About nested PMs

Nested planned maintenance (nested PMs) is a scheduled maintenance feature that allows you to manage an asset’s repeating tasks that can be completed together, but at different intervals. It can reduce the number of scheduled maintenance records and unnecessary work orders generated for an asset.

For example, an asset may have three regular maintenance procedures:

• Task A is performed every 500 kilometres, 
• Task B every 1000 kilometres, and
• Task C every 2000 kilometres.

Every time you perform task B, it will always be time to perform task A, and every time task C is performed, it is also time for task A and B to be performed. In other words, tasks B and C never need to be performed alone and can always be grouped together with other tasks. Instead of using 3 scheduled maintenance records to track these tasks, you can manage all of them on one record with nested PMs.

Nested PMs are best used for situations like the above, where an asset has multiple tasks or task groups that can be grouped together and performed at the same time. They are not suitable for situations where maintenance procedures cannot be performed together. They also may not offer the same level of resource planning as single-task, single-asset scheduled maintenance.

This article includes the following:

• Feature overview
• Example

Feature overview

You can view and edit nested PMs in the Nested PMs tab on a scheduled maintenance record:

As shown above, nested PMs have a code, a parent, and a multiplier (aside from the PM with the greatest frequency):

• Codes (N1, N2, etc.) are automatically assigned based on the order of creation. For example, the first PM created on the scheduled maintenance record is N1, the second is N2, and so on. 
• Multipliers are set by the user and determine the time or meter reading interval of each maintenance procedure. The most frequent PM (N1) has no multiplier. 
  For example, giving a PM a multiplier of 2 means that the interval will be twice as long as its parent's. If its parent's interval is 6 months, then the PM in question has an interval of 6 × 2 = 12 months. In other words, it would be performed yearly. 
• Parents are any pre-existing nested PM that the PM uses to calculate its own interval. When creating a new nested PM, you select which PM to use as a parent. Any nested PM can be a parent; however, N1 PMs can only be a parent, and never a child. 

The Next Iteration Cycle section displays the PMs that are set to be completed the next time a work order is generated. An iteration refers to a specific instance where the relevant trigger is set off and a work order is generated. 

After you've created your nested PMs, they can be assigned to any tasks on the scheduled maintenance record to determine their frequency. Using the example above, a work order is generated weekly for N1 tasks. However, any N2 tasks will only appear on every fourth work order, since they occur on a monthly frequency.

To learn more, see Create a time-based nested PM and Create a meter-based nested PM.

Example

A machine could require the following service:

• Oil change every 500 hours
• Filter change every 1000 hours
• Motor shaft alignment every 3000 hours

At 500 hours, only an oil change is needed, but at 1000 hours, both an oil and filter change is needed, and at 3000 hours, all three maintenance procedures need to be performed. The nested PMs for these maintenance procedures might look like the following: