When referring to maintenance, people often forget to distinguish between different kinds of maintenance. Yet, correctly separating each kind is a pre-requisity for a well-managed business.
The first kind of maintenance is one we all know from taking our cars to the garage for a time- (i.e. annual) or distance-(i.e. every 10,000 miles) based check. During these routine maintenance, several parts, such as oil filters or brake pads, are being replaced as part of a preventive maintenance schedule. The rationale is that the economic cost is low enough to afford a ‘no matter what’ replacement as it’ll improve the reliability and safety of the car far beyond this cost. These maintenance schemes can be derived from historic data on a vast group of machines (in the case of cars) but can also purely result from engineering decisions made during the design phase (i.e. nuclear power plant maintenance). In both cases, cost and safety indicators are evaluated for both acting and not acting. The great advantage of preventive maintenance is that it can be planned and therefore, maintenance schedules can be optimized (some parts may last longer but are replaced because the machine is down for maintenance anyway).
The second kind of maintenance is reactive maintenance. As the name implies, this happens in reaction to an event (a failure or an indication of a problem – which doesn’t necessarily mean there actually is a problem). As one can’t plan for these events to happen, reactive maintenance is much more disruptive to the organization. Depending on the criticality of the failure, where it happens (in the case of moving assets), whether the machine is on a critical production path, etc. the failure can require an urgent intervention. When this can be served by maintenance teams not assigned to any other tasks, the disruption can be minimal (but one had to budget for the extra capacity!) but in most cases, rush interventions mean something else has to yield and the overall planned schedule gets turned upside down. This, and other direct and indirect costs means that reactive (and therefore unplanned) maintenance is 3-9 times more expansive than planned maintenance.
The third kind of maintenance is actually a subset of the first kind (preventive maintenance). It is, however, a fairly recent evolution in that techniques and technology now allow us to introduce predictive maintenance. It differs from pure preventive maintenance in that not fixed maintenance counters are put in place but rather a whole environment which allows the capture of both machine and non-machine data (i.e. weather, production schedule,…). This data is then gathered and (preferably automatically) analyzed in order to detect early warning signs of upcoming events. As such, the task of predictive maintenance is to foresee events which would have lead to reactive maintenance and transform them into planned events. This has the advantage of avoiding an unplanned event (which, as we saw, is 3-9 times more expensive) and allows the creation of a planned intervention which can become part of a preventive maintenance schedule.
Ideally, all events would eventually become planned. We all know this is pretty utopic. However, there are economic as well as qualitative arguments to set on a path towards predictive maintenance. Even if a few percent of the unplanned events an be turned into planned ones, the investment in predictive analytics (data capture, analytics software, new processes, etc.) is rapidly outweighed by the lower maintenance costs. However, other factors such as increased availability, employee morale, reputation and customer satisfaction may have even greater returns. So, when evaluating predictive maintenance, don’t just consider the many faces of maintenance but also look at the many faces of benefit to your organization.