Using a System Reliability Model to Optimize Maintenance Costs A Best Practices Guide
SAE JA6097 (“Using a System Reliability Model to Optimize Maintenance”) shows how to determine which maintenance to perform on a system when that system requires corrective maintenance to achieve the lowest long-term operating cost. While this document may focus on applications to Jet Engines and Aircraft, this methodology could be applied to nearly any type of system. However, it would be most effective for systems that are tightly integrated, where a failure in any part of the system causes the entire system to go off-line, and the process of accessing a failed component can require additional maintenance on other unrelated components.
Complex repairable systems that consist of many individual components can be designed to be quite reliable, at least when they’re still new. However, as such a system continues to be used and repairs are made to address failures that occur, the interval between failures gets shorter and shorter. Eventually, that complex system becomes a collection of parts, each with a different amount of operating time and differing reliabilities. Maintenance intervals that may have aligned with one another when the system was new will eventually become misaligned, making maintenance more complicated, or at least sub-optimal and more expensive. It is not uncommon to have a repaired system returned to service only to be shut down shortly thereafter because of another failure.
The classical Reliability Centered Maintenance (RCM) process does a good job of focusing attention on the actual reliability and failure modes that is (or will be) exhibited by a particular system, and helps a system designer, implementer, or operator develop an effective maintenance strategy for that system. However, the RCM decision logic only looks at the individual components and doesn’t address how to reconcile different maintenance intervals for each component across the entire system. Furthermore, RCM focuses more on preventive maintenance (lubrication and failure finding tasks) and doesn’t really address corrective maintenance. So when a complex system is taken out service for maintenance, there is no guidance as to what other optional maintenance should be performed to increase the time until the next failure and/or reduce long-term operating costs.
This “Best Practices Guide” describes a proven approach for objectively determining what other maintenance should be performed when a system is being repaired to improve system reliability and reduce long-term operating costs.