In a process plant, a crane is being used to lift new equipment to be installed in the plant. The lift consists of the crane wire, the crane hook, and the strap securing the equipment so it can be lifted. Further, the wire is equipped with two braking systems: an engine brake that is normally operating and a brake pad that automatically engages if the engine brake fails. Assume that only one lift takes place. If the lifted equipment drops, people may be killed only if they are present in the area, and then, it may occur due to one of the following two reasons: The dropped equipment may hit a tank containing self-igniting liquid. It is assumed that if the tank is hit, liquid will always be released and ignited. If people are present, they will always be killed. If the dropped equipment does not hit the tank, it may hit people on the ground directly, if present. If people are hit, they will always be killed. The wire, the hook, and the strap can all fail. The engine brake and the brake pads can also fail. The following information is given: People present in area (Probability 0.1) Hit tank (Probability 0.1) People hit directly if present (Probability 0.1) Wire/strap/hook fails (Total probability of one of them failing 0.01) Engine brake fails (Probability 0.02) Brake pads fail (Probability 0.01)
Draw an event tree with hazardous event “Equipment being lifted” and with two end events: “Fatal accident” and “Nonfatal accident,” and calculate the probability of “Fatal accident” based on the event tree.