Exposure to hand-arm vibration caused by woodworking machines

Status:

completed 05/2003

Aims:

The exposure to vibration caused by selected floor-standing machines and a range of hand-held machines was measured under practical conditions in consideration of hazard assessment for woodworking machines as required under EU Directive 2002/44/EC, governing the protection of employees against vibration. The EU Machinery Directive contains no provisions for compulsory declaration of vibration emissions data on stationary woodworking machines. In the absence of a measurement regulation, a measurement strategy first had to be drawn up in order for the continually changing point of transmission betewen hand and workpiece to be recorded. The vibration impact caused by typical woodworking machines is measured and can be employed for hazard assessment. The existing measurement and assessment procedure does not adequately consider the hand-arm system on all hand-held machines. Hazard assessment may consequently lead to incorrect conclusions. To address this deficit, comparative measurements were performed under working conditions for a range of different machines.

Activities/Methods:

On stationary machines, vibration is usually transmitted through the workpiece and not, as in the case of the mobile machines, through the machine handles. The acceleration sensor was therefore attached to the workpiece in consideration of the work process concerned and corresponding as closely as possible to the operator's grip, and the vibration measured experimentally over several work processes. To date, the measurements have been performed under representative operating and work conditions on the following machines: surface planer, vertical spindle moulder, panel sizing circular saw, jigsaw and sanding machine, deep-hole drilling machine, belt sanding machine, edge sanding machine, bandsaw, random orbital sander, top spindle moulder, biscuit jointer. The "total vibration value" exposure parameter was measured repeatedly on each machine.

Results:

The studies measured the weighted vibration acceleration of a number of stationary woodworking machines under operational conditions, for assessment of the risk of hand-arm vibration under EU Directive 2002/44/EC. A surface planer was the only machine to exceed the trigger exposure value of 2.5 m/s², which relates to a period of eight hours. Of the manual machines selected, the sanding machines and the jigsaw in particular exhibited total vibration values at which the exposure limit value of 5 m/s² was exceeded after only brief exposure duration. With transposition of the EU Directive into German law, the vector sum of the weighted vibration acceleration values for all three directions in space must be considered for assessment of the hazard. By contrast, the available manufacturer's data refer only to the strongest direction of vibration as specified under the emissions standards, a discrepancy which may lead to considerable deviation. In the context of hazard assessment, this means that the information in manufacturers' instructions for the manual machines cannot be employed for estimation of a health risk posed by hand-arm vibration without being subjected to critical examination.

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