BHOPAL GAS DISASTER

BHOPAL GAS DISASTER

It was the night of 2nd December 1984 when the night shift staff of the Union Carbide Factory, Bhopal, took a round at @ II pm. There were three double walled, partly buried S.S. tanks (No. 610, 611 and 619) each of 60 tonne capacity and all containing the poisonous gas MIC (Methyl isocyanate) to be used to produce a deadly pesticide Carbaryl. At @ 11-30 pm. workers in the plant realised that there was a MIC leak some where : their eyes began to tear. A few of them went to the MIC structure and noticed a drip of liquid with yellowish-white gas, about 50 feet of the ground. They told .the supervisor who, however, decided to deal with the leak after the tea-break which ended at 1240 night. Meanwhile the events had moved very fast.

 The temperature of the tank 610 had reached 25°C the top of its scale and the pressure was increased twenty times rushing towards 40 psi at which the emergency safety valve was to open. Soon the pressure gauge showed 55 psi, the top of the scale and the safety valve had opened releasing MIC With a loud hissing sound and the tremendous heat.  A white cloud drifting over. the plant was. moving towards the sleeping neighbourhood.

 The workers tried to operate the safety devices, but nothing seemed to work. The water jet failed to reach the top of the 120 feet stack from which MIC was escaping.  The vent gas scrubber to neutralise the escaping gas did not work. The scrubber was under maintenance,, the flow meter was not indicating the circulation of caustic soda whose concentration was also not known since October. The flare tower to burn off the gas could not be 'used because its piping was corroded and not replaced. The refrigeration system, of 30 tonne capacity, to keep the MIC in liquid state at 0°C was closed down since June 1984 as an economy drive and the gas was at 15°-20°C Which was unsafe. For approximately two hours, the safety valve remained opened releasing over 50000 pounds of MIC (might also containing Phosgene, Chloroform, Hydrogen cyanide. Carbon dioxide etc.) out of 90000 pounds stored in the tank No. 610 at the time of the incident. Sometime between 1-30 to 2-30 am. the safety valve reseated as the tank pressure went below 40 psi.