Golden rules of improving reliability are
- Summation of all stress and strains must be < than the strength, stiffness and resilience of the system to eliminate early, repetitive or infant failures. This addresses 3 to 5% of all failures in a system
- Balance all interactions to eliminate all random failures. This addresses 80 to 90% of all failures in a system
- Improve wear resistance and prevent accelerated deterioration to prolong life and eliminate all wear out failures. This addresses 5 to 7% of all failures in the system
- Think in systems and Baysian Probability to anticipate, monitor and eliminate all failures
Classification of Failure Modes of an engineered system:
- Early Failure Modes — due to stress, strain, pressure, flow, thermal gradients — 3 to 5% of all failures
- Random Failure Modes — related to interactions, balance and feedback loops — 80 to 90% of all failures
- Wear Out Failure Modes — due to tribological imperfections of surfaces, interfaces and materials — 5 to 7% of all failures
Basic Theorems
- Machines are complex systems with hidden imperfections.
- Higher the interactions; more are the feedback loops and more are the chances of random failures
- Small changes create dramatic changes in the output, performance quality and failures
- Right Interactions of opposites play a vital role in maintaining the integrity and reliability of an engineered system
- Improvement can only be done by continually negating the imperfections hidden in the interdependent interactions
Steps of the Reliability Improvement Process:
- Improve Inherent Reliability by eliminating failures (Analysis)
- Avoid Consequences of Failures (Planning)
- Maintain a system based on conditional probability of a failure hidden in the interactions (Algorithms)
- Prevent accelerated deterioration (Engineering actions and practices)
- Draw up a superior specification for the next engineered system to be procured.