The Flixborough Explosion.
Introduction
On
the afternoon of Saturday 1st July 1974 a major explosion
destroyed part of the Nypro chemical plant at Flixborough, near
Scunthorpe. The blast was the equivalent of 15 tonnes of TNT. A
total of 28 people lost their lives, a further 36 were seriously
injured and there were 53 off site injuries.
The BBC made a documentary programme analysing the events which occurred
on that fateful day which is available as a safety training
DVD called "Flixborough
Disaster".
Background
Nypro
(UK), owners 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). It had been built to supply
caprolactam, used in the production of Nylon. Production began
in 1967.
The chemical process to produce caprolactam involved the
oxidation of cyclohexane,.
Cyclohexane is highly combustible and it was a vapour cloud of
this chemical that eventually destroyed the plant in an explosion.
Background
to the Explosion
On
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 there was a vertical crack in reactor
number 5 that was allowing cyclohexane to escape.
In order to continue production it was decided to temporarily
isolate the damaged reactor by linking together reactors 4 and 6
using a 20 inch diameter pipe. The modification was quickly
completed and production 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. Also the pipe was not
pressure tested before being put into service. A few months
later these factors proved to have fatal consequences.
The
Explosion
In
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 a few
hundred 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 18 people
were killed by flying glass from the shattered windows and the
collapsing of the roof.
A
Public Inquiry
A
public enquiry was held following the disaster. This criticised
the lack of an adequate change control procedure 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.
Safety
Training
Material
The BBC's
"Flixborough Disaster" DVD is about the explosion at
Flixborough. Details can be found here.
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