Developing Your Electric Motor Diagnostics Program Part 2

One of the first things that has to be considered when putting together your motor management program is that your motor system will not ‘instantaneously’ fail. This is a fact supported by consistent research projects on reliability, regardless of any negative commercial suggestions to the contrary. If faults occurred instantaneously, there would be no need for testing, predictive and preventive programs, industrial or reliability engineering, product warranties, assurances that equipment would be able to operate as designed nor would business survive the chaos of systems that failed without warning. In every single case, without fail, there is some condition that leads to a fault.

The good news is that all systems wear out gradually over time. This is viewed in reliability and industrial engineering terms as availability or resistance to failure. As equipment ages, its resistance to failure decreases as does the availability, both of which change as a natural log that consists of time and the mean time between failure (MTBF). This amount never quite reduces to zero until the equipment actually fails. 

With all of this in mind, a motor management program can be developed that utilizes motor diagnostics, and other test systems, to evaluate, trend and estimate time to failure. 

There are two basic types of motor system failures: Passive and active.

In a passive failure, winding insulation breaks down, winding contamination occurs, rotor fractures or voids and similar faults. As long as the motor is running, these problems may not be obvious until the fault becomes active.

In an active fault, the motor ceases to operate. It may stall or experience a catastrophic failure of some component of the system such that it can no longer perform its job. 

The purpose of the conditioned based monitoring portion of your motor management and motor diagnostics program, you will be observing, using instrument measurements, the condition of the equipment. The time to failure estimation begins once degradation is indicated. 

The proper implementation of your motor management program will nearly eliminate all unplanned failures, but not all. There will always be problems caused by improper operation, ‘lightning strikes,’ improper maintenance, sabotage and other un-plannable problems which may quickly degrade equipment condition. These are not high risk conditions, in most environments, and, as such, should not be given high regard when managing your program. You need to consider just those conditions that you can manage.

In the next lecture, we will begin to review the seven steps to developing a successful program.