A major pressing company had received information from their client about risks to health from hand arm vibration during the rework of pressings. My client invited me to measure vibration levels on their random orbital sanders. What made this survey different from other HAV surveys was that my client had also invited a representative from the tool manufacturer to trial different accessories as well. The idea was to measure vibration levels on normal work and to identify what made the vibration increase and decrease and by how much. This information would be used by my client to manage hand arm vibration exposure.
I used a Castle vibration meter with the triaxial accelerometer held on with cable ties, tightened with a cable tie tightener.
Factors predisposing operators to high levels of vibration were found to be
- Machine condition/ age
- Compatibility of attachments to machines
- Machine speed
- Pressure applied to machine
- Use of the machine at an angle
- Use of the machine with the centre of rotation off the workpiece
- Operator technique.
The 3M pad was not weight-mated to the Dynabrade system and therefore it was not balanced in its rotation; giving vibration about the spindle axis.
The above factors could create a before-and-after difference of 10m/s2. It was concluded that hand arm vibration from sanding could be reduced by
- Training the operator to let the machine do the work,
- Use same make sanders and accessories such as pads,
- Maintain the air pressure at the pressure recommended by the manufacturer,
- Use the optimum tool for the job, particularly in narrow areas (use a belt sander rather than an orbital sander on its edge),
- Maintain the tools in good condition.
The hand arm vibration exposures of the operators were reduced and my client asked me to present the findings of the survey to a meeting of the health and safety managers of its other sites.
