The question gets asked...
- How often should an electric motor be pulled for preventive maintenance (PM) cleaning?
- How many years should go in-between motor reconditions?
- How often should i have the bearings changed on my motor?
There are countless ways to ask the question and it is a common question that all electric motor repair shops get. A plant wants to know how often we recommend pulling the motors for a recondition, or as others call it, a "clean and bake". This is essentially a repair before a failure; a repair to make sure everything is "ok" before an actual failure occurs. This also allows for cleaning of any debris that has accumulated on or even in an electric motor while it was running, in-service.
There are a variety of standard timeframes and answers that are used and given. Some plants live by their PM (Preventive Maintenance) schedules and that works very well for them. Others swear that PM is dead and depend solely on PdM (Predictive Maintenance) to tell them when a motor should be pulled. Some plants, even today, still choose to Run to Failure (Breakdown Maintenance) on all items in their plant. I think a good place to start is clearly distinguishing the three different maintenance strategies:
- Breakdown Maintenance: Run a machine until it fails. Requires stocking spare parts and results in high unscheduled downtime. Very difficult to plan maintenance activities and does not work well for "just-in-time" manufacturing.
- Preventive Maintenance (PM): Time based maintenance. This allows for scheduling maintenance activities based on history and spare parts are ordered, as needed. This can result in over-maintenance of machines as machines do not always wear out on a time scheduled basis. This could also result in excessive "planned" downtime or outages.
- Predictive Maintenance (PdM): Condition based maintenance. Schedule maintenance activities based on machinery condition (Vibration, Thermography, Ultrasound, Temperature, etc.) This keeps scheduled and unscheduled downtime to a minimum. When technicians are untrained this could cause false and/or missed faults.
So... Whats the answer?
The answer on how often an electric motor should be pulled for recondition is all dependent on your plant and your maintenance practices. We find that most plants have a combination of all three maintenance strategies.
Based on history, certain motors will only last three years, therefore they are pulled every three years (or one, or four, or five, etc.). (However, the correct repair facility should evaluate and help determine if this can be stretched longer or not, or at least attempt to improve on the design to make the motor last longer) Everything else is on a vibration route to try and "predict" the failure and then schedule it to be changed during their next scheduled outage. However, almost every plant has some equipment that is easily changed and replaced, for this equipment they will run it to failure and change when needed.
If you are thinking about this, then you are on the right track. However, it really is not an easy question a repair shop can answer for you on the front side. A conversation must be had to discuss what your situation is. Evaluations must be performed and even then it is generally not a definite answer. It is always changing and evolving. That's just maintenance.
However, whichever way it is detected, either by time or by PdM, it is always better to pull your critical assets before a failure occurs. When a failure occurs, typically more damage is done to the unit than just what the actual failure was. The bearing fails and causes a rewind, etc. This can increase your repair cost significantly when a much less expensive repair could have been done earlier.
At HECO, we focus on improving everything we touch. That's why we always start a repair by asking "why?" We can then direct our efforts in optimizing the performance of the electric motor driven powertrain. We do things differently, just check us out and you will see for yourself.
HECO - All Systems Go
About the author:
Justin Hatfield is Vice President of Operations of HECO. He is responsible for Electric Motor & Drive Sales, Electric Motor & Generator Repairs, Spare Solutions, and Predictive Services. Justin was instrumental in developing HECO MAPPS (Motor And Powertrain Performance Systems) which focuses on “why” you have a motor problem instead of simply “What” product or service should be recommended. HECO is an EASA Accredited Service Center.