Manufacturers and processors are improving the energy efficiency of their plant motor-driven systems by as much as 30 percent under the auspices of the Motor Challenge program of the US Department of Energy (DOE). Among the facilities that are beneficiaries of the Motor Challenge are a Chevron petroleum refinery in Richmond, California, a Cummins Engine diesel engine assembly plant in Columbus, IN, and a Blue Circle quarry in Lithonia, GA. Petroleum refineries are prime candidates for improvement in energy efficiency; roughly 40 percent of their operating cost is incurred by energy demands. Chevron, one of the largest petroleum refiners in the United States, operates six gasoline-producing refineries, including one in Richmond, CA. McBroom Electric used the DOE's MotorMaster+ software to perform the audit. The audit forecast a short payback period for replacing standard motors withenergy efficient models. Blue Circle now uses MotorMaster+ at its cement plant and several ready-mix facilities to evaluate replacement motor purchases based on life cycle costs instead of initial costs.
Manufacturing and processors are improving the energy efficiency of their plant motor-driven systems by as much as 30 percent under the auspices of the Motor Challenge program of the U.S, Department of Energy. The program , run by the DOE's Office of Industrial Technologies, brings together specialists from energy service companies, electric motor system suppliers, and academic research programs, and introduces them to energy-intensive facilities that can benefit from advanced, improved electric motor-driven systems.
Among the facilities that are beneficiaries of the Motor Challenge are a Chevron petroleum refinery in Richmond, Calif.; a Cummins Engine diesel engine assembly plant in Columbus, Ind.; and a Blue Circle quarry in Lithonia, Ga.
The Department of Energy instituted its Motor Challenge program in 1993 to bring about a voluntary partnership between government and industry to promote more efficient industrial motors, according to Paul Scheihing, an ASME member and the program's manager at the Office of Industrial Technologies in Washington.
"The OIT has a whole suite of tools to assist companies in selecting and designing the appropriate energy- efficient motor system technology, including best practices, case studies, and training curriculum," Scheihing said. "We provide technical assistance based on their needs as well as an independent validation on the costs of energy- efficient motor technologies. Independent validation demonstrates the accomplishments of companies that optimize their motor system applications. In addition, OLT validation lends the improved motor system technology credibility through our end user case studies."
Petroleum refineries are prime candidates for improvement in energy efficiency; roughly 40 percent of their operating cost is incurred by energy demands. Chevron, one of the largest petroleum refiners in the United States, operates six gasoline-producing refineries, including one in Richmond, Calif. This facility typically processes 240,000 barrels of crude oil per day, producing diesel fuel, gasoline, jet fuel, and lubrication oil. Its annual electricity costs are just over $25 million.
Like all refineries, Richmond is energy intensive. Mike Lubcyik, operating assistant, and Art Mares, reliability analyst, both in the Richmond plant's distilling and reforming business division, were convinced that they could improve the energy efficiency of the pumps used in the refinery's diesel hydrotreater, or OHT. Raw diesel is pumped to the hydrotreater and processed to produce 20,000 to 25,000 barrels of finished fuel each day, accounting for about 10 percent of the Richmond refinery's daily output.
The hydrotreater began operating in 1993, replacing an earlier vacuum gas oil plant, and decreasing the feed rate by 60 percent. As a result, the pumps were grossly oversized, according to Mares. Several pumps were operating 40 percent below their optimum capacity, reducing hydraulic efficiency and producing excessive vibration. "Because of the high vibration caused by running the pumps back on their performance curve, we would typically repair a mechanical seal or bearing more than once per year," said Mares.
Lubcyik and Mares determined that they could improve the efficiency of the hydrotreater by investigating variable speed drives , rerating internal pump elements, and changing operating procedures. Variable speed drives, or VSDs, adjust the voltage and frequency of the electricity sent to the motor to provide the optimum energy needed for an application.
However, there were no in-house funds for this project, despite vigorous campaigning by Lubcyik and Mares in early 1995 . At the time, a Motor Challenge member, Planergy Services Inc., a San Francisco Bay Area energy services company, which became New Century Energy Services in September, had contracted with Pacific Gas & Electric Co. to reduce industrial consumption by 23 million killowatt-hours per year. Among Planergy's proposals was an offer to provide Chevron with variable speed drives and pump upgrades at no cost to the oil company. Instead, Chevron would pay Planergy out of the energy savings realized from efficiency improvements. Work began in November 1996 and was completed by May 1997.
"We collected trend data from Chevron to study one year's worth of OHT pump operation and put it into a database. We used our own savings analysis spreadsheets to calculate the flows and pressures that would be needed for most of the PU1T1PS' opera ting time," said Gary Koelbl, an electrical engineer and director of engineering for mechanical projects at Planergy. Based on those findings, Planergy installed two All en-Bradley Model 1557, 4,1 60-voltac variable speed drives, one on the hydrotreater's 2,250-horsepower primary first stage feed pump and the other on the 700-hp product pump to reduce power lost through flow control valves. Planergy also rerated one pump and one hydraulic turbine.
The control packages were integrated directly into the Chevron refinery's process-control system so that operators could use the Allen-Bradley drives instead of the control valves for precise process control. The variable speed drives save a total of 4.4 million kWh per year, improve process control, and reduce vibration amplitudes of each pump by two-thirds.
In the case of the hydrotreater's secondary feed pump, also rated at 2,250 hp, Ingersoll-Dresser personnel assisted Planergy in replacing the internal elements, specifically the impellers (rotating elements) and diffusers (stationary elements) to improve pump efficiency.
"We installed impellers with narrower shroud passages to reduce flow passage while maintaining needed pressure, and narrower, milled-vane diffusers to impart the precise flow control geometry. This obviated the need for a VSD," Koelbl said. It also saves 2.1 million kWh per year, reducing vibration amplitude from 0.45 inch per second to 0.05 ipso
The internal elements of the hydrotreater's hydraulic power recovery turbine were similarly changed to accommodate the reduction in flow of the second stage charge pump. The width of the turbine's flow passages was narrowed, and its vane angles were redesigned, but the impeller diameters were unchanged. The changes saved 1.9 million kWh per year in electrical consumption.
In the gasoline-processing portion of the Richmond refinery, Planergy suggested that Chevron change its operating procedures for the main 5,000-hp and 4,000-hp charge pumps to operate the more efficient pump, based on the plant's feed rate. "Chevron was running the 5,000-hp pump 90 percent of the time, and only switched over to the 4,000-hp pump when the flow was so slow that the larger pump was shaking. Rather than use a VSD, we recommended that Chevron use the 4,000-hp pump until it reached maximum load, and then use the 5,000-hp pump, which was only about 20 percent of the time," Koelbl noted.
According to Mares: "We have not had mechanical failures since the drives went into service and vibration has dropped by a factor of 10. Since the pumps were started, we have had no repairs of any kind."
Following the diesel hydrotreater upgrade, the refinery's energy consumption has been reduced by one million kWh per month, or about 30 percent. This resulted in a cost savings of $700,000 per year with no capital investment by the refinery.
Cummins Engine Co. saved more than $200,000 per year in energy costs at its diesel engine assembly plant in Columbus, Ind., by installing nearly 800 energy efficient motors with the assistance of McBroom Electric Co. Inc. of Indianapolis, an electric motor distributor and a Motor Challenge Allied Partner since 1995 . A Cummins Engine employee who participated in the 1995 Motor Challenge Efficient Motor System teleconference, set up to promote the program, contacted both McBroom Electric and U.S. Electrical Motors in St. Louis, another Motor Challenge participant, to discuss improving the Columbus plant's energy efficiency. As a result, McBroom Electric was asked to perform a comprehensive audit of the motors used in Cummins Engines' manufacturing processes.
McBroom Electric used the DOE's MotorMaster+ software to perform the audit. The audit forecast a short payback period for replacing standard motors with energy efficient models. In addition, McBroom Electric directed four Class A motor mechanics to work in the Columbus plant for a week, to examine the machining and transfer lines along with their associated pumps, air handling equipment, and machining tools.
The McBroom Electric analysis showed that Cummins Engines could save nearly $80,000 per year by replacing 296 standard U-frame motors, most 10 years old or older, on its engine block, rod, and insert machining lines with more efficient T- and U -frame motors.
"Higher-efficiency motors were developed by electric motor manufacturers about 10 years ago, using more efficient materials, such as silicon steel in place of lower grade electrical steel and copper wire windings in place of aluminum windings, in designs that optimized the conversion of electricity into horsepower," said Frank Renick, a Hawthorne, N.J. , representative of Baldor Electric Motors, which is based in Fort Smith, Ark. "In the wake of those developments, the National Electrical Manufacturers Association established a higher requirement performance output for the premium efficient motors," said Renick. For example, 10 years ago, a 2S-hp motor converted 91. 7 percent of the electricity it received into horsepower. An energy-efficient 2S-hp motor now converts up to 93.9 percent of electricity into motive power.
Cummins agreed to the massive and complex changeover, beginning in 1996. Personnel from McBroom, Cummins, and U.S. Electrical Motors, the manufacturer of the new motors, joined in the effort.
Motors were replaced gradually on weekends and during planned shutdowns over nearly a year to prevent interference with the production schedule. During this time, Cummins Engines was convinced that energy- efficient motors would be valuable for the two new machining lines it was constructing at the Columbus plant to manufacture the Signature 600 diesel engines, used on heavy-duty Mack and Tristar trucks.
The new machining lines require d 500 motors whose output ranged from 112 hp to 200 hp each. McBroom Electric performed an analysis that showed Cummins Engines would save $128,000 per year by replacing standard motors with energy efficient motors. The Signature 600 engine diesel engine lines began operating in June 1998 and are realizing projected savings.
Savings Etched in Stone
Many of the 30 universities around the country serving as DOE Industrial Assessment Centers are also advancing the Motor Challenge. Engineering faculty and students from each center provide assessments to make plants cleaner, more energy efficient, and more productive.
One participant is the Energy and Environmental Management Center, or EEMC, of Georgia Institute of Techno logy in Atlanta. Blue Circle Aggregates approached the center in January 1997 and asked it to assess the energy use at a quarry in Lithonia, Ga., outside Atlanta. The Lithonia quarry consumes approximately 4 million kWh of electricity at a 500 kW demand to produce 1.8 million tons of aggregate and manufactured sand for construction and road building annually.
Georgia Tech's EEMC recommended three major upgrades at Lithonia: reducing the horsepower of its water kW, and energy use by 39,000 kW per year," said Adams. This redesign cost approximately $5,100 and provides savings of $3,400 per year.
There are about 40 large electric motors, ranging from. 50 to 250 hp, used at the Blue Circle quarry. "The dusty, noisy environment made it difficult to obtain motor data, such as horsepower and measuring loads, so we selected four examples . We used MotorMaster+ software to show that replacing heavy service motors, serving 3,000 hours per year or more, would provide substantial savings," explained Adams. The EEMC staff selected a 200-hp motor on a stone crusher, and three motors, rated at 200, 150, and 140 hp respectively, that powered stone-washing pumps.
New motors were installed in the fall of 1997 and reduced demand by 9.8 kW and energy use by approximately 30,000 kWh per year, representing a savings of more than $2,500. Blue Circle now uses MotorMaster+ at its cement plant and several ready-mix facilities to evaluate replacement motor purchases based on life cycle costs instead of initial costs.