Hydraulic System; General; Hydraulic Hygiene; Hydraulic Oils - Husqvarna Rider 15V2 Workshop Manual

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General

Hydraulic Hygiene

Keep the hydraulic system clean. Remember to:
• Thoroughly clean before the filler cap is opened
or any connector loosened.
• Use clean containers when topping up the oil.
• Only use pure oil that has been stored in a
sealed container.
• Do not reuse drained oil.
• Change the oil and filter according to the
intervals specified in the Service Schedule.
In order for a hydraulic system to function without
problem, it must be free from foreign objects. When
used, the system produces particles, which can
cause both wear and abnormal function. In order to
remove these particles, the system contains filters.
The filters are sized so as to capture the produced
particles, but if contaminants are introduced from
outside the system, the filters can quickly become
clogged and fail to function as intended. If there are
contaminants in the system, further contamination
will be produced in a self-propagating cycle. The
result will be function disruptions and much work to
clean the system.
The particles that do the most damage are of the
same size as the play between the moving parts in
the components. Normal play in pumps and valves
is from 3-5 m and up (1 m = a thousandth of a
mm). In this context, we can mention that a particle
measuring 40 mm can be seen with the naked eye.
The particles, which are generated during operation
or enter the system during repairs and service, are
usually comprised of:
• Wear and tear products from components,
mainly those with moving parts, such as pumps
and motors.
• Dust, which enters through the hydraulic tank's
vent.
• Water, which is formed through condensation.
(Steam enters with the ventilation air.)
• Dirt particles, which enter the system with, for
example, moving piston rods.
• Sludge etc. from the oil decomposing.
• Corrosion products from the system, which are
due to the oil not being changed in time and
containing water and other aggressive
substances.
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Hydraulic System

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• Dirt particles that enter the system include:
- Contaminants entering when topping up with oil.
- Dust particles from the workshop.
- Gasket and thread sealants from assembly.
- Dirt from storage and handling before assembly.
- Fibres from rags, filters, etc.
- Dirt from maintenance areas due to insufficient
cleaning before disassembly.
- Dirt and dust entering the system via unclean
protective plugs.
Water, even in small amounts, can cause rust build-
up on sanded surfaces, especially if the system is
not used, and contributes to the production of
sludge products. These clog the filters, leading to
circulation problems and the hydraulic pumps can
begin to draw air (cavitation).
Small fibres and threads from drying cloths or
clothing can build up in jets and throttles. The
actual fibres do not cause much damage, but the
build-up can clog the system and cause wear on
system components.
Each dirt particle is an abrasive, which causes
more contamination, which in turn leads to perma-
nent damage. Each time the hydraulic system is
opened, the number of particles increases. After a
few hours operation, most of the particles are
captured by the filters. Avoid, therefore, opening the
hydraulic system unless necessary, as every action
entails a risk of more contaminants entering the
system, even if the work is carried out
professionally.

Hydraulic Oils

The oil is as important as every other part of the
hydraulic system. It has been noted that about 70%
of all hydraulic problems are caused by the use of
unsuitable oil types, which contain dirt or other
contaminants, to fill the system. The greater part of
the contaminants in the oil comprise, in general, dirt
that has entered the system from the outside.

Fixing Oil Leaks

Cavitation due to penetrating air can cause internal
damage to pumps and motors. Air can enter the
system when there is an oil leak. It is therefore
important to rectify oil leaks as soon as possible.