RCFA problem statements are key to solving the right problem at your plant but sometimes the problem statement that we write down isn’t a fact. We pick something that’s not quite true. It’s a little bit off, and that makes our root cause very long. Sometimes we miss the root cause altogether because it’s wrong.
What we typically do is go out and collect data and we take that data, add a couple of assumptions, and then write our problem statement using that information. Let’s take a look at the following examples.
RCFA problem statements – avoid writing down assumptions without facts
Here’s a great RCFA problem statement example where an assumption is treated as a fact.
Say we are presented with the root cause “hydraulic cylinder was moving erratically and too slowly.” The group saw that and assumed that there was some type of mechanical resistance on the rod. So, they start working on that assumption. A couple of hours later without finding anything there, we rewrite the problem statement to reflect what we actually saw, which was “hydraulic cylinder moving too slowly.” We found out there was an internal leakage in the cylinder itself. We had the wrong problem statement to start. The problem statement wasn’t a fact. It was an assumption from what we saw, plus we added a little bit.
For the next RCFA problem statement example, see the picture below. There is a circle around the filter. The problem statement was “the filter is clogged” because there was no flow coming out of the filter.
So, what we observed was that “there’s no flow out of the filter,” but we wrote “the filter is clogged.” You can see how those two things are different. This assumption led us to checking the filter, and we found that it was not clogged. The stoppage was somewhere else. This is an easy type of mistake to make when we follow assumptions instead of facts. Make sure to watch out for this next time you do a Root Cause Failure Analysis.