The basic idea behind condition-based maintenance (CBM) is not new. It answers the question, "Should maintenance or replacement be carried out on a piece of equipment?" If the equipment is in "good" condition, it should remain in service, but if it is in a sufficiently degraded condition, maintenance or replacement should be performed to prevent a breakdown on the job, which could potentially help avoid a major catastrophe.
Like many good ideas, implementing the principles of CBM can be difficult. What measurements are required to determine a machine's condition? What's the relative importance of each measurement? How do industrial operators obtain their data? what mathematical models are most appropriate for interpreting it? Which computer systems do industry decision makers employ? How can the eventual solution be designed to work on all of them? Condition-Based Maintenance, as its label implies, takes into consideration the actual condition of equipment when deciding whether maintenance is necessary. Measurements of the equipment's condition were, in earlier times, often quite crude. For example, engineers were once known to place a thin steel ruler against a bearing housing and hold the other end to their ear to pick up vibrations . . . if the vibrations were "as expected" or "normal", no maintenance was called for, but if they indicated a "rough" condition then replacement would be ordered. This technique is NOT one the CBM Lab has built into it model! Instead, to determine the risk of failure, measurements will be taken that will provide input of a much more reliable nature.
CBM represents the leading edge of maintenance decision-making, and its application in military aviation as well as in industry will mean significant economic gains for maintenance programs. To better understand CBM, it is useful to know where maintenance has been, where it is today and where it is going. The first, and most elementary approach by far, is Breakdown Maintenance — a strategy that simply specifies that when a machine fails, it is time for maintenance or replacement. This may indeed be the best choice, even today, under certain conditions, but almost all decision makers would agree it shouldn't be the only choice. Most organizations have progressed beyond this concept, and today employ what is often called Time-Based Maintenance. Time-Based Maintenance policies are founded on the belief that, given a history of failures of a given component, one can workout the probability of the component failing after a certain number of hours of use . . . or number of revolutions, or packages filled . . . or some other measurement.