| Abstrakt: |
The handle vibration of a typical pneumatic jack-leg rock drill has been measured under common operating conditions. The dominant component acceleration was recorded in the direction of the percussion axis, and was unaffected by drill height, hand grip or operator. The handle vibration increased at the percussion frequency when drilling with a new, or re-sharpened, drill bit, and when the air pressure was increased above that commonly available in a mine. By extending the frequency range of measurements above those recommended by ISO 5349 (1986) for the assessment of vibration hazard, a large amplitude peak in the spectrum was detected at frequencies around 3 kHz. A comparison of predicted and observed latencies for vibration-induced white finger in population groups whose members operate this rock drill, or drills with similar vibration, suggests that the frequency weighting employed by ISO 5349 (1986) overestimates the hazard attributable to rock drill vibration, by up to a factor of two. Use of frequency unweighted accelerations from 5·6 to 5600 Hz, as recommended by NIOSH, fails to improve the accuracy of assessing the vibration hazard. For the acceleration spectra in this study, the NIOSH recommendation results in an overestimate of the vibration hazard associated with rock drill operation by at least a factor of six, and identifies frequencies ≈ kHz as being primarily responsible for the vascular hazard. Copyright 1994, 1999 Academic Press |
