The search for failure modes is very similar to the search for failure mechanisms except it is more specific. As we have discussed in other chapters of this book, a properly executed design should include design elements that prevent the susceptibility of components and subcomponents to failure mechanisms that are present in the environment where the asset is being used. When a failure mode occurs, its presence should be viewed as an exception or a mistake. If the asset has been created by professional designers, failure modes should be truly few and far between.
Despite the best efforts of designers and builders of assets, complex systems typically contain a number of instances where components or subcomponents are susceptible to failure mechanisms present in the working environment and that susceptibility results in one or more chronic failure modes.
While the presence of a failure mode or several failure modes in an asset may appear to be a failure on the part of the designer, that is only one possible cause. Frequently, assets are used in a different way than they were intended. They may be used in an operating environment that contains different failure mechanisms. The asset may be used at higher rates or at greater loading than designed. Assets may simply be operated or maintained in a more strenuous manner than intended. In any case, the realities of real-life application of the asset will determine the failure modes that exist. It is up to the owner and operator of an asset to identify all those failure modes and take steps that will apply some form of intervention before the failure modes can cause an asset failure.
Preventing failures require that the owner of assets identify all the failure modes that are present and take some form of action to prevent the failure modes from causing an asset failure. Prevention can take the form of a permanent fix that eliminates the deterioration being caused by the failure mechanisms. Prevention also can take the form of some combination of predictive maintenance and preventive maintenance that will identify when action must be taken and what action must be taken to avoid failures.
The news media seems to be full of stories about instances where failure modes have been allowed to proceed, causing failures that result in injuries, fatalities, or environmental insult. After some investigation, it is often concluded that failures were the result of “accidents” or “nature,” rather than the failure of the owner to identify the presence of failure mechanisms and the resulting failure modes. This conclusion is improper in that identifying failure mechanisms and failure modes is one of the responsibilities of owners who operate assets that expose individuals or the environment to risks.
Tip from Critical Connections: Linking Failure Modes and Failure Mechanisms to Predictive and Preventive Maintenance by Daniel T. Daley