Reliability Engineering Redundant Structure and Standby Units
Cold Standby, Perfect Switching, With Repairs
Possible States of a 2-Unit System with Cold Standby and Perfect Switching Unit A Unit B 4 O S 3 F 2 1
State Space Diagram 4 3 2 1
State Equations
Eliminating the Failed State
Laplace Transform Substitute s=0 Note that
Solution
Mean Time to Failure
Mean Time to Failure Take Laplace transform of R(t) Substitute s=0
Mean Time to Failure
Cold Standby, Perfect Switching, With Repairs, A Main Operating Unit
Possible States System Unit A (Main Unit) Unit B 4 O S 3 F 2 1
State Space Diagram 4 3
State Equations Where
Steady State Probabilities
Availability and Unavailability
Eliminate Failed State from State Equations Where
Treating State 0 as An Absorbing State Take Laplace transform and let s=0 Solution
Mean Times to Failure and to Repair Mean time to failure Mean time to repair
Cold Standby, Imperfect Switching, With Repairs, A Main Operating Unit
State Space Diagram 4 3
Steady State Probabilities
Availability and Unavailability
Mean Time to Failure
Partly-Loaded Standby, Perfect Switching, With Repairs, A Main Operating Unit
Possible States of a 2-Unit System with Partly-Loaded Standby and Perfect Switching Unit A Unit B 4 O S 3 F 2 1
State Space Diagram 4 3 1
Steady State Probabilities
L Spares, With Replacements and Repairs
State Space Diagram 2 2j 2L 1
Notation State 2j (j = 0, 1, …,L): A total of j spare units are in a repair queue, and (L-j) spares are normal. A failed unit in the system is being replaced by a normal spared unit, the system is working. State 2j+1 (j = 0, 1, …, L-1): A total of j spare units are in a repair queue, and (L-j) spares are normal. A failed unit in the system is being replaced by a normal spared unit, the system does not work. State 2L+1: All spares are in a repair queue. A failed unit in the system is under priority repair. This is a type of quasi-replacement.
Notation λ: Constant failure rate μ: Constant repair rate ε: Constant replacement rate
Steady-State State Equations
Steady-State Availability