Ergonomics - Atlas Copco

Pressure drop and ease of operation
are two contradictory criteria and the final
choice is always a compromise. The ex-
traction hood requires a specific airflow to
achieve sufficient intake velocity for effi-
cient extraction.
The pressure drop in the hose is deter-
mined by the diameter and length of the
hose. During installation there are always
discussions between the customer and the
supplier regarding the length of the suc-
tion hose. The customer naturally wants to
work over the widest area possible, and the
supplier has to explain that extending the
length of the suction hose will merely result
in poorer suction and extraction capability.
For the operator, the hose is just
another restriction on his mobility. There-
fore he wants it to be as thin and flexible
as possible. One alternative is to have a
small diameter hose close to the tool and
change to a larger diameter hose as soon
as possible.
Fig. 3.26 Air velocity outside
a blowing and a sucking nozzle.
5 3
Flow
Fig. 3.27 Plot of pressure drop in hoses for
different diameters, length and air flow.
Swing arm
In fixed extraction installations, the suction
hose should be supported on a swing arm
since this is the best way to keep the hose
clear of the workshop floor. It is particularly
important to avoid people stepping on it,
since a deformed suction hose will gener-
ate a much higher pressure drop than an
undamaged hose with the same flow.
When different hose dimensions are
used it is a common practice to attach the
thinner hose permanently to the machine
and to have a connection between the hoses
for easy change of machine.
The one disadvantage of this system is
that the hoses take up a lot of space in the
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