Ergonomics - Atlas Copco

144
SHOCK REACTION
There are no shock reactions when this tool
is used. Thus, shock reaction does not apply
for chipping hammers.
VIBRATION
The design of this tool includes an isolation
system in the handle. It is a mass spring
system, with a preloaded spring, the mass
being the handle itself. The preloaded spring
causes the isolation system to take effect
from a certain minimum feed force, up to
a maximum feed force when the spring is
bottoming. A preloaded spring is needed
because the stiffness (k factor) of the spring
must be low in order to achieve a low natural
frequency of the system.
The declared vibration value is 3.5 m/s 2
and the correction factor, to get an estimated
vibration value for chipping hammers used
in a cleaning operation, is 2. Using the daily
exposure time of two hours, the estimated
vibration exposure will be
A (8) = (2/8) 1/2 • 3.5 • 2 = 3.5 m/s 2
This represents a score of 31.
NOISE
The measured and declared level is 94
dB(A). The continued equivalent
noise level for eight hours exposure is:
L eq(8) = 10 log (1/8 • 10 9.4 • 2) = 88 dB(A)
The score is thus 28. This value does not
include process noise which can be much
higher, as indicated in the diagram. The
process noise is unique and depends on the
characteristics of the casting being cleaned,
the operator’s technique and the design of
the workstation.
DUST AND OIL
The chipping hammer is often used in a very
dusty environment. The work involves cleaning
cavities containing sand and burn deposits on
the surface of the casting. A dust collector fitted
to the tool interferes with the work. Therefore a
well ventilated fettling booth is the best solu-
tion. The overall stressor evaluation for dust is
0-20 depending on the quality of the ventilation
system.
These tools are provided with a small
amount of oil. The concentration of oil mist in
the breathing zone is less than 5 mg/m 3 .
From Table 3.15 a score of 4+2 can be
found if the working pace is assumed to be low.
The total score for dust and oil will then be 6.
This score is only valid when the ventilation
system at the workplace is of average quality or
better.