4.8 Failure Mode Assessment

Opening a function launches a new tab named after the function. This tab contains all the defined failure modes within the function, to identify the failure consequence and define maintenance tasks using the decision logic from the selected RCM configuration (see RCM Management).

The process in this tab involves first selecting a failure mode, then answering the decision logic questions, followed by assigning additional tasks if required, and finally filling in the worksheets for the assigned tasks (see Maintenance Tasks).

If a function has multiple failure modes, one of the failure modes is selected by default and displayed in the header of this tab. The displayed text presents the failure mode name and its end effect in a cause-and-effect relationship where "failure mode name" causes the "end effect" (Figure 57).

To switch to another failure mode, use the navigation controls in the tab.

4.8.1 Failure Mode Details

This section displays the Failure Mode name, the Maintainable Item it relates to, the Failure Effect Category based on the answers entered in the decision logic, the baseline P(f) of the failure mode, the adjusted P(f) of the failure mode calculated based on the tasks assigned (editable), and the Severity of the Failure Mode.

The baseline P(f) is calculated by considering the item's failure distribution, duration of operation, and FMR (Failure Mode Ratio) of failure modes obtained from the FMEA source (model or excel). It is non-editable within the analysis.

Adjusted P(f) formula:

Adjusted P(f) = P(f)_baseline × (1 − ε_combined)

Where:

• ε_combined = 1 − Π(1 − ε_i) for all assigned tasks i (i.e., the combined effectiveness across all tasks marked "Assigned" to a failure mode is one minus the product of (1 minus each task's individual effectiveness factor))
• ε_i refers to the Effectiveness Factor (see Failure Mode Metrics, section 4.9.1.1) defined in task worksheets that are checked as "Assigned" to a failure mode.

Note: Refer to section 4.9.1.1 (Failure Mode Metrics) for information on the Baseline P(f) calculation.

(Figure 58: Failure Mode Details section)

4.8.2 Decision Tree

This section includes the decision logic from the selected RCM configuration (see RCM Management) to evaluate the failure consequences and allocate tasks for the failure mode. It also allows the ability to capture narratives/justifications for answers to the logic questions.

To assess a failure mode

1. Navigate to the Task Evaluation Decision Tree section
2. Answer the questions in the Decision Tree Workflow
3. Enter narrative/justification (optional)

(Figure 59: Decision tree section to assess failure mode)

4.8.3 Failure Effect Category Task

This section contains a list of tasks assigned to the failure mode based on the answers provided in the decision logic. It also allows for the addition of extra tasks if needed. This section enables editing of the maintenance task names and the import of maintenance tasks defined for any item in the project. It displays the result of the task feasibility assessment, task interval, downtime, and cost, which are referenced from the task tabs (Figure 60: "Tasks originated from decision tree are assigned to failure mode by default").

To assign additional task(s)

1. Click Create Maintenance Task
2. Select Maintenance Task(s) (Figure 61)
3. Click Ok

Note: It is a prerequisite to set the Maintenance Task Taxonomy in Preferences (see section 4.1 Maintenance Type Terminology) before initiating MBRCM.

The corresponding task tab is added as a new horizontal tab (colored blue, green, and orange in Figure 62) and is discussed in section 4.9 (Maintenance Tasks).

To edit the name of the maintenance task

1. Select the maintenance task
2. Click Edit

To delete a maintenance task

1. Select the maintenance task
2. Click Delete

Note: Tasks originating from the decision tree can't be deleted.

To import a maintenance task defined for any item within the project and applicable to the failure mode

1. Click Import
2. Select an action to view its details (Figure 63)
3. Click on the checkbox to select the action (multiple selection allowed)
4. Click Ok

Select the maintenance task tab (colored horizontal tabs, Figure 62) to define feasibility metrics, cost metrics, and actions for each of the assigned tasks. Alternatively, double-click on the tasks that are assigned to the failure mode.