How on earth moving equipment can ISO 2631.1 be used to evaluate whole body vibration?

Exposure to whole body vibration (WBV) is a hazard for operators of earth-moving equipment. ISO2631.1 “Evaluation of human exposure to whole-body vibration. Part 1 General Requirements” is referred to within guidance provided to obligation holders such as mine operators and equipment manufacturers. Measurements gathered from dozers in operation at a surface coal mine are examined to both gain insight into the vibration to which operators of this plant are exposed, and to illustrate issues related to the application of ISO 2631.1. Twenty-six measurements were gathered from ten dozers undertaking a range of activities at a surface coal mine. Unlike most equipment types, the WBV exposure associated with dozers is characterised by vibration in the fore-aft (X) direction which is frequently greater than that measured in the vertical direction (Z). If Z direction vibration expressed as r.m.s. only is considered, the vibration exposure of the dozer operators lies within or below the “Health Guidance Caution Zone” (HGCZ) proposed by ISO2631.1 for an 8 hour exposure to the 26 situations measured. A similar conclusion would be drawn from consideration of the X direction acceleration values. However, if X direction accelerations are multiplied by 1.4 as suggested by ISO2631.1, half of the measurements exceed the HGCZ. If the accelerations in different directions are combined into a Vibration Total Value as defined in ISO2631.1, all except four of the measurements exceeded the HGCZ. ISO2631.1 is ambiguous regarding which measures should be utilised and its application is problematic. Task-dependent variability in vibration measurements was noted. The implication for equipment manufacturers is that measurements must be taken in the range of realistic operating conditions. The implication for mine operators is that systematic measurement of whole body vibration correlated with information such as the activity being undertaken has potential to assist in the identification of appropriate control measures.