December 1, 2009 | Barb Carr

Root Cause Analysis Tip: Using Equipment’s Role to help Build a Better SnapChart®

A mechanic has been burned from exposure to Hazardous Fluid and this is your Spring SnapChart®. What Events are missing from the SnapChart® above? As a trained TapRooT® Investigator, you probably want to know more about what the mechanic was working on and what PPE s/he was wearing.

In this case, the mechanic was walking by a closed system when the spray occurred. No work was being performed on or next to the ruptured line.

Now the investigator could perform a Safeguard Analysis to find out what error allowed the Target (the mechanic) to get too close to the Hazard (the uncontrolled flow of Hazardous Material) but as a Safety and Health Incident Investigator, you still have missing events with what error allowed the Hazard to grow and what error allowed a Safeguard to fail. What do you do now if you are not an Equipment or System Expert?

First Hint, You have two key items that stand out: “Hydraulic Supply Control Valve” and “High Pressure Warning Light”. Does the Warning Light illuminate every time you open the Control Valve? How does the Control Valve Operate and What Triggers the Warning Light to come on? Think of it this way… when I turn the light switch on in a room does the light just turn on magically or are there missing events in between both Events mentioned?

So let’s work backwards from “High Pressure Warning Light Illuminated.” What triggered the light to illuminate? Have the equipment expert pull out the system diagram.


So in order for this light to work per design… the Hydraulic Pump would need to be turned on, the Fluid would need to be pumped out of the Fluid Tank, the Fluid would need to go through the Control valve, and to the Cylinder; simultaneously, fluid is also being displaced back to the Fluid Tank through the Pressure Regulator where the Pressure Switch is installed. Hydraulic Pressure would have to exceed a certain set limit with an electrical signal sent to the High Pressure Light….. Looks like we have a lot of missing events.

Keep in mind, as a trained TapRooT® Incident Investigator, you are still in the “What ” phase and do not know the Causal Factors or Root Causes. We do have a better idea on what happened and what Events were Missing. The next step would be to troubleshoot the failed equipment items using Equifactor® to collect more “What Facts”.

Why show this tip to non-equipment experts? Rarely have I seen an investigation that did not include some type of equipment. Understanding how a component is controlled and how it operates is key in mapping out a good SnapChart®. Often Health and Environment members avoid our Equifactor® because they do not have enough mechanical or system experience to answer the questions effectively…. of course if you think about it, as the investigator you are the facilitator getting answers out of the experts. This tool then helps you get the facts out of the experts.

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