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"Cost Effective Predictive Maintenance" a Quarter-Century Later

Back in 1987, "Cost Effective Predictive Maintenance" by B.C. Howes, B.R. Long, and V. Zacharias, was published on eight pages in Pulp & Paper Canada, now in its second century as a digital, annual publication chronicling one of that nation's oldest industries.

The abstract reads, "Predictive maintenance is a concept that is generally accepted in the pulp and paper industry today.  For those mills considering the implementation of such a program, a key consideration should be whether the method chosen will be cost effective.  This paper briefly identifies several alternatives, and attempts to provide a method for evaluating the economics involved."

The study defines the target of its predictive maintenance as "machinery on which increasing vibration is a sufficient indicator of a potential problem and provides enough warning to allow repairs to be made in a timely fashion."

In Figure 1, they display a fanciful timeline showing the "Advance of maintenance practice."  This begins at the bottom with "TECHNOLOGICALLY BACKWARD MILLS" and proceeds through eight stages to TECHNOLOGICALLY ADVANCED MILLS," the latter a veritable maintenance Shangri-La noted for:

"AUTOMATED PREDICTIVE MAINTENANCE
WITH DIAGNOSTICS AS APPROPRIATE"
(survey everything: computer records & trends)
(use skilled workers to identify solutions)"

What dates the analysis most obviously is that, when it was written, "the state-of-the-art" was one or more maintenance specialists with "a portable instrument...used to take readings," one that "remembers them until they can be transferred back to the computer."  That computer then "keeps track of all the machines, test-points, and recorded data, " in addition to which "trending and historical analysis are done by the computer."

Major concerns of this early iteration of predictive maintenance were the cost of training and the high salaries of the specialized personnel needed to make the system work well, and the substantial expense of the machinery needed to make "periodic planned vibration checks on every piece of machinery" in a plant that could have hundreds of them.

It was felt that "...automation dramatically reduces the tedium of the job.  Fewer people are required to collect data, because using the instrument is so much faster than collecting data by had."

Today, vibration sensors take measurements at intervals chosen by the user, the results of which can, in real time, be fed straight into a computer with the specialized software to display and interpret them almost instantaneously.  With few exceptions, costly, complex, cumbersome manual meters have pretty much gone the way of the dodo bird.

However, the study concludes with words as true today as they were 26 years ago: "Predictive maintenance programs that improve maintenance practice can be a reality in every plant.  It is time to apply/benefit evaluation techniques, in order to make these programs as cost effective as possible.  Only in this way can predictive maintenance make the best contribution to the overall profitability of your plant."

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