Filter System - Husqvarna 371K Workshop Manual Supplement

For Husqvarna Parts Call 606-678-9623 or 606-561-4983

FILTER SYSTEM

Dust
The cutting of stone and concrete produces small particles of dust that must not be
allowed to get into the engine under any circumstances. The design of the air filter
and its maintenance are by far the most important factors that affect the service life
of a power cutter. Designing a good air filter is a question of getting the right
balance between effective filtration and long intervals between services.
The development of more effective filters has improved air filtration, but for power
cutters the service interval has remained impractically short. Tool hire companies
often have problems due to service work that is not carried out by the user during
the hire period, or due to the cost of regular service visits that have to be made to
the work site.
Dust consists of very fine particles, usually so small that we cannot see a single
particle with the naked eye, but in large quantities it appears as a dust cloud. The
stone and concrete dust particles that are often produced during cutting operations
cause the greatest damage to the sliding or rotating components of an engine. If it
gets into the engine this dust combines with oil to produce the perfect grinding paste,
resulting in rapid wear to pistons, piston rings, cylinder walls and engine bearings.
We usually measure dust particles in microns, µm (1 µm = 0.001 mm) or thou-
sandths of a millimetre, and the particles that are trapped by the filter system are
generally in the size range 50 µm down to 5 µm. (It takes about 2 minutes for a 10
µm stone particle to fall one metre in stationary air).
One physical property that is vital to the effectiveness of Husqvarna Air Injection
Filtration is the way that the size of dust particles affects their behaviour in a stream
of air:
A small particle is affected more by a moving air stream than a large particle.
The reason for this is that small particles have a larger surface area in relation to
their mass. A small particle is therefore deflected more easily by moving air, while a
larger particle is affected more by centrifugal force or gravity.
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