Probabilistic Risk Assessment of the Warning System:

Read Lesson VI - Reliability Block Diagram:

CDC: System Safety and Risk Management: NIOSH Instructional Module, PDF (Links to an external site.)

Management needs to make a risk-based decision. Perform a PRA on your chosen warning system given the probabilities shown in Figure 5.1. Note that events are NOT mutually exclusive in this problem. Assume that:

P(internal light failure) = 1 x 10-5
P(no voltage applied to light bulb) = 1 x 10-4

(The probability of no voltage being applied is given in order to simplify the problem.)

What is the probability the system will fail? What is the probability the system will not fail?

(Note: Reliability analysis calculates probabilities of success for stated periods of time under assumed conditions. Those ground rules apply here too.)

 

Warning System Circuit (with Probabilities) 1 (10) Float Switch 1 (10)3 Fuse 1 (10)3 Battery Supply Warning Light 1 (10)3 Cable/connector Probability