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The Scoop: Starting a Motor Policy
 | Key Points - A well-designed motor policy can save on energy and repair costs, and improve overall productivity.
- Inventory all equipment and develop replacement guidelines and repair specifications.
- To be successful, a motor policy should be coordinated with a regular maintenance program.
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Motors are critical to facility operations and account for 50% of the electricity used in industrial facilities. A well-designed motor policy can increase motor system efficiency and your overall productivity. What is It?A motor policy is a set of schedules and procedures that guide maintenance personnel in properly managing motor systems. The ultimate goals are to minimize utility costs and repair expenses, as well as downtime. Major components of a successful motor policy include replacement guidelines, repair specifications, and a maintenance program. Legislative changes, such as the 2010 Energy Independence and Security Act (EISA) motor standards, also need to be taken into consideration since they improve the economics of replacement motors.Start With a Plan
A successful policy starts with proper planning. The following key steps will help to ensure that you have the information you need to optimize your motor systems:
- Inventory all equipment with identification numbers, nameplate information, and hours of operation.
- Develop a motor replacement plan for all of your equipment. Include supplier information, as well as details about replacement type—new versus rebuild.
- Set guidelines for proper disposal of all discarded equipment, and update regularly to ensure that they meet all federal, state, and local environmental regulations.
- Maintain a list of trusted suppliers for each type of motor in inventory. Contact multiple suppliers to ensure high quality and value-added service at the lowest price.
- Make sure all newly purchased motors meet federal energy-efficiency regulations.
Replacement GuidelinesMotor repair and replacement decisions are often made to satisfy immediate needs, with little thought given to long-term consequences. A number of factors can come into play: the age of the equipment, its general condition, and the availability of similar equipment. In addition, motors are very often oversized for the application, so it is not always appropriate to size a replacement motor based on existing nameplate data. The standards that follow can form the guidelines for an effective decision-making process:
- Do not rewind motors with a defective stator core. If the core cannot be restored to its original integrity, the motor should be replaced.
- Verify that the motor is sized properly. Motors that are oversized are stronger candidates for replacement.
- Compare the efficiency of the existing motor to the new EISA standards. Operating cost can be a significant factor, and the efficiency gains of a new motor can warrant replacement.
- Motors that are 100 horsepower (hp) or larger with an annual operating time of less than 4,000 hours can be rewound if core iron specifications are acceptable.
- Motors that are 50 hp or more should be rewound a maximum of three times, after which the motor should be replaced.
- Do not rewind motors if the repair costs exceed 60% of the cost of replacement.
Repair SpecificationsIf the decision is made to repair a motor, the following procedures can help to ensure quality and reduce overall costs:
- When selecting repair contractors, consider their capabilities, experience, and workmanship—not just the cost.
- Make sure contractors are certified by the Electrical Apparatus Service Association (EASA).
- Obtain a written report specifying the cause of equipment failure and suggested steps for repair.
- Repair motors to their original design with respect to turns, winding, configuration, and other specifications.
The U.S. Department of Energy Standards for Electric Motors suggests that rewinding or repairing a motor, even at a quality service center, can degrade the efficiency by 0.5% to 1.0% per rewind. The impact of a poorly rewound motor may not be readily apparent, but the long-term effects may include reduced energy efficiency and shorter operating life. Repair specifications should be well designed and consistently applied to minimize any loss in efficiency or performance.Maintenance ProgramWhile replacement and repair guidelines are important, regular maintenance is the key to realizing motor policy goals of minimizing costs and downtime. The following should be part of an ongoing program of inspection, testing, and service:
- Dirt—dirt attacks the insulation of a motor through abrasion or absorption. It can contaminate lubricants and damage bearings. Dirt buildup on the housing, fan, and inlet openings increases motor temperature, which reduces efficiency and shortens motor life.
- Alignment—look for a soft foot condition during the installation alignment process. A gap between the motor foot and mounting surface will result in housing strain and excessive bearing load when tightened down. Bearing failure represents 50% of all motor failures.
- Lubrication—larger motors require periodic greasing of bearings. Excess grease can increase friction or enter the windings, causing failure. To avoid this problem, clean the fittings before injecting grease.
- Vibration—a noticeable increase or change in motor vibration is an indication of a bearing problem, load imbalance, a bent shaft, a coupling misalignment, or electrical irregularities.
- Voltage—operating motors outside of plus or minus 10% of nominal voltage reduces efficiency and shortens equipment life. Measure and log the voltage while the machine is loaded. Comparing measurements against established norms may help to identify problems.
- Insulation—resistance testing of critical motors on a routine basis is an important predictive test that can reveal degradation of insulation. Readings should be taken once or twice a year. Long-term trending provides a good picture of winding quality.
A well-designed motor repair and replacement policy, combined with an effective maintenance program, can improve your bottom line by reducing energy and maintenance costs, and increasing production.