The Unfolding of Bhopal Disaster - Assignment Example

Health and Safety Introduction: Environmental Risk Assessment Health and safety is relatively a new field. It is developed into various disciplines such as epidemiology, toxicology, engineering, and statistics. These fields have developed different approaches of risk assessment. The methods of risk assessment developed focus on types of risks of concern. Failure Tracing Methods In the hazard identification phase, failure tracing methods are identified. There is several failure tracing methods that can be used to predict or investigate failure in high consequence installations such as nuclear power stations. These methods are: Fault Tree Analysis (FTA) Event Tree Analysis (ETA) Hazard and Operability Study (HAZOP) and Failure Modes and Effects Analysis (FMEA). Failure tracing methods are used in detailed risk assessments and also referred to as advanced risk methods. They do not apply to simple cases and their complexity offers a systematic method in identifying hazards, calculating failure probabilities and quantifying risk assessment. This discussion will focus on Fault Tree Analysis (FTA) and Hazard and Operability Study (HAZOP) (Khan & Abbasi 1998, pp.263-266). Fault Tree Analysis (FTA) This model is an analytical technique that highlights an undesired state of a system, especially a state that tends to be harmful to the environment. The analysis is done based on the dangers the system posses to the environment, and credible ways through which a harmful event may occur. The faults could arise from human errors, hardware failure, or a pertinent event that leads to an undesired occurrence. From the fault tree, logical interrelationships between the events that lead to the undesired event are shown. The undesired event is placed as the top event in the fault tree. The fault tree uses graphic models combines parallel and sequential faults that derive to the predefined undesired event (Donohoe 2003, pp. 576-580). The model does not point out to all possible failures of a system. It is only tailored to the top event that corresponds to a particular mode of failure. It therefore includes faults that are not exhaustive though they cover the most credible faults analysed by analysts and do contribute to the top event. The model is also not quantitative but qualitative. This makes FTA to be qualitatively evaluated although it can be quantified. The model consist of entities called gates that serve as permits or inhibits to passages in the fault logic up the tree. From the gates, a relationship between the events required for a higher event is established. The higher event becomes the output for the gate, as the lower event retains the input level. The gates serve as analogous switches (U.S. Nuclear Regulatory Commission, 1981, p. IV-1). Symbols Symbols are the building blocks of the fault tree. Primary events are undeveloped events due to some reason or reasons. Therefore, probabilities for occurrence of other related events resulting from the primary event are provided to arrive at the top event. Primary events exist in four types: Basic Event Conditioning Event Undeveloped Event External Event. A simple Fault Tree Analysis looks like this: Fig. 1 Major Symbols Used FTA symbols are grouped into primary event symbols, intermediate event symbols, gate symbols and transfer symbols (U.S. Nuclear Regulatory Commission, 1981, p.IV-4). Table 1 NAME SYMBOL USED OR GATE: Output fault occurs if at least one of the input faults occurs AND GATE: Output fault occurs if all input faults occur PRIMARY FAILURE or BASIC EVENT: This event requires no further development. INTERMEDIATE EVENT : A fault event that occurs due to one or more antecedent causes acting via logic gates UNEXPLORED EVENT: This is for an undeveloped event due to insufficient consequences or unavailable information. CONDITIONING EVENT: Grants specific, conditions or restrictions applying to any logic gate. Applications This model can be applied to the following cases: Issues with large perceived threats of loss. Several potential contributors to mishaps, Multi-element systems or processes Undesirable events already identified and Autopsies Benefits of Fault Tree Analysis The model displays chains of events or conditions that lead to a loss event. From identification of potential contributors to failure, critical issues are highlighted. This gives further insight into the characteristics of the system. The probability factor gives room for qualitative and quantitative insights into the loss event highlighted for analysis. From this insight, resources required to prevent failure are easily identified. Guidance for deploying resources is simplified, utilising control of risk and enabling documentation of analytical results (Clemens, 1993, p.7). Assumptions and Limitations of FTA The model is non-repairable and has no room for sabotage. According to Markov, Fault rates are constant, as the future is independent of the past. This implies that the future states the system relies on the present state and the pathways currently available to it but not how it was achieved. Bernoulli further criticises the model by stating that each system analysed has two mutually exclusive states (Clemens, 1993, p. 9). Analysing Fault Trees Analysis of the model is achieved through quantification of the probability of each event. This is achieved from calculations, measurement, and manufacturers’ data amid other factors. After the Fault Tree has been constructed, probability data is keyed in to calculate the probability of the occurrence of the Top Event. This gives the safety practitioner ideas on controlling any hazard. The simple rules followed are: For an AND gate, multiply the probabilities and For an OR gate, add the probabilities. Failure probability sources can come from manufacturers’ data, industry consensus standards, MIL standards, historical evidence from same or similar systems, simulation, Delphi estimates and ERDA Log Average Method. FTA Analysis The Gates define the cause of the model, later on used to derive the cause of the top event. There are two gates commonly used in FTA: OR-gate and the AND-gate. Other gates are used under special cases of these two. They include INHIBIT-gate and EXCLUSIVE OR-gate. The OR-gate This gate shows that the output event happens when one or more of the input event occurs. The input events could be many to an OR-gate. Example 1: Analysing Causes of Failure of a Valve in a Nuclear Plant: The top event is Valve B closed. Therefore probable events that could lead to this happening could be that the valve closed due to; hardware failure or human error or testing. The fault tree will look like this: Fig. 2 The OR-gate implies that the input faults do not validate the output fault since the inputs are identical to the output are identified as a source of cause. The subevents can be developed further. For example, valid reasons can be developed as to why the valve closed due to human error. It could arise from a reason that the valve could have been inadvertently closed during maintenance or that the valve was not opened after the last test (U.S. Nuclear Regulatory Commission, 1981, p.IV-6). The AND-gate This gate is used to validate that the output fault happens when all the input faults occur. The input faults could be several to an AND-gate. Example of an AND-gate: DC Power Failure in a Chemical Processing Plant For the DC power failure to happen, the diesel generator 1 and 2 failed, as well as the battery. All these inputs collectively resulted to total failure of the DC power. Fig. 3 Dependencies must be incorporated when explaining input events in an AND-gate. This is applied only when the dependencies affect the system logic. These dependencies exist when the first failure happens, causing the system to adopt a standby unit automatically. The second failure is analysed from the standby unit, defined as input B arising from occurrence of A (U.S. Nuclear Regulatory Commission, 1981, p. IV-7). Hazard and Operability Study (HAZOP) Introduction Hazard and Operability Analysis (HAZOP) is a technique used for system examination and risk management. It is well structured and systematic, used to identify potential hazards and operability problems that may lead to compromised products. This model relies on a theory that assumes that sources of risk events arise from deviations from design or operating intentions. This helps stimulate team members through brain storming, exploring possible deviations. HAZOP is used as a risk assessment tool, and described as a brainstorming technique of a qualitative risk assessment, with an inductive approach. Unlike FTA, HAZOP is a bottom-up risk identification model. It applies best in environmental and safety cases. Definitions Hazard is any operation that causes a catastrophe through release of toxic or flammable chemicals and results in injury to workers and environment. Operability refers to an inside operation designed to envelope and cause a shutdown. The shutdown could probably relay a violation of the environment, health or safety regulations. Importance/ Applications This model is used to assess hazards in facilities, equipment and processes. It has the potential of assessing systems from several perspectives. These are: Design: The design of a plant is assessed to confirm its conformity with specifications and safety standards. The weakness of a system is analysed to its best. Physical and operational environments: The environment where the plant is situated is assessed to ensure that the plant is well placed, supported, serviced and contained. Operational and procedural controls: Engineering tools are assessed. The operations involved and procedures are controlled. Operational modes such as start-up, standby, normal operation, steady and unsteady states, normal shutdown and emergency shutdown are analysed. Advantages The model is the best for confronting hazards that are not easily quantified. These could be hazards rooted in human performance and behaviours, undetectable, isolated, uncountable and unpredictable events. The model does not require quantification through rates, measure of deviation probability, and severity of impact. Ideas are easily developed through room for creativity by brainstorming technique. The system stands to be systematic and comprehensive, making it simpler than FTA. Its intuitive approach makes it a commonly used approach as a risk management tool. Disadvantages Hazards that involve interactions between different parts of a process cannot be assessed. Since risks are not ranked in order of priority, teams are likely to opt for build-in capability, ignoring other important issues that could be used in mitigation measures and decision making. The existing controls have no outlined protocol of assessment. This may require interface HAZOP with other risk management tools. HAZOP Methodology The model is executed through four phases, namely definition, preparation, examination and documentation and follow-up. Definition Phase In this phase, team members are identified since the model applies a cross-functional team effort and specialists. The specialists must come from different disciplines, skilled and experienced. Their ability in intuition and good judgment makes the model successful. Knowledge in system deviation, positive thinking and frank discussion play key roles in guiding the specialists. The team identifies assessment scope so that a focus effort is achieved. Study boundaries must be earmarked, as the key interfaces and key assumptions are highlighted. Preparation Phase Activities involved in this phase are: Supporting data and information required are identified and located The users and audience in study are identified Issues of project management are prepared A template format is developed by consensus. The template is used to record study outputs. HAZOP guide words are arrived at through a consensus during the study. In the execution phase of HAZOP, HAZOP guide words are used as supporting elements. Guide words stimulate imaginative thinking that helps in studying and creating elicits ideas and discussion. The guide words identify deviations from the intended design through a questioning process. It is the responsibility of the risk assessment teams to identify appropriate guide words. Some of the guide words used are: no or not, other than, more, early, late, less, after, and before. The guide words can also stimulate potential risk analysis available in other risk assessment tools. The guide words developed provide a systematic approach towards brainstorming potential deviations necessary for operations. For example, a guide word like ‘No’ or ‘Not’ will be followed by a statement such as ‘No detergent added’. Selection of guide words paves way for examination phase. Examination Phase All elements required in the system or process is examined. The physical systems may require simplification, achieved through breaking down of the system into smaller parts of importance. Processes will require further breakdown into simple, discrete phases, as similar steps are grouped together to make assessment easier. The guide words are applied to each element. It is not compulsory that the guide words and elements will always be sensible. The reasonable and misused conditions are further challenged, to determine their credibility. In case they lack credibility in deviations, documentation should be avoided (Kletz 2006, pp. 65-67). Documentation and Follow-up Phase A template that meets IEC Standard 61882 is used for documentation. The risk assessment team has the ability to modify the template to fit its assessment. From the template, study outputs and conclusions are derived depending on the nature of risk assessed. HAZOP is an effective communication tool and must be presented to stakeholders frequently. Example of HAZOP Analysis A common mistake in industries is taking of unwarranted credit for safeguards. HAZOP analysis can be used for a solution. In most cases, teams identify alarms, shut-downs and controls, and assume them as sources of safeguards. Most alarms are never tested and may fail when required to work. Frequent alarms are viewed as a nuisance. This creates room for ignorance, rendering them ineffective. Operators are never keen on monitoring the control panel as automatic control routines take the manual mode. In this example, we look at a chemical industry that produces its products from chemical reactions. Sodium is mixed with hydrochloric acid to produce sodium chloride and water. Sodium chloride is used as table salt for human consumption. Too much or too little sodium or hydrochloric acid will lead to inadequate reaction and production of toxic substances. It is the responsibility of the HAZOP team to review adequacy of the design. Guide words and process of the parameters reveal the flow at a study node. Table 2 Guide Word Parameter Deviation Consequence Cause Action No flow No flow Inadequate chemical reaction. Sodium chloride required is not produced There could be a pump, and valve failure. Sodium could be exhausted Hydrochloric valve should automatically close. Less Flow Less flow Low chemical reaction, hence the sodium chloride required will not be produced HCL valve partly closed, Sodium valve partly closed. HCL pump could be erratic or there could some leakage. The valve responsible for discharge of sodium chloride should automatically close. Part of Flow Decrease he normal flow of chemicals Chemical reaction inadequate Wrong product delivered Confirm the product supplied its concentration and conformity to required standards. Case Study: The Bhopal Disaster Background Information The Bhopal Disaster occurred on 2nd and 3rd December, 1984, in the city of Bhopal. The Union Carbide Pest Plant is located five miles away from the city. The plant released poisonous gases that killed 3,000 people, with 8,000 fatalities. Some of the gases attacked wet parts of the body such as eyes, mouth and throat. When inhaled, it reacted with the body organs, drowning the person to death. The death toll rose to 20,000 to date, as more than 120,000 continue to suffer from ill health problems. The disaster is termed as ‘an accident waiting to happen’, when compared to other similar plants in US and India. Negligence by management in the design phase in the name of cutting costs is attributed to the disaster. The cost of safety and the value of human life were neglected. The reports issued by scientists from Union Carbide Corporation and warning of possible accidents were ignored and the senior staff were never informed (Eckerman 2005, pp. 213-217). Fault Tree Analysis was used to identify lessons learnt from the disaster to verify that it was an accident in waiting to happen. This is achieved by: Discovering technical sources of system failure due to design: carbon steel pipes used instead of stainless steel pipes were susceptible to corrosion. Quality safety devices were reduced in number yet manual. Emergency planning measures were ignored. Identify the cause of system failure Use FTA to determine such probability and Derive recommendations (Khan & etal (2001, pp. 45-50). Fig. 4 Fig. 5 Fig. 6 Fig. 7 Discussion The safety and maintenance standards of the plant deteriorated to cataclysmic levels despite the previous warning reports from UC internal report. The management dropped operating and safety standards of the Bhopal plant below maintenance levels of other such facilities. This was due to lack of safety and environmental laws and regulations not enforced by the Indian government (Eckerman 2011, pp.302-305). The UC never identified the cause of the accident but shut down the plant until safety devices were put in place. The FTA analysis helps to highlight areas of weakness in a system, areas that need attention through addition such as built-in-testing, redundancy, or preventive maintenance. The model also acts as a knowledge-base of system failure and can be used to diagnose or find faults in the system. The system’s reliability is then derived to help in improving the system (Labib and Champaneri, 2012, pp.41-45). Conclusion As most countries are interested in attracting foreign investment, basic safety requirement for employees is necessary. For such projects, the designs of installation must be reviewed and stringent environmental, health and safety measures adopted. The standard of building material and equipment should be tested and meet the required standards. Safety standards should not be compromised in return of profit margins (Gupta 2005, pp.197-199). Government institutions must be aware of the need for segregation of dangerous operations from such facilities and the domestic population around them. For example, the Bhopal community should have been relocated before the company could be given permission for mass production of dangerous substances. Operating processes must be guarded to develop a habitual safety culture. A safety culture developed creates a questioning attitude rather than a chastised one. Safety should be the optimum driver but not profit margin. Safety training of employees on hazard awareness plays the key role in controlling disasters in the work place (Chouhan 2005, pp. 205-208). Significance of Study The study illustrates that learning is achieved through three perspectives: Communication from the users in charge of maintenance to design, Incorporation of advanced models such as FTA, HAZOP and other models in innovative application, and Implementation of interdisciplinary approaches. The outcome is that future disasters from such projects can be mitigated through recommendations derived from the models of analysis. Governments are responsible for health and safety considerations to employees. The models such as FTA and HAZOP act as tools used to develop a generic approach for any future disasters. References Chouhan, T.R (2005). The unfolding of Bhopal disaster. Journal of Loss Prevention in the Process Industries 18. Elsevier. Pp. 205-208. CLEMENS, P. L. (1993) Fault Tree Analysis. 4th ed. Available from: http://www.fault tree.net [Accessed 23rd March 2013]. Donohoe, M. (2003). Causes and health consequences of environmental degradation and social injustice. Social Science & Medicine 56. Elsevier. Pp.573-587. Eckerman, I. (2011). Bhopal Gas Catastrophe 1984: Causes and Consequences. Encyclopaedia of Environmental Health. Elsevier BV. Pp 302-316. Eckerman, I. (2005). The Bhopal gas leak: Analysis of causes and consequences by three different models. Journal of Loss Prevention in the Process Industries, Vol. 18, Issues 4 6. Elsevier BV. Pp. 213-217. Gupta, J.P. (2005). Brief Report on the conference; Bhopal Gas Tragedy and its effects on process safety. Journal of Loss Prevention in the Process Industries 18. Elsevier. Pp.197 199. Khan, F. I. & Abbasi, S.A. (1998). Techniques and methodologies for risk analysis in chemical process industries. Journal of Loss in the Process Industries 11. Elsevier. Pp.261-277. Khan, F.I. & etal (2001). SCAP: a new methodology for safety management based on feedback from credible accident-probabilistic fault tree analysis system. Journal of Hazardous Materials A87. Elsevier. Pp.23-56. Kletz, T.A. (2006). Accident investigation: Keep asking “why?”. Journal of Hazardous Materials 130. Elsevier. Pp. 69-75. LABIB, W.A. and CHAMPANERI, R. (2012) The Bhopal disaster – Learning from failures and evaluating risk. Maintenance & Asset Management, 27 (3). USA. U.S. Nuclear Regulatory Commission (1981) Fault Tree Handbook. Systems and Reliability Research Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission Washington, D.C. 20555. Read More