WHAT YOU DONT HAVE CAN'T LEAK - BHOPAL GAS TRAGEDY REMEMBERANCE WITH A ??? of "ARE WE REALLY LEARNING?

What happened?

The shift supervisor asked an operator to wash the piping around one of the three MIC storage tanks at 10:15 p.m. on Sunday, December 2, 1984, suspecting a leak in the tank valve which was a usual phenomenon. Then the valve on the tank was blinded off to prevent ingress of water, entry of which would initiate a polymerization reaction which is highly exothermic. (The investigation report states that water had already entered the tank.)

At 11:00 p.m. the night shift operator noticed a pressure rise in the tank. He ignored it on the assumption that it was pressurized in the previous shift for the purpose of transferring the contents to the next pesticide unit. At about 11:30 p.m. the operators sensed irritation in their eyes. They knew that it was due to a small leak of MIC. Again, that was not an unusual phenomenon to them, so they ignored it.

Temperature and pressure continued to build in the MIC tank, irrespective of water being sprayed over the tank. Pressure in the tank built up to several times the permissible limit.

The catastrophe actually began when the above-mentioned storage tank of MIC became contaminated with water and a runaway reaction occurred. The temperature and pressure rose, the relief valve lifted and MIC vapour was discharged into the atmosphere. The protective equipment, which should have prevented or at least minimised the discharge, was out of action or not in full working order. The refrigeration system, which should have cooled the storage tank, was shut down. The scrubbing system, which should have absorbed the vapour, was not immediately available. And the flare system, which should have burnt any vapour which got past the scrubbing system, was out of use.

The ANATOMY OF DISASTER

At midnight, the undue pressure build-up in the tank burst a rupture disk, blew off the safety valve, and MIC gas rushed straight through an atmospheric vent line out into Bhopal's cool night air in the early hours of Monday, December 3, 1984, affecting innocent citizens and animals.

Many people died in their sleep because of the heavy gas cloud, which affected the greater part of the city in no time. Others woke up to intense irritation in their eyes, choking and suffocating sensation in their throats and lungs. They rushed out onto the streets, grasping for fresh air, only to make matters worse for themselves.

Over 8000 people died in the immediate aftermath. About 250,000 were left with permanent disabilities. In the year 1998, i.e., 14 years later, the death toll had risen to over 16,000. In this context numbers have little meaning as the actual figures are much more than the official figures. All the members of many families were completely wiped out. No one was left to claim anyone else. Since then 10 to 15 persons die every month from exposure-related diseases and their complications. Over 120,000 children, men and women continue to suffer acutely from a host of exposure-related illnesses and complications.

Management's lack of Knowledge - a key factor cannot be ignored

1. The Chief Medical Officer and the Works Manager maintained that 'MIC is an acute irritant, but certainly not lethal'.
2. The Head of HSE openly denied the hazardous, poisonous and noxious effects of MIC and dismissed the chemical as 'a potent tear gas; nothing more than that'.
3. Top Management View 'It was an unusual incident, rather abnormal, which cannot be explained. Normally, when the gas pressure builds up it immediately gets diverted to the scrubbing system through the vent. The gas release was stopped as soon as the abnormal pressure level was detected, and the plant was shut down.'
4. The local medical professionals had to rush to the library to get the correct technical information and possible antidotes.
5. Many Investigation concluded that no system safety engineering and management established and practiced.
6. It is a gross mismanagement during and after the entire disaster to such an extent that the disaster became an Unforgettable tragedy.

PROCESS SAFETY NOTEWORTHY LAPSES

1. Adequate in-built safety systems were not provided and those provided were not checked and maintained as scheduled.
2. In all, five safety systems namely:?Vent gas scrubber, Flare stack, Water curtain, Refrigeration system and a spare storage tank?were provided in the plant. But none of these ever worked or came to the rescue in the emergency.
3. Safe operating procedures were not laid down and followed under strict supervision.
4. Total lack of 'on-site' and 'offsite' emergency control measures.
5. No hazard and operability study (HAZOP) was carried out on the design and no follow-up by any risk analysis.
6. Evacuation drills for fire and release of toxic gases were never held and practiced.
7. The community living in the vicinity of the plant had never been alerted and warned about the dangers.
8. The local authorities had never been informed of the hazards so that they would know what to do in the event of such an emergency. It was the responsibility of both the local as well as central authorities to request the management to disclose all the relevant information with regard to the major hazard installations and their control procedures, identifying key personnel responsible for taking the appropriate measures in emergency as per the provisions under the Factories Act, 1948.

Danger signals and warnings were not observed and followed.

LESSONS WORTH OF LEARNING TO PREVENT RE-OCCURANCE

1. Wherever and whenever possible, we should reduce or eliminate inventories of hazardous materials, in process and in storage.

At the Bhopal plant, MID is an intermediate, not a product or raw material, and though it was convenient, it was not at all essential to store it. Originally MIC was imported and had to be stored but later it was manufactured on site. Nevertheless over 100 tones were in store, some of it in drums.

After this mishap, similar processes upgraded the design with intention to eliminate intermediate storage by which instead of storing, they use the MIC as soon as it is produced, so that instead of 40 tonnes in a tank, there would be only 5–10 kg in a pipeline.

An alternative to intermediate storage is substitution, i.e., using a safer material or route, especially when reducing inventories, or intensification as it is called, is not practicable.

The product carbaryl was made from alpha-naphthol, methylamine andphosgene which react together to form make MIC which reacts with phosgene.

Research developed an alternative process, in which alpha-naphthol and phosgene react together to make a chloroformate ester, which is then made to react with methylamine to make carbaryl.

The same raw materials are used but MIC is not formed at all. Phosgene, of course, is hazardous and its inventory should be kept as low as possible or avoided altogether.

Just as "materials which are not there cannot leak", "people who are not there cannot be killed".

A large shanty township, mostly consisting of shacks and huts, was allowed to grow adjacent and around the Bhopal plant. It was crowded and thickly populated. The death toll would have been much smaller if this town had not been allowed to grow up near the plant.

Though it is very difficult to prevent the growth of such hutments, it is essential to stop them springing up close to hazardous plants. Both the local government and industry should consider this issue sincerely and seriously.

For major hazard installations like the Bhopal plant, hazard and operability study (HAZOP) should be carried out on the design as it is a powerful tool for identifying routes by which contamination and other unwanted deviations can occur.

No water should had been allowed anywhere near the equipment, for washing out lines or for any other purpose, since it was well known that water reacts violently with MIC. A HAZOP study would have changed the design of water routes. (New age HAZOP Studies must consider the Reactivity Behavior of Raw, Intermediate as well as final products and those LOC's to limit the inventory of releases to as low as possible).

1. Keep protective equipment in working order and size it correctly. The refrigeration system, fitted with the storage tank, was not in use. The scrubbing system was not in full working order and incapable of absorbing the MIC discharged through the relief valve. The flare system was disconnected from the plant for repairs and hence MIC which got past the scrubbing system had not flared. The high temperature and pressure on the MIC tank were at first ignored as the instruments were poorly maintained and known to be unreliable. The high temperature alarm did not operate as the set point was altered and was maintained too high.

Maintain all protective equipment or Safety Critical Equipment in full working order all the time, even when the plant is shut down.

1. Training in Loss Prevention

Loss prevention should be an integral part of design. Hazards should, whenever possible, be removed by a change in design, such as "Reduction in Inventory" rather than by adding on protective equipment. The designer should not need to ask the safety adviser to add on the safety features for him; he should be taught to design a plant which does not require added-on safety features.

1. Handling 'on-site' and 'offsite' emergencies

A well-planned, organized and monitored 'on-site' emergency control plan is the responsibility of the individual industry, whereas the responsibility of the 'offsite' plan is with the local authorities. Its effectiveness shall be checked through combined industry and government implementing the plans and practicing the drills.

TATA VENKATA SURYA PRAKASH