"What does spike energy indicate?"
Spike energy is a term more associated with vibration analysis than with any of the other predictive maintenance technologies. Basically, as a machine begins to fail and the interior working surfaces degrade, varying levels of vibration emanate from the bearing while wear progresses. Spike energy is the high frequency levels of the vibration being produced by the "ringing" of the internal surfaces rubbing together.
As with any predictive technology, the power is in the vigilant monitoring of the equipment. To get the maximum return, you should establish a baseline when the machine is first put into service. This will serve as a point against which all future results will be compared.
As wear continues, the level of vibration or "noise" will trend upward. By understanding the natural frequency of the metals that are degrading, you can begin to make calculated guesses at the amount of wear as well as the relative life remaining in the component.
This can be related to trending wear debris with oil analysis. When a machine is put into service, the first sample is usually the cleanest in terms of wear debris. While contaminants such as dirt and water are introduced into the system, the surfaces begin to degrade and produce more wear debris. By tracking not only the amount of wear debris but the rate of generation of these particles, you begin to get a better picture of the degradation rate and the machine's overall health.
With oil analysis, you have the added benefit of looking at wear debris shapes to monitor wear and diagnose the root cause. It is harder to do this when simply using vibration.
Consistency is paramount to catch any incipient machine failures and to accurately predict machine health. If you are using vibration to monitor wear generation or a machine's failure modes, you must capture the vibration results from the same spot on the equipment each time it is to be monitored. The same is true for oil analysis. To trend properly, you must sample from the same location using the same procedure each time a sample is extracted.
In a world-class facility, you wouldn't simply rely on a single technology to accurately predict the wear and failure of machine parts. Vibration is a powerful tool, as is oil analysis. When you merge the two together, you get a much clearer picture of what is happening inside the machine and can better predict when a failure might occur. Be sure to integrate all of your predictive maintenance systems for maximum reliability.