Root cause example

The causes of low pressure, for example, could be cither hydraulic or mechanical. In many cases of failure analysis, asking Wliy. and Wliat and answering those questions, until you can no longer ask why , will almost always get you to the answer. If all evidence leads to a mechanical reason for the failure, the problem is probably maintenance induced. If the evidence leads to a hydraulic reason for the failure, the problem is eitJier operations or design induced. In cases where the reason for failure was not determined, a more extensive analysis is necessary. The additional analysis is recommended to take advantage of the pump supplier experience in identifying the root cause. 

An FMEA is a qualitative, systematic table of equipment, failure modes, and their effects. For each item of equipment, the failure modes and root causes for that failure are identified along with a worst-case estimate of the consequences, the method of detecting the failure and mi "ation ofits effects. Tables 3.3.5-2 and 3.3.5-3 present partial examples ofFMEAs addressing the Cuoling Tower Chlorination System, and the Dock 8 HF Supply System. 

In addition to incident reporting systems, root cause analysis techniques can be used to evaluate the causes of serious incidents where resources are usually available for in-depth investigations. A practical example of root cause investigation methods is provided in Chapter 7. 

In the shorter case studies, only the immediate causes of the errors are described. However, the more extended examples in the latter part of the appendix illustrate two important points about accident causation. First, the precondihons for errors are often created by incorrect policies in areas such as training, procedures, systems of work, communications, or design. These "root causes" underlie many of the direct causes of errors which are described in this section. Second, the more comprehensive examples illustrate the fact that incidents almost always involve more than one cause. These issues will... 

A specific example of a causal model is the root cause tree described in Section 6.8.4 and Figure 6.8. This is a very elaborate model which includes several levels of detail for both equipment and human causes of incidents. The root causes tree is a generic causal model, and may require tailoring for application to specific plants and processes (e.g., in the offshore sector) where other error causes may need to be considered. 

The change management process should also ensure that a root cause analysis has been conducted to make sure the real problem has been identified and corrected. For example, if a pump seal fails it could simply be replaced with an identical seal. However, it may have failed because it was left in service beyond its natural life and the real failure was in the preventative maintenance program that should have replaced it earlier. 

For example, if tube failure occurs due to caustic gouging corrosion, the root causes are most likely related to the effects resulting from the availability offree sodium hydroxide in the BW, coupled with the development of localized caustic concentration. Control generally requires a twofold approach to remove the causes of this particular problem ... 

This example illustrates how numeric-symbolic interpreters are combined with symbolic-symbolic interpretation for root cause diagnosis. It... 

The root cause of this accident was poor operating procedures and poor process infoiv mation. The operating procedure, for example, did not cover the safety consequences of deviations from the normal operating conditions, such as the possibility of a runaway reaction and the specific steps to be taken to avoid or recover from such deviations. 

Show the (root)causes (technical, human, organizational) of the operational deviations leading to the accident. For example by classifying the (root)causes using the 7-stage protocol or other existing method. 

This example clearly shows that developing and accepting a hypothesis based on accurate and complete information is necessary for setting an acceptable technical solution. If the plant manager could have persuaded the resin manufacturer to develop a new resin that was similar to the incumbent resin, then the defect would still be there, the cost of the troubleshooting process would have been extremely high, the supplier would have incurred unnecessary development costs, and a high level of defective parts would still have occurred because the root cause would not have been removed. 

Inspection of the barrel and screw for wear can provide information on the root cause for the wear. For example, if wear occurs at an axial location on only one side of the barrei and on all sides (angular direction) of the screw, then the likely root cause is that the barrel is out of alignment at that axial location. Conversely, if the barrei is worn on all sides and the screw is worn on only one side at the same axial location, then the root cause is likely a local bend in the screw. 

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. 

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. 

Disciplinary action may be appropriate if malicious or criminal intent is positively identified as a root cause. An example would be when an investigation reveals horseplay, practical jokes, fights, or even sabotage was among the root causes. These activities have no place in any workplace and are especially undesirable in the chemical processing industry. It is most likely that a company s employee handbook, human resources documents, or union contract addresses these situations and communicates the policy in advance of an incident. In short, the investi-... 

In this example, there are two detection systems and two reaction opportunities. These yield three paths that lead to no adverse consequences and four paths that lead to failure with overflow as the consequence. The point is that sometimes there are more opportunities for things to go wrong than to go right. When a system or process fails, it may he difficult to trace the reasons for its failure. Based on available historic incident data, the anatomy of a major incident is rarely simple and rarely results from a single root cause. Serious incidents typically involve a complex sequence of occurrences and conditions. This sequence can include ... 

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