Development of a new frequency weighting filter for the assessment of grinder exposure to wrist-transmitted vibration

The risk assessment of hand tool workers exposed to hand-arm vibrations is still problematic. It is based, accordingly to ISO 5349, on a frequency-weighted measurement recorded at the handle of the tool. Unfortunately, the frequency-weighted filter recommended by ISO 5349 does not take into account any amplification of the hand-arm system and underestimates the global rms acceleration transmitted to the hand. In this study, the vibration transmitted from the tool handle to the worker's wrist is investigated in an industrial environment for seven commercial grinders, two subjects and three push forces. The results are compared with the ISO-5349 and ACGIH threshold limit values, and a new frequency weighting filter is proposed, by which the amplification close to the natural frequencies of the hand-arm system can be considered in the evaluation of the vibration transmitted to the wrist from vibration measurements at the tool handle in a grinding operation.