Case Name, Disaster of Chemical Plant at Flixborough. Pictograph. Date, June 1, Place, Flixborough, UK. Location, Cyclohexanone oxidation plant. Flixborough. disaster. vapour cloud explosion. cyclohexane. loss prevention. risk assessment J.G. BallAfter the Flixborough Report: do we know the real truth?. 1 June is the 40th anniversary of the Flixborough disaster, The Flixborough Plant before the explosion – official report, TS 84/37/1.

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The report of the court of inquiry was critical of the installation of the bypass pipework on a number of counts: An initial investigation at the site found flibxorough “S” shape 20in. They had also been torn off the reactor nozzles. The cyclohexane oxidation process was performed in a series of six reactors, each holding about 20tonnes. Several serious incidents in the last 3 years have shown that we dare not flixboruogh breaking into lines that are not properly isolated.

Flixborough (Nypro UK) Explosion 1st June 1974

The reaction took place in six vessels, each holding about 20 tonnes. Chemical Engineering Progress, Vol. For any given distance feport the comparison can be made, Flixborough gives a higher estimated over-pressure than Buncefield, and other things being equal — overpressure estimation techniques might have changed so much in 30 years that the comparison is meaningless is therefore presumably to be judged the larger explosion.

Furthermore, it was shown that rapid creep cavitation of stainless steel may occur within minutes at temperatures of degree C or more and under a stress of 4. These tests showed that the bellows squired into on “S” shape repory a pressure only disastwr above the operating pressure. As a result of the rupture of the bellows, a great amount of cyclohexane escaped from the holes in the bellows and formed a cloud of cyclohexane vapour, which subsequently caused the explosion Fig.

Unconfined vapour cloud explosions had been experienced since the s; by the early s there had been about known incidents, with about 5 more reporrt year.

During the late afternoon on 1 June the temporary bypass pipe ruptured, and a huge quantity of cyclohexane leaked from the pipe, forming a vapour cloud which then found a source of ignition. Prior to the explosion, on 27 Marchit was discovered that a vertical crack in reactor No.

The company would have to show that “it possesses the appropriate management system, safety philosophy, and competent people, that it has effective methods of identifying and evaluating hazards, that it has designed and operates the installation in accordance with appropriate regulations, standards and codes of practice, that it has adequate procedures for dealing fliborough emergencies, and that it makes use of independent checks where appropriate”.


However, [12] gives a graphical presentation of the raw data overpressure inferred from damage vs repogt from explosion source for Flixborough Fig 3. If the bellows were ‘stiff’ resistant to squirmthe shock loading could cause the bellows disastdr tear at pressures below the safety valve setting; it was not impossible that this could occur at pressures experienced during start-up, when pressure was less tightly repkrt.

During start-up the bleed valve was normally isolated and there was no route for excess pressure to escape; pressure was kept within acceptable limits slightly wider than those achieved under automatic control by operator intervention manual operation of vent valves.

The report also didaster on matters to be covered by the Advisory Committee on Major Hazards. Lees’ Loss Prevention in the Process Industry 3rd edition.

Flixborough disaster

The plant as designed therefore could be destroyed by a single failure and had a much greater risk of killing workers than the designers had intended. English Choose a language for shopping.

For two months after fitting the bypass was operated continuously at temperature and pressure and gave no trouble. Both of the bellows had torn away from the temporary pipe. Instead [w] installations with an inventory of flammable fluids above a certain threshold or of toxic materials above a certain ‘chlorine equivalent’ threshold should be ‘ notifiable installations ‘.

The occupants of the works laboratory had seen the release and evacuated the building before the release ignited; most survived. To avoid the danger of systems and procedures being disregarded, there should be a requirement for a periodic form of audit of them.

However theoretical modelling suggested that the expansion of the bellows as a result of squirm would lead to a significant amount of work being done on them by the reactor contents, and there would be considerable shock loading on the bellows when they reached the end of their travel.

In area B, there should not be any other hazardous plants or site roads. So,it is necessary to consider methods for detecting and preventing leaks. ACMH felt that for major hazard installations [z] the plan should be formal and include.


On the other hand, permission for highly hazardous process plants only involves satisfying a technically unqualified local planning committee, which lacks even the most rudimentary powers once the plant goes on stream.

The initial site investigation had revealed a 50in.

Flixborough, 1 June | The National Archives blog

Critics felt that the Flixborough explosion was not the result of multiple basic engineering design errors unlikely to coincide again; the errors were rather multiple instances of one underlying cause: Retrieved 8 July We believe that to this end considerable formality is essential in relation to such matters as permits to work and clearance certificates to enter vessels or plant areas.

Retrieved 7 July We would not contest that the best run companies achieve high standards of safety, but we believe this is because they have Health and Safety Executive.

The Secretary of State for Employment set up a Court of Inquiry to establish the causes and circumstances of the disaster and identify any immediate lessons to be learned, and also an expert committee to identify major hazard sites and advise on appropriate measures of control for them.

Nypro argued that the bolts had been loose, there had consequently been a slow leak of process fluid onto lagging leading eventually to a lagging fire, which had worsened the leak to the point where a flame had played undetected upon the elbow, burnt away its lagging and exposed the line to molten zinc, the line then failing with a bulk release of process fluid which extinguished the original fire, but subsequently ignited giving a small explosion which had caused failure of the bypass, a second larger release and a larger explosion.

In the absence of inch nominal bore pipe mm DNinch nominal bore pipe mm DN was used to fabricate the bypass pipe for linking reactor 4 outlet to reactor 6 inlet. My grandfather in Grimsby heard the explosion and thought it was very strange thunder. A pipe was installed to bypass the leaking reactor so that the plant could continue production. Because the plant suffered wide-scale destruction, the first step of the countermeasure was to rebuild the plant according to the lessons learned from the disaster.

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