Recursive operability analysis as a tool for risk assessment in plants managing metal dusts

In industrial processes, it is not uncommon to replace regular processes and procedures with temporary ones, due to factors such as maintenance operations, breakdown of equipment or machines. All risks associated with the implementation of these temporary procedures are not analyzed, because they are applied usually for short periods. Nevertheless, the lack of proper attention levels towards the introduction of such modified procedures can lead to unfortunate and unpredictable accidents. In order to update the risk assessment document properly, fast and effective methods are needed but widely acknowledged methods are not currently available. In this work we propose the Recursive Operability Analysis-Cause Consequence Diagrams as a fast and efficient tool to include temporary and/or special procedures in an already developed risk analyses. The model was applied to the Zhong Rong Metal Products Co case study, which witnessed a severe explosion of an aluminum-alloy dust. The accident was mainly due to the implementation of a manual procedure to perform the cleaning of the bag filters present in the plant, subsequent to the breakdown of an electric motor. Results show that the update of the risk analysis can be performed in a fast and efficient way.