42 – English
5.6 Hydraulic system
5.6.1 Hydraulic hygiene
Keep the hydraulic system clean. Remember to:
• Clean thoroughly before opening the ller cap or
disconnecting anything.
• Use clean vessels with topping up oil.
• Use only clean oil that has been stored in sealed
containers.
• Do not reuse drained oil.
• Change the oil and lter according to the intervals
specied in the Service Schedule.
A system that is contamination-free is required to give
a functioning hydraulic system without shutdowns.
Particles are generated during operation that can
cause both wear damage and malfunctions. The
system has lters to separate these particles. The
lter is dimensioned to trap the generated particles,
but if dirt enters the system from outside the lters will
rapidly clog so that they do not work as intended. If
there is dirt in the system, further contaminants will be
generated, creating a vicious circle. This will result in
breakdowns and the need for large resources to
clean the system.
The particles that cause the most damage are the
same size as the play between the moving parts and
the components. Normal play in pumps and valves is
from 3-5 µm and up (1 µm = one thousandth of a
mm). In connection with this, it can be noted that one
particle of size 40 µm can only just be seen with the
human eye.
Each particle of dirt is an abrasive that generates
more contaminants, which will eventually result in
permanent damage. The number of particles will
increase each time the hydraulic system is opened.
After a few hours in operation, most of the particles
that have entered are trapped in the lters. Therefore,
do not open the hydraulic system unless really
necessary because each intervention increases the
risk of contamination even when the work is carried
out in a professional manner.
Rectify oil leaks
Cavitation caused by air entering can cause internal
damage to pumps and engines. Air can enter the
system where there is an oil leak. That is why it is so
important that oil leaks are rectied as soon as
possible.
Keep hydraulic system uid clean
You must be completely sure that when opening a
can of oil for the hydraulic system, the area around
the ller cover is absolutely free from dust, dirt, cotton
waste and water. If a vessel, funnel or hose is
required to ll the system, make sure that they are
clean.
Use only the type of oil specied in the lubrication
schedule. Make sure that oil levels are checked at
established intervals and maintained correctly.
Working methods
Cleanliness also applies to components that are
removed or are going to be tted. Remember that an
exchanged component will probably be examined
with test equipment at a workshop. It is important that
the component is in the same condition when
examined as it was when it was taken from the
product. Otherwise the actual fault can not be
established and the test equipment will be
contaminated. It is also possible that submitted
component is not the fault and is therefore returned
without action.
The points below should be taken as routine
procedures when working on hydraulic systems:
• Clean roughly as necessary.
• Protect the area where the work is to be done
against dust and other impurities in the air. Plastic
cloth and the like can be used.
• Wash very thoroughly with white spirit or the like.
Only washing the parts that are directly aected
will not suce. Even areas from where dirt can
fall onto the point of entry while work is in
progress must be cleaned, as well as the tools
being used. Use a suitable brush to wash with,
wipe dry and then wash again if necessary.
Finally shower o the area being dismantled,
hose connections and the like with pure white
spirit.
• Apply appropriate protection immediately after all
pipes and hoses have been removed.
Components (also exchanged) as well as hoses
and pipes should be protected.
• All components included in pipe xtures shall be
replaced or cleaned in pure white spirit and blown
clean with compressed air before being retted.
• Maintain cleanliness when measuring pressure.
Shower both parts of quick couplings with white
spirit before connecting. Make sure any
protection is clean before returning it.
Hydraulic system
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