What is Root Cause Analysis (RCA) ?

When a failure occurs with serious consequences, RCA is a powerful tool to find out what went wrong and how to prevent it being repeated.

You may have experienced the endless and tiresome debates, often circular and repetitive, aimed at working out what went wrong, who or what is to blame.

RCA cuts through all that.  This rigorous and systematic approach starts with gathering relevant evidence about the failure, then uses a workshop approach with a small core team of engineers to work through a Fault Tree.  That indicates where extra information would be valuable, which may be obtained by extra investigation or tests.

The method gives due attention to the whole range of possibilities, but homes in quickly to the most likely, and provides a clear traceable and record of how those conclusions were reached.  The results give clear indications of what needs to be done to avoid repetition of the failure.

The objectives are to -

• understand the failures as fully as possible; what and where are the failures, how did they occur;
• determine what steps are needed to prevent the failures from recurring on subsequent installations;
• determine what other tests may be useful to help understand the problem.

A systematic process is used, based on the structure of a Fault Tree. The steps are:

1. Collect and review evidence (written reports  / links to knowledgeable people);
2. Define the symptoms of failure;
3. Identify potential failure modes – that fit the symptoms of failure;
4. Construct a Fault Tree from the potential failure modes;
5. Review (in a structured workshop session) all those potential failure modes, one-by-one, against the evidence :

• Close all the lines of enquiry that don’t fit the evidence;
• Highlight all the lines that do fit – these indicate the Possible Causes;

1. Look for analogues in other projects;
2. Identify what further evidence is needed to confirm each Possible Cause (ie extra tests);
3. Propose further (characterisation) tests and other actions that will help avoid future failures.