Table 2. Failure Types and Frequencies for Steam Boiler. Failure Type Frequency (per year) Effect 0.15 Water level detector Electrical fault 0.05 0.2 Pressure switch fail Relief valve fail (a) or (b) (b) (b) 0.05 (11) Using the expected frequencies provided in Table 2, quantify this fault tree to show the expected frequency of the top event. Please note that the operator is at risk for 20 percent of the time that the boiler is operating. [20] Table 2. Failure Types and Frequencies for Steam Boiler. Failure Type Frequency (per year) Effect 0.15 Water level detector Electrical fault 0.05 0.2 Pressure switch fail Relief valve fail (a) or (b) (b) (b) 0.05 (11) Using the expected frequencies provided in Table 2, quantify this fault tree to show the expected frequency of the top event. Please note that the operator is at risk for 20 percent of the time that the boiler is operating. [20]