9 - AHP Merkle GmbH

4.5 Assembly and commissioning of hydraulic cylinders
!
Tip
!
88
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 specifi cations 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 fl uid, while
also using fi lter equipment. Once all of the hydraulic supply lines have been cleaned and fi tted pressure-tight,
the actual commissioning can begin.
The subsequent fi lling of the hydraulics with the specifi ed pressure fl uid should be performed using separate
fi lling units that clean the new hydraulic fl uid 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 fl uid 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 fi ttings 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 in the low-pressure range. 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 fi ttings 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 fl uid 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.
1
2