Hydraulic System; Hydraulic Hygiene - Husqvarna Rider ProFlex 21 II Workshop Manual

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Hydraulic System

Hydraulic Hygiene

Keep the hydraulic system clean. Remember to:
• Thoroughly clean before the top-up 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.
• Not reuse drained oil.
• Change the oil and filter according to the intervals specified in Service Schedule on page 10
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 µm and up (1 µm = a thousandth of a mm). In
this context, we can mention that a particle measuring 40 µm 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.
• 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 permanent
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 SYSTEM
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