1 June is the 40th anniversary of the Flixborough disaster, an explosion at a chemical plant sited on the banks of the River Trent in Lincolnshire. It was the biggest explosion to ever occur in Britain (during peacetime), until the fire at the Hertfordshire oil storage terminal (Buncefield) in December 2005. At Flixborough, 28 workers were killed and 36 others onsite suffered injuries. Outside the works, injuries and damage occurred on a widespread scale but there were no fatalities. It was recognised that the number of casualties would have been even higher had the incident occurred on a weekday.
The explosion was estimated to be equivalent to 16 tonnes of TNT and the subsequent fires raged for ten days. A considerable amount of property was destroyed in Flixborough and the surrounding villages, and the explosion was heard over 30 miles away in Grimsby. The Atomic Weapons and Research Establishment at Aldermaston produced a report on the infrasonic and seismic waves which resulted.
The plant, owned by Nypro UK, produced caprolactum, a chemical used in the manufacture of nylon. Some two months before the disaster, a crack was found in one of the reactors. A pipe was installed to bypass the leaking reactor so that the plant could continue production. During the late afternoon on 1 June 1974 the temporary bypass pipe ruptured, and a huge quantity of cyclohexane leaked from the pipe, forming a vapour cloud which then found a source of ignition. The massive explosion destroyed the plant. Eighteen fatalities occurred in the Control Room as a result of the windows shattering and the roof collapsing.
The official report into the accident (published in 1975) found that the bypass pipe had failed because of unanticipated stresses in the pipe during a pressure surge - the pipe had been inadequately supported, and the modification had been made without a full assessment of all the potential factors. Following the disaster there was a huge public debate about the safety of industrial plants and regulations regarding industrial processes were made considerably more rigorous – the newly formed Heath and Safety Commission took a close interest in these developments.
New theories about the causes of the disaster have been advanced since 1975, notably by engineer Ralph King and Dr John Cox. Ralph King suggested that a reaction between water (which had settled in one of the reactors) and the hot cyclohexane above it caused a massive rise in pressure that blew apart the piping. The causes of the disaster were complex (it is impossible to do justice to all the technical explanations here) and the debate continues.
The National Archives holds a great deal of documentation about the disaster and its aftermath, including numerous plans, drawings, photographs and witness statements as well as the Report of the Court of Inquiry. Witness statements include vivid accounts by onsite workers – powerful testimony describing the sudden descent into hellish conditions, and nightmarish experiences, such as this extract from a statement: ‘I felt the blast from a terrific explosion which had occurred somewhere behind me. The blast was such that it threw me full length across the road. Debris then began to fall all around me and I was covered with oil which fell out of the sky’ (LAB 104/387).
Evidence such as this conveys the horrific nature of that cataclysmic explosion 40 years ago – a terrible tragedy that had a major impact on health and safety practices in the UK.