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Incident Prevention Magazine

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Incident Analysis

The essence of safety is preventing incidents from having the opportunity to occur. When they do occur, it is usually the result of one or more safety systems failures. Failures, however, are the seeds of opportunity. Incidents provide us with opportunities, albeit unfortunate, to improve our safety systems and prevent future incidents. The process used to identify what improvements are needed is called Incident Analysis.

Oftentimes, we in the utility industry treat safety events like plant events, such as unit trips, and only perform a surface level incident analysis on them. Such was the case with one company I was asked to give an incident analysis presentation to at their Corporate EH&S Conference. My objective was to inspire them to raise the standard of their incident analysis efforts. My hope is that this article will inspire you to do the same.

An incident analysis involves gathering facts by inspecting the incident scene, interviewing witnesses, reviewing documentation, and analyzing those facts to determine the causal factors. The causal analysis is easier and more effective when it is done in two phases, a primary event analysis and a causal factor analysis. The objective of the primary event analysis is to determine what exactly happened, and the results provide the basis for the causal factor analysis. The objective of the causal factor analysis is to determine why it happened, and the results provide the basis for the corrective actions.

Primary Event Analysis
Incidents usually involve a sequence of events, sometimes multiple sequences. The primary event is when a person or property comes in contact with a hazardous energy and has both a cause and a consequence. The primary event analysis determines its immediate (direct) cause. The immediate cause is what resulted in the primary event happening and consists of both an action and condition element.

Let us consider an actual case study: During the mid-1990s, before it was such a hot topic, I investigated an arc-flash incident. The primary event was an electrician (person) being exposed to an arc flash (energy) that came from the 480V breaker he was working on. When you define the primary event in those terms, you direct your focus toward both the unsafe condition(s) and the unsafe action(s) that contributed to the event, as well as the relationship between the two.

Through investigation, it was discovered that the breaker was open but still connected to the energized bus when the electrician attempted to replace the operating handle for it. The operating handle shared the same mounting bolts as the metal guard that prevented access to the hot leads on top of the breaker. When the electrician removed the mounting bolts (action), it caused the metal guard to fall (relationship) against the energized leads (condition). This resulted in an arc flash that caused a burn injury. Figure 1 shows the relationships associated with the primary event.

Figure 1

It would be easy to end our causal analysis there, blame the incident on an unsafe act, and reprimand and/or train the employee. After all, we identified the cause and came up with an appropriate corrective action, right? Wrong! All we did so far was identify what happened to cause the primary event. We did not determine what caused the overall incident. What we did, hopefully, was raise more questions than we answered, and that should prompt us to investigate further.

The primary event analysis then determines the proximate (indirect) causes. Proximate causes are what contribute to or result in the immediate cause. While there is only one immediate cause, there can be several proximate causes.

The following are some of the proximate causes in our case study. The breaker guard shared the same mounting bolts and was made of conductive metal. The work was performed while the breaker was racked in. The electrician did not perceive the hazard associated with removing the mounting bolts. The electrician was not wearing arc-flash protection. The elimination of any one of those proximate causes could have prevented the incident or at least reduced the severity of it. Therefore, it is important to determine their causes.

Causal Factor Analysis
The purpose of the causal factor analysis is to determine the approximate (underlying) and ultimate (root) causes of the proximate causes. There can be any number of approximate causes associated with each proximate cause, either in parallel or in series, but there is only one ultimate cause in each causal chain. Ultimate causes are not always easy to define. They are usually either systems design or implementation failures. In some cases, they are the cultural aspect involved. Figure 2 shows you what a causal chain might look like.

Figure 2

One simple way to determine the various causes in a causal chain is by using the 5 Whys Method. The example below applies that method to one of the proximate causes in our case study.

The electrician was not wearing arc-flash protection.

•Why? He was not trained in arc-flash hazards and the associated precautions.
•Why? The safety training program did not include arc-flash hazard training.
•Why? The Electrical Safety Program did not require arc-flash training.
•Why? The Electrical Safety Program did not address arc-flash hazards.
•Why? Arc-flash safety was not a high priority in the industry at the time.

There are many other methodologies available for performing a causal factor analysis, but those are beyond the scope of this article. Whatever methodology you use, the objective is to identify the failures that caused the incident. Those failures will likely fall under one or more of the following primary categories: human factors, systems factors, engineering factors, and cultural factors.

Those primary categories represent the barriers we erect to prevent incidents. When those barriers have failures in them, the opportunity exists for an accident to occur. The more failures, the more likely an incident will occur. Figure 3 shows some of the failures identified in our case study using this barrier concept, which is based on James Reason’s “Swiss Cheese” Model of accident causation.

Figure 3

The failures you identify during your causal factor analysis become the basis for your corrective actions. The more in-depth you go, the more likely you are to determine the ultimate causes. By addressing the ultimate causes, not only will you prevent similar incidents, you will also improve safety in other areas. Case in point, consider the far-reaching effect placing a higher priority on arc-flash safety is having within our industry.

Incident analysis is by far the best tool we have, from a reactive perspective, for preventing future incidents. However, it is even more effective as a proactive tool. You do not have to wait for an accident to use this tool; you can use it for near-misses, too. I have done so for years, and it has helped me to maintain injury rates well below the industry average. I even apply it to safety discrepancies such as a lockout/tagout discrepancy. So why wait? Take every opportunity you can to use it, and use it well, because someone’s life might depend on it.

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