Alarming Your Tank Farm Why safety-critical alarms can prevent another tank farm explosion. By Gary BradshawNov 18, 2019 Twenty-five years on from a major explosion at an oil refinery, what can we learn about alarm annunciation? Here, Gary Bradshaw explains why many sites that fall within the scope of the Control of Major Hazards (COMAH) regulations are in urgent need of physical alarm panels that emit light and sound in the event of imminent danger. At 1:23pm on Sunday July 24, 1994, twenty-six people were injured when an explosion erupted through an oil refinery in an otherwise quiet corner of South Wales. The site was occupied by two companies: Texaco’s Pembroke Refinery and the Pembroke Cracking Company (PCC), a joint venture between Texaco Ltd and Gulf Oil (Great Britain) Ltd. The site produced hydrocarbon fuels such as gasoline, diesel, kerosene and liquid petroleum gases (LPG) from crude oil. The incident started before 9am when an electrical storm in the area caused lightning to strike the crude distillation unit that provided feed to the PCC units. This resulted in a fire that caused disturbances that affected the vacuum distillation, alkylation and butamer units, as well as the fluidised catalytic cracking unit (FCCU). What followed was a cascade of failures that highlighted severe shortcomings in the plant’s safety and control systems. The report produced by the Health and Safety Executive (HSE) following an investigation into the events concluded that “the direct cause of the explosion that occurred some five hours later was a combination of failures in management, equipment and control systems during the plant upset. These led to the release of about 20 tonnes of flammable hydrocarbons from the outlet pipe of the flare knock-out drum of the FCCU. “The released hydrocarbons formed a drifting cloud of vapour and droplets that found a source of ignition about 110 metres from the flare drum. The force of the consequent explosion was calculated to be the equivalent of at least four tonnes of high explosive. This caused a major hydrocarbon fire at the flare drum outlet itself and a number of secondary fires.” Let's block ads! (Why?)