Maintenance schedules

What is preventive maintenance scheduling

Preventive maintenance scheduling can be classified into two distinct methods: Fixed PMs and floating PMs. Both methods can be used to track assets and determine when they should be inspected, repaired, recalibrated, or replaced. These two strategies for scheduling PMs allow maintenance facilities to accurately track maintenance triggers, maintain assets as effectively as possible, and use maintenance resources efficiently. The result is that assets run better and for longer without facilities incurring unnecessary costs or downtime.

What is fixed preventive maintenance scheduling?

Fixed preventive maintenance scheduling is when regular maintenance is scheduled at a certain time or usage interval, regardless of when the last PM was completed. Fixed PM scheduling helps plan work based on the target start date of the previous work.

For instance, a PM may be scheduled on an asset every Monday. Even if last Monday’s task was completed on Wednesday, or was never completed at all, a new work order is triggered for the following Monday. The schedule does not account for what has happened in the past, only for what is planned for the future.

Example of fixed PM scheduling

Since a time-based PM was covered in the section above, let’s take an example of fixed preventive maintenance scheduling using a meter-based trigger.

Your facility might have a truck that requires maintenance every 1,000 miles. As soon as the odometer rolls from 999 to 1,000, a PM is triggered and a work order is created. Because the PM is set up on a fixed schedule, the next PM will trigger when the truck has been driven 2,000 miles, regardless of how long it takes for that to occur or the circumstances in which the truck has been driving.

But let’s say that the truck is on the road when it hits 1,000 miles and the PM can’t be completed until it has 1,200 miles of use. A fixed schedule means this late PM isn’t taken into account when scheduling the next one — the vehicle is serviced at 2,000 miles, not 2,200 miles.

What is floating preventive maintenance scheduling?

Floating PMs are preventive maintenance tasks that are scheduled based on the timing of the previous PM. These tasks do not have a specific date attached to them. Instead, the date of the work order changes depending on the maintenance history and/or past usage of an asset.

For instance, let’s say the preventive maintenance interval for an asset is 10 days. If this PM schedule is floating, it means the work order is not created 10 days from when the last PM was supposed to happen, but rather 10 days from when it is actually completed, regardless of if it’s on time or late.

If a work order is left open, it means the next PM will not be triggered. That is why it takes a little extra diligence to track and use floating preventive maintenance scheduling.

Example of floating PM scheduling

Let’s use an example of floating preventive maintenance scheduling with a usage-based trigger.

Let’s say a fan is scheduled for maintenance every 100 hours of operation. However, because your facility had a tight deadline and a large order to process, the fan operated for 120 hours, at which time it was serviced. The next round of preventive maintenance on the fan would not occur when it has run for 200 hours, as it would on a fixed schedule. Rather, a work order would be triggered when it has been running for 220 hours.

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The bottom line on preventive maintenance scheduling

The key to successful preventive maintenance is to get the right maintenance intervals in order to reduce the chance of failure while maximizing resources. Fixed and floating PM schedules help maintenance teams achieve this goal. The two methods help to build policies and processes that make it easier to use labour, budget, time, and parts more effectively while ensuring unplanned downtime doesn’t haunt your organization. The different PM scheduling strategies allow for flexibility when it’s needed and enforce the rules when they are crucial to the health of assets.

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