The vibration data provided by suppliers can also help to identify high or low

vibration tools. Figure 2 shows data for two chipping hammers. Both hammers

have a large range in their vibration emission depending on task, etc but it is clear

both from the `intended' use data and the supplier's data that one of the hammers is

a generally lower vibration tool than the other.

Figure 2

30 ..........................................................................................................

chipping hammer B

25 ...........................................................................................................

20 ...........................................................................................................

15 ...........................................................................................................

chipping hammer C

10

5 ...........................................................................................................

range of vibration in intended use

measured emission

mean of vibration level in intended use

31

Comparisons based on suppliers' vibration data are usually most reliable

when there is no overlap in the range of uncertainty of the measured emission

levels, a to a+K for each of the tools. The uncertainty can be more than 40% of the

measured emission a and is often several m/s2. If an uncertainty K is not quoted it is

reasonable to assume it is 40%. If it is necessary to make close comparisons there

will probably be a need to conduct measurements for the tasks in question.

32

Many of the first generation of vibration emission test codes produce levels

below the threshold of 2.5m/s2 for reporting to users even though there is a vibration

hazard that requires management (see also paragraphs 16-18 and 22). For

example, the standard test data for chipping hammer C in Figure 2 suggests that the

emission is about 2 m/s2, ie below the threshold for reporting actual vibration levels,

while the `intended' use data clearly shows that the tool can generate hazardous

levels of vibration.