Planning and Scheduling / Wrench Time

The most dangerous metric in scheduling

Doc Palmer examines why measuring schedule compliance is a sometimes controversial (but vital) task.

By Doc Palmer, PE, CMRP, Richard Palmer and Associates

The sixth principle of scheduling pertains to the use of schedule compliance. Schedule compliance is probably the most dangerous of all maintenance metrics or key performance indicators (KPIs). Schedule compliance is a critical metric for managing maintenance to improve productivity and reliability. Unfortunately, most plants use this metric in such a wrong way as to keep both from improving.

The primary purpose of schedule compliance should be to determine whether the plant is properly preparing the weekly schedule, but most plants incorrectly use it to see whether supervisors are honoring the schedule. In school, the best grade is an “A” – usually 90% to 100%. If plants use the metric to find out whether supervisors honor the schedule, they would expect an “A.”

But consider that fairly reliable plants might have roughly 20% reactive work and 80% proactive work. Right away, if crews start weeks with fully loaded schedules, the most they should expect from schedule compliance would be 80%. Let’s say that to compensate, the plant slightly loads the schedules to allow some break-in work and unexpected absences. Therefore, the plant might schedule only 70% of the available labor hours, expect 95% subsequent schedule compliance, and complete a normal amount of work. Crew supervisors would receive an “A.” Unfortunately, the plant may have unwittingly sabotaged itself by not loading crews with enough work to increase productivity.

Better plants use scheduling to go beyond their normal productivity. Normal plants have typical maintenance productivity at only 35% wrench time. These plants are profitable, and their maintenance teams complete all the reactive work. Nevertheless, to increase productivity beyond normal, better plants should schedule more work than normal. By scheduling only a normal amount of work, wrench time will stay at the normal 35%. To increase productivity beyond 35% wrench time, schedules must give crews more work.

For superior wrench-time productivity, a plant should create weekly schedules loaded with 100% of the next week’s available labor hours. Management should expect 40%–90% schedule compliance. Scores below 40% might mean that supervisors aren’t honoring the schedules; scores higher than 90% usually mean schedules aren’t being loaded properly.

Measuring schedule compliance also involves controversy about whether to measure daily compliance, whether to use hours or simple quantities of work orders, and whether to give rewards or penalties for any extra work. First, there is so much churn in a normal maintenance day that supervisors frequently move things around. Focusing on the week as a whole leads to high productivity without obsession about the daily result. Second, with respect to hours or work orders, using sheer numbers of work orders rather than the hours makes it easier to communicate results. Hours get a bit confusing to explain. Consider if the schedule compliance calculation used hours: Strictly speaking, a job that was estimated for 10 hours but actually took 20 hours would get schedule credit for only 10 hours.

It is easier to explain and analyze numbers of work orders instead. Consider a crew that was scheduled 100 work orders and completed only 50 of those work orders. It is easy to show that the crew achieved 50% schedule compliance. Finally, avoid giving rewards or penalties for extra work so as to keep the focus on the success of the original schedule. Consider a crew that was scheduled 100 work orders but completed 200 work orders, of which only 50 were on the original schedule. Schedule compliance is properly measured at 50% (50/100). Schedule compliance is not 200% (200/100), which would reward the crew, nor is it 25% (50/200), which would penalize the crew.

A secondary purpose of the metric is to help the plant improve its reliability by identifying and analyzing the gap in its work management processes. What are the reasons the plant could not execute all of the work it thought it could? Management can best identify and correct work management issues if the plant properly loads the maintenance schedule and analyzes its success.