On 27th March 1974, a crack was discovered in reactor No.5 at the Nypro Works Chemical Plant at Flixborough, Lincolnshire. As a result, the plant was closed down for investigation. The decision was taken to remove reactor No.5 and, in its place, install a 20 inch bypass pipe to connect reactors No.4 and No.6 in order that the plant could continue production.
On the afternoon of Saturday, 1st June 1974, this 20 inch by-pass pipe ruptured. This may have been caused by a fire on a nearby 8 inch pipe. The rupture resulted in the escape of a large quantity of cyclohexane which, when mixed with air, forms a highly-flammable mixture. This mixture then found an ignition source, causing the largest peacetime explosion in the UK. The explosion was estimated to be equivalent to 15 tons of TNT!
The Lincolnshire Fire Brigade Control received a call to the site at 16.32 and forwarded it to station D1 (Scunthorpe) by automatic alarm. A pre-determined attendance of 2 pumps along with an Emergency Tender with a Station Officer was mobilised. Within a minute of the call, and while the appliances were on route, the explosion occurred. The crews at this time were in Scunthorpe High Street and, observing a large number of casualties in this area, ordered ambulances to the High Street. At the same time the Station Officer made pumps 5.
Whilst the officer in charge was still 2.5 miles away from the Flixborough site he made pumps 10 as it became apparent that a serious fire situation could be seen in the distance. On arrival it could be seen that the whole of the chemical plant covering an area of over 60 acres was involved so the message make pumps 20 was sent. The large amount of smoke and the intense heat prevented any appliances accessing the site from the East, so they had to detour to gain access from the West.
The officer in charge of the first appliance was then told by site officials that up to 30 personnel were unaccounted for. BA teams were tasked with a search and rescue operation to find any possible survivors. At the same time pumps were set into the River Trent and 2 jets got to work. At 17.06, 2 Senior Officers arrived and at 17.14 made pumps 25 followed, eighteen minutes later, with make pumps 30.
Pumps were used to supply ground monitors to protect parts of the plant. As other appliances arrived an attack on the tank farm on the East side commenced under the command of the Assistant Chief Officer.
A message from the Deputy Chief Officer was sent at 19.10 which read "A site of about 60 acres heavily involved in fire following an explosion; 25 persons unaccounted for; site is being surrounded by ground monitors; further search in progress"
BA teams managed to find and successfully rescue 2 workers, but also reported that they had seen several bodies on the site. They also reported that much of the plant and auxiliary buildings had been completely demolished and were on fire.
The Chief Officer sent the Stop Message at 21.20. 22 jets consisting of 18 ground monitors and 4 hand-held branches were still in use.
Twenty-eight workers were killed and a further 36 suffered injuries. Of those twenty eight, eighteen occurred in the control room as a result of the windows shattering and the collapse of the roof. No one escaped from the control room. Nine others died in various areas of the site and one delivery driver died in his cab from a heart attack.
If the incident had occurred on a weekday, more than 500 plant employees may have been killed. It took until Thursday 13th June, almost 2 weeks later, to finally extinguish all the fires and cool the site to make it safe.
90% of the plant had been destroyed by the explosion and fire. 18,000 tons of flammable liquids and several hundred tons of acids had been destroyed.
One thing of note about this incident is that the Fire Brigade were not tasked with removing the bodies from the site. This was carried out by the Mines Rescue Teams of the National Coal Board. Around 100 homes in the village of Flixborough had been destroyed or badly damaged and extensive damage had been caused to other many other properties within a 5 mile radius of the site. Windows were broken over an even larger area. The blast was heard over 25 miles away. The explosion also resulted in over 100 reported injuries offsite.
During the course of firefighting, 16 brigade personnel were injured, mainly by acid burns. All were discharged after treatment and all returned to duty.
At an early stage in the Flixborough incident the manager of the nearby Normanby Park Steel Works informed the brigade that the cooling water supplies to the steel works had failed as a result of the explosion, and that 10,000 litres of water per minute were required within an hour to prevent the furnaces from exploding. A further 10 pumps in addition to those at Flixborough were used until Monday, June 3rd to supply the water to the steel works until the damaged 30 inch main was repaired. Despite protests from the local community the Nypro plant was re-built, but due to a subsequent collapse in the price of nylon, it closed down a few years later.
The site today is home to the Flixborough Industrial Estate, and is now occupied by various businesses.
The Guinness Book of World Records still lists it as the worst industrial explosion in U.K. history.
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