Stretch blow molding equipment requires a significant amount of energy—both compressed air and electrical—to produce bottles. Creating an effective and efficient process, as well as monitoring and maintaining optimal process settings, can result in significant energy cost reduction. These efforts will also help produce containers that meet all of the required quality standards.
Air gaging relies on a law of physics that states flow and pressure are directly proportionate to clearance and react inversely to each other. As clearance increases, air flow also increases and air pressure decreases portionately. As clearance decreases, air flow also decreases and air pressure increases.
This article reviews portions of an audit report of a compressed air system in a food industry factory located in the U.S. Although the audit explored different supply-side options the client should consider to improve dynamic efficiency, we will focus on the demand side of the system for this article.
This brewery is a relatively large operation with nine production lines plus a keg line. There are five bottle lines and four can lines. Operations in the plant include palletizing de-palletizing, filling, packaging operations, and brewing. Annual plant electric costs for compressed air production, as operating today, are $693,161 per year. If the electric costs of $43,016 per year associated with operating ancillary equipment such as the blower purge dryers are included, the total electric costs for operating the air system are $736,177 per year. These estimates are based upon a blended electric rate of $0.06 /kWh.
The plant air system consists of eight, single-stage, lubricated, Sullair rotary screw compressors. All units are in good working order. Units 2, 3, 4 and 7 are water-cooled and units 6, 8, 9, 10 and 11 are air-cooled. The main plant air system has two primary compressed air dryers, a Thompson Gordon model TG 2000 refrigerated dryer, and a Sullair model SAR 1350 heatless desiccant dryer. Both units are working according to their design. The TG 2000 uses approximately 11.2 kW and is a non-cycling type unit, and the SAR 1350 uses approximately 200 cfm of purge air to regenerate the wet tower.
When an air system requires large quantities of air (ca. >100 m3/min) and air demand highly fluctuates during the day, it is common belief among end-users that large variable speed screw compressors can deliver significant savings opportunities by precisely matching the compressed airflow to the system’s demand. Where the daily flow demand has a variability of up to 90% of the maximum air demand, the study compares the energy consumption of six alternative solutions in terms of number of installed compressors, compressor sizes and types of compression technologies (i.e., oil free centrifugal and oil free rotary).
This factory, located in the U.S. northeast, spent an estimated $120,000 annually on energy to operate the compressed air system. The group of projects recommended below reduced these energy costs by $73,700 or 61% of current use. These estimates are based upon a blended electric rate of $0.114/kWh.
This meat processing and packaging factory spent an estimated $203,640 annually on energy to operate the compressed air system at their Midwestern facility. Based on the air system operating 8,760 hours per year, the group of projects recommended below could reduce these energy costs by an estimated $107,522 or 47% of current use. In addition, these projects will decrease compressor maintenance costs. Estimated costs for completing the recommended projects total $21,900. This figure represents a simple payback period of 2 months.
Over the years, analyzing compressed air system operation and efficiency has gone under various names and taken many different shapes and forms. You may know these as; Assessments, Audits, Studies, and Surveys, but in all cases the compressed systems are analyzed using techniques, such as metering and measuring, to assess the system’s performance and identify opportunities for improvement. The problem is that the results of these activities have varied widely; leaving the end-user to try and determine what is usable, credible and implementable. This has led to a lot of “no actions“, resulting in assessments, audits, studies, and surveys being put on the shelf to collect dust.
This facility is part of a corporation producing molded plastic products. There are many injection and extrusion molding processes. The factory was spending $94,934 annually on energy to operate their compressed air system. This system assessment detailed seven (7) project areas where yearly energy savings totaling $53,191 could be found with a minimal investment of $4,170.
BC Hydro is a sponsor of Compressed Air Challenge and one of two Canadian utilities represented on the Board of Directors. BC Hydro’s Power Smart Compressed Air Optimization program helps customers assess how their air system is working, helps with project implementation costs and provides for onsite training of plant personnel. The following profiles tell how two of their customers discovered excellent savings through the application of low cost measures.
- 1 of 5