Predefined trees example

This useful companion disk contains root cause analysis examples, predefined tree examples, practical checklists that can be customized, and incident evidence photograph examples. It includes a quick checklist for investigators traveling to an incident, examples of methodologies that may be usefiil in training the onsite team, and checklists and samples from the text that can be printed out at the incident site to help organize the team s work. 

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. 

The use of predefined trees is also discussed in detail in Chapter 9. See the accompanying CD-ROM for examples of predefined trees, including Comprehensive List of Causes (CLC) and SOURCE/Root Cause Map. 

After the predefined tree has been used, a final generic cause test should be applied. The plant operating history, especially previous incidents, is considered to indicate if other generic management system problems exist. For example, repetitive failures may indicate generic causes that would not be apparent by only investigating the current incident. It is also an opportunity for a final overall review of the investigation to focus on the big picture, not just individual facts or causal factors. The team should ask, Are there any other causes that anyone has in mind that have not been included ... 

The following is an example of the use of a predefined tree to analyze an environmental incident. While the structure (numher of branches and levels) and terminology of predefined trees vary, this example demonstrates the basic method. 

The following is an analysis of one of these causal factors contractor operator (CO) falls asleep. The basic technique works with any of the predefined trees commonly used within the process industry. However, for the purposes of this example, a proprietary tool C) has been selected, and therefore the structure of the tree and the terminology used is specific to that tree. 

Varieties of public and proprietary predefined trees are available for use, although most owe some allegiance to MORT. The comprehensiveness of the different trees varies from some that may not fully reach root causes, to others that are very detailed with numerous categories and sub-categories. Several of these trees are listed in the appendix and examples of TapRooT SOURCE /Root Cause Map and Comprehensive List of Causes (CLC) < 4) are included on the CD-ROM. 

Suppose that a causal factor chart is developed (see example in Fig. 1). However, there is no warranty, that each of the specific chains of underlying causes from the causal factor chart wiU be coimected to a corresponding generic chain of underlying causes from the predefined tree. Some of causal factors may have no root causes. 

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