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VIBRATION EMISSIONS
Employers are advised to refer to the HSE publication “Guide for Employers”.
All hand held power tools vibrate to some extent, and this vibration is
transmitted to the operator via the handle, or hand used to steady the tool.
Vibration from about 2 to 1500 hertz is potentially damaging and is most
hazardous in the range from about 5 to 20 hertz.
Operators who are regularly exposed to vibration may suffer from Hand Arm
Vibration Syndrome (HAVS), which includes ‘dead hand’, ‘dead finger’, and
‘white finger’. These are painful conditions and are widespread in industries
where vibrating tools are used.
The health risk depends upon the vibration level and the length of time of
exposure to it……in effect, a daily vibration dose.
Tools are tested using specialised equipment, to approximate the vibration
level generated under normal, acceptable operating conditions for the tool in
question. For example, a grinder used at 45° on mild steel plate, or a sander on
soft wood in a horizontal plane etc.
These tests produce a value ‘a’, expressed in metres per second per second,
which represents the average vibration level of all tests taken, in three axes
where necessary, and a second figure ‘K’, which represents the uncertainty
factor, i.e. a value in excess of ‘a’, to which the tool could vibrate under
normal conditions. These values appear in “Specifications” on page 12.
‘a’ values in excess of 2.5 m/s
2
are considered hazardous when used for
prolonged periods. A tool with a vibration value of 2.8 m/s
2
may be used for up
to 8 hours (cumulative) per day, whereas a tool with a value of 11.2 m/s
2
may
be used for ½ hour per day only.
The graph on the right shows the
vibration value against the maximum
time the respective tool may be
used, per day.
The uncertainty factor should also be
taken into account when assessing a
risk. The two figures ‘a’ and ‘K’ may
be added together and the resultant
value used to assess the risk.
It should be noted that if a tool is
used under abnormal, or unusual
conditions, then the vibration level
could possibly increase significantly. Users must always take this into account
and make their own risk assessment, using the graph above as a reference.
