Flixborough Accident

This accident occurred on June 1, 1974 at the Flixborough Works of Nypro (United Kingdom) Limited when a bypass system ruptured and released cyclohexane, which in turn formed a combustible mixture with air and then exploded on coming in contact with an ignition source [1,10,11]. As the result of this accident, 28 workers were killed and 36 injured [1,10,11]. Two of the active influencing maintenance factors were as follows [1,10]  

Lack of maintenance after plant modification, the bypass line was not pressure tested. 

Lack of maintenance limited calculations were performed on fhe bypass line. 

All in all, the influence of maintenance also included poor planning, poor checking, and poor execution [1]. Additional information on Flixborough accident is available in References 1,10, and 11. 

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The Flixborough accident (Section 7.1.2.3) is an often-cited example of a UVCE. 

Inventory. The larger tlie inventory of material, tlie greater is the loss potential (see discussion on Flixborough accident in Chapter 1). 

The Flixborough accident is perhaps the most documented chemical plant disaster. The British government insisted on an extensive investigation. 

Figure 1-10 A failure of a temporary pipe section replacing reactor 5 caused the Flixborough accident.

The Bhopal, India, accident, on December 3, 1984, has received considerably more attention than the Flixborough accident. This is due to the more than 2000 civilian casualties that resulted. 

These are gas fires accompanied by an explosion, which causes mechanical damage as well as thermal damage. The nature of the explosion is different according to whether it takes place in a confined space, which is the general case of domestic gas explosions in buildings, or in an unconfined environment, when organic vapours spread in the atmosphere (UVCE = Unconfined Vapour Cloud Explosion) an example of this is the FLIXBOROUGH accident which is described below. 

In process industry plants, the concept of more inherently safe design is a recurring theme in the three reports of the Advisory Committee on Major Hazards (ACMH - set up in the UK after the Flixborough accident). These reports set the general principles of new process industry safety in the UK and they represent in their field what, for example, the IAEA Safety Fundamentals documents do in the nuclear industry. 

European Agency for Safety and Health at Work (EU-OSHA) Flixborough Accident, retrieved on June 29, 2012 from website http //www.hse.gov.uk/ comah/sragtech/caseflixboroug74.htm. 

Although the Flixborough accident was very tragic, it did lead to some positive developments. In particular, as discussed above, the onshore process industries... 

Probably the most important lesson from Flixborough for the offshore industries is that it is necessary to have a Safety Management System. The Flixborough accident did not occur because one or two of the elements of PSM/SEMS were badly implemented. It occurred because Nypro did not have a Safety Management System and because there was inadequate oversight of the industry on the part of the government regulators. 

E)ocumentation of flash fires is scarce. In several accident descriptions of vapor cloud explosions, flash fires appear to have occurred as well, including those at Flixborough, Port Hudson, East St. Louis, and Ufa. The selection and descriptions of flash fires were based primarily on the availability of information. 

If a significant volume of gas (caused by a leak, for example) is exposed to an ignition source and this gas is mixed with air in proportions that are close to stoichiometric, the gas cloud can cause a lot of damage when it gives rise to a detonation. The accident at Flixborough is one example. The lower explosive limit of hydrocarbons is extremely low. If the carbon chain length exceeds 8, the autoinflammation temperature of a linear hydrocarbon is close to 200°C. All these parameters decrease with pressure. The table below shows to which extent pressure influences the AIT of ethylene ... 

The Flixborough Disaster Report of the Court of Enquiry." Formal Investigation into Accident on 1st June 1974 at the Nypro Factory at Flixborough. London Her Majesty s Stationery Office. 

The four most cited accidents (Flixborough, England Bhopal, India Seveso, Italy and Pasadena, Texas) are presented here. All these accidents had a significant impact on public perceptions and the chemical engineering profession that added new emphasis and standards in the practice of safety. Chapter 13 presents case histories in considerably more detail. 

The accident at Flixborough, England, occurred on a Saturday in June 1974. Although it was not reported to any great extent in the United States, it had a major impact on chemical engineering in the United Kingdom. As a result of the accident, safety achieved a much higher priority in that country. 

The accident at Flixborough, England, is a classic example of a VCE. A sudden failure of a 20-inch cyclohexane line between reactors led to vaporization of an estimated 30 tons of cyclohexane. The vapor cloud dispersed throughout the plant site and was ignited by an unknown source 45 seconds after the release. The entire plant site was leveled and 28 people were killed. 

Use the Flixborough Works accident described in chapter 1 to develop an investigation similar to Example 12-1. 

Use the Flixborough Works accident and the investigation developed in Problem 12-1 to develop an investigation summary similar to Example 12-2. Include layered recommendations to cover the accident causes and underlying causes. 

Ever since the inception of the petroleum industry the level of fires, explosions and environmental pollution that have precipitated from it, has generally paralleled its growth. As the industry has grown so has the magnitude of its accidental events. Relatively recent events such as the Flixborough incident (1974), Occidental s Piper Alpha disaster (1988), and Exxon s Valdez oil spill (1989) have all amply demonstrated the extreme financial impact these accidents can produce. 

The first positive step is the remedial action of cleaning up the environment that has already been damaged by the release of chemicals. This includes the restorations following the disastrous accidents of mercury in Minamata Bay, the Flixborough explosion of a vapor cloud, the Bhopal leaking of methyl isocyanate, and the Valdez oil tanker spill. 

Some of the most tragic and well-remembered accidents also had a start with a mini-modification made with a hose connection. The Bhopal Tragedy, the Three-Mile Island Incident, and the Flixborough Disaster were initiated by the improper use of hoses. 

The Flixborough disaster in June, 1974 (Lees, 1980), is an example of a case where a modification was introduced into a mostly well designed and constructed plant. This modification destroyed the plant s integrity and contributed to a major accident. The modification was made when a reactor failed (a large crack had formed). The modification was inadequate and the remaining reactors were not examined. 

The Flixborough nylon plant accident in the UK (1974) was caused by an open-air explosion of a flammable gas released into the air. It killed the 28 plant employees present and caused extensive property damage in the surrounding area. The failure to perform a full technical assessment of a modification was given as the main cause of the event. The Seveso pesticide plant accident in Italy (1976) is well known for the dangerous release of dioxin due to poor plant safety features and to the underestimation of the possibility of a runaway reaction. The Bhopal incident in India (1984), at another pesticide plant, killed an estimated 4000 (although the total number is still unknown). This disaster was attributed to too large an inventory of toxic substances and to very poor staff attention to the operability of safety features. 

Turning to the hazards and the impact of industrial processes. Many disasters such as Flixborough, Seveso and Bhopal (see section 1.6) have ably illustrated the environmental impact of human errors and the need for rigorous safety controls. The capacities and productivity of chemical plants are driven upwards as are the magnitudes of losses in terms of economic cost and fatalities. Analysis of the major causes of accidents in the U.S. chemical industry in the 1978-1980 period highlighted that ... 

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