Multiple root cause

This chapter addresses methods and tools used successfully to identify multiple root causes. Process safety incidents are usually the result of more than one root cause. This chapter provides a structured approach for determining root causes. It details some powerful, widely used tools and techniques available to incident investigation teams including timelines, logic trees, predefined trees, checklists, and fact/hypothesis. Examples are included to demonstrate how they apply to the types of incidents readers are likely to encounter. 

In recognition that most incidents have multiple root causes, the team is generally required to identify a minimum of three factors one from each of the following categories organizational, human, and material factors. 

MULTIPLE CAUSES - Most current methods recognize the concept of multiple root causes. 

This chapter addresses typical data gathering needs of major investigations. A team may need to augment the activities in this chapter for the unique circumstances of the incident. Performing the activities oudined in this chapter plus special activities provides the incident investigation team with the data needed to complete the next step—systematic determination of the multiple root causes of the incident. However, data gathering and analysis typically involve much iteration as shown in Figure 8-1. 

To give further insight into the role of management systems and the distinction between multiple root causes and non-root causes, consider the following actual case histories. 

The causal factors need to be examined further to determine why those factors existed. The investigation team may use a predefined tree to examine each causal factor individually. The first causal factor is analyzed starting at the top of the tree, and then working down all of the branches as far as the facts permit. When an appropriate subcategory on one of the branches is identified, it is recorded as a root cause. The remaining branches are checked as one causal factor may have multiple root causes. The procedure is then repeated for each causal factor in turn. 

Analysis of Esso Longford as well as analysis in the UK Health and Safety Executive (HSE) investigation report into petrochemical complex major incidents all show that common underlying causes are often repeated. The Longford incident clearly illustrates the multiple root cause concept. A number of PSM system failures occurred either in... 

The following case study describes the investigation work process for a hypothetical occurrence using a logic tree based multiple root-cause systems approach. An example incident investigation report follows the work process description. The example is intended for instructive purposes only descriptions of process equipment and conditions are not intended to reflect actual operating conditions. 

Jack Philley began his article, Investigate Incidents with Multiple Root Cause, as follows ... 

Report on the multiple root causes including management system related causes. 

The terms root cause or multiple root causes appear several times without a clear definition. When Jack Philley teaches the Investigating Process Safety Incidents course for the AIChE, he offers several clear definitions. He describes a root cause as a prime reason, underlying cause, and most often associated with breakdowns or flaws in the management systems. Furthermore, Philley s class notes point out definitions from the Department of Energy Guidelines in his handout, which states ... 

Report on the multiple root causes including management system related cau.ses. (Remember, Deming believes that most industry problems are system problems.)... 

Philley, Jack, Investigate Incidents with Multiple Root Causes, Hydrocarbon Processing, Sept. 1992, pp. 77-80. 

Philley J. Investigate incidents with multiple root cause. Hydrocarbon Process 1992 Sept 77-80. 

What were the (multiple) root causes of the problem ... 

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