What Is an Independent Failure?

An independent failure is a malfunction of a system component that does not affect any other component in the system. It is a key concept in assembly design for manufacturing. Although it is not feasible to build a system where components are completely independent of one another, building in a certain level of independence can be helpful. This potentially ensures that a single failure does not stop the entire manufacturing process, component failure can be fixed without replacing the entire system and certain safety protocols are in place.

Manufacturing relies heavily on industrial machinery that operates in an assembly, or linked, fashion. The assembly system is designed to optimize the manufacturing process, so each part of building a product follows smoothly within the operational design. Every mechanical system has components that can fail at any time. The extent to which the failure of any one component affects the ability of the entire machine to keep operating is a decision that can often be made proactively by the mechanical designers.

For example, a vacuum cleaner is a mechanical device that has an internal operating system. The designer of the machine decides whether the vacuum will turn on and continue to operate, even if the belt that turns one of the sweeping parts breaks. With many vacuum designs, a broken belt is not noticeable except in the way the device is able to pick up materials as intended. The broken belt is designed to be an independent failure within the vacuum's system that affects the quality of operation but does not cause the failure of any other component.

In manufacturing, the establishment of dependent and independent failures within an assembly is critical. On a basic level, the allocation determines whether the entire assembly will have to shut down because of the failure of a single component. Shutting down the entire assembly increases costs exponentially, because production has stopped while costs continue to accrue.

On another level, independent failure is an important concept that allows companies to replace a single broken part, instead of replacing an entire system. An assembly that is too dependent with too many components that are interrelated must often be replaced in its entirety. It is a similar scenario to a consumer taking a car into a garage to replace a broken sideview mirror and being told that the entire casing must be replaced, because there is no effective way to simply replace the broken mirror. The two parts are totally dependent.

Another significant factor in designing systems for independent failure is safety. Mechanical systems design must often take into account what could happen in the event of a catastrophic systems failure. In some situations, independent failure might be an optimal design choice to prevent the system from ever shutting down, such as in the case of nuclear reactors. Other situations might require dependent failure design to stop a malfunctioning system completely upon component failure so workers do not get hurt.