Nested PM

The old way of doing preventive maintenance

In the past, if you had multiple PM cycles for a given piece of equipment that landed on the same date, you would have had to create multiple scheduled maintenance triggers in the CMMS (opens in new tab) to handle the cumulative tasks. For example, lets say you own a car. The PM that are required are as follows:

1. Change the oil every 3000km
2. Change the oil filter every 12000km
3. Change the spark plugs every 12000km
4. Change the air filter every 12,000km
5. Change the timing belt every 60,000km

Using a CMMS without the nested PM feature would mean that you would have to create 3 scheduled maintenance items and then line them up so they triggered on the same day. This would then have resulted in three work orders being created, adding to your paperwork pile. This strategy works fine when you only have a few assets or tasks, but quickly becomes very complex when dealing with a large number of assets.

What is a nested PM?

The nested PM feature is unique to Fiix. It lets you group PMs of different length and complexity together when they are due to occur at the same time. By nesting your PMs together, you only have one single PM to manage. The nested PMs determine which tasks are released to the work order based on the schedule. In the monthly/annual example above, the monthly and annual PMs can be grouped into a single PM. When the monthly PM is due, the nested PM only releases the monthly takes. Similarly, when the annual PM is due, the nested PM will release both the monthly and annual tasks.

Nested PM functionality assumes the organization includes all activities and tasks from more frequent cycles into less frequent cycles. For example, monthly tasks are included in every annual PM.

Lets say you have a piece of equipment with the following PM cycle:

PM cycle	Tasks	Nesting code
Weekly	4 tasks	N1
Monthly	Weekly tasks + 2 additional monthly tasks	N2
Quarterly	Weekly tasks + 4 additional tasks	N3
Annual	Quarterly tasks + 2 additional annual tasks	N4

The nesting setup looks like the following:

During the annual PM for example, you perform the entire weekly, monthly and quarterly task groups plus a few additional annual tasks. The task manager will look like the following:

How do nested PMs work?

When setting up nesting PMs, each PM activity is considered a multiplier of the lowest PM cycle. Let's take a look at a time based PM example. In this example, the weekly PM is the shortest PM cycle so it has a nesting code of N1, which is our root PM. The weekly cycle becomes the basis on which all other PMs are built on. As there are 52 weeks in a year, the annual PM has a multiplier of 52.

PM cycle	Number of weeks	Multiplier
Weekly	1	1
Monthly	4	4
Quarterly	13	13
Annual	52	52
5 year PM	260	260 (52 weeks x 5 years)

Here’s a meter-based example:

PM Cycle	Multiplier	Nesting Code
250 hour PM	1	N1
500 hour PM	2	N2
1000 hour PM	4	N3
2000 hour PM	8	N4
10000 hour PM	40	N5

In this example, the 250 hour PM is the N1 root PM. Everything else becomes a multiplier of that. Its simple math!