Exposure to whole-body vibration and seat transmissibility in a large sample of earth scrapers

Abstract

Background: It is often difficult to access a large sample of vehicles in various work environments to evaluate worker exposure to vibration such as in construction and mining. Thus the main purpose of the present research was to test vibration exposure in a relatively large number of earth scrapers. The second aim was to assess vibration exposure values on seat transmissibility.

Study Design: 33earth scrapers were assessed for both exposure to whole-body vibration and seat transmissibility.

Method: Two triaxial accelerometers, one placed on the seat and one on the floor directly below the seat, were used to gather whole-body vibration values ( $a_{w}$ ). Each machine was tested for a minimum of three complete work cycles: idling, scraping, travelling full, dumping, travelling empty back to the scrape site.

Results: Results showed that idling and scraping produced low levels of vibration when compared to travelling and dumping. Second, when the $a_{w}$ values were compared to the EU safety standards [12] for an eight hour work day, the data (z axis) exceeded the exposure action value (0.5 m/s $^{2}<FORMULA>) in all machines, and the exposure limit value (1.15 m/s<FORMULA>^{2}$ ) in some. Implications; Operators of the scrapers were being exposed to unsafe levels of whole-body vibration. When the seats were assessed to see whether they were attenuating operator exposure to vibration, many of the seat effective amplitude transmissibility (SEAT) values exceeded 1.0. This meant that some of the seats were actually amplifying the vibration present at the floor, particularly in the y axis.

Conclusion: Travelways should be kept smooth, operating speeds reduced, and new seats, effective in all three axes, designed.