Flixborough disaster
Encyclopedia
The Flixborough disaster was an explosion
at a chemical plant
close to the village of Flixborough
, England
, on 1 June 1974. It killed 28 people and seriously injured 36.
and the British National Coal Board
) and in operation since 1967, produced caprolactam
, a precursor chemical used in the manufacture of nylon
. Residents of the village of Flixborough were not happy to have such a large industrial
development so close to their homes and had expressed concern when the plant was first proposed.
The process involved oxidation of cyclohexane
with air in a series of six reactors
to produce a mixture of cyclohexanol
and cyclohexanone
. Two months prior to the explosion, a crack was discovered in the number 5 reactor. It was decided to install a temporary 50 cm (20 inch) diameter pipe to bypass the leak
ing reactor to allow continued operation of the plant while repairs were made.
(10 bar
)) ruptured, possibly as a result of a fire
on a nearby 8 inch (20 cm) pipe which had been burning for nearly an hour. Within a minute, about 40 tonnes of the plant's 400 tonne store of cyclohexane
leaked from the pipe and formed a vapour cloud 100–200 metres (320–650 feet) in diameter. The cloud, on coming in contact with an ignition
source (probably a furnace at a nearby hydrogen
production plant) exploded, completely destroying the plant. Around 1,800 buildings within a mile radius of the site were damaged.
The fuel-air explosion
was estimated to be equivalent to 15 tonnes of TNT (60 gigajoules
) and it killed all 18 employees in the nearby control room
. Nine other site workers were killed, and a delivery driver died of a heart attack
in his cab.
Observers have said that had the explosion occurred on a weekday it is likely that more than 500 plant employees would have been killed. Resulting fires raged in the area for over 10 days. It was Britain's biggest peacetime explosion until the Buncefield Depot
explosion in 2005.
Substantial destruction of property was recorded in Flixborough itself, as well as in the neighbouring villages of Burton-upon-Stather and Amcotts. Significant structural damage affected Scunthorpe
(eight miles away) and the blast was heard over thirty miles away in Grimsby
.
Although the area was quite remote, graphic images of the disaster were soon shown on television due to BBC
and Yorkshire Television
film crews who had been covering the Appleby-Frodingham Gala in Scunthorpe that afternoon.
surge. The bypass had been designed by engineer
s who were not experienced in high-pressure pipework, no plans or calculations had been produced, the pipe was not pressure-tested, and was mounted on temporary scaffolding poles that allowed the pipe to twist under pressure. The by-pass pipe was a smaller diameter (20") than the reactor flange
s (24") and in order to align the flanges, short sections of steel bellows
were added at each end of the by-pass - under pressure such bellows tend to squirm or twist. These shortcomings led to a widespread public outcry over industrial plant safety
, and significant tightening of the UK government's regulations covering hazardous industrial processes. See COMAH Regulations.
Despite protests from the local community the plant was re-built but, as a result of a subsequent collapse in the price of nylon
, it closed down a few years later. The site was demolished in 1981, although the administration block still remains. The site today is home to the Flixborough Industrial Estate, occupied by various businesses and Glanford Power Station
.
The foundations of properties severely damaged by the blast and subsequently demolished can be found on land between the estate and the village, on the route known as Stather Road. A memorial to those who died was erected in front of offices at the rebuilt site in 1977. Cast in bronze
, it showed a number of mallard
s in flight landing on water: When the plant was closed the statue was moved to the pond at the parish church in Flixborough. During the early hours of New Year's Day
1984 the sculpture was stolen. It has never been recovered and those responsible for the crime have never been found.
The plinth it stood on, featuring a plaque listing all those who died that day, can still be found outside the church.
. Dr Cox argued there were two explosions, a smaller one, which was overlooked, happening before the massive blast. An eyewitness backed the claims and explained how she had tried to contact the police but the incident was never followed up. Dr Cox criticised the Health and Safety Executive
(HSE) for "[coming] up with the safe conclusion to allay public fears, rather than a significant conclusion which is that it was quite a complex issue".
Previously, in April 2000, allegations of a cover-up had been unveiled by a whistle-blowing scientist earlier sacked from the original investigation team. His name was Dr Ralph King, an eminent author of chemical engineering text books and an expert in the thermodynamics of large scale chemical reactions. He carried out numerous and complex calculations which suggested a build up of water in the base of the cyclohexane reactors could have led to a sudden explosive release of pressure which displaced the temporary by-pass pipe causing it to fail due to twisting and rupture of the bellows. This became known as the "water theory", an alternative explanantion to the causation set out in the Official Inquiry Report. The significance of Dr King's findings was that the disaster did not occur due to a failure of the local engineering team in constructing the temporary by-pass pipe (even though their methods might have been lacking in finesse), but was esentially a failure in the design of the process by the factory owners (Dutch State Mines)who failked to take account of the possibility of water build up in the reactors, especially at start up. He said the original inquiry was wrong to blame a simple mechanical failure: "I realised that what we were really there for was to come up with a cause which would not embarrass the company". His criticism led to the HSE ordering laboratory scale experiments at their Buxton Research Centre. The early laboratory experiments were inconclusive but seemed to indicate that Dr King's "Water Theory" might have some merit. Since the design fault suggested by Dr King, if correct, could have an impact on other similar reactors currently operating in the UK and overseas, HSE decided to scale up the experiments to take place in a stainless steel pressurized reactor at their Buxton site. The HSE research facilities at Buxton possesses features which can allow potentially dangerous experiments to be carried in 'bunkers' shielded by earth bunds with the controls for the experiment located in a concrete blockhouse a safe distance away. A miniaturized version of the Flixborough cyclohexane oxidation reactor was operated within such a safe facility at Buxton. After numerous test runs, HSE were unable to replicate Dr King's findings and the test results released in November 2000 did not seem to support Mr King's theory that even if water had been present inside the reactors at start up it could not have generated a level of build-up of pressure that would have caused the bypass pipe to fail. In spite of these findings by HSE (which are still questioned by some who have personal knowledge of the Flixborough Disaster) it is remarkable that Dr King managed to keep his "water theory" on the agenda for the best part of 20 years unflaggingly raising the isuue with politicians, civil servants, trade union leaders, heath and safety experts and many others until at last, he was finally taken seriously by HSE. Dr King's main concern was not one of personal vindication or status, simply a genuine concern that unless his theory was tested, another similar disaster would one day take place somwhere in the world. Unfortunately Dr King was never to learn whether his theory was proven or not by HSE, since he sadly died just a few months before the larger scale experiments were carried out.
Explosion
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
at a chemical plant
Chemical plant
A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials. Chemical plants use special equipment,...
close to the village of Flixborough
Flixborough
Flixborough is a village and civil parish in North Lincolnshire, England. It is situated near to the River Trent, about 3 miles north-west of Scunthorpe. The village is noted for the 1974 Flixborough disaster....
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, on 1 June 1974. It killed 28 people and seriously injured 36.
Background
The chemical plant, owned by Nypro UK (a joint venture between Dutch State MinesDSM (company)
DSM is a multinational life sciences and materials sciences-based company. DSM's global end markets include food and dietary supplements, personal care, feed, pharmaceuticals, medical devices, automotive, paints, electrical and electronics, life protection, alternative energy and bio-based materials...
and the British National Coal Board
National Coal Board
The National Coal Board was the statutory corporation created to run the nationalised coal mining industry in the United Kingdom. Set up under the Coal Industry Nationalisation Act 1946, it took over the mines on "vesting day", 1 January 1947...
) and in operation since 1967, produced caprolactam
Caprolactam
Caprolactam is an organic compound with the formula 5CNH. This colourless solid is a lactam or a cyclic amide of caproic acid. Approximately 2 billion kilograms are produced annually...
, a precursor chemical used in the manufacture of nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
. Residents of the village of Flixborough were not happy to have such a large industrial
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...
development so close to their homes and had expressed concern when the plant was first proposed.
The process involved oxidation of cyclohexane
Cyclohexane
Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...
with air in a series of six reactors
Chemical reactor
In chemical engineering, chemical reactors are vessels designed to contain chemical reactions. The design of a chemical reactor deals with multiple aspects of chemical engineering. Chemical engineers design reactors to maximize net present value for the given reaction...
to produce a mixture of cyclohexanol
Cyclohexanol
Cyclohexanol is the organic compound with the formula 5CHOH. The molecule is related to cyclohexane ring by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid, which, when very pure, melts near room temperature...
and cyclohexanone
Cyclohexanone
Cyclohexanone is the organic compound with the formula 5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oil has an odor reminiscent of peardrop sweets as well as acetone. Over time, samples assume a yellow color due to oxidation...
. Two months prior to the explosion, a crack was discovered in the number 5 reactor. It was decided to install a temporary 50 cm (20 inch) diameter pipe to bypass the leak
Leak
A leak is a hole or other opening, usually unintended and therefore undesired, in a container or fluid-containing system, such as a tank or a ship's hull, through which the contents of the container can escape or outside matter can enter the container...
ing reactor to allow continued operation of the plant while repairs were made.
The disaster
At 16:53 on Saturday 1 June 1974, the temporary bypass pipe (containing cyclohexane at 150°C (302°F) and 1 MPaPascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
(10 bar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
)) ruptured, possibly as a result of a fire
Conflagration
A conflagration or a blaze is an uncontrolled burning that threatens human life, health, or property. A conflagration can be accidentally begun, naturally caused , or intentionally created . Arson can be accomplished for the purpose of sabotage or diversion, and also can be the consequence of...
on a nearby 8 inch (20 cm) pipe which had been burning for nearly an hour. Within a minute, about 40 tonnes of the plant's 400 tonne store of cyclohexane
Cyclohexane
Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...
leaked from the pipe and formed a vapour cloud 100–200 metres (320–650 feet) in diameter. The cloud, on coming in contact with an ignition
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
source (probably a furnace at a nearby hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
production plant) exploded, completely destroying the plant. Around 1,800 buildings within a mile radius of the site were damaged.
The fuel-air explosion
Fuel-air explosive
A fuel-air explosive device consists of a container of fuel and two separate explosive charges. After the munition is dropped or fired, the first explosive charge bursts open the container at a predetermined height and disperses the fuel in a cloud that mixes with atmospheric oxygen...
was estimated to be equivalent to 15 tonnes of TNT (60 gigajoules
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
) and it killed all 18 employees in the nearby control room
Control room
A control room is a room serving as an operations centre where a facility or service can be monitored and controlled. Examples include:*in television production, the master control is the technical hub of a broadcast operation common among most over-the-air television stations, television networks...
. Nine other site workers were killed, and a delivery driver died of a heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
in his cab.
Observers have said that had the explosion occurred on a weekday it is likely that more than 500 plant employees would have been killed. Resulting fires raged in the area for over 10 days. It was Britain's biggest peacetime explosion until the Buncefield Depot
2005 Hertfordshire Oil Storage Terminal fire
The Buncefield fire was a major conflagration caused by a series of explosions on 11 December 2005 at the Hertfordshire Oil Storage Terminal, an oil storage facility located near the M1 motorway by Hemel Hempstead in Hertfordshire, England. The terminal was the fifth largest oil-products...
explosion in 2005.
Substantial destruction of property was recorded in Flixborough itself, as well as in the neighbouring villages of Burton-upon-Stather and Amcotts. Significant structural damage affected Scunthorpe
Scunthorpe
Scunthorpe is a town within North Lincolnshire, England. It is the administrative centre of the North Lincolnshire unitary authority, and had an estimated total resident population of 72,514 in 2010. A predominantly industrial town, Scunthorpe, the United Kingdom's largest steel processing centre,...
(eight miles away) and the blast was heard over thirty miles away in Grimsby
Grimsby
Grimsby is a seaport on the Humber Estuary in Lincolnshire, England. It has been the administrative centre of the unitary authority area of North East Lincolnshire since 1996...
.
Although the area was quite remote, graphic images of the disaster were soon shown on television due to BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
and Yorkshire Television
Yorkshire Television
Yorkshire Television, now officially known as ITV Yorkshire and sometimes unofficially abbreviated to YTV, is a British television broadcaster and the contractor for the Yorkshire franchise area on the ITV network...
film crews who had been covering the Appleby-Frodingham Gala in Scunthorpe that afternoon.
Consequences
The official inquiry into the accident determined that the bypass pipe had failed because of unforeseen lateral stresses in the pipe during a pressurePressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
surge. The bypass had been designed by engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
s who were not experienced in high-pressure pipework, no plans or calculations had been produced, the pipe was not pressure-tested, and was mounted on temporary scaffolding poles that allowed the pipe to twist under pressure. The by-pass pipe was a smaller diameter (20") than the reactor flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
s (24") and in order to align the flanges, short sections of steel bellows
Bellows
A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location.Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet...
were added at each end of the by-pass - under pressure such bellows tend to squirm or twist. These shortcomings led to a widespread public outcry over industrial plant safety
Safety
Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...
, and significant tightening of the UK government's regulations covering hazardous industrial processes. See COMAH Regulations.
Despite protests from the local community the plant was re-built but, as a result of a subsequent collapse in the price of nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
, it closed down a few years later. The site was demolished in 1981, although the administration block still remains. The site today is home to the Flixborough Industrial Estate, occupied by various businesses and Glanford Power Station
Glanford Power Station
Glanford Power Station is an electricity generating plant located on the Flixborough Industrial Estate near Scunthorpe in North Lincolnshire. It generates around 13.5 megawatts of electricity, which is enough to provide power to about 32,000 homes...
.
The foundations of properties severely damaged by the blast and subsequently demolished can be found on land between the estate and the village, on the route known as Stather Road. A memorial to those who died was erected in front of offices at the rebuilt site in 1977. Cast in bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
, it showed a number of mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
s in flight landing on water: When the plant was closed the statue was moved to the pond at the parish church in Flixborough. During the early hours of New Year's Day
New Year's Day
New Year's Day is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar used in ancient Rome...
1984 the sculpture was stolen. It has never been recovered and those responsible for the crime have never been found.
The plinth it stood on, featuring a plaque listing all those who died that day, can still be found outside the church.
New theories on the causes of the disaster
In April 2007 new evidence was presented by Dr John Cox at a one-day symposium at University College LondonUniversity College London
University College London is a public research university located in London, United Kingdom and the oldest and largest constituent college of the federal University of London...
. Dr Cox argued there were two explosions, a smaller one, which was overlooked, happening before the massive blast. An eyewitness backed the claims and explained how she had tried to contact the police but the incident was never followed up. Dr Cox criticised the Health and Safety Executive
Health and Safety Executive
The Health and Safety Executive is a non-departmental public body in the United Kingdom. It is the body responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare, and for research into occupational risks in England and Wales and Scotland...
(HSE) for "[coming] up with the safe conclusion to allay public fears, rather than a significant conclusion which is that it was quite a complex issue".
Previously, in April 2000, allegations of a cover-up had been unveiled by a whistle-blowing scientist earlier sacked from the original investigation team. His name was Dr Ralph King, an eminent author of chemical engineering text books and an expert in the thermodynamics of large scale chemical reactions. He carried out numerous and complex calculations which suggested a build up of water in the base of the cyclohexane reactors could have led to a sudden explosive release of pressure which displaced the temporary by-pass pipe causing it to fail due to twisting and rupture of the bellows. This became known as the "water theory", an alternative explanantion to the causation set out in the Official Inquiry Report. The significance of Dr King's findings was that the disaster did not occur due to a failure of the local engineering team in constructing the temporary by-pass pipe (even though their methods might have been lacking in finesse), but was esentially a failure in the design of the process by the factory owners (Dutch State Mines)who failked to take account of the possibility of water build up in the reactors, especially at start up. He said the original inquiry was wrong to blame a simple mechanical failure: "I realised that what we were really there for was to come up with a cause which would not embarrass the company". His criticism led to the HSE ordering laboratory scale experiments at their Buxton Research Centre. The early laboratory experiments were inconclusive but seemed to indicate that Dr King's "Water Theory" might have some merit. Since the design fault suggested by Dr King, if correct, could have an impact on other similar reactors currently operating in the UK and overseas, HSE decided to scale up the experiments to take place in a stainless steel pressurized reactor at their Buxton site. The HSE research facilities at Buxton possesses features which can allow potentially dangerous experiments to be carried in 'bunkers' shielded by earth bunds with the controls for the experiment located in a concrete blockhouse a safe distance away. A miniaturized version of the Flixborough cyclohexane oxidation reactor was operated within such a safe facility at Buxton. After numerous test runs, HSE were unable to replicate Dr King's findings and the test results released in November 2000 did not seem to support Mr King's theory that even if water had been present inside the reactors at start up it could not have generated a level of build-up of pressure that would have caused the bypass pipe to fail. In spite of these findings by HSE (which are still questioned by some who have personal knowledge of the Flixborough Disaster) it is remarkable that Dr King managed to keep his "water theory" on the agenda for the best part of 20 years unflaggingly raising the isuue with politicians, civil servants, trade union leaders, heath and safety experts and many others until at last, he was finally taken seriously by HSE. Dr King's main concern was not one of personal vindication or status, simply a genuine concern that unless his theory was tested, another similar disaster would one day take place somwhere in the world. Unfortunately Dr King was never to learn whether his theory was proven or not by HSE, since he sadly died just a few months before the larger scale experiments were carried out.
See also
- List of United Kingdom disasters by death toll
- Health and Safety ExecutiveHealth and Safety ExecutiveThe Health and Safety Executive is a non-departmental public body in the United Kingdom. It is the body responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare, and for research into occupational risks in England and Wales and Scotland...
- 2005 Hertfordshire Oil Storage Terminal fire2005 Hertfordshire Oil Storage Terminal fireThe Buncefield fire was a major conflagration caused by a series of explosions on 11 December 2005 at the Hertfordshire Oil Storage Terminal, an oil storage facility located near the M1 motorway by Hemel Hempstead in Hertfordshire, England. The terminal was the fifth largest oil-products...
External links
- The Flixborough Disaster, Report of the Court of Inquiry, 1975
- Summary of the official inquiry into the accident
- Flixborough memories on h2g2H2g2h2g2 is a British-based collaborative online encyclopedia project engaged in the construction of, in its own words, "an unconventional guide to life, the universe, and everything", in the spirit of the fictional publication The Hitchhiker's Guide to the Galaxy from the science fiction comedy series...
- Flixborough: 20 years on, Loss Prevention Bulletin issue 117, 1994