A continuation of the top 10 major accidents over the last century that have had a major influence on our regulatory regimes and industry standards on risk management. Click here to see Part 1: Major Accidents in the World.
Disaster #6 - Fixborough Chemical Plant
On June 1st, 1974 at 4:53 PM a large vapour cloud explosion demolished a chemical plant about 1/2 a mile from Flixborough, UK. The plant was owned and operated by Nypro, who were in the business of producing caprolactam, a basic raw material for the manufacturing of Nylon 6. The explosion killed 28 people at the plant site and injured 36 others. Fortunately the chemical plant was located in a rural area of England, adjacent to the River Trent, with no direct neighbors near enough to be killed by the event. Despite the site location the blast wave still caused widespread damage in the neighbouring houses and towns and approximately 53 people were injured outside the plant.
The event resulted in significant investigation and an official inquiry, commonly referred to as the Flixborough Report. There were many lessons learned from this and other investigations into this event. As is always the case, the event was the result of a series of decisions and smaller events that led to the eventual large vapour cloud release and subsequent explosion. The vapour cloud leak originated from a large 20 inch bypass pipe that had been installed between two of the six large reactor vessels used in the process. The bypass was required when a large crack had been discovered in one reactor which then needed to be shut down and removed. The engineers that designed the bypass to bridge the large gap between were not experienced to do such work and the site lacked full time site engineering support. The entire bypass assembly was not designed and installed per the applicable codes and standards in place at the time. There were no formal plant modification procedures in place to manage the changes safely. The plant management team and plant operators were not experienced in dealing with the stresses and critical decisions related to operating the plant during upset or abnormal conditions. The control room building was inadeqately located and was not designed for the potential accident events it could be exposed to (it was completely destroyed and all 18 people inside were killed). The main office building on site was also inadequately located and designed for the potential accident events. It was completely destroyed but since it was a Saturday there were no casualties as a result (~200 people worked there). The towns near the site were not informed of the potential hazards they were exposed to from the plant. Emergency planning for the potential major hazards was inadequate.
The numerous recommendations from the investigations and reports led to a major review of UK regulations regarding chemical plants, emergency planning procedures and major improvement in the field of safety engineering and plant management. The Advisory Committee on Major Hazards (ACMH) was set up and produced three key reports (published respectively in 1976, 1979, 1984). Process Hazard Management (PHA) became a major engineering field and the use of formal Hazard assessments in the design and operation phases of a project become common place. Management of Change (MOC) became a commonly used phrase and MOC programs became commonly applied at chemical plants.
Disaster #5 - Bhopal Disaster
On the night of December 2, 1984 a large toxic vapour cloud containing methyl isocyanate (MIC) leaked from a pesticide plant owned by Union Carbide India Limited in Bhopal, India. The cloud was carried by the prevailing winds of that night directly over the city of Bhopal a few kilometres away and the adjacent shanty towns, exposing well over 500,000 people. MIC is an extremely toxic chemical to humans, effecting the eyes, mouth, respiratory and neurological systems. The event caused thousands of fatalities, injured tens of thousands more and compensation claims continue to be made (the most recent one was on June 24, 2010 by the Indian government). The actual number of casualties will never be known due to the lack of accurate records of people living in the shantytowns in the area and the negative influence of the government in the overall investigation. Commonly referenced numbers state the number of casualties to be around 8000 people killed and over 50,000 injured or disabled.
The event was a classic example of mismanagement at every level of organization; government, regulators, emergency response and company operations. Union Carbide was unable to provide specific details of the effects of MIC and the immediate medical treatment required for those exposed and there was no emergency response plan in place for this type of event. The initial poor response from all levels was a good example of how humans respond under stress when they are not properly prepared.
The pesticide plant was the result of a large campaign by the Indian government to manufacture industrial products locally rather than rely on foreign imports. Union Carbide's plant was one of the first large scale developments under this initiatives and the failure of the plant reflected poorly on the government, who were therefore reluctant to respond openly and effectively.
The event itself was caused by water being misdirected to one of the two large MIC storage tanks during a routine pipework cleaning activity. MIC mixed with water causes an exothermic reaction causing vapour release, so the water/MIC mix resulted in a large volume of this toxic mixture forming and eventually releasing to the atmosphere through the plants flare tower. Knowing this, there were numerous safeguards designed into the plant that should have prevented the flare release: 1. The MIC tanks were stored in heat sheltering concrete bunkers and had a cooling system installed to ensure the MIC temperature was kept under control. 2. The MIC tanks had temperature gauges to warn of any dangerous temperature increases. 3. The vented gas from the MIC tanks went through a gas scrubber to remove any carried over MIC in the vapour phase. 4. The flare tower was designed to flare off any vented vapours from the plant, including any from the MIC tanks. Unfortunately, only one of these safeguards was in place at the time of the event: the concrete bunkers. All other safeguards listed above were inactive or were not monitored. The pressure gauges on the MIC tanks were so poorly maintained that even though they indicated an increase in tank pressure due to the water reacting with the MIC, they were ignored by operators who though they were giving false readings.
It is difficult to comprehend how a management team would allow such breaches in safety but that is what was in place at the time. Such widespread negligence was unprecedented. It does explain why the plant management team (all Indian nationals) were sentenced to 2 years in jail (and a ~$ 2,000 dollar fine - neither of which was considered severe enough punishment) and why the CEO of UC Corporation (Warren Anderson) left the country after being arrested and released on bail to avoid any further prosecution. He has never returned. The Indian government tried to extradite him from the US but was not successful.
The aftermath continues to this day with compensation claims still being argued in the courts. The event is still considered the worst chemical plant disaster in industrial history. The most notable positive legacy from the event was the widespread adoption of Process Safety as a professional engineering discipline and as a plant specialty requirement throughout the chemical industries worldwide. The event allowed this fledgling discipline to become widely accepted along with the resulting development of standards (such as the OSHA's Process Safety Management), practices (such as Process Safety Assessment) and regulations (such as the US Clean Air Act Amendments) that addressed stronger enforcement, prosecution and penalties.
Bhopal is a terrible legacy for the Process Safety field. Such legacies are the unfortunate reality when considering development by mankind. The only positive things we can take from any tragic accident event is the assurance that we will learn from our mistakes so that we can prevent similar events in the future. What we cannot accept when these events occur is to not learn from them, hence allowing the potential for history to repeat itself.
We are getting better at this but still have a long way to go in some industries and countries. Part of this is due to the valuations applied to a human life are not the same for all countries or companies of the world. In western countries the valuation applied is typically much higher than the valuation applied in developing countries. In Bhopal that was certainly the case, whether anyone actually admitted that or not. How else could the plant or the government allow poor people to build shantytowns adjacent to a chemical plant with known hazards. And having allowed this, how then could they have not have had an emergency response plan in place that addressed the possible hazard events.
We must learn to leverage technology to minimize risk potential and also to properly archive and allow access to lessons learned from our operating plants, so that we do not repeat history we would like to forget...but cannot.
See Part 4: Major Accidents that influenced the world
Wikipedia: Bhopal Disaster, Flixborough disaster
American University: TED Case Studies: Case 233
Loss Prevention in the Process Industries, Lees. Second Edition, 1996, Volume 3, Appendix 2, Flixborough