1. FLIXBOROUGH DISASTER
"The disaster was caused by the introduction into a well designed and constructed plant of a
modification which destroyed its integrity."
Cost of JUGAD ”Make shift arrangement”
In 1964, Fisons and Dutch State Mines (DSM) set up a joint venture, Nypro, to produce
DSM’s process produced caprolactam (the chemical precursor to Nylon-6 from
This allowed Nypro to compete head-on with ICI and Dupont’s patented method for
By 1967, the Flixborough plant — the only one of its kind in the UK —was supplying
caprolactam to textiles and chemicals manufacturer Courtaulds
In 1969 Nypro announced it was trebling capacity to 75,000 tonnes a year.
3. How it Happened 1 June 1974 ………
• The reactors were filled with liquid cyclohexane under pressure at 155 °C, through
which compressed air was bubbled to cause the reaction.
• The plant was shut down and the reactor, one of a series of six, was removed and a
bypass installed to link reactor numbers 4 and 6.
• The 50cm diameter bypass pipe was designed by Nypro engineers who were not
experienced in high-pressure pipework.
• No plans or calculations were produced, the pipework was not pressure tested and was
mounted on temporary scaffolding, unsupported from above.
• Bellows were used to join the pipe to the 60cm reactor flanges and crucially, because
the gravity-assisted reactor series was built on a slope, the pipe included a “dog-leg”
bend to accommodate the change in height.
• The plant was restarted but shut down again two months later when, on 29 May, a
small leak was discovered on a sight glass on a pressure vessel in the plant.
• Once the leak was repaired, in the early hours of the morning of 1 June 1974, the plant
started up for what would be the last time.
• “At 4.52pm the 50cm(20 inch) dog-leg pipe and the bellows attached to it ruptured, causing the
entire contents of all five reactors to escape at sonic velocity to form a vast flammable vapour
cloud the size of a football pitch. The vapour’s ignition less than a minute later resulted in an ‘open
flammable cloud explosion.”
• Of the 70 staff on site that weekend, 28 were killed and 36 injured. None of the 18 men working in
the control room survived.
• It was a scene of utter devastation: cars in the works’ car park were compressed to the size of
dustbins, a neighbouring field of wheat was sucked into the partial vacuum created by the blast
and large pieces of the plant came to rest in ironstone workings nearly eight kilometres away.
• Fifty three people off site reported injuries and hundreds more patched up their own cuts and
• Almost all homes in Flixborough, and nearby Amcotts and Burton were affected, along with 789 in
Scunthorpe, more than six kilometres away.
• In all, 1821 houses and 167 shops and factories were damaged. The blaze that enveloped the plant
took 250 fire fighters with 50 fire engines three days to contain, and fires burned for a week and a
half. While the plant burned, reaction began.
8. Failings in technical measures
• Plant Modification / Change Procedures: HAZOP
• Design Codes - Pipework: use of flexible pipes
• No pressure testing was carried out on the installed pipework modification.
• Maintenance Procedures: recommissioning
• Those concerned with the design, construction and layout of the plant did not consider the
potential for a major disaster happening instantaneously.
• Plant Layout: positioning of occupied buildings
• Control Room Design: structural design to withstand major hazards events
• Operating Procedures: As the incident happened during start up when critical decisions were
made under operational stress. In particular the shortage of nitrogen for inerting would tend
to inhibit the venting of off-gas as a method of pressure control/reduction
• Inerting: reliability/back-up/proof testing
• Had it been decided to strip and examine the other reactors and await a report on
the cause of the failure of reactor number 5, the plant must have remained shut
down for several days.The design and construction of the bypass assembly would not
then have been conducted as a rush job.
• The services engineer who provided cover was not qualified to do the job, as a
result, nobody realised that the pressurised bypass assembly would twist and buckle
and ultimately fail.
• The immediate lesson to be learned is that measures must be taken to ensure that
the technical integrity of plant is not violated,” the inquiry concluded.
• It also noted that had the control room’s layout “been differently sited or
constructed or both, loss of life might have been avoided”.
• “The unwise decisions people make about cutting costs or deferring maintenance
are because people have got detached from the consequences of things going
10. Out come of flixborough……..
• Two European Directives, Seveso I and Seveso II,
The outcome, implemented in the UK as the
Control of Industrial Major Accident Hazards (CIMAH)
Control of Major Accident Hazards (COMAH) Regulations
• Today’s process safety, change management and risk management techniques are also rooted in
• “Flixborough destroyed the confident feeling that we can always keep large quantities of hazardous
chemicals under control, and therefore we should keep the amounts of them in our plants as low
as reasonably practicable or use safer materials instead”
• Flixborough has left us with a useful legacy of preventative work practices.
• We no longer wait for things to go wrong, rather we have developed techniques to minimise the
risks posed by our workplaces.”
Thank you ……..