Hydraulic System; Hydraulic Hygiene; Rectify Oil Leaks; Keep Hydraulic System Fluid Clean - Husqvarna P 520D Workshop Manual

HYDRAULIC SYSTEM

Hydraulic Hygiene

Keep the hydraulic system clean. Remember to:
• Clean thoroughly before opening the filler 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 filter according to the intervals specified 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
filters to separate these particles. The filter is dimensioned to trap the generated particles, but if dirt enters the
system from outside the filters 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 = a 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 filters. Therefore, avoid opening 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 is 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 rectified as soon as possible.

Keep Hydraulic System Fluid Clean

You must be completely sure that when opening a can of oil for the hydraulic system, the area around the filler
cover is absolutely free from dust, dirt, cotton waste and water. If a vessel, funnel or hose is required to fill the
system, make sure they are clean.
Use only the type of oil specified in the lubrication schedule. Make sure levels are checked at established
intervals and maintained correctly.

Working Methods

Cleanliness also applies to components that are removed or are going to be fitted. 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 machine. Otherwise
the actual fault can not be established and the test equipment will be contaminated. It is also possible that
submitted component is not faults 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 affected will not
suffice. Even areas from where dirt can fall onto the point of entry while work is in progress must be cleaned,
just as the tools being used. Use a suitable brush to wash with, wipe dry and then wash again if necessary.
Finally shower off 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 fixtures shall be replaced or cleaned in pure white spirit and blown clean
with compressed air before being refitted.
• 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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