Continuous energy improvement for motor systems pay off

You have more control over how much your plant spends on energy than you might think. Learn how to reap the benefits of applying continuous energy improvement to your motor systems.

By Dennis Bowns

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There appears to be no relief in sight from rising energy prices. Without exception, industrial facilities nationwide are feeling the bite of soaring energy costs. Plant managers and their corporate counterparts, however, have more control over this important, highly manageable cost than they might think.

Buying system components on the basis of first cost or low bid frequently overlooks potential improvement opportunities in both reliability and efficiency. Sometimes, companies take advantage of utility incentives by replacing single inefficient system components with upgrades that are more efficient by 1% to 5%, providing long-term potential savings of thousands of dollars. Unfortunately, without reviewing the efficiency opportunities available throughout the system, upgrades usually fall well short of their full potential.

The best approach to energy efficiency for companies with lean margins or aggressive goals is continuous improvement. A continuous energy improvement program starts with a commitment from management to develop a long-term plan for improved energy productivity and performance. It then continues with a strategic energy management plan having measurable cost reduction goals and key performance indicators at the plant, product line and systems level. A continuous improvement plan assigns accountabilities for achieving energy performance goals, engages employees with training and recognition and provides opportunities for vendor involvement. In addition, it may include utility and public assistance for technical support and financial incentives.

A continuous improvement program for motor systems can help industrial facilities realize significant energy savings; improved reliability, systems management and spares utilization; and improved productivity for maintenance personnel. Add to this better control of downtime duration, and a motor system continuous improvement program becomes an essential success strategy in a highly competitive, global marketplace.

The first step in a motor systems continuous energy improvement program is making a commitment to change either in business practices or systems, preferably both. Of course, you’ll also want to establish an energy management policy. Assign an electric motor system champion, or several champions, to supervise efficiency initiatives for pumps, compressors, refrigeration and air-handling equipment and constant-torque loads. Set goals and objectives. Identify key performance indicators such as the ratio of output to energy consumption, build an up-to-date motor system analytical database and get your motor service center test results on file along with records of root cause failure analyses. Review system component baseline performance at specific intervals.

Manage your motor purchase, operations and maintenance from a life-cycle cost perspective. Record and assess your motor and driven-equipment population. Document and assess electrical output, load measurements and hours of operation. Document process output measurements and assess true needs or requirements. Establish system component pre-failure action plans. Work with, and encourage, qualified vendors that recognize the wisdom of unselfishly focusing on your big picture and supporting your facility systems. Educate your staff using available systems training tools, but avoid using product-specific or biased materials.

Most importantly, commit to continuing the search for lasting value. Measure success based on the answers to four key questions:

  • Did we make money?
  • Did anyone get hurt?
  • Did we pollute anything?
  • Did we minimize our lifecycle cost (including energy)?

Why driven systems?

The following example demonstrates why driven systems are important. Chronic maintenance and high energy cost on an effluent pumping system plagued a certain paper mill. The system for treating wastewater used three 100-hp pumps. Because the system’s control scheme permitted excess pumping, it needed a combination of throttling and bypass valves to modulate the flow. The system cavitated and vibration fatigued the process piping and shortened equipment life.

A systems analysis evaluated ways to improve the motor, pump, distribution system and desired output characteristics. The result was a motor system optimization project that installed variable-frequency drives, replaced worn pump impellers and other components, and integrated system control and instrumentation. The efficiency improvement project saved the mill an estimated 700,000 kWh of electrical energy per year valued at $32,000. The reliability improvement will contribute $10,000 in maintenance cost reductions. In short, the estimated project payback of 15 months represents a simple ROI of nearly 70%.

But a continuous energy improvement program doesn’t end there. The champion involved in the assessment and optimization decisions continues to monitor, document and factor system characteristics with KPIs, using the newly installed instrumentation. If an undesirable system trend or change emerges, the plant deals with it appropriately using its pre-failure action planning. This continuous improvement step ensures that process needs are met, payback is realized and additional efficiency and reliability savings can continue to accrue well beyond the original payback period.

Electrical systems

Electrical supply systems also benefit from efficiency improvements and optimization. The common byproduct of inefficiency in many electrical supply systems is heat, the most virulent enemy of electrical component reliability.

Heat reduces a motor’s useful life and adversely affects supply feeder components. A 2% voltage imbalance can increase motor loss by as much as 10%, raise motor winding temperature by 8ºC and decrease efficiency by 1%. A 10ºC temperature rise halves motor winding life expectancy, according to the Electrical Apparatus Service Association (EASA). Not only does the motor suffer, but every electrical component and conductor in that same unbalanced circuit suffers the same exposure and ultimate fate. Other thieves of efficiency and enemies of electrical system reliability include poor power conditions, voltage drop, harmonics, line transients and mechanical over- and under-loading.

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