Risk Assessment Model Regarding Allowable Extent of Construction Activities during Normal Operation in the Process Industry

One of the challenges in the process industry is to carry out reconstruction and maintenance work on continuously operating plants. Improvements and necessary inspections in order to increase or preserve capacity and long-term safety need to be implemented with as little interference as possible with production. A solution often used is to carry out part of the work during normal operation or partial shutdowns. However, this compromises short-term safety, as more people are exposed to inherent plant hazards, and as the activities themselves may increase the risk for process related accidents. There is a lack of support for decisions concerning this type of compounded risk with high financial impact, and final judgement too often comes down to the individual. This paper aims at presenting a tool that gives support, in a consistent manner, for decisions regarding the size of construction and maintenance work in specific plants in different operating modes. The principal idea is to assume a defined risk level for the actual plant in normal operation (with ordinary staffing) and investigate the safety margin, compared to a societal risk criteria, when the staffing level is increased for a short period in order to carry out a specific amount and complexity of work. The tool must be calibrated to the specific plant circumstances.