• Author / Uploaded
• Addison Juttie

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LAYERS OF PROTECTION ANALYSIS FOR BHOPAL INCIDENT Layer 1: Process Design One of the reasons or causes of the Bhopal incident was that there were too much MIC filled into one tank. If the tank should only be filled up to 50% of capacity, the workers should not exceed the limit. According to D’Silva, T., the worker anticipated that the plant would be dismantled and closing, thus that decision of overfilling is justified as the worker assumes that excess inventory would be temporary. In addition, the intent of the original instruction may have been lost over time among the designers, the hazards analysis team, and the plant operators. As 1984 began, the plant was losing money and operating at one-third of its capacity. This led to layoffs and transfers, and fewer shift operators were assigned to monitor the process. The 50% volume rule might have gotten lost in the transitions. (D’Silva, T., “The Black Box of Bhopal: A Closer Look at the World’s Deadliest Industrial Disaster,” Trafford Publishing, Victoria, BC (2006).)

Layer 2: Basic process control system The refrigeration system installed to remove the exothermic heat of reaction within the tank was disabled by plant management. This was portrayed as a cost-saving measure and a way to obtain hard currency, as plant management was under pressure to cut costs to avoid a plant closure. The management continually looks for ways to reduce costs. Engineers need to communicate to management that cost reductions should not be undertaken for critical safety systems.

Layer 3: Critical alarm and human intervention The plant had high-temperature and high-level indicators and alarms to alert personnel. Operators were aware of the rising pressure and temperature in Tank 610. However, there is no record of a manual intervention to transfer material to Tank 619. Human intervention is important in any plant especially by the engineers as they are trained in troubleshooting, identifying what should be done if something unplanned happens in the plant.

Layer 4: Safety instrumented functions In the Bhopal incident, there was no automated trigger device that might quench a runaway reaction within the storage tank. Undeniably 40 tons is a considerable amount of material and it is way too much to quench effectively. Thus, from this the importance of advanced process control of instruments in critical process system is important especially when in a plant. A critical process system can be identified as one which, once running and an operational problem occurs, may need to be put into a "Safe State" to avoid adverse Safety, Health and Environmental consequences. This is essential in Bhopal incident especially considering the fact that MIC is highly toxic.

Layer 5: Physical protection (Relief devices) The rupture disc followed by the relief valve worked on demand. The Relief Valve Vent Header (RVVH) had sufficient capacity. This prevented what could have been an even more catastrophic explosion. However, the relief system failed because the flare was out of service awaiting the replacement of section of corroded pipeline. With the flare system out of service, the material in the RVVH had nowhere to go but into the air.

Layer 6: Post release physical protection (Dikes) The existence of a dike is not relevant, as this was a toxic gas release. Diking around the storage tanks would not have affected the outcome of this disaster as dikes are usually applied for then there is a release of liquid.

Layer 7: Plant emergency response A few operators tried spraying water on the gas plume leaving the scrubber. The hoses were insufficiently pressurized, and the 100-ft-high stream could not reach the plume, which was exiting at 120 ft. For every plant, emergency response must be practiced, as the saying goes, practice makes perfect. Emergency response training is essential in combating all possible events that may happen in the plant. The plant’s response team needs to run through mock scenarios and practice so they will be prepared to respond to a major event. In that way, things like low water pressure or the need for gas masks will be discovered beforehand.

Layer 8: Community emergency response In any plant, either being planned or already running, needs to know the importance of community emergency response. There should be several teams dedicated to responding to the community if there is any emergency as they are living or staying in the danger zone. To prevent any loss of life, this should be emphasised. Communities that do not possess infrastructure and technical expertise to respond adequately to such industrial accidents should not be chosen as sites for hazardous industry. For the Bhopal incident, the plant was built in the slums area, and with the community lacking any knowledge on the emergency responses, the plant should carry out their responsibility in educating and informing the community nearby regarding the possible dangers and how to act when it does happen. In Bhopal, the community had never been informed about the dangers posed by the materials used in the plant. Several people thought that the plant made medicines. This contrasts sharply with the right-to-know laws in the US states. In West Virginia, Union Carbide is forced by law to inform people regularly about the dangers they face and instruct them about appropriate action during an emergency.