The Preventive Maintenance application supports both time and meter-based PMs or a mix of the two. Maximo also supports a PM hierarchy.

Preventive Maintenance – Meter-Based

If you think of car maintenance the recommendation might be maintain the car every 18,000 miles, this is a meter-based PM using a continuous type of meter. It is only continuous meters that can be used with PMs. The recommendation may be to maintain the car every 12,000 miles or every year, whichever occurs first. This is an example of a mixed time and meter-based PM, Maximo supports this.

In the Frequency tab and Meter Based Frequency subtab, you’ll find that there is a table window allowing multiple continuous meters to be used. In this case, whichever of those meters occurs first will cause the work order to be generated. The Select Value shows the meters of the asset or location referenced on the PM.

The three fields above the Meter Based Frequency tab in the Work Order Generation Information section play a part in determining when a work order is generated:

  • Use Last Work Order’s Start Date to Calculate Next Due Date – When set the due date is determined from the target start date of the last generated work order, a fixed schedule. When unchecked it uses the Last Completion Date which is normally set when the last generated work order is completed, but it may be when it is closed, a floating schedule.
  • Generate Work Order Based on Meter Readings (Do Not Estimate) – When set a work order is generated based on an actual meter reading and not one that is based on the average units/day. You need to create a PM Meter before this field is enabled. This is normally set when there is variable use of the asset, for example vehicles. It is left blank if the asset is continuously being used, as in a manufacturing plant, or when meter readings are infrequent.
  • Generate Work Order When Meter Frequency is Reached – When set and Generate Work Order Based on Meter Readings (Do Not Estimate) is also set, will allow a work order to be automatically generated when the actual meter reading has reached the frequency for generating a work order.

In the Meter Based Frequency tab the Frequency field determines how often a work order is generated based on the meter’s unit of measure.

The two fields in the Last Work Order Information section are populated from the latest meter reading when a work order is generated from the PM. The Meter Reading field may be referred to as the Life To Date Meter Reading. It is not the latest meter reading because that may have occurred since the last work order was generated.

In the Next Work Order Projections section, the ‘Next Meter Reading’ is the ‘Meter Reading’ field plus the ‘Frequency’. The ‘Units to Go’ is calculated as the ‘Next Meter Reading’ minus the ‘Life to Date for Asset’ field which will be found on the Asset meter, minus a tolerance of how many units before reaching the ‘Next Meter Reading’ you would like the work order to be generated. The tolerance is entered in the ‘Generate WO Ahead By’ field.

You can use the ‘Units to Go’ and divide this by the ‘Average Units/Day’ to derive a ‘Days to Go’ value. Maximo does not calculate this value, but it will be easier to understand the next passage if you consider this term, ‘Days to Go’ as the number of days before you need to generate a meter based PM.

The ‘Estimated Next Due Date’ is determined by:

  • For fixed intervals, ‘Use Last Work Order’s Start Date to Calculate Next Due Date?’ is set, then use ‘Last Start Date’ field and add the ‘Days to Go’.
  • For floating intervals ‘Use Last Work Order’s Start Date to Calculate Next Due Date?’ is not set, then use the later of the ‘Meter Reading Date’ field or ‘Last Completion Date’ field and add the ‘Days to Go’.

If no previous work order has been generated from the PM, then the ‘Estimated Next Due Date’ is todays date plus ‘Days to Go’.

If you are creating a PM for an asset with existing meters you can use the action Set Reading at Last WO. There are two fields:

  • ‘Meter Reading’ is the meter reading at the last work order generation, as displayed in the Last Work Order Information section, this field is read-only.
  • ‘New Reading’ is used to update the reading at the last work order generation. The value entered is shown in the ‘Meter Reading’ field in the Last Work Order Information section.

Using this action does not change or set the Meter Reading Date field.

As you enter new meter readings the ‘Units to Go’ is decremented by the delta in the meter reading. The ‘Average Units/Day’ is recalculated, and the ‘Estimated Next Due Date’ is also recalculated by projecting the new ‘Average Units/Day’ forward until the ‘Units to Go’ value would become zero or negative.

The ‘Next Meter Reading’ field in the Next Work Order Projections section is also used with alerts for meter-based PMs.

Time and Meter Based PMs

When a PM is both time and meter based then the Earliest Next Due Date on the PM main tab is set to the earliest of the Estimated Next Due Date on the Time Based Frequency tab and the Estimated Next Due Date on the Meter Based Frequency tab. However, if both of those dates are in the past then it will show todays date. If the Estimated Next Due Date on the Meter Based Frequency tab is still in the future, then this will continue to be used.

The Estimated Next Due Date on the Time Based Frequency tab may be overridden by an Extended Date. Therefore, if there is an Extended Date then the comparison with the Estimated Next Due Date on the Meter Based Frequency tab is with the Extended Date.

There is no ability to add an extension to the meter-based PM, for example to say that the next work order can be performed at 15,000 miles rather than 12,000. You can change the frequency, but you would need to remember to change it back after the next work order is generated.

PM Hierarchies

In the PM Hierarchy tab, you can add a parent PM or add a set of children PMs. The children PMs can also have children. This might be used to mimic an asset and its subassemblies or a location hierarchy. For example, when we perform the maintenance on the pump, we should also perform the maintenance of its motor. If time based the two PMs should have the same frequency.

A PM hierarchy may be several levels deep and involve multiple PMs, but four levels might be considered a practical limit as there is no visualisation of the hierarchy as a whole. Two-levels used for grouping PMs together is quite common. When the PM Hierarchy generates work orders it creates a work order hierarchy with child work orders which may have themselves children. A sequence field on the children is used to provide order, the sequence is copied to the work order.

Modifying the PM hierarchy is straightforward, change the parent, or use delete row on the Children table, this does not delete the PM, just removes it from the hierarchy. The Duplicate PM action on the parent PM does not duplicate the PM hierarchy.

Normally the PMs in the PM Hierarchy have the same frequency, but variable frequencies are allowed. When evaluating whether to generate a PM hierarchy it evaluates the parent at the top of the hierarchy, then it works down the hierarchy to see if a descendent is due and the field ‘Use this PM to Trigger PM Hierarchy?’ is set. If this is not set, it will continue to check other PMs in the hierarchy for the same conditions. Maximo will only generate the work orders for a whole PM hierarchy and not part of one. The field ‘Use this PM to Trigger PM Hierarchy?’ is tucked away in the Resource Information section at the bottom of the main tab.

One technique you should be aware of is to have a PM hierarchy with a zero frequency. The work order hierarchy will not be generated except manually if you deselect ‘Use Frequency Criteria?’ in the Generate Work Orders dialog. This allows you to create a work order hierarchy, when it is needed, for example, the work regularly performed for a shutdown, or when a production line is halted for a change over. The shutdown or change over may be on a variable frequency and so would not be appropriate for frequency-based PMs.

When you change status on the PM hierarchy you can set the ‘Roll New Status to All Child PMs?’ field to change status for the children PMs.

Links

IBM Support – Formula for PM Work Generation PM Work Order Generation

IBM Support – Average Units Per Day Calculation Average Units Per Day Calculation