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11. The tanks storing MIC have to be, for reasons of safety, twice the volume of the MIC to be stored. It was also advised by UCC itself that an empty tank should also be kept available at all times for transferring MIC from its storage tank to the stand by tank on occasions of emergency. MIC has to be stored in the tanks under pressure by using nitrogen which does not react with MIC- The temperature of the tank with MIC has to be maintained below 15 degree Celsius and preferably at about 0 degree Celsius. The storage system and the transfer lines have to be free of any contaminants as even trace quantities of contaminants are sufficient to initiate reaction which could become runaway reaction. On reaction set-ting in, there could be dangerous and rapid trimerization. The induction period could vary from several hours to several days. The heat generated could cause reaction of explosive violence. In particular, water reacts exothermically to produce heat and carbon dioxide. Consequently, the pressure in the tank will rise rapidly if MIC is contaminated with water. The reaction may begin slowly, especially if there is no agitation, but it will become violent. UCC itself states that with bulk systems contamination is more likely than with tightly sealed drums. All these properties of MIC show that despite all the safety precautions that could be taken, storage of large quantities of MIC in big tanks was fraught with consider-able risk.
12. Investigation has disclosed that at the time when the incident took place there were thee partially buried tanks in the factory at Bhopal. These were numbered E 610. E 611 and E 619. MIC was being stored generally in the tanks E 610 and E 611. E 619 was supposed to be the stand by tank. In the normal running of the factory, MIC from E 610 and E 611 was being transferred (o the Sevin plant through stainless steel pipe lines. MIC is kept under pressure by nitrogen which is supplied by a carbon steel header common to all the storage tanks. There is a strainer in the nitrogen line. Subsequent to the strainer the pipe is of carbon steel and leads to make up control valve (DMV) which also has a body of carbon steel These carbon steel parts could get exposed to ( MIC vapours and get corroded, providing a source of contaminant which could enter the MIC storage tank and cause dangerous reactions in the MIC, During the normal working of the factory, MIC fumes and other gases that escape pass first through a pipe line called Process Vent Header (PVH) of 2" diameter. The escaping gases were carried by the PVH line to a Vent Gas Scrubber (VGS) containing alkali solution which would neutralize the escaping gases and release them into the atmosphere- Another escape line of such gases that was provided from the tanks was the Relief Valve Vent Header (RVVH) of 4"diameter. Normal pressure of the MIC tank is shown by a pressure indicator. When the pressure in the tank exceeded 40 psig, a rupture disc (RD) leading to a safety relief Valve (SRV) had to break and the said SRV in the RWH line open automatically to allow the escaping gas to travel through the RWH line to the VGS for neutralization;

Along with this chargesheet a detailed abstract was filed supported by documentary evidence to show how the conclusions reached by the investigating agency were supported by this documentary evidence. In this abstract it was recited that in that plant there were no facilities for collecting MIC produced separately in each shift and the material is directly laid into the storage tanks without batchwise analysis. It was also found that there are no On-line analysers. Similarly, nitrogen from a neigh-bouring factory is fed directly into the storage tanks, without full inter-mediate storage and quality determination. Carbon steel sections are used in the connectors to the storage tanks. Copper tubes are used in connectors to the level instruments of the tank, The system of instruments for alarm to indicate sudden increase in temperature are not suited to the conditions of operation. Only a single refrigeration system for cooling of MIC in two tanks was installed and it had not been operated for some considerable time. MIC has the combination of properties of very high reactivity with minimum contaminants, ready volatility to become gas and very high in-halation toxicity. The installed facilities provided for disposal of unstable liquid MIC in alkali or for the neutralisation of gaseous emissions from violent reaction, on examination are found to be not capable of meeting the objectives of such disposal in a very short time of two hours. The abstract also recited that the ingress of about 500 kg, of water alone, was not the sole cause of the escape of a huge quantity of toxic gas. hi this connection the following averments found in the abstract were relied upon by the prosecution.:

"MIC is kept under a pressure of nitrogen which is supplied by a carbon steel header common to all the storage tanks: There is a strainer in the nitrogen line. Subsequent to the strainer the pipe is of carbon steel and leads to make-up DMV which also has as body of carbon steel. Similarly, the blowdown DMV is also of carbon steel body. These carbon steel parts may be exposed to MIG vapours and get corroded, providing a source of contaminant which can enter the MIC storage tank."
. * At paragraph 4.4 dealing with 'Instrumentation and Control System' it was observed in the Report of the Vardarajan Committee as under :