Title: Accident analysis and Fault Tree exercise

Question 1 - Investigate one major industrial accident of your choice within one of the following industries:

• Energy (e.g. oil and gas, renewables, nuclear, etc.)
• Transportation (e.g. aviation, shipping, rail, etc.)
• Chemical (e.g. a solvent plant, a fertilizer plant, etc.)

Your answer should be presented as a concise (short) report in which you outline the context of the accident, identify the causes and consequences, and critically discuss the lessons learnt within the industry. The report should end with some brief conclusions.

You should include the Sequence of an Accident Diagram to support your answer. Feel free to use bullet points, graphs, tables, etc. if you think it will make your presentation clearer.

Ensure you search for appropriate sources of literature before developing your answer. Follow the Harvard referencing system.

Question 2 - A fault tree analysis is conducted for a chemical plant. The Top Event (TE) is already identified from the analysis of the failure data record. TE is caused by the occurrence of either intermediate event X1 or intermediate event X2. It is known that the occurrence of either intermediate events X11, X12, or basic event D, leads to the occurrence of event X1. When two basic events B and E occur simultaneously, X11 happens. When both basic events A and B occur simultaneously, X12 happens. It is also known that event X2 is caused by the simultaneous occurrence of another two intermediate events X21 and X22. Furthermore, X21 happens if basic events A and C occur together. Event X22 happens if basic events A, C and D occur simultaneously.

It is assumed that basic events A, B, C, D, and E all follow an exponential distribution. The failure rates for basic events A, B, C, D, and E are 0.00004/hr, 0.00002/hr, 0.00005/hr, 0.00003/hr, and 0.00001/hr respectively. Answer the following questions showing all calculations where relevant:

i. Using the Reliability Workbench software, draw the fault tree leading to top event TE. The TE should be labelled "Top Event: Chlorine gas release".

ii. Find the minimal cut sets.

iii. Using the minimal cut sets, explain how to avoid the occurrence of the top event TE.

iv. Calculate the occurrence probability of the top event TE at t=2,500 hours assuming that basic events A, B, C, D, and E are independent of each other. Present your answer to 5 decimal places.

Note: For parts ii and iv you may use the Reliability Workbench software or make manual calculations.