Ergonomics - Atlas Copco

How can we use declared values?
We can compare machines of different de-
signs or makes. It is probable that machines
with low values in a laboratory test will
have low values in an actual work situation.
Anyone who has been involved in vibration
measurements knows that these are dif-
ficult to perform in a laboratory situation.
Vibration measurements are even more
difficult to perform in a real work situation,
and far more costly as well.
Bearing this in mind, it is natural that
persons with the task of assessing the expo-
sure risk will base their calculations on the
declared values. The standards for meas-
uring vibration, use just one transducer
location. Yet along a handle, vibrations can
vary by a factor of five. The standard figure
is derived with an artificial load on the ma-
chine. Taking into consideration all types
of inserted tools and the different ways in
which operators use their machines, results
from one transducer location will vary by a
factor of three in practice.
The other important parameter is
exposure time. A simple parameter one
would think, yet difficult to estimate unless
the task to be analysed is cyclical. In addi-
tion, operators often use several different
machines, therefore the total accumulated
exposure should be calculated.
Even standard ISO 5349 itself contains
pitfalls. For example, the dose-response
relationship is based on a limited number of
research reports and is intended to give an
indication of what is likely to happen when
a number of operators are exposed over a
period of several years.
Taking all this into consideration, one
might conclude that the declared values
cannot be used at all. It is our belief, how-
ever, that we can use this information for
rough screening purposes, particularly
when conducting multi-stressor analyses.
The CE standardization group work-
ing with the question of how to implement
2002/44/EG, the Physical Agents (Vibration)
Directive has reached the same conclusion.
In a technical report CEN/TR 15350 it is sug-
gested that the first rough exposure assess-
ment could be based on the declared values
multiplied by a given correction factor.
For most industrial tools the correction
factor is 1.5. For chipping hammers in fet-
tling operations the correction is set to 2.
Another important correction is for tools
with declared values below 2.5 m/s 2 . For
those tools, 2.5 m/s 2 should be used as the
declared value in exposure assessments
even when a lower declared value is given.
In the following evaluation we use the
guidelines from CEN/TR 15350. It should
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