It was late afternoon at a recent maintenance and reliability conference when a young aerospace engineer asked a session presenter, “How can we measure the improvement in our preventive maintenance (PM) program? We've started putting much effort into PM optimization, and we want to see tangible results.”
That question resonates deeply with many people on the plant floor, and it's not hard to understand why. After investing time, resources, and hope into optimizing PM programs, the crux lies in gauging the effectiveness of these improvements.
To do this, first, ensure the maintenance system and associated processes are implemented to help get the correct data. Ask, “Without opening individually completed PMs, can I query the system and report the specific PMs where corrective actions were generated from the inspection?” Then, ensure the technicians follow the proper business process to get the data based on the system implementation.
Depending on the system implementation, leverage corrective actions from the PM or PdM as a work type or the ability to generate follow-on (child) corrective work orders that link to a specific PM as needed. Simply adding notes to the PM work order itself will not typically enable you to efficiently analyze the value of any PM task list across many work orders. The same concept applies to items like failure codes as well.
Let's break down some metrics and indicators that can help you determine the effectiveness of your PM optimization efforts.
The ratio of reactive work hours to total maintenance labor hours—Trend the ratio, as effective PM optimizations should reduce reactive maintenance work. A decline in emergency repairs compared to proactive maintenance tasks is a promising sign.
Bad actor reporting—Compile a Pareto listing of the top 10 or 20 assets creating the most downtime across the plant for a specific period (i.e., 30 days). If the PMs have been optimized for the assets in the listing, then the optimization did not address the failure modes if they are maintenance related. Query to determine what corrective actions were identified from the PM or PdM activities and act to resolve future potential failures accordingly. If the asset PMs have not been optimized, these assets should be next in line for improvement.
Root Cause Analysis (RCA) outcomes—If you consistently address the same issues even after your PM optimization, something is amiss. Effective PM strategies should lead to fewer recurring problems.
Overall Equipment Effectiveness (OEE)—Three components (availability, productivity, and quality) within the calculation can provide insights into PM optimization's effectiveness when contrasted with historical data. As preventive maintenance becomes more effective, unscheduled downtimes should decrease, increasing both equipment availability and OEE.
Mean Time Between Failures (MTBF)—PM optimization should lead to an increase in the MTBF of your assets. If you find that your MTBF is growing, it's a strong indicator that the health and reliability of your assets have improved. In the maintenance system, equipment types or classes provide a mechanism to determine MTBF improvements in a specific size of pumps or motors (i.e., 48 months to 60 months to 72 months).
Qualitative feedback—While not a metric, don’t overlook the value of operator and technician feedback from the plant floor. Their frontline feedback about machine behaviors, asset efficiencies, and the effectiveness of the PM tasks can provide nuanced insights that numbers might miss.
PM optimization activities should provide increased precision maintenance approaches by incorporating specifications like torque, gaps, fits, and tension as examples. Yet, success is dependent on the skills of the workforce as well. With more than 70% of failures self-induced and 40% driven by human error, are operators and technicians making fewer errors? Is additional training required? Does management enforce the precision approach? Is rework as a metric declining?
These metrics and insights, when taken together, provide a holistic view of the health of your maintenance program. Conversely, be aware of overly conservative PM approaches. Too much maintenance wastes resources and money. The challenge is to strike a balance based on the business risk.
Finally, remember that the process is iterative for those on the journey of PM optimization. Regularly review and tweak your strategies based on the feedback from these metrics. In doing so, you ensure your preventive maintenance program is optimized, continually evolving, and improving.
