Ageing assets at major hazard chemical sites – The Dutch experience

Operators of major hazard chemical sites increasingly face the problem that their assets are ageing. This paper highlights the major hazard aspects of ageing, particularly in the Netherlands where there are around 400 major hazard chemical sites, many coming to the end of or exceeding their design lifetime. Targeted inspections find failures in the safety management of ageing and every year there are ageing related accidents. Dutch investigated major accidents are analysed in a bow-tie structured database called Storybuilder, which contains 83 major accidents resulting from material degradation, this being 25% of all accidents in the database. The paper provides unique details on the accident causes and the difficulties operators have in foreseeing the outcomes. It explains the reasons for taking a holistic approach to modelling, which considers management, human and technical aspects. The analysis results provide information on the safety barrier, barrier task and barrier management failures. A detailed ageing accident scenario is also illustrated within the holistic model. Two prevention approaches are suggested. One uses scenarios as a basis for identifying the necessary prevention measures. The other results from a Dutch multi-disciplinary maintenance programme concerning smart maintenance, a shared initiative approach of companies looking for innovative solutions. The conclusion is that a scenario-based approach is needed for identifying currently unanticipated material degradation causal events and that, given the condition of ageing assets, a shift to condition-based maintenance, combined with technical, organisational and cultural changes, underpins the future approach to physical ageing.