The Technical Causes of Failure from a Design Perspective
The Bhopal disaster was the result of a combination of technological, organizational, and human errors.Eccleston & March (2003) indicated that some observers have indicated that the accident was more the product of lack of human forethought, lax or casual attitudes, reluctance to stand p to supervisors and management and poor leadership than flaws in the system or technology.
According to Gruner (1995) the Bhopal disaster had many contributing causes many of them related to the management of the Union Carbide subsidiary in direct control of the plant. Problems at the plant includes operating errors, design flaws, maintenance failures, training deficiencies and economy measures that increased risks harm. Gruner (1995) says that no one of the risks raised by these problems was appreciated by plant personnel. Observers have concluded that the gas leak stemmed from lack of oversight of Bhopal operations by officials from the American parent company of the plant operator.
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Between 1958 and 1973, Union Carbide used an alternative way of producing carbamate pesticides without using MIC. Eckerman (2005) says that for economic reasons this was changed to a more hazardous method. MIC is produced by a reaction of phosgene and monomethylamine (MMA) into methylcaramyl chloride (MMC) and hydrogen chloride (HCI). MCC is then pyrolysed to yield MIC and HCI. Chloroform is used as a solvent in the MIC process and caustic lye for the neutralization of any toxic material that needs to be disposed of.
The design had flaws in that instead of using a closed loop process, where MIC was converted as soon as it was manufactured, UCC applied for large scale storage of MIC, consisting of three horizontally mounted stainless steel tanks. Eckerman (2005) however indicated that normally two of the tanks labeled No. 610 and 611 were used to store the product when it was of acceptable quality. The third tank NO 619 was used for temporary storage of off-specification material until it was reprocessed. One tank was to be always kept empty that the tanks should not be filled to more than 60% capacity, that the tanks were to be kept under an atmosphere of nitrogen with pressure 1.0 kg/cm2 and that the temperature was to be kept below + 5 degrees Celsius. It was noted that only stainless steel tanks were supposed be used hence the use of iron, tin, copper and their alloys presented a major design challenge.
The written design instructions for the plant which the workers were to follow in washing out the lines at the MIC unit omitted the procedure that a slip-bind be inserted, according to a report in 1985 by the Union Research Group of Mumbai. Eckerman (2005) also says that until 1984, the lines to the RVVH and the PVH had been unconnected and each performed a separate function. The management wanted a standby line in the event of either the PVH or the RVVH having to be shut down for repair.
Another design flaw was that when the plant was first designed, the managing director of UCIL recommended that the preliminary design of the Bhopal MIC facility be altered to involve only token storage in small individual containers. To the contrary, UCIL was changed but the parent corporation which insisted on a design similar to the West Virginia plant (Eckerman, 2005). As a result of economic reasons, Bhopal’s plant would not be provided with all the safety equipment and security systems the engineers in South Charleston and envisaged.
Kovel (2007) noted that another technical cause of the disaster was that the flare tower that burned escaping gas had been out of service for more than five months as was the vent gas scrubber. Kovel (2007) says that the refrigeration system installed to inhibit the volatilization of MIC was also idle, to save power costs. The steam boiler was not designed to help clean the pipes in active operation. It was also noted that every relevant safety instrument from shutdown devices, to monitoring tools, to temperature gauges, was either in short supply or malfunctioning or designed improperly (Kovel, 2007). Kovel (2007) indicated the tank that exploded had been malfunctioning for a week. Instead of dealing with it, the plant authorities used other tanks, and let this one sit, and in effect stew. The plants safety systems had been designed negligently.
Consequences of Failure
The gas leakage from Union Carbide’s plant in Bhopal India in 1984 is the largest industrial hazard ever experienced in the world. Eckerman (2005) says that over 500,000 persons were exposed to the gases whereby between 3,000 and 10,000 people died within the first weeks and between 100,000 and 200,000 got [permanent injuries. Deadly gas floated over the fence to nearby. It was also noted that an estimated 50,000 people became invalids or developed chronic respiratory conditions. Choking on the deadly gas, which smelled like burning chilies, many victims suffocated within minutes, either in their homes or on the streets as they fled.
Eckerman (2005) says that in 1984, Bhopal had around 800,000 inhabitants. In 1981, 38% of the population was in the age group 0-14 years. The 36 wards that were classified as affected had around 520,000 inhabitants. This means that6 around 200,000 children between 0-14 years were affected by the gases. Eckerman (2005) noted that in 1985, of the total affected, 80% earned below Rs 145 per month. 1.2% earned more than Rs 465 per month; 47% lived in a non permanent house; 50% were Hindus and 49% Muslims. After the gas disaster it was found that 55% of the population in the Old City was Hindu and 43% Muslim.
Another consequence was the long term health effects which include blindness, lung disease, neurological disorder, and genetic damage. Krech, McNeill & Merchant (2004) says that the as a result of the disaster, environmental effects also persist. In 1999, a study by the environmental organization Greenpeace found that the long abandoned plant was leaking toxins into the groundwater, the only water source for the many people still living nearby (Krech, McNeill & Merchant, 2004).
Researchers say that catastrophe had multiple effects on workers and their families including income reduction. Fischlin & Nandorfy (2007) noted that people were faced with the inability to find adequate safe water, inability of women known to have been exposed to find marriage partners. There were also numerous health related disorders ranging from anemia, breathlessness, weakness and loss of vision.
The Cause of the Failure, using Fault Tree Analysis (FTA), and Reliability Block Diagram (RBD)
In a fault tree analysis the engineer starts from a definite system failure or an undesirable event and goes backwards to trace possible causes of the fault. This method is useful for emergency situations. Eccleston & March (2003) says that in the case of Bhopal disaster, the fault tree analysis will entail three important aspects that caused the disaster and they include design, operation, plant management and design plant management. Other faults include corporate neglect and regulatory neglect.
The Realistic Probabilities of the Various Events Highlighted
Ineffective workforce – it can be estimated that reduction of operators with education of high school education in a period of 5 years was 9 will the number of operators at the time of disaster is 6 hence the number of workers with high school education in 1979 was 15. The number of hours in a five year period is 24*365*5 = 43800.
Probability 9/6+15/43800 = 9.6*10-8
Stainless steel piping - To calculate the probability of failure attributed to stainless steel piping replaced by carbon steel first we assume that the number of new repairs performed was 1000. This implies that the number of repairs done to the plant since it was first opened in 1979 was 25000. Therefore probability = 1000/25000 + 1000 = 40*10-3
Probability of failure attributed to ineffective water spray system- Assuming that the system would fail to suppress gases as a result of design error associated with the height in MIC area which captures only 1/5000 of the plant. The system failed in MIC area on day over 5 year period of MIC production = 365*5 = 1825. Therefore the probability of failure would be (1/5000) /1825 = 109.6 * 10-9
Probability of failure attributed to defective blow down valve in MIC tank- Assuming that the sum of days defective in past 5 years = 12 then the total number of days in 5 years is 1825. The probability will then be 12/1825 = 6.6 *10-3
Probability of failure due to the plant being operated outside design parameters- In this case we assume that 10% of the plant was being operated outside design parameters for a period of 5 years. This implies that (10/100)/1825 = 54.8*10-6.
The probability that the plant was unable to deal with quantity of gases- The manufacturing plant was not designed to deal with volume of gases. This implies that the system failed to hold this volume of gas for 2.5 hours. Therefore the duration in hour’s system operating over 5 years is 24 * 365 * 5 = 43800 hours. Therefore 2.5/43800 = 57.1*10-6.
Use Boolean algebra to Find the Minimal Cut Set
The minimal cut set is the smallest combination of component failures which if they occur will cause the top event to occur. The minimal cut set is therefore a combination of primary events sufficient for the top event. The combination is a smallest combination in that all failures are needed for the top event to occur and if one of the failures in the cut set does not occur then the top event will not occur.
Using the fault tee indicated above it can be determined that
TE = A.B.C.D
We will first perform the top-down substitution. We start with the top event equation and substitute and expand until the minimal set expression for the top event is obtained.
B = 4+5+6+7+F+G
Considering that G = 10*11 and F = 8*9
We can substitute as follows B = 4+5+6+7+ (8*9) + (10*11)
Therefore the minimum cut set for the Bhopal tragedy was B hence
Plant failure of as a result of diminished design specifications
TE = 4+5+6+7+ 8+9+ 10+11
Recommendations on What Should have Been done in Terms of Emergency and Contingency Planning
Although the Indian government wanted to attract foreign investment in to the country it should have considered the safety of its citizens. The design for the plant should have been clearly reviewed with strict environmental considerations put in place. In future regulatory authorities should come up with standards of equipments and raw materials used in the construction plants to reflect those of Western counterparts. Reduction and ignoring of safety standards should be met with strict penalties because they should not be taken as part of cost cutting mechanisms for companies. Cost cutting is not an option in the future in the wake of Bhopal disaster.
It is important for governments to consider considering separating risk operations from equipments or plants near settled areas. In the context of Bhopal tragedy the government and local authorities should have taken the ini9tiative of relocating people before the company was authorized to start its production processes. Regulators and government authorities should come up with ways of guarding operating processes combined with safety check measures so as to ensure a certain degree of safety of dangerous plants. At the same time employees should be trained on high levels of safety and awareness should be created through training programs to avert such disasters. Organizations should strive to maintain high levels of employee quality hence the number of workers should be decreased in the view of cutting cost.
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