Читать книгу Root Cause Failure Analysis - Trinath Sahoo - Страница 27

A failure is often the result of multiple causes at different levels. Some causes might affect other causes that, in turn, create the visible problem. Causes can be classified as one of the following:

 Symptoms. These are not regarded as actual causes, but rather as signs of existing problems.

 First‐level causes. Causes that directly lead to a problem.

 Higher‐level causes. Causes that lead to the first‐level causes. They may not directly cause the problem, but form links in the chain of cause‐and‐effect relationships that ultimately create the problem.

Some failures often have compound reasons, where different factors combine to cause the problem. Examples of the levels of causes follow.

The highest‐level cause of a problem is called the root cause:

Hence, the root cause is “the evil at the bottom” that sets in motion the entire cause‐and‐effect chain causing the problem(s).

TrevoKletz said

…root cause investigation is like peeling an onion. The outer layers deal with technical causes, while the inner layers are concerned with weaknesses in the management system. I am not suggesting that technical causes are less important. But putting technical causes right will prevent only the LAST event from happening again; attending to the underlying causes may prevent MANY SIMILAR INCIDENCES.

The difference between failure analysis and root cause analysis is that failure analysis is a discipline used for identifying the physical roots of failures, whereas the root cause analysis (RCA) techniques is a discipline used in exploring some of the other contributors to failures, such as the human and latent root causes. Root cause analysis is intended to identify the fundamental cause(s) that if corrected will prevent recurrence. The principles of RCA may be applied to ensure that the real root cause is identified to initiate appropriate corrective actions. RCA helps in correcting and preventing failures, achieving higher levels of quality and reliability, and ultimately enhancing customer satisfaction

Depending on the objectives of the RCA, one should decide how deeply one should analyze the case. These objectives are typically based on the risk associated with the failures and the complexity of the situation. The three levels of root cause analysis are physical roots, human roots, and latent roots. Physical roots, or the roots of equipment problems, are where many failure analyses stop. Physical root causes are derived from laboratory investigation or engineering analysis and are often component‐level or materials‐level findings. Human roots (i.e., people issues) involve human factors, where the error may be happened due to human judgment that may have caused the failure. Latent roots include roots that are organizational or procedural in nature, as well as environmental or other roots that are outside the realm of control.