A Re-Examination of Failure Analysis and Root Cause Determination

3I. IntroductionThe purpose of failure analysis is entirely positive: to prevent further failures. Failuresoccur when some system or part of a system fails to perform up to the expectations forwhich it was created. A transmission fails. A pipeline leaks. A cell phone explodes. Theconcept of failure is easy to understand intuitively. But underneath that intuitiveunderstanding are important conceptual principles which are commonly eithermisunderstood or not considered at all.Failure itself is a human concept. Materials do not fail in and of themselves. They followthe laws of nature perfectly. If a part is loaded beyond its tensile strength, it breaks.Until that stress level is reached, it does not break. When a part fails in service, it wasunder-designed or poorly manufactured for the circumstances in which it was used.II. Failures Are Caused by Human ErrorsThat being understood, then all failures are caused by human errors, of which there arethree general types:a) Errors of knowledgeb) Errors of performance (which might be caused by negligence), orc) Errors of intent (which may come down to acts of greed)What are often called “acts of God” are more or less widely spaced natural events, suchas the flooding associated with unusually large storms, earthquakes, and so forth. Interms of geologic time rather than the very short human experience, these events arecertainties, not exceptions. They will happen, given enough time. Failures associatedwith “acts of God” are, again, the results of under-design for the actual conditions thecomponent or system faces in service.Errors of knowledge usually involve insufficient knowledge, education, training,and/or experience. Here are a few examples of such errors of knowledge– Ancient Romans used lead in their wine goblets. Using them over longperiods produced lead poisoning and ultimately insanity. 19 th centuryArctic explorers repeated this failure in their food containers.– Dendrite growth on metals in conductive ionic environments producesshort circuits in electronic components for computers.– Hydrogen Embrittlement (HE) causes otherwise stable high strength steelcomponents to fail.– Degassing produces bubbles and ultimately corrosion in coated cast ironpipes.– Internal and external corrosion of gas lines in the early 20th centurycaused frequent urban explosions.– NASA Shuttle disasters involved both O-ring and ceramic insulationfailures.