Assembly and commissioning of hydraulic cylinders


Mounting screws for cylinders and add-on parts have to be designed and mounted in such a way that they can absorb all foreseeable forces. As much as possible the screws should be free of shear forces. (see also „General safety instructions“)

When installing cylinders it must be ensured that no distortion of the cylinder occurs. This can always happen when the machine or system does not meet the mounting specifications due to improper mechanical construction or excessive manufacturing tolerances. The result of this is that mounting points are not properly aligned or undesirable side forces occur.

Before commissioning of hydraulic cylinders hydraulic systems, the technical personnel must make sure that there is no contamination or residue from manufacture or assembly of the component parts (e .g . chips) remaining in the system. To do this, it is advisable to clean the hydraulic system several times with rinsing fluid, while also using filter equipment. 



Once all of the hydraulic supply lines have been cleaned and fitted pressure-tight, the actual commissioning can begin.

The subsequent filling of the hydraulics with the specified pressure fluid should be performed using separate  filling units that clean the new hydraulic fluid already. This is because practice has shown that new oil is in no way clean enough to meet the requirements of certain hydraulic systems. The same also applies, naturally, whenever hydraulic fluid is added later.

Before the hydraulic system is brought up to the system pressure, the entire system has to be vented.

Venting of the hydraulic system is performed via suitable ports. The hydraulic cylinders have optional dedicated venting screws. At idle pressure, simply loosen the venting screw and the fittings at the bottom and rod ends. This is done by unscrewing the screw by not more than a half turn (image 1). Close them again only when the escaping oil is free of bubbles (image 2).


After that, move the system only with significantly reduced operating pressure. This process has to be repeated several times in order to guarantee that the hydraulic system is completely free of air and gases.

Finally, re-seal all venting screws and fittings so that they are pressure-tight. The function of the cylinder can be checked by moving it in and out several times under low pressure.


Because under certain circumstances the air dissolved in the hydraulic fluid can be desorbed, it is advisable to vent the system again when maintenance is performed at the latest. Before the hydraulic system is brought to operating pressure, all components should be checked again for proper installation.