After the team has preserved the failure data, the team can begin to analyze the data. To help you visualize the event and organize the team's hypotheses, you should create an Event Diagram and a Logic Tree to facilitate and organize the team's analysis.
To analyze failure event data for our example:
Access the Event Diagram page, and define the failure event by creating an RCA Event record. For this example, you would complete the RCA Failure Event datasheet as the following image shows.
Diagram the events that led up to and immediately followed the failure event. For this example, you would create the Event Diagram as shown in the following image. The team should note the trend in the failures that occurred in the past. In this way, the team may be able to identify a pattern in the events prior to the RCA Analysis that may indicate the underlying cause(s) for these failures.
Diagram each failure mode in detail. For this example, you would create a Logic Tree like the one shown in the following image.
In the Logic Tree in this image, you can see that two Failure Mode nodes are linked to the Failure Event node, and multiple Hypothesis nodes are linked to the Motor Tripped due to high temperature Failure Mode node.
Now that several likely hypotheses have been introduced, the team will need to rule out hypotheses. To rule out a hypothesis or prove a hypothesis, the hypothesis will need to be tested against the data that is available to the team (i.e., the failure event data and the team of experts).
The Principal Analyst should create RCA Verification records and assign them to team members who will be responsible for completing the associated task. The following image shows an example of an RCA Verification record that contains a task to test the Mechanical hypothesis. The record is assigned to the team member Pete Handy, the mechanic.
The task defined in this RCA Verification record instructs Pete Handy to inspect the wiring for the cooling water pump to ensure that the problem was not electrical, but mechanical.
When a hypothesis has been tested using the task specified in the RCA Verification record, the state of the associated RCA Hypothesis record should be set to True if the hypothesis is true or Not True if the hypothesis is not true. For example, the following image shows the Logic Tree after Pete Handy has completed the RCA Verification record to which he was assigned. Pete Handy concluded that the wiring did not the cause the pump to overheat, so the problem must be mechanical.
After the state of the Mechanical RCA Hypothesis record is set to True, the team can continue down the logic tree until they identify the root cause. Causes can be further identified as physical, human, or latent. For example, the following image shows the Logic Tree after ALL the RCA Verification records have been completed. The team has concluded that inadequate accountability of workers has led to insufficient lubricant being applied to the outboard bearing, which caused the motor's temperature to increase and the pump to overheat.
In this case, the root cause for the pump failure would be identified as latent (i.e., inadequate accountability of workers), which lead to human (i.e., too little applied) and physical (i.e., lubrication issue) causes. Now that a hypothesis has been verified and the root cause has been determined, you can create RCA Recommendation records to communicate your findings on how to prevent this failure in the future.