mass is determined by how it is moved. The force of the cylinder should always be high enough to allow for margin of error.

How a cylinder moves also impacts which cylinder to choose. If it is only going to go up and down like in a hydraulic press, then the geometry is simple. However, when the centre of the load is not centred on the point of lift force and moves at perpendicular angles to that point of lift force, the force required by the cylinder changes.

Once you have determined the mass, the geometry and the force required by your cylinder, the next step is to determine the bore size. To calculate the bore size you need to multiply the force produced by the cylinder by the area of the internal piston surface upon which the pressure acts. Once this have been done, only then can the appropriate rod size be determined.

Another consideration is that the Piston-rod diameter needs to be correct, otherwise the cylinder could be more susceptible to stress, wear and failure. Diameters can range from 0.5 to 20 inches but need to also be able to handle the available loads. In push applications the rod diameter must be sized correctly to avoid rod buckling. When a cylinder is designed to generate a required force, the sizing rod is an important consideration. When selecting standard rod options, it is suggested that the smaller rod for a given bore only be used for short stroke push loading or reduced pressure applications, while the larger rods be used when there is need to obtain maximum reliability and fatigue life of the rod.

The last element to consider are the cushions. Once the bore, rod and stroke sizes have been determined the internal cushions at the end of the cylinder stroke is required. Cushions are used to decelerate high speed rods in order to reduce energy of the impact of the piston assembly against the cylinder end cap. They are optional and can be placed at either one or both ends of the cylinder. It does not affect the cylinder envelope or mounting dimensions.

If you require assistance in determining the correct cylinder size for your hydraulic system Power Team SA is available to help with any of your hydraulic needs. With years within the hydraulic industry Power Team SA is on hand to help with any applications, maintenance or sales of hydraulic components together with guaranteed expertise.