Mechanical integrity of process installations: Barrier alarm management based on bowties

A Safety Research project was carried out in an ammonia plant of OCI Nitrogen, located at the Chemelot site in Geleen, The Netherlands. This research focused on the development of a method to monitor accident processes in the chemical industry mainly caused by mechanical integrity of static equipment like vessels, tanks and heat exchangers. A significant part of the mechanical integrity failure scenarios originates from material degradation and corrosion mechanisms which may develop over a relatively long-time period, possibly taking months, years or even longer. Mechanical failure scenarios from two process units have been worked out and visualized using a bowtie. The research project shows that the monitoring of early warnings can provide information about the current development of mechanical failure scenarios. In addition, early warnings can be used to initiate inspections if there is a likelihood that the mechanical failure scenario has been activated. Considering the shift from breakdown maintenance to preventive and predictive maintenance and risk-based inspection (RBI), inspections based on early warnings could also be a new step in the field of maintenance efficiency.