Assessing occupational risk for contact with moving parts of machines during maintenance

Abstract

In this paper a methodology for managing occupational risk owing to contact with moving parts while maintaining machines is presented. The methodology is based on the principles of quantified risk assessment. A probabilistic model has been developed to assess the risk from contact with moving parts of machines while maintaining them as a function of working conditions and time exposure. 62 other models have been developed to cover different hazards in all working activities. They have been developed under the Workgroup Occupational Risk Model (WORM - Metamorphosis) project, financed by the Dutch government. These models allow the delineation of accidents into sequences of events describing measures (technical and/or procedural) in place to prevent them or to mitigate their consequences. Identification of these sequences enables the identification of specific root causes of such accidents and hence the determination of specific and practical actions that can influence the probability of an accident. Quantification of these models provides, furthermore, a way for assessing the relative value of such measures and hence a basis for supporting decisions aiming at reducing the consequences of accidents in the work fields. Qualitative information on the safety functions, measures and barriers the failure of which constitute the causes of accidents have been derived from the analysis of actual accidents occurred and reported under the Dutch law over a period of years. The information contained in the accident reports, required by Dutch law and composed by investigating labor inspectors, has been systematically analyzed. The results of this analysis provide a Bowtie-like visual aid of the various events that contribute to the accident. This information is then used to develop the logical models describing the logic interconnection of the various events corresponding to technical and/or procedural safety related measures and is amenable to quantification according to the laws of probability theory. The relative importance of each measure to risk reduction is depicted with the aid of sensitivity calculations. Optimization, thus minimization of risk with specific initial conditions and constraints is achieved through alterations in the working conditions.