According to the latest pro-gress report on the investigation, published recently by the UK Health & Safety Executive, unleaded gasoline continued to be pumped into one of the storage tanks at the site for a period of three hours after the reading of the servo gauge on the tank, monitored by the site’s SCADA system, stopped changing. Moreover, pumping continued and even increased for a further 40 minutes even after the tank started to overflow, because a separate “ultimate”’ high-level switch failed to alert the site control room or to initiate automatic shutdown of the pipeline manifold valve feeding the tank, as it was designed to do.
What has surprised safety experts is that gasoline simply spilling out of the tank and splashing on to obstructions could form a vapour cloud that, when ignited, resulted in a devastating explosion and the largest fire in Western Europe since the Second World War. As a result, as well as apportioning immediate blame, the investigation is likely to lead to a reassessment of the hazards posed by such facilities and a recommendation to extend the sort of safety systems already familiar on hazardous plant to facilities storing and handling hazardous substances.
