Let's spend 15 minutes to look at a problem initially solved by 5 Whys and use a Risk matrix to indicate that a more thorough investigation is required. The subsequent RCA Rt investigation reveals that the initial 5 Why only revealed a part of the problem and that the problem would have reoccurred, with associated high costs.

The scenario

The operators on a Semi Autogenous Mill at the Cow Creek mine site report that the mill shut down on overload and will not restart. Subsequent investigations by maintenance workers find the mill drive seized.

They carry out a 5 Why investigation and feel that they have identified the reason why the failure occurred and are happy to leave it there. Click here to see their 5 Why investigation. However they also check their Risk Matrix which tells them they need a full RCA Rt investigation.

The RCA Rt investigation helps them to look more deeply into the problem and they identify other factors which would have caused a reoccurrence of the problem if not attended to.

Comments

We will find that in this case, because of the nature of the problem, the 5 Why analysis is not adequate. Further investigation reveals that reliance on the 5 Why alone would have led to the problem reoccurring with a large loss in production and maintenance cost.

Click here to see Case2 solving.