This article is adapted from the U.S. Department of Energy's tip sheet "Extend the Operating Life of Your Motor," originally prepared by the Washington State University Energy Program and Lawrence Berkeley National Laboratory.

When it comes to the operation of industrial processes, life cycle cost (LCC) analysis is an often-ignored methodology that can lead to significantly reduced facility operating costs. This is not a new concept—it has been standard practice in the development and procurement of complex military systems for many years. Federal government guidelines require life cycle analysis for federal agencies considering energy and water conservation projects and renewable energy projects in all federal buildings. Even the Hydraulic Institute (a manufacturers' trade association) has published a handbook on the subject, to help lead facilities personnel through the analysis for pumping systems.

LCC analysis need not always be a time-consuming and expensive en-deavor, however. Such analysis is essentially a methodology for calculating and comparing the installation and operating costs of alternative proposed projects over the life of the equipment, process or facility. Experience has shown that for motor-driven systems in general, energy and maintenance costs tend to dominate operating costs. Thus, quantifying these costs over the life of the system goes a long way in identifying opportunities for savings.

While many organizations do not regularly conduct LCC analyses, most do have some form of an asset management program. Understanding and maximizing the life of electric motors should be a part of asset management for any organization with significant quantities of electric motors.

The Industrial Technologies Program within the U.S. Department of Energy (DOE) has a variety of materials addressing potential opportunities to reduce energy and maintenance costs in industrial process systems. This includes software tools, a series of guidebooks, case studies, tip sheets and other materials. Many of these materials relate to motors and motor systems, including a specific series of tip sheets on energy and maintenance opportunities. The following information comes from the tip sheet on how to extend motor operating life.

Why care about motors?
Over 1.2 million integral horsepower motors are sold each year in the United States, and about 3 million motors are repaired annually.

On average, motors account for almost 70 percent of the total electricity consumption for manufacturing facilities, and 23 percent of total U.S. electricity consumption—equal to about 680 billion kWh/year.

Even small improvements in motor operating life or efficiencies can result in significant cost savings at energy-intensive facilities.

Why do motors fail?
Certain components of motors degrade with time and operating stress.

• Electrical insulation weakens over time with exposure to voltage unbalance, over and under-voltage, voltage disturbances and temperature.
• Contact between moving surfaces causes wear. Wear is affected by dirt, moisture and corrosive fumes, and is greatly accelerated when lubricant is misapplied, becomes overheated or contaminated, or is not replaced at regular intervals.
• When any components are degraded beyond the point of economical repair, the motor's economic life is ended.

For the smallest and least expensive motors, the motor is put out of service when a component such as a bearing fails. Depending upon type and replacement cost, larger motors—up to 20 or 50 horsepower (hp)—may be refurbished and get new bearings, but are usually scrapped after a winding burnout. Still larger and more expensive motors may be refurbished and rewound to extend life indefinitely.

An economic analysis should always be completed prior to a motor's failure so as to ensure that the appropriate repair/replace decision is made.

How long do motors last?
Answers vary, with some manufacturers stating 30,000 hours, others 40,000 hours, and still others saying "It depends." The useful answer is "probably a lot longer with a conscientious motor systems maintenance plan than without one."

Motor life can range from less than two years to several decades under varying circumstances. In the best circumstances, degradation still proceeds, and a failure can occur if it is not detected. Much of this progressive deterioration can be detected by modern predictive maintenance techniques in time for life-extending intervention.

Even with excellent selection and care, motors...(Read whole article)