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Failures vs. Human Errors

All failures are caused by human errors, of which there are three general types:

What are often called “acts of God” are more or less widely spaced natural events, such as the flooding associated with unusually large storms, earthquakes, and so forth. In terms of geologic time rather than the very short human experience, these events are certainties, not exceptions. They will happen, given enough time. Failures associated with “acts of God” are, again, the results of under-design for the actual conditions the component or system faces in service. (reference: Dr. Zee)

Errors of knowledge usually involve insufficient knowledge, education, training, and/or experience. Here are a few examples of such errors of knowledge:

Errors of performance result from lack of sufficient care or from negligence. Negligence involves such things as misreading of drawings, inadequate specifications, and defective manufacturing and workmanship. Some examples are:

Errors of intent very commonly involve greed. Greed leads to actions usually carried out with a conscious or unconscious denial of full knowledge of the potential consequences. In other words, the perpetrators convince themselves that their actions will not have serious impacts. For example:

An interesting example of combining various types of errors is found in the production of galvanized steel. Since the 1930's it has been known that introduction of approximately 0.15% of aluminum into a hot-dip galvanizing bath will cause the formation of a thin aluminum-iron-zinc intermetallic layer at the steel surface. This intermetallic layer acts as a barrier to iron migration into the zinc, preventing the formation of brittle iron-zinc intermetallics. With this Al-Fe-Zn layer in place, when the galvanized component is bent during service, the zinc layer deforms plastically, rather than fracturing. When manufacturers experience high rates of cracking in their galvanizing layers, they have often let the aluminum concentration in their galvanizing bath slip out of control.

This failure may be a combination of all three kinds of errors. The manufacturer may simply not know that the aluminum concentration is so vital to the success of his product, he may just be letting his quality control function slip out of negligence, or he may be unwilling to spend the money necessary to mount an effective quality control program in his plant.

These ideas provide the philosophical underpinnings for a study of failures. It is important to recognize that many failures are preventable if we understand the materials and their intended applications well enough and are willing to pay the required costs for safety and durability.