Root cause causal factors

The causes of the specific types of accidents/incidents that have occurred within your workplace must be assessed. The approach you wish to use in the assessment and analysis process depends greatly on your familiarity with and the types of occurrences that have transpired in your workplace. Analyses covered in this book are root cause, causal factor, change, and barrier analysis. 

The intention of this section is to provide a selection of case studies of varying complexity and from different stages of chemical process plant operation. The purpose of these case studies is to indicate that human error occurs at all stages of plant operation, and to emphasize the need to get at root causes. The case studies are grouped under a number of headings to illustrate some of the commonly recurring causal factors. Many of these factors will be discussed in later chapters. 

Error analysis techniques can be used in accident analysis to identify the events and contributory factors that led to an accident, to represent this information in a clear and simple manner and to suggest suitable error reduction strategies. This is achieved in practice by identification of the causal event sequence that led to the accident and the analysis of this sequence to identify the root causes of the system malfunction. A discussion of accident analysis techniques is included in Chapter 6. 

In the following sections, a number of methodologies for accident analysis will be presented. These focus primarily on the sequence and structure of an accident and the external causal factors involved. These methods provide valuable information for the interpretation process and the development of remedial measures. Because most of these techniques include a procedure for delineating the structure of an incident, and are therefore likely to be time consuming, they will usually be applied in the root cause analysis of incidents with severe consequences. 

Using the ECFC representation of the incident, a series of defailed questions which address specific causal factors (e.g., poor procedures), are applied to evaluate direct and indirect root causes. These detailed questions are contained in a series of HPIP modules. 

In the second case study, variation tree analysis and the events and causal factors chart/root cause analysis method are applied to an incident in a resin plant. This case study illustrates the application of retrospective analysis methods to identify the imderlying causes of an incident and to prescribe remedial actions. This approach is one of the recommended strategies in the overall error management framework described in Chapter 8. 

The events and causal factors chart for this incident is shown in Figure 7.9. The primary sequence of events is shown horizontally in bold boxes. Secondary events are shown in the other boxes, and conditions are in ovals. From the diagram three causal factors were identified and carried forward to the Root Cause Coding to establish the root causes of the causal factors. 

Causal Factor 1 Operator A Connects Pump to 21A Pipe Not 12A Pipe Root cause coding identified the following root causes ... 

EPA ARIP Responses to questionnaires sent by EPA from facilities that have had significant releases purpose is to learn about causes and consequences of hazardous material incidents 1986-Present Supplements NRC reports for more significant events Additional information on causal factors, consequences, and company safety programs Data are easily analyzed for common causes Includes all states and localities Survey relies on voluntary compliance Not comprehensive limited to select cases Checklist approach limits value of information to understand root cause Not designed to be a lessons-leamed database... 

One approach is to mesh all investigation and root cause analysis activities under one management system for investigation. Such a system must address all four business drivers (1) process and personnel safety, (2) environmental responsibility, (3) quality, and (4) profitability. This approach works well since techniques used for data collection, causal factor analysis, and root cause analysis can be the same regardless of the type of incident. Many companies realize that root causes of a quality or reliability incident may become the root cause of a safety or process safety incident in the future and vice versa. 

Restart criteria should focus on short-term prevention of one or more causal factors while the other causal factors and root causes are determined. One best practice is to have a task force quickly evaluate potential similar underlying causes elsewhere in the plant. Limitations imposed for restart are often undesirable for long-term operation as severe operational limits may be set. These limits, however, allow the system to run with minimal risk of recurrence of the incident. It is the duty of a company to demonstrate it is safe to restart. It is the duty of the regulator to prohibit restart if there is evidence of significant deficiencies. 

Training Agenda Data collection Causal factor determination Root cause identification Writing... 

Tool—A device or means used at a discrete stage of the incident investigation to facilitate understanding of event chronology, causal factors, and/or root causes. 

In general, the companies surveyed use one of two main methodologies to determine root causes. The first involves timeline construction followed by logic tree development. The second involves timeline construction, identification of causal factors, followed by the use of predefined trees or checklists. These two approaches are discussed in detail in Chapter 9. 

Causal factor identification tools are relatively easy to learn and easy to apply to simple incidents. For more complex incidents with complicated timelines, one or more causal factors can be overlooked, ultimately leading to missed root causes. Another disadvantage is that an inexperienced investigator could potentially assume that suppositions are causal factors, when in reality the supposed event or condition did not occur. 

Once the causal factors have been identified, the factors are analyzed using a root cause analysis tool, such as 5-AVhys or predefined trees. See Chapter 9 for a more detailed discussion of Barrier Analysis (sometimes called hazard-barrier-target analysis or HBTA) and Change Analysis (also referred to as Change Evaluation/Analysis or CE/A). In essence, these tools act as a filter to limit the number of factors, which are subjected to further analysis to determine root causes. 

Checklist analysis tools can be a user-friendly means to assist investigation teams as they conduct root cause analysis.h) Each causal factor is reviewed against the checklist to determine why that factor existed at the time of the incident. The Systematic Cause Analysis Technique (SCAT)(9> is an example of a proprietary checklist tool. 

A disadvantage is that a checklist may allow an investigation team to jump to conclusions, and does not provide the opportunity to think outside the box. This is especially important if the checklist is one of the less comprehensive types. It is also tempting to use the checklist too early, before all causal factors have been identified. Be sure to determine what happened and how it happened before determining why it happened. Otherwise, the team will think it has identified the right root causes, when in reality not all of the root causes have been determined. 

It helps to define two terms to understand the hierarchy of sequencing for the occurrences that make up an incident. The most widely accepted terms are causal factor and root cause ... 

Find the root causes (management system weaknesses) of each causal factor and write recommendations that address the root causes, not the causal factors. 

Provide training to an appropriate number of operations and maintenance personnel on a consistent approach to investigation, which includes causal factors and root causes determination. 

Potential team leaders learn how to determine the appropriate investigation methodology, how to gather data, how to analyze data for causal factors, how to determine root causes of causal factors, and how to develop effective recommendations and reports. 

This step is always performed. Using analysis tools and methods such as fault trees, causal factor charting, checklists, predeveloped trees, or alternative methodologies will help to identify the root causes of the failures. 

Find the facts in the main sequence on the Causal Factor Chart that describe a component failure or a human error. Ensure the fact is not describing a management system failure (i.e., ensure the fact is not a root cause, near root cause, or root cause category). The identified negative events/conditions are candidate causal factors. Any candidate causal factor that is not dependent on another candidate causal factor is a valid causal factor. 

Once the sequence diagram has been developed, the investigator may proceed to identify the causal factors and/or root causes. However, the investigator should resist the temptation to begin this step until he is certain that he fully understand what happened. 

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. 

If the answer is YES, that is, the incident would have heen prevented or mitigated, and it is a negative event or undesirable condition, then the fact is a causal factor. Generally, process safety incidents involve multiple causal factors. This technique is equivalent to step 15 in Figure 9-7. Once identihed, the causal factors become the candidates to undergo root cause analysis. 

The identification of causal factors points us to the key areas that need to he examined further for why that factor existed. It acts as a filter to limit the number of areas that are subjected to further analysis to determine root causes. This critical activity must be performed diligently and systematically to identify every causal factor applicable to the specific incident. If a causal factor is missed, one or more root causes will likely be omitted as well, which could lead to similar incidents in the future. 

Once the actual incident scenario is understood and its multiple causal factors identified, this information may be used to determine the incident s root causes. One means of performing root cause analysis involves the use of ready-made, predefined trees. A predefined tree provides a systematic approach for analyzing and selecting the relevant elements of the incident scenario. It is a deductive approach, looking backward in time to examine preceding events necessary to produce the specified incident. 

Unlike the procedure followed in developing logic trees, the investigation team does not construct the tree. Rather they apply each causal factor to each branch of the predefined tree in turn, and those branches that are not relevant to the incident are discarded. This prescriptive approach offers consistency and repeatability by presenting different investigators with the same standard set of possible root causes for each incident. 

While the use of predefined trees does not directly challenge the investigation team to think laterally of other possible causes, many predefined trees present a wide range of causal factors, some of which the team may not have otherwise considered. It is therefore possible, but unlikely, that the incident could involve a novel root cause that was not previously experienced by those who developed the predefined tree. The addition of a final test based on another tool, such as brainstorming, can overcome this apparent weakness. 

All branches and sub-branches should be considered because an individual causal factor can have more than one root cause. 

Each of the causal factors can now he analyzed for its specific root causes using a predefined tree, as shown in Figure 9-3 f. 

To analyze the causal factor, the investigator starts at the top of the tree and works down the tree through a process of selection and elimination. The investigator asks and answers questions to identify the specific root causes for the causal factor. 

Each lower sub-branch (near-root cause) is then considered in turn to determine if any of the potential root causes on that sub-branch is a valid reason for why the causal factor existed at the time of the incident. Valid root causes are recorded and invalid causes are eliminated. 

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