Modeling multiple preventative maintenance actions in a RAMS analysis

This paper describes how multiple preventative maintenance (PM) activities can be modeled in the availability and reliability analyses of complex systems, while using popular off the shelf software packages. This modeling method is a necessary and critical step for an understanding of the downtime implications of certain electromechanical subsystems and systems, but is not explained, nor easy to model with all software packages. Quite often, maintenance and service related actions are an afterthought in reliability and availability calculations. This is because most electronic systems require minimal maintenance of electronic circuit boards, components and sub systems. Electromechanical devices and assemblies are different. There are many situations where several maintenance activities on an ongoing, repeatable schedule are required in order to prevent premature faults and extend the useful life of the device. This is especially true of engines, motors, generators, cooling fans and any device that includes bearings or mechanical movement. This paper discusses an actual example of a radar power plant reliability block diagram (originally consisting of over 10 00 blocks) with redundant gensets that shows how the preventative maintenance dominates the down time and how failure rates play a lesser role in the availability of the power plant.