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Preventative vs Corrective Maintenance

I have mentioned the magic of numbers in previous posts. Recently I read that HVAC manufacturers and maintenance professionals recommend that 70% of your maintenance budget should be spent on preventative maintenance and the remainder (30%) spent on corrective maintenance.

While this is an admiral goal, I have to disagree (albeit in a positive sense).

I will be the first to agree that doing things by the numbers is not a good management methodology. Using a theory to manage a maintenance process can only lead to blind spots, missed opportunities, and lack of insight into the daily status of your operation.

However, it continues to amaze me how often the summary data from a client's operation continues to conform to long-held numerical guidelines. Data that matches the 80/20 rule shows up so often that we no longer consider it a rule, but a "law", and just like gravity we always look deeper when this particular ratio is breached. In other words, if your maintenance budget is not falling within the 80/20 rule for preventative vs corrective, then something is ripe for improvement. The greater the percentages vary from this magic ratio, the more likely there is opportunity to make improvements.

Can you improve on this ratio? Maybe, but I have never seen a client consistently maintain a higher ratio than 80/20. In fact, the majority of clients are still working towards reaching this elusive goal.

Is it possible for assets used in heavy industries (like mining, gas, materials processing, chemical) to ever reach this ratio? The answer is a qualified 'Yes". Static assets like pipe work and non-moving part assemblies often reach, or exceed the 80/20 rule. Of course the decision as to what  forms maintenance on these kinds of assets is germane to the question. Assets with moving parts, subject to temperature extremes or very heavy loads, high RPM counts, or very dusty/wet conditions often experience higher corrective maintenance rations.

Interestingly, static assets are often difficult to bring to the required ratio depending on the maintenance performed. On the other hand, assets that might be considered poor candidates for the target ration often lend themselves to improvements in lubrication regimes and increased frequency of maintenance cycles that result in closer scores to the 80/20 ratio.

It should go without saying that the goal is NOT to reach the 80/20 ratio as an isolated objective. The goal, as always, is to minimize downtime so the operations/production department can maximize utilisation.

Posted by Mark Chimes
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