09-07-2018, 10:37 PM
Candidate 5's attempt.
Question B1
A piece of equipment is used to prevent an unsafe action being implemented on a railway. It fails, on average, 80% right side and 20% wrong side, with a mean time between all failures of 10,000 hours. It has a mean time to repair of ten hours.
Three identical sets of this equipment are configured in a two-out-of-three voting system. The voting activity has a response time of one second. If the failure rate of the voting subsystem is ignored, calculate:
Question B1
A piece of equipment is used to prevent an unsafe action being implemented on a railway. It fails, on average, 80% right side and 20% wrong side, with a mean time between all failures of 10,000 hours. It has a mean time to repair of ten hours.
Three identical sets of this equipment are configured in a two-out-of-three voting system. The voting activity has a response time of one second. If the failure rate of the voting subsystem is ignored, calculate:
- how often a technician is required to attend to repair the triplicated system;
- the proportion of time that, through multiple failure, the system unnecessarily prevents operation of the railway;
- the mean time of the system being in a state where it would not prevent an unsafe action. [25 Marks]
PJW