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 On this day in engineering history, a fuel-air explosion at a chemical plant near the village Flixborough, England killed 28 people and produced a blast loud enough to be heard 25 miles away. The chemical plant, a joint venture between the British National Coal Board and Dutch State Mines, manufactured caprolactam, a precursor chemical used in the production of nylon. Two months before the deadly explosion that became known as the Flixborough Disaster, a crack was discovered in one of the six reactors that oxidized cyclohexane to produce a mixture of cyclohexanol and cyclohexanone. By installing a temporary 20 in. (50 cm) pipe to bypass the leaking reactor, the Flixborough facility planned to continue operations until repairs could be made.
Shortly before 5:00 PM on Saturday June 1, 1974, the temporary bypass pipe ruptured. In less than a minute, 10% of the plant's 400 tons of cyclohexane leaked out, forming a vapor cloud 100 to 200 m (320 – 650 ft) in diameter. When the cloud came in contact with an ignition source – probably from a furnace at a nearby hydrogen production facility – the resulting fuel-air explosion was equivalent to 15 tons of TNT. The blast destroyed the chemical plant, killing all 18 workers in a nearby control room and 9 other employees who were onsite. The 28th fatality, a delivery driver, died of a heart attack. If the Flixborough Disaster had occurred on a weekday during a regular shift, 500 plant employees would have been killed.
An official inquiry into the Flixborough Disaster determined that the bypass pipe had failed because of lateral stresses during a pressure surge. The engineers who designed the temporary conduit were inexperienced with high-pressure piping, and failed to perform adequate high-pressure testing. When a sudden pressure surge ripped through the bypass, the temporary scaffolding poles that allowed the pipe to twist under pressure buckled. Dr. John Cox, a critic of this official explanation, recently argued that Britain's Health and Safety Executive (HSE) arrived at "the safe conclusion to allay public fears, rather than a significant conclusion which is that it was quite a complex issue". During a one-day symposium at in London in April 2007, Cox argued that the Flixborough Disaster began with a smaller explosion before the massive blast. An eyewitness who had tried to warn the police supported Cox's theory, claiming that authorities had ignored his warning.
Resource:
http://en.wikipedia.org/wiki/Flixborough_disaster
http://en.wikipedia.org/wiki/Cyclohexane
http://en.wikipedia.org/wiki/Health_and_Safety_Executive
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Re: June 1, 1974 – The Flixborough Disaster
