Root causes

Nuclear power has achieved an excellent safety record. Exceptions are the accidents at Three Mile Island in 1979 and at Chernobyl in 1986. In the United States, safety can be attributed in part to the strict regulation provided by the Nuclear Regulatory Commission, which reviews proposed reactor designs, processes appHcations forUcenses to constmct and operate plants, and provides surveillance of all safety-related activities of a utiUty. The utiUties seek continued improvement in capabiUty, use procedures extensively, and analy2e any plant incidents for their root causes. Similar programs intended to ensure reactor safety are in place in other countries. 

Leak or spill source Characteristics Root causes Preventive measures... 

Establish the timeline of the problem hypothesizing that changes in operation, equipment, or response are the root cause of the problem. 

Excessive number of alarms resulting in confusion and reduction in efficiency of pinpointing the root cause of the upset. Operators may miss or ignore critical alarms. 

Incident Investigation Previous incidents related to the chemicals or equipment involved in the new toll should be considered during the PHA and must be considered if subject to PSM/RMP compliance. In addition, procedures should be in place to describe how the client will be informed and involved in the investigation. It is veiy important to ensure that action plans addressing the root cause of past incidents were implemented. 

If yes, for each incident, attach the incident report or give the following information Description of the incident, chronology of verifiable events, other pertinent facts, root causes and contributing factors, and proposals for corrective action. 

Is the root cause ascertained before taking corrective measures ... 

Check whether a documented system is in place, which covers the reporting, investigation, root cause analysis and corrective actions taken. 

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. 

If the process uses a single large study node, deviations may be missed. If study nodes are small, many are needed and the HAZOP may be tedious, moreover the root cause of deviations and their potential consequences may be lost because part of the cause may be in a different nude. 

Cause(s). Root causes of the failure mode are identified to aid in preparing subsequeni i... 

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. 

FMEA is particularly suited for root cause analysis and is quite useful for environmental qualification and aging analysis. It is extensively used in the aerospace and nuclear ]iowei indiistrii-s but seldom used in PSAs, Possibly one reason for this is that FMEA, like parts count. ,s not chrectlv suita lundant systems such as those that occur in nuclear power plants Table i 4... 

Auditor has to advise supplier to conduct root cause analysis on all NCs. 

You will be required to perform a root cause analysis on each detected nonconformity. 

As stated previously, traceability is fundamental to establishing and eliminating the root cause of nonconforming product and therefore it should be mandatory in view of the requirements for Corrective Action. Providing traceability can be an onerous task. Some applications require products to be traced back to the original ingot from which they were produced. In situations of safety or national security it is necessary to identify product in such a manner because if a product is used in a critical application and subsequently found defective, it may be necessary to track down all other products of the same batch and eliminate them before there is a disaster. It happens in product recall situations. It is also very important in the automobile and food industries in fact, any industry where human life may be at risk due to a defective product being in circulation. 

There are many tools you can use to help you determine the root cause of problems. These are known as disciplined problem solving methods. 

There are other techniques such as force field analysis and the simple Why Why technique which very quickly often reveals the root cause of a problem. 

Once you have identified the root cause of the nonconformity you can propose corrective action to prevent its recurrence. Eliminating the cause of nonconformity and preventing the recurrence of nonconformity are essentially the same thing. The key to successful diagnosis of causes is to keep asking the question why When you encounter a don t know then continue the investigation to find an answer. 

Establish the root cause of the nonconformity and prevent its recurrence. 

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. 

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. 

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... 

Analysis of Incident Root Causes Using the Sequential Error Model... 

In addition to the proactive uses of the SRK model described in the two previous sections, it can also be employed retrospectively as a means of identifying the underlying causes of incidents attributed to human error. This is a particularly useful application, since causal analyses can be used to identify recurrent vmderlying problems which may be responsible for errors which at a surface level are very different. It has already been indicated in Section 2.4.1 that the same observable error can arise from a variety of alternative causes. In this section it will be shown how several of the concepts discussed up to this point can be combined to provide a powerful analytical framework that can be used to identify the root causes of incidents. 

Evaluate the effectiveness of the strategy by reviewing operational experience when the task has been performed for some time, and identifying the error root causes by the process set out below. 

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