Fixed or Floating Maintenance Scheduling

Fixed or floating maintenance scheduling

Planned maintenance (PM) refers to a scheduled job that is performed on a specific asset at a specific time interval to prevent unscheduled downtime or breakdowns in the future. The perfect example of scheduled maintenance is the annual service on your car. You pay your mechanic to complete a specific set of tasks to ensure your vehicle continues to run smoothly. By replacing the oil in your engine, the service also reduces the chances the engine seizes, saving you money in the long run.

However, as humans tend to forget things, many organizations use a scheduled maintenance tracker to efficiently track any preventive maintenance or inspections that occur at regular intervals. A scheduled maintenance tracker is a standard feature in many CMMS packages. Commonly, the schedule could be time, event or meter-based. There are two configurations for these triggers and Fiix has both. They are fixed schedule type or float schedule type.

Fixed maintenance schedules

For a time-based schedule (eg. every week), a fixed schedule type means the preventive maintenance occurs as the schedule dictates, irrespective of when the last PM was completed. The interval is fixed. For example, a PM due every week on Sunday is triggered every week on Sunday regardless.  Fixed schedules help you plan work based on the target start date of the previous work. Fixed time interval maintenance PMs are generally used for regulatory compliance.


Advantages of fixed-time intervals

  1. You can easily tell how many PMs are missed.
  2. For organizations with a large amounts of PMs, fixed intervals help you spread out PMs evenly and plan resources. For example, you could block book a subset of your technicians for X hours per day to focus on PMs.
  3. Fixed are suited to shorter intervals – daily and weekly maintenance PMs.
  4. They encourage PM compliance. If technicians have the luxury of pushing PMs out, they will postpone them and focus on reactive repairs. This will kill your PM compliance.
  5. Fixed intervals are used to enforce warranty requirements. If you don’t PM a piece of equipment as the manufacturer recommended, they won’t stand over their warranty.

Let’s also take an example with a meter reading based trigger.

Screen Shot 2014-03-31 at 4.26.24 PM

Now let’s say we enter the following readings:

March 3, 2014: 500 miles

March 12, 2014: 800 miles

March 15, 2014: 900 miles

March 30, 2014: 1,200 miles

At 1200 miles, the scheduled maintenance is triggered, and a work order is created. Now, given that we’ve selected “fixed” as the schedule type, when will the next work order be triggered? The answer is at 2000 miles or greater (ie: the first reading that is above 2000 miles will trigger the work order). Even though we triggered the previous work order late, at 1200 miles instead of the intended 1000, the schedule doesn’t change. Work orders will still get triggered at 2000 miles, 3000 miles, 4000 miles, etc.


Float schedule type

Float maintenance scheduling type means the interval moves depending on when the last PM was created. The most obvious example of this is the annual service on a car. If it is pushed by 2 months, the next is scheduled 12 months from that point. But what happens if you do not complete one task in the PM and leave it open? Then your next PM will never be created. Floating Maintenance PMs require that little bit of extra diligence to police.

Advantages of float-type intervals

  1. Float PMs are ideal for PMs that are spread further apart. A few extra days won’t cause any major damage!
  2. Floating type intervals are ideal for low priority mundane PMs tasks that need to be completed on a regular basis but not necessarily on time. For example, checking drains for any signs of buildups that could cause blockages.
  3. They are also ideal for situations where late PMs will not affect the safety of the equipment or personnel that operate it.

Let’s examine how float maintenance scheduling affects a meter reading based on scheduled maintenance.

Floating PM Schedules

For this experiment, we’ll we enter the following readings:

March 3, 2015: 500 miles

March 12, 2015: 800 miles

March 15, 2015: 900 miles

March 30, 2015: 1,200 miles

Again, the work order is triggered at 1200 miles. The question is, given that we selected “floating schedule” type, when will the next work order be triggered. As you might have guessed, this time it’s not until 2200 miles (or greater). If I enter a reading of 2100 miles, nothing will happen. The next trigger point has been pushed out because the previous work order was triggered at 1200 miles, instead of the intended 1000 miles.

New addition to float Maintenance PMs

What if you trigger the PM at 1200 but it takes a few days to get the vehicle into the maintenance shop. When you do, the vehicle now has 1400 miles.

March 3, 2015: 500 miles

March 12, 2015: 800 miles

March 15, 2015: 900 miles

March 30, 2015: 1,200 miles

April 3rd, 2015: 1,400 miles when vehicle is getting its scheduled PM.

If you checked the “By work order closed“, the trigger will be set to the last logged meter reading. So, during the PM, log the latest reading and when you close it, it will adjust the trigger to 1,400 miles so the next is due at 2,400 miles.

Floating PM scheudles for fleet

If you are ever in doubt, check the Next Trigger Threshold in the scheduled maintenance to verify your work:

Pm Next Threshold

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