Ergonomics - Atlas Copco

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This method has not been used by manufac-
turers so far. A few test stations have been
built, one at BIA (Berufsgenossenschaftli-
ches Institut für Arbeitssicherheit) in
Germany. It is not yet compulsory to declare
dust emission values.
Dust control
The most efficient way to extract dust is to
remove it by suction from as near the source
as possible. For power tools this means that
a dust collector should be integrated into
the machine. Thus, less airflow is required
to ventilate the work booth, the heating cost
is less and the method creates no draught
for the operator. If the system is capable of
removing dust, it will also cope with oil
mist. Oil is, however, best treated in the
machine itself, i.e., oil-free machines.
Collecting dust as close to
the source as possible
There is a big difference between blowing air
and sucking air. If air is blown through a noz-
zle, with a diameter D, at a speed of V, the air
velocity at 10 D will be 0.1 V. If air is sucked
into a nozzle with diameter D, at a speed of V,
the air velocity outside the nozzle will be 0.1
V at a distance of D from the nozzle. For this
reason, dust should be removed by suction
near the point at which it is created.
Extraction hoods
The most common extraction hoods have brush
lips around the periphery. Part of the hood is
cut away, enabling the operator to see the disc
in operation. During the work cycle the spray
generated by grinding is arrested by the brush
lip. The brush lip limits the spread of grinding
spray and dust. The flow velocities of
the inlet air can thus be kept
low and the system can
operate with a
low flow.
Suction hose
The suction hose is one of the most impor-
tant components in any dust extraction
system. While having a considerable effect
on the system’s ease of operation, it is also
the component which produces the greatest
pressure drop in the system.
Fig.
3.25 The
extraction
hood with brush
lips is the most common type.