Types of Equipment Maintenance Strategies

Condition-based maintenance (CBM or CBM+) is a strategy of performing maintenance on a machine or system only when there is objective evidence of need or impending failure. CBM is enabled by the evolution of key technologies, including improvements in - sensors, microprocessors, digital signal processing, simulation modeling, multisensor data fusion, reliability engineering, Internet of Things (IoT) connectivity, data warehousing, cloud computing, machine learning (ML), artificial intelligence (AI), and predictive analytics. CBM involves monitoring the health or performance of a component or system and performing maintenance based on that inferred health and in some cases, predicted remaining useful life (RUL). This predictive maintenance philosophy contrasts with earlier ideologies, such as corrective maintenance — in which action is taken after a component or system fails — and preventive maintenance — which is based on event or time milestones. Each involves a cost tradeoff. Corrective maintenance incurs low maintenance cost (minimal preventative actions), but high performance costs caused by operational failures. Conversely, preventative maintenance produces low operational costs, but greater maintenance department costs. The result is the additional hidden cost associated with disposing of components that still retain significant remaining useful life. Such early retirements also drive more demand for spares and higher procurement costs over the life cycle.

 

Operational availability (military) or overall equipment effectiveness (industrial) is also affected by maintenance choices. Overly corrective or overly preventive maintenance strategies can reduce true availability through too much downtime due to maintenance. On the corrective side, running to failure or near failure typically leads to more significant operational issues and consequential damage. Lost production, downtime, and more significant maintenance often result. On the preventive side, the equipment is often unavailable because it is being more frequently maintained than optimally required in order to conservatively prevent failures. There is also a greater likelihood of maintenance-induced failures, which can have a negative effect on cost and availability. The more one disassembles or modifies well functioning equipment, the greater the chance that one will introduce a new problem or confounding issue.

Implementing better maintenance practices is driven by the desire to reduce the risk of catastrophic failures, minimize maintenance costs, maximize system availability, and increase platform reliability. These goals are desirable for aircraft, ships, ground vehicles, and industrial manufacturing of all types. Given that maintenance is a key cost driver in military and commercial applications, it is an important area in which to focus research and development efforts and drive continued engineering improvements.

About the Author

Carl Byington became an expert in prognostics and health management (PHM) technologies and next-generation condition-based maintenance plus (CBM+) solutions. You can view some of Carl’s past work on his Slideshare and Researchgate pages. Also see PHM Design company, located in the Atlanta, GA area, services offered for some potential engagement roles.