The Flixborough Explosion
the afternoon of Saturday 1st July 1974 a major explosion
destroyed part of the Nypro chemical plant at Flixborough, near
Scunthorpe, North lincolnshire. The blast was the equivalent of 15 tonnes of TNT. A
total of 28 people lost their lives on-site, a further 36 were seriously
injured and there were 53 off-site injuries.
The BBC made a documentary programme analysing the events on that
day, which is available as a safety training
DVD called "Flixborough
(UK), owner of the Flixborough plant, was set up as a joint venture between
the British National Coal Board (NCB) and the Dutch state mines
(De Nederlandse Staatmijnen or DSM). The Flixborough plant been built to supply
caprolactam, used in the production of nylon. Production began
The chemical process to produce caprolactam involves the
oxidation of cyclohexane.
Cyclohexane is highly combustible, and it was a vapour cloud of
this chemical that destroyed the plant in an explosion.
to the Explosion
27th March 1974 it was noticed that cyclohexane was leaking from
Reactor Number 5, and the plant was shut down for safety reasons.
Investigations revealed a vertical crack in Reactor Number 5 was allowing cyclohexane to escape.
In order to continue production it was decided to isolate temporarily the damaged reactor by linking
Reactors 4 and 6
using a 20-inch diameter pipe. The modification was quickly
completed and production was resumed.
Unfortunately, the modification was made following only rudimentary
calculations being made, and no allowance at all was made for
the fact that the pipe had to be kinked. Furthermore the pipe was not
tested under pressure before being put into service. A few months
later these factors had fatal consequences.
the late afternoon on 1st July 1974 the temporary bypass pipe
carrying cyclohexane under pressure at 150 degrees Centigrade
ruptured. About 40 tons escaped and formed a vapour cloud hundreds
of feet in diameter. The vapour cloud came into contact
with a source of ignition and exploded, destroying the plant.
There were no survivors in the Control Centre, where eighteen people
were killed by flying glass from the shattered windows and by the
collapsing of the roof.
public inquiry was held following the disaster. This criticized
the inadequacy of the change control arrangements and the
incorrect use, under high pressure, of a pipe which could flex, on supports which could
flex and linked by bellows which could deform.
"Flixborough Disaster" DVD is about the explosion at
Flixborough. Details can be found here.
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