Flixborough England Disaster 1974 The Flextorog disaster was an explosion ata chemical plant near the village of Flextoro in North Lincolnshire, England,on Saturday, 1 June 1974. Twenty-eight people were killed and 36 seriouslyinjured at the site at the time.
. Thecasualties could have been much higher, if the explosion occurred on a weekday,when the head office was occupied. “Shockwaves shook the confidence of all chemical engineers in the country,”wrote a contemporary operational safety activistThe disasteris involved and may be the result of a hasty change.
Therewas no large on-site manager with experience in mechanical engineering (almostall of the plant management had chemical engineering qualifications); managerswho agreed to mechanical engineering problems had been neglected with themodification, and the seriousness of the possible consequences of their failurewas not appreciatedFlixborough has caused a public outcry overthe safety of the processing plants. Inparallel with the adoption of the Occupational Health and Safety Act in thesame year, a more systematic approach to process safety in the UK’s processindustries was introduced (and often cited), and – in inconjunction with the Seveso disaster and therefore the EU Seveso Directives -to clarify the UK Government’s regulation of plant treatment or storage oflarge stocks of hazardous materials, currently (2014) under the HazardousMaterials Regulations MajorAccident Report of 1999 (COMAH).Inthe DSM process, cyclohexane was heated to about 155 ° C before moving into aseries of six reactors. Thereactors were constructed of mild steel with a stainless steel liner; inoperation, they contained a total of about 145 tons of flammable liquid at anoperating pressure of 8.6 bar pressure 125 psi. Ineach of the reactors, compressed air was passed through the cyclohexane,causing oxidation of a small percentage of cyclohexane and production ofcyclohexanone, with some cyclohexanol also being produced. Eachreactor was slightly less than 14 inches lower than the previous one, so thatthe reaction mixture flowed from one to the other by gravity through truncatedtubes with a nominal diameter of 28 inches DN 700 mm with bellows recessed.
Theinlet of each reactor was deflected so that the liquid enters the reactors at alow level; theoutflow flowed down a spillway with a ridge slightly above the top of theoutlet pipe. Themixture leaving the reactor 6 was treated to remove the reaction products, andthe unreacted cyclohexane only about 6% reacted at each pass and then returnedto the beginning of the reactor loop.Althoughthe operating pressure was maintained by an automatically controlled purgevalve once the installation was stabilized, the valve could not be used atstartup, in the absence of air supply, the installation being pressurized with nitrogen. Duringstartup, the purge valve was normally insulated and there was no way to escapeexcessive pressure; thepressure was kept within acceptable limits (slightly wider than those obtainedunder automatic control) by the intervention of the operator (manual operationof the vent valves A pressure relief valve with a pressure of 11 kg / cm 2 (156psi) was installed.Atapproximately 16:53 on Saturday, 1 June 1974, there was a massive release ofhot cyclohexane in the lost reactor area 5 shortly after the resultingflammable vapor cloud ignited and a huge explosion at the plant. Demolition of the site. Theincident occurred on the weekend, relatively few people were on site:immediately, 28 people were killed and 36 injured.
The fires continued on sitefor more than ten days. Abroad,deaths have not occurred, but 50 cases have been reported and about 2,000properties have been damaged.Theoccupants of the factory laboratory saw the removal and evacuated the buildingbefore it was released. Most survived. Noneof the 18 occupants of the plant control room survived, more than the plantsurveys. Theexplosion appeared to have occurred in the general area of ??the reactors, andafter the incident two sites were identified the report concluded that the 20-inchhypothesis involving ‘a single low-probability event’ was overall more crediblethan the 8-inch hypothesis according to ‘a succession of events, most of whichare improbableThesurvey report identified “lessons learned” that he presented underdifferent headings; “Generalcomment (on the cultural problems underlying the disaster),” specificlessons directlyrelevant to the disaster, but of general applicability are reported below; therewere also “general lessons” and “various lessons” of lesserimportance for the disaster.
Thereport also commented on the issues to be addressed by the Major HazardsAdvisory Committee.Noone in the design or construction of the plant has considered the possibilityof a major disaster occurring instantly. Itwas now obvious that such a possibility exists when large quantities ofpotentially explosive materials are processed or stored. Itwas of utmost importance that plants presenting an instantaneous disaster riskas opposed to a growing disaster be identified.
Onceidentified, steps should be taken both to prevent such a disaster to thegreatest extent possible and to minimize its consequences, despite all thenecessary precautions. Thereshould be coordination between the planning authorities and the health andsafety committee so that planning authorities can be advised on safety issuesbefore granting planning permission; Similarly,emergency services should have information to develop an emergency plan.Theinvestigation summarized its findings as follows:Webelieve, however, that if the measures we recommend are implemented, thesimilar risk of disaster, already low, will be reduced. Weuse the term “already far” wisely because we want to make it clearthat we did not find anything that suggests that the facility, as originallydesigned and built, created an unacceptable risk. Thedisaster was caused entirely by the coincidence of a number of improbableerrors in the design and installation of a modification. Sucha combination of errors is very unlikely to be repeated. Ourrecommendations should ensure that no similar combination occurs again and thateven if this happens, errors will be detected before serious consequences occur.