Project Summary Sara Lee now has a better compressed air system at its industrial bakery , because of an energy efficiency project recently completed. Earlier, a pressure/flow controller had failed, causing a substantial decline in the compressed air system
Plant/Project Background Sara Lee Bakery Group, a division of Sara Lee Corporation, prepares and markets a full line of branded, packaged baked goods in the United States, Europe, and Australia. The Sacramento facility is a 300,000-square-foot industrial bakery built in 1929. With 450 full-time employees, it operates a high-speed bread and bun line seven days per week. Compressed air is an important element that directly supports the stacking, blowing, and cleaning operations required by the bread-making machines.
Before the project, one 100-hp and two 150-hp rotary screw compressors served the bakery’s compressed air system. After a pressure/fl ow controller failed, air demand patterns began fl uctuating severely, and staff had to operate all three compressors simultaneously to meet production targets. In addition, the compressor controls were out of adjustment; this caused them to react to different control pressures, so more than one compressor would activate when only one unit was actually needed. Compressed air leaks accounted for 15% to 20% of the system’s demand, and uncontrolled open blowing applications were found. Those two conditions exacerbated the pressure fl uctuations and wasted even more compressed air. After the project, however, the system’s performance improved considerably. The plant now has a consistent air supply and stable pressure, and fewer compressors are needed to meet the air demand.
The 100-hp fixed-speed compressor is now the base unit, and the 100-hp VSD unit is the trim compressor. Plant staff were able to dispose of one of the two 150-hp compressors; the remaining one serves as a backup.
Project Results
The compressed air system project at the Sara Lee Bakery is yielding impressive energy savings while making production more reliable. Measurements taken after the project was completed indicate energy savings of 471,000 kWh and cost savings of $40,000 per year. These figures are consistent with AIRMaster+ estimates. Also, because two compressors can be off-line, maintenance costs have declined, saving another $10,000 per year, for a total annual savings of $50,000. An $11,000 rebate from the Sacramento Municipal Utility District reduced the total project costs to $27,000, for a simple payback of 6.5 months.
Lesson Learned
Inoperative and improperly functioning components can reduce compressed air system performance, leading to higher energy and maintenance costs. Using a system-level approach to repairing or replacing malfunctioning components is the best way to optimize system efficiency, reduce energy consumption, and ensure reliable production. At Sara Lee’s Sacramento bakery, a misadjusted compressor controls package and a failed pressure/flow controller caused the compressed air system’s performance to be erratic and increased energy and maintenance costs. A system-level assessment that included an AIRMaster+ analysis resulted in a comprehensive project to achieve greater efficiency and improve the system’s performance.
