What Triggered the Disaster?

The horrific event of December 3, 1984 was not an accident. It was the result of years of concerted effort by Union Carbide to save money by cutting safety procedures and regulations at their factory in Bhopal. The actual disaster was set off by a runaway chemical reaction in the methyl isocynate (MIC) unit – a reaction that could not be stopped because of Union Carbide’s negligence and deliberate ill-planning.

Water Entered the MIC Tank

In May 1984, on the say-so of US engineers,  an update was made to the plant’s process safety system. They made a design modification and installed a “jumper line,” which was a cheap solution to a maintenance problem. The jumper line connected a relief valve header to a pressure vent header and enabled water from routine washing operations to pass between the two headers, on through a pressure valve, and into MIC storage tank 610.  On December 3, 1984 the exposure of the water to the MIC tank (made possible because of the leaky pressure valve in the jumper line) led to an uncontrolled reaction; a deadly cloud of MIC, hydrogen cyanide, mono methyl amine soon settled over much of Bhopal, and people began to die. In Carbide’s initial investigation into the disaster, they agreed that the pressure valve was leaking but declined to mention the role of the jumper line and how it enabled the entrance of leaking water into the MIC tank.

Carbide’s Safety Meltdown

“Well, that’s always a potential [for industrial sabotage] and you have to worry about it. That’s why you need the redundancy… Built into the safety system are a whole series of capabilities that can take care of whatever inadvertent action or co-mission has taken place so you’re not all dependent on just one item to either make it safe or make it unsafe.”
 -Union Carbide CEO Warren Anderson, quoted at a March 1985 press briefing.

Due to Union Carbide’s negligence, on that night NOT ONE of the SIX safety systems designed to prevent and warn of a leak of toxic gas were operational:

  1. Flare Tower: Disconnected
  2. Vent Gas Scrubber: Out of caustic soda and inadequate for the excessive amount of MIC gas stored
  3. Water Curtain: Not functional; designed with inadequate height
  4. Pressure Valve: Leaking
  5. Run Off Tank: Already contained MIC
  6. Mandatory Refrigeration for MIC Unit: Shut down for 3 months to save money

Safety systems at Union Carbide factory

Even if the safety systems had been working, Union Carbide installed technology which was not adequate to stop a disaster of this magnitude:

  • The vent gas scrubber, the chief safety system, was designed to take a feed rate of 190 pounds per hour at 35 degrees Celsius, with a maximum working pressure of 15 psig. At the time of the disaster, MIC poured through it at 40,000 pounds per hour and at over 200 degrees C, with an average pressure of 180 psig.
  • The flare tower also would have been utterly useless, even if it had been connected that night. Its piping was too small to handle a large flow of gas. The works manager estimated that if workers had tried to light it with that amount of MIC pushing through it would have created a huge explosion that would have 
disintegrated it.

In addition, the plant siren, which could have warned the surrounding neighborhoods of danger, was not functional. Thousands of lives could have been saved if they had been woken up by a early warning siren system. Instead they continued to sleep as the gas drifted closer and closer to their homes.

Read more about Union Carbide’s mismanagement and why the safety systems were dysfunctional in Union Carbide Enters Bhopal (1969-1979) and The Lead Up to Disaster (1980-1984).

Learn More:

1. Creating the Disaster: 1969-1984

3. The Aftermath: 1985-Present

Return to 2. December 3, 1984

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