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Incidents: Bhopal



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Bhopal was bad; Bhopal was very bad. The release of about 40 tons of vapor of the chemical methyl isocyanate (MIC) from a chemical plant in Bhopal, India on December 3rd 1984 created the world's worst industrial disaster. In excess of 3,000 persons died, 200,000 more were injured and there was extensive loss of livestock.

The Event

Details of the event are in dispute. Extensive litigation has failed to resolve the causes of the event. In particular, there is still disagreement as to whether a water hose was connected to the tank by a disgruntled operator, or whether the water entered the tank through leaking valves. If the act was malicious then normal risk management procedures provide no defense; there is little that management can do to protect a facility against a knowledgeable, aggrieved operator. Bhopal chemical accident

Regardless of the cause of entry of water into the tank, the operating and safety systems that should have prevented and/or mitigated the event were not working. Specifically:
  • A refrigeration system that cooled the MIC had been shut down. Had it been operating, the magnitude of the event would have been considerably less.
  • The facility's Vent Gas Scrubber cleaned any vented gases by contacting those gases with circulating sodium hydroxide solution, thus converting the MIC to a relatively harmless by-product. On the night of the disaster the Scrubber was not working.
  • Some of the toxic gases could have been burned off in a flare tower, but the tower was out of service.

Elements of Safety Management

Each of the incidents discussed in this section of the site are analyzed in terms of Inherent Safety, Process Safety and Health and Human Factors. Those judged as being particularly relevant to the Bhopal event are highlighted.

Inherent Safety

  1. Eliminate
  2. Substitute
  3. Minimize
  4. Moderate
  5. Simplify

Process Safety

  1. Culture
  2. Compliance
  3. Competence
  4. Workforce Involvement
  5. Stakeholder Outreach
  6. Knowledge Management
  7. Hazard Identification and Risk Management
  8. Operating Procedures
  9. Safe Work Practices
  10. Asset Integrity / Reliability
  11. Contractor Management
  12. Training / Performance
  13. Management of Change
  14. Operational Readiness
  15. Conduct of Operations
  16. Emergency Management
  17. Incident Investigation
  18. Measurement and Metrics
  19. Auditing
  20. Management Review

Health and Human Factors

  1. Human Factors Engineering
  2. Noise Analysis
  3. Health Risk Assessment

Inherent Safety: Minimization of Inventory

One of the principles of Inherent Safety is that the inventory of hazardous chemicals should be minimized. (Ideally they should be removed altogether). If the quantity of MIC stored at Bhopal had been radically reduced, then the consequences of the catastrophe would have been much less serious. Even if the amount of MIC needed to be stored could not have been reduced, the chemical could have been stored in multiple small tanks rather than one big one.

Moreover, other companies that manufactured MIC were able to do so using processes that immediately converted the MIC into a more stable final product.

Inherent Safety: Moderate

The shutdown of the refrigeration system and the failure of the Scrubber circulation system meant that the consequences of the event were not moderated in any way. The worst case became the actual case.

Process Safety: Culture and Conduct of Operations

Bhopal chemical accident Many management and operational factors contributed to the event. The plant was losing money, so many cutbacks had been made (including turning off the refrigeration system) in order to reduce costs. High staff turnover had led to the use of a relatively unqualified workforce (whether or not the cause of the event was a malicious act).

Process Safety: Hazard Identification and Risk Management

No quantitative risk analysis was carried out to calculate the facility's risk profile (Stix 1989). The value of such analysis is often questioned due to the uncertainties associated with the results. However, given the highly toxic nature of MIC, such an analysis may have made sense in this case. 

Process Safety: Auditing

Management at Union Carbide recognized that the Bhopal facility was potentially hazardous. For example, an inspection led by the company's technical team in the United States had been performed two years prior to the accident. The report stated that it found no situations "involving imminent danger or requiring immediate correction".

Long-Term Consequences

The Bhopal event was seminal, i.e., it lead to fundamental changes in the manner in which high consequence risk was understood and managed. (Other seminal events were Santa Barbara, Flixborough, Three Mile Island and Blackbeard.) Specific changes included the following:

  • The formation of the Center for Chemical Process Safety - a division of the American Institute of Chemical Engineers.
  • The use of quantitative risk analysis.
  • Understanding how corporate goals, government and the attitudes of the public affect the manner in which process facilities are run.
  • The introduction in the United Sates of the Emergency Planning and Community Right to Know Act (EPCRA).

The Bhopal plant was permanently shuttered following this event. However, Union Carbide had a similar facility at its site in Institute, West Virginia. Naturally this facility was subject to the most intense scrutiny following the Bhopal accident. Yet, in August 1985, that facility had a release of aldicarb oxime, another chemical used for making pesticides. The gas sent 134 local residents to hospital. All the attention in the review had been on the MIC section of the plant.

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