Top 10 worst process safety incidents in history

This article discusses what the Mary Kay O’Connor Process Safety Center at Texas A&M University in College Station, Texas, consider the top 10 process safety incidents in history. The incidents were ranked based on the cumulative impact on loss of lives and economic losses, and the resulting impact on the development of what today we know as process safety.

1. Bhopal

On the early morning of December 3, 1984, at the Union Carbide plant in India, a storage tank containing methyl isocyanate (MIC) was contaminated with water leading to a runaway reaction causing the release of more than 40 tons of toxic MIC gas through a relief valve. The incident killed more than 3,000 people and injured hundreds of thousands more. This was arguably the worst chemical industry incident in terms of people affected, however; it was just after this fatal tragedy that the chemical process industry became really conscientious of the importance of process safety and it gained complete acceptance as a standard practice.¹ As a direct response to Bhopal, many regulatory initiatives were implemented worldwide. In India, this event led to the Environment Protection Act (1986), the Air Act (1987), the Hazardous Waste (Management and Handling) Rules (1989), the Public Liability Insurance Act (1991) and the Environmental Protection (Second Amendment) Rules (1992). In the US, the Emergency Planning and Community Right-to-Know Act (EPCRA) was promulgated in 1986,² and the Clean Air Act Amendments (CAAA) were signed into law in 1990.¹

2. Chernobyl

On April 28, 1986, in a power plant in Chernobyl, Ukraine, an experiment performed in order to verify the emergency power supply of a reactor resulted in unfortunate consequences. The core of the reactor was blown out by two violent explosions causing a series of fires and the release of tons of radioactive materials. It is considered to be the worst nuclear disaster in history. The incident directly killed 56 people and influenced the development of cancer and radiation sickness of hundreds in the subsequent years.³ Before the incident, there were no written rules for the test that led to the catastrophic consequences. This fact has made the adherence to safety-related instructions as the most highlighted lesson learned regarding to process safety.⁴

3. Piper Alpha

Piper Alpha was a North Sea oil production platform. On July 6, 1988, the backup condensate pump pressure safety valve was removed for routine maintenance. However, since the maintenance could not be completed within the shift, it was decided to complete the remaining work the next day. As a temporary measure, the condensate pipe was sealed with a blind flange. Communication gaps between different shifts resulted in a catastrophe when the night shift crew unknowingly started the backup condensate pump after the failure of the primary pump. In just 22 minutes, fire broke out everywhere and the event escalated further because of design and operational flaws resulting in 167 deaths. The Piper Alpha incident was a wakeup call for the offshore industries. Significant changes in safety practice include development and implementation of safety case regulations in UK, adherence to a permit-to-work system and realistic training for emergency response.⁴

4. The Macondo blowout

The Macondo exploration well located in the Gulf of Mexico (GoM) was drilled by a deep water horizontal semi-submersible rig. On April 20, 2010, a blowout caused a fire and explosion on the rig that killed 11 employees and caused a major oil spill that continued uncontrolled for 87 days. A series of mechanical failures, lack of human judgment, faulty engineering design and improper team interaction came together to result in the largest oil spill known to mankind. The blowout was the biggest offshore incident in the US and it had a profound impact on safety regulations in the GoM. As a direct outcome of the Macondo incident, the Drilling Safety Rule regarding wellbore reliability and well control equipment was implemented on October 14, 2010. The Modified Workplace Safety Rule was also implemented on October 15, 2010, based on the lessons learned from the Macondo blowout.^5–6

5. BP Texas City

On March 23, 2005, during the startup of an isomerization unit, the safety relief valves of a distillation tower opened due to overfilling, allowing hydrocarbon liquids to flow into a disposal blowdown drum with a stack, which were also overfilled, resulting in a liquid release. The evaporation of the hydrocarbons produced a flammable vapor cloud that ignited and led to a series of fires and explosions. Fifteen workers died and about 180 were injured.⁷ This incident led to major investigations including the milestone Baker panel report headed by former US Secretary of State James Baker III. This incident also resulted in significantly more interest in and attention to issues such as facility siting, atmospheric venting, leading and lagging indicators and safety culture.

6. The Flixborough disaster

On June 1, 1974, in a caprolactam production plant, a temporary bypass line ruptured, resulting in the leak of almost 40 tons of cyclohexane that caused a huge vapor-cloud explosion. The tragic disaster killed 28 people including all the employees working in the control room. There was the alarming possibility of killing more than 500 employees if it were a normal working day instead of weekend. Also, widespread damage to property within a 6-mile radius around the plant was another major consequence. The Flixborough explosion was a critical driver in moving process safety issues forward in the UK. As a result of the Flixborough incident, at the end of 1974, the Advisory Committee on Major Hazards (ACMH) was formed. The lessons learned from this disaster highlight the importance of HAZOP analysis, blast resistant control rooms and thorough studies prior to any modification in process plants.⁴

7. Mexico City

On November 19, 1984, in an LPG installation in Mexico City, the failure of the safety valve of an LPG storage tank caused an overpressure inside the tank and a pipe rupture, leading to a leakage of LPG followed by an ignition and violent explosions. Approximately 500 people were killed and more than 700 were injured.⁹ This incident represents the largest series of boiling liquid expanding vapor explosions (BLEVEs) in history.⁴ Mexico City clearly demonstrated the risk of BLEVEs in process facilities and lessons learned from this event have significantly impacted standards for design and operation.

8. Phillips

On October 23, 1989, in the Phillips 66 plant in Pasadena, Texas, the rupture of a seal on a polyethylene reactor caused the release of highly flammable ethylene and isobutene gas, forming a gas cloud and leading to a massive explosion in less than two minutes. Twenty-three people were killed and more than 300 injured. The day before the incident, a maintenance procedure had been performed by contractor personnel. This incident underscored the importance of rigid adherence to operating procedures and the implementation of an appropriate management system for contract workers. In response to this incident and other incidents that occurred before in the 1980s (including Bhopal, Shell Norco, Arco Channelview and Exxon Baton Rouge), the US Department of Labor, Occupational Safety and Health Administration developed the Process Safety Management (PSM) regulation.¹⁰

9. Columbia disaster

The physical cause of the Columbia shuttle disaster was separation of insulation foam that then hit the carbon–carbon reinforced panel of the left wing, thus damaging the thermal protection system. Aerodynamic pressure caused by superheated air destroyed the wing when the shuttle was reentering earth’s atmosphere at about 10,000 mph on February 1, 2003. The tragic incident caused the death of all seven astronauts and resulted in shuttle debris being scattered over 2,000 square miles in Texas. However, the underlying causes for the disaster can be traced back to flaws in decision making at NASA. The Columbia incident also provided important lessons for crisis communication professionals, as well. In fact, the lessons learned from the Columbia incident can be mapped to many other catastrophes such as the Piper Alpha or the Flixborough incident, covering issues such as sense of vulnerability, establishing an imperative for safety and valid on-time risk assessment.¹¹

10. Fukushima Daiichi nuclear incident

On March 11, 2011, this incident drew the attention of the process and power industries around the world, encouraging them to incorporate natural disaster risk in any hazard analysis study. When a powerful earthquake hit the plant, the reactors shut down automatically. However, because of the earthquake and the following tsunami, a power blackout ensued, leading to the loss of cooling, which, in turn, led to overheating of the reactors (creating serious radiation hazards). Fortunately, no one was killed because of the radiation, but there may be long-term consequences to the workers and to the neighboring communities who were exposed to radiation.

Conclusions

These tragic events and the consequences of these events have provided us with numerous lessons that help our understanding of the hazards and risks of the modern process industry and, more importantly, how design, technology, equipment, management systems, human factors and safety culture can be used to improve the safety performance of the industry. Understanding the root causes of incidents and learning from mistakes within the company, as well as other organizations, is vital. These lessons need to be implemented both in the engineering and the management sectors.

LITERATURE CITED

¹ Mannan, M. S., et al., “The legacy of Bhopal: The impact over the last 20 years and future direction,” Journal of Loss Prevention in the Process Industries, 2005. 18(4–6): pp. 218–224.
² Mannan, M. S., J. Makris and H. J. Overman, Process Safety and Risk Management Regulations: Impact on Process Industry, Encyclopedia of Chemical Processing and Design, ed. R. G. Anthony, Vol. 69, Supplement 1, pp. 168–193, Marcel Dekker, Inc., New York, 2002.
³ Dara, S. I. and J. C. Farmer, “Preparedness Lessons from Modern Disasters and Wars,” Critical Care Clinics, 2009. 25(1): pp. 47–65.
⁴ Mannan, M. S., Lees’ Loss Prevention in the Process Industries, 3rd Edition, Elsevier, 2005.
⁵ McAndrews, K. L., “Consequences of Macondo: A Summary of Recently Proposed and Enacted Changes to US Offshore Drilling Safety and Environmental Regulation,” Society of Petroleum Engineers Americas E&P Health, Safety, Security and Environmental Conference, Houston 2011. Available online: http://www.jsg.utexas.edu/news/files/mcandrews_spe_143718-pp.pdf, accessed on March 16, 2012.
⁷ Kaszniak, M. and D. Holmstrom, “Trailer siting issues: BP Texas City,” Journal of Hazardous Materials, 2008. 159(1): pp. 105-111.
⁸ Snorre, S., “Comparison of some selected methods for incident investigation,” Journal of Hazardous Materials, 2004. 111(1–3): pp. 29–37.
⁹ C.M, P., “Analysis of the LPG-disaster in Mexico City,” Journal of Hazardous Materials, 1988. 20(0): pp. 85-107.
¹⁰ Guidelines for Vapor Cloud Explosion, Pressure Vessel Burst, BLEVE, and Flash Fire Hazards, 2nd Edition, August 2010, Process Safety Progress, 2011. 30(2): p. 187.
¹¹ American Institute of Chemical Engineers (AIChE), Lessons from the Columbia Disaster-Safety and Organizational Culture, Center for Chemical Process Safety, 2005.