Primary failure:A primary failure is the first detectable signal that a defect exists. For example, if you are dealing with equipment the first detectable signal a component is failing could be a vibration signature that exposes a bearing fault frequency.
Secondary failure:If the same bearing as above fails catastrophically all the additional damage incurred is considered secondary failure. When the bearing that was identified in the primary state fails catastrophically the shaft will drop from lack of support causing shaft and housing damage. The shaft and housing damage did not have to occur, but did. Therefore it is considered secondary failure. Secondary failure is most often a result of not taking action on items exposed from the predictive maintenance technologies exception reports. When the primary bearing defect is exposed, the fate of the component can only be imminent failure. Whether secondary damage occurs, is up to the management since they control when the repairs take place. Unfortunately, the first usual response to a high priority defect is “will it make it to the next shutdown?” Then the premise of condition based maintenance has been at best diluted or at worst ignored.
Taking the predictive maintenance job to the next step:No one cares more about making a correct defect call than the Reliability technician. Whether it is a defect discovered using vibration, ultrasonic, infrared, or any other of the numerous predictive maintenance technologies available, the Reliability technician wants to confirm it was a valid diagnosis. What normally happens is the Reliability technician will wait for the components of the diagnosed defect’s to be removed and retrieve it for examination. When confirmed as a valid call, the component is normally saved as a trophy of sorts. This is understandable as the technician is proud of the fact the call produced a defect that could be corrected before secondary damage could occur. It should only make sense they would have the most interest in finding the solution. With some additional basic knowledge they could determine how the defect materialized. With basic fracture pattern knowledge, technician’s would be able to identify the failure mechanism by reading a fractured component’s surface. To determine if a part failed due to fatigue or overload is a great step toward knowledge and/or solution because the two failure mechanisms only can occur under conditions specific to each mechanism. As an example, let’s say a shaft failed and the technician can determine it is due to fatigue. Let’s further say he or she can also determine the fatigue was due to misalignment. The technician can show proof both by reading the vibration signature and by reading the failed shaft’s surface.
What is there to gain from this?
- Predictive Maintenance Technicians that truly understand failure mechanisms and how they occur.
- Solutions and corrections in the field that last longer because they are based on verified knowledge.
- Higher level of documentation accuracy on work order closeout.
- Technicians that participate from a higher level of knowledge on root cause analysis teams.
- Higher morale because of value-added input.
- Higher overall equipment Reliability.