Managing whole-body vibration at surface and underground coal mines

Abstract

Operators of mobile equipment at surface and underground coal mines are exposed to whole-body vibration. Long term exposure to high amplitude whole-body vibration is associated with the subsequent development of back pain, and has also been linked to multi-system health related issues. The issue has been recognised by the mining industry, however, the management of the hazard has been hampered by difficulties obtaining whole-body vibration measurements during normal operations. The research utilises a novel measurement technique to gather extensive whole-body vibration data from surface and underground mining equipment during normal operation in order to identify the principal sources of hazardous whole-body vibration exposures, and to explore potential control measures.The accuracy of an iOS application (WBV) installed on an iPod Touch was assessed against gold standard measurements (SV106) via ninety-six simultaneous measurements obtained across a range of surface mining equipment during normal operations. The results indicated a 95% confidence interval of +/- 0.077ms-2 r.m.s. for vertical whole-body vibration. The validity of the application has subsequently been confirmed by two independent groups.A total of 172 long duration whole-body vibration measurements were collected from three surface coal mines from August 2014 to May 2016. An initial survey (64 measurements) of a variety of equipment types in operation at one site, revealed that while the majority of measurements were within, or above the ISO2631.1 health guidance caution zone; track-mounted tractors fitted with a blades and rippers, (commonly referred to as “dozers”) were highlighted as being associated with very high, and in some case, extreme whole-body vibration levels. Dozers were the subsequent focus of further work at the three sites, and the prevalence of very high amplitude whole-body vibration measurements was confirmed at each. The data gathered from individual dozers during different shifts demonstrated considerable variability across the measurements obtained which suggested that the variability seen was a function of some combination of task and/or operator characteristics, rather than equipment characteristics. Although information was gathered regarding tasks, location and ground conditions in which the equipment operated, no consistent relationships between these variables and the vibration levels measured could be discerned.The deployment of whole-body measurement equipment is normally very difficult within underground coal mines because of the precautions required to eliminate ignition sources. However, three low-methane coal mines were identified where these precautions were not required. A total of 265 long duration measurements were obtained over 16 weeks of data collection between November 2015 and March 2019. 274 short duration measurements were also obtained during investigations of whole-body vibration that correlates with speed and roadway maintenance.An initial survey of mobile equipment operated at the underground coal mines revealed that shuttle cars, load-haul-dump equipment, and personnel transport vehicles returned elevated whole-body vibration levels. Shuttle cars in particular were associated with very high whole-body vibration amplitudes. These equipment were targeted with a range of control measures during normal mining operations. A positive impact of roadway maintenance on vertical whole-body vibration amplitude was recorded, with reductions in vertical whole-body vibration amplitudes for both driver and rear passenger. The effect of increasing vehicle speed on increasing vertical vibration amplitudes was consistent regardless of seating position, and the effect on the rear passenger was much greater. Vertical vibration measurements well exceeded the health guidance caution zone for speeds greater than10 km/hr, and were extremely high for higher speeds. The small sample size of measurements from shuttle car seat changeout precluded meaningful statistical comparison, however the vertical whole-body vibration amplitudes measured after change were lower for both shuttle cars measured.The relatively low cost of the iPod Touch hardware, and the accuracy and simplicity of the WBV application, provides the opportunity for site-based workplace safety and health staff to routinely collect long duration whole-body vibration exposure data. This information, when correlated with secondary information such as the activity being undertaken, operating conditions and equipment characteristics, has the potential to assist sites in the identification of appropriate control measures and evaluate the effectiveness of those measures as part of a whole-body vibration risk management program.