As a fundamental rule, only qualified personnel may perform work on hydraulic cylinders. At the beginning of maintenance work on hydraulic cylinders it must be ensured that no load motions are possible when

the hydraulic system is depressurized. Suitable measures must be taken to ensure this, and the work safety rules must be observed. When installing or removing the hydraulic cylinder, the instructions of the machine manufacturer and/or systems integrator must be observed.

The use of system-based safety systems such as check valves or the like is not sufficient by itself.

Before the cylinder is opened or screw or hose connections are detached, it must be ensured that the entire hydraulic system has been depressurized – and also that it is not possible for pressure to build up unintentionally. All of the lines connected to the cylinder have to be removed before the fastening is released. It must be ensured that releasing the fastening will not endanger the maintenance personnel or any other persons.



It is advisable to ensure that no large quantities of oil can escape when the hydraulic system is opened at the cylinder. It may be possible to do this using shut off valves or quick disconnects within the hydraulic system, which can be used to cut off large volumes of oil from the rest of the system.



Once all of the preparatory work has been completed, the cylinder can be opened and the piston rod can be removed. This is best done from the rod end.

The removed parts should first be cleaned and then checked for damage such as scoring, scratches and the like. Cleaning should be performed using only lint-free cloths and suitable cleaning agents.

Even the smallest scratches and scoring cause damage to the seals, and lead to premature wear on the seals. More heavily damaged parts must be replaced.
In the case of normal signs of wear, maintenance at certain intervals is a necessary effort. In cases of premature damage, it is essential to find the cause so that the new seal can achieve a longer service life.




When installing the new seals, ensure that they are installed in the right location and with the right orientation.



When installing rod seals, special care must be taken because the grooves for different types of seals and seal sizes often look very similar.

It is generally recommended that new seals be installed as soon as possible after the old seals have been removed.

A comparison of the old and new seals helps with the correct assignment. AHP Merkle can also provide information for the correct arrangement.



Any damage to seal interfaces (e.g. wrench surfaces) have to be rounded or polished before assembly.
Damaged or defective hydraulic cylinders may no longer be used.



It has also proven very useful to use a digital camera to take a picture of the seal arrangement before removal, and possibly also pictures of other machine elements, so as to be able to verify them once assembly is complete.