Is preventive maintenance a second class effort?

Stanton McGroarty asks when the schedule tightens, which work gets cut.

By J. Stanton McGroarty, CMfgE, CMRP, senior technical editor

The KPI for the percent of preventive work completed on time is the percentage of the PM, PdM, and condition-monitoring work completed during a time period that was done on schedule. For the balance of this document, we will use PM as the shorthand for all three classes of work under discussion.

Derivation: To be completed on time, PM work must first be completed. Work that is begun but not completed is excluded from the computation until next period. PM work is not truly completed until the data, costs, and lessons learned have been captured for future decision making. This is the organization’s best defense against solving the same problems time after time. A PM work order has been completed when data have been collected, periodic maintenance has been performed, work orders for corrective maintenance have been placed as required, and any other necessary data have been entered to the CMMS system.

As with corrective work orders, maintaining this KPI requires the establishment of a method for setting expected completion dates. Some maintenance scheduling systems have start and finish date fields for work orders. Some have only start dates and estimated durations. It may be necessary for the organization to agree on what it will use for work order due dates. Consistency is more important here than the precise definition, but a clear definition of completion is essential.
Percentage completion can be computed in two ways:

  1. Percent of PM Work Completed on Time = Total Number of PM Work Orders Completed on Time/Total Number of PM Work Orders Completed in the Same Period
  2. Percent of PM Work Completed on Time = Total Man Hours of PM Work Completed on Time/Total Man Hours of PM Work Completed in the Same Period.
J. Stanton McGroarty, CMfgE, CMRP, is senior technical editor of Plant Services. He was formerly consulting manager for Strategic Asset Management International (SAMI), where he focused on project management and training for manufacturing, maintenance and reliability engineering. He has more than 30 years of manufacturing and maintenance experience in the automotive, defense, consumer products and process manufacturing industries. He holds a bachelor of science degree in mechanical engineering from the Detroit Institute of Technology and a master’s degree in management from Central Michigan University. He can be reached at smcgroarty@putman.net or check out his .

Tracking the percentage of PM work orders completed is recommended, as the two measures tend to track closely. There may be a tendency at first to reduce the scope of work orders to provide earlier closure and a higher score. This is to be avoided, since it tends to leave work undone.

Significance: The ability to plan, estimate, schedule, and complete PM work predictably is the foundation of all preventive maintenance. If this basic sequence of operations cannot be established or is constantly interrupted, all asset health care performance is in jeopardy. There is often a tendency to postpone PM work first when schedule breakers occur. This is a mistake. It may reduce the pain of schedule changes somewhat, but it begins a trip down the slippery slope to unplanned maintenance.

As with corrective maintenance, on-time PM completion rates of less than 80% indicate that a maintenance area is out of control. Sadly, measurement and improvement often start with effective rates of 0%, since definitions of completion are often not in place to support scorekeeping.

The journey from 80% to 90% on our PM-completion KPI indicates predictability has been achieved. OEE control can also be achieved as predictability of maintenance completion approaches 90%.

Getting started: The PM-completion-rate KPI demonstrates the degree of commitment to PM. PM planning must be established and woven into the routine of all PM work. Planning must include accurate estimation of resources involved in executing work orders. This requires a closed-loop system for improving inaccurate estimates. Scheduling that is driven by accurate estimates and balanced against actual staff availability must follow. Weekly planning and scheduling meetings will be required to develop and publicize accurate schedules. Finally, each work order must be closed with the return of equipment to production, the documentation of lessons learned, and the return of maintenance resources for the next job.

Want to learn more about KPIs? Check out "A process for developing key performance indicators (KPIs)" by Daryl Mather.

Assessment of today’s situation: Using today’s KPI, we would say that effective PM requires that PM planning and execution run as a predictable routine 90% of the time. If the maintenance organization gives in to the temptation to routinely perform unplanned maintenance at the expense of PM work, the system will become more and more reactive as missed PM work causes unplanned failures in the production system. Once this change occurs, reactive maintenance destroys OEE, creating a huge competitive disadvantage.

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