The Journey of Reliability
A machine is identified by the vibration analyst and recommendations are made for repair, the planner orders the parts, management gets together and determines when the repairs are made, and the maintenance team carries out the plan to replace the defective component. Success! We averted disaster once again!
… And the cycle continues.
This all sounds good; we are doing all of what was expected and we avoided catastrophic failure. This is the story many, many times over, and it’s always a great one. This is predictive maintenance in action and it has changed the culture of maintenance drastically over the past few decades, making equipment reliability a cost savings several times over the expense it involves.
… Let’s continue the story!
The component that was replaced was a motor, and the story repeats itself a couple of years later. Success again, right? This is a cycle that will continue until we discover and correct the issue that caused the failure in the first place. An investigation needs to be conducted.
Pieces of Predictive Maintenance
There were still some pieces of the puzzle left over, and there is still more we can do. As vibration analysts, we have data showing the failure and progression toward failure. There is a bearing or other machine component, which was changed out, that we can examine. We also have records in the maintenance management system. These pieces are all clues that can give us a cause of failure. We sift through all these details and continuously ask why we should get down to the root cause of the failure and eliminate or mitigate it as much as possible.
One of the “puzzle” pieces is in the vibration data itself. This wasn’t a typical bearing failure, rather the spectrum showed outer race defect as sidebands in the higher frequency range, indicating electrical fluting. The motor was run on a VFD, and upon disassembly of the motor we found the grease in one of the motor bearings to be black or burned. The bearing had the telltale signs of electrical fluting with that beautiful washboard pattern.
Questioning Your Reliability?
Are you asking why?
- Why did the motor fail?
- Electrical Fluting.
- The machine wasn’t grounded properly and current was being passed through the bearings.
- No grounding brush where one was needed.
Fixing Failures and Adding Reliability to Equipment
This time we put a grounding brush on the motor and the failures stopped. The loop is closed on this failure and the motor will hopefully live a full and productive life.
The story above is a relatively common one, and it is not limited to motor fluting. By eliminating these failures and then closing the loop to their causes, we can bring even more reliability to the equipment that we monitor. This will help the maintenance strategy switch from predictive to proactive, which will save money, time, and energy and improve the working lives of everyone involved in the process.