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Sunday, March 13, 2011

Alternative Strategies for Low-Pressure End Uses

Compressed air is expensive to produce. Because compressed air is also clean, readily available, and simple to use, it is often chosen for applications in which other methods or sources of air are more economical. To reduce compressed air energy costs, alternative methods of supplying low-pressure end uses should be considered before using compressed air in such applications. Many alternative methods of supplying low-pressure end uses can allow a plant to achieve its production requirements effectively.

Before deciding to replace a low-pressure end use with an alternative source, it is important to determine the minimum practical pressure level required for the application.

Alternative Applications to Low-Pressure End Uses

Existing Low-Pressure End Use: Open blowing, mixing
Potential Alternatives: Fans, blower, mixers, nozzles
Reasoning: Open-blowing applications waste compressed air. For existing open-blowing applications, high efficiency nozzles could be applied, or if high-pressure air isn’t needed, consider a blower or a fan. Mechanical methods of mixing typically use less energy than compressed air.

Existing Low-Pressure End Use: Personnel cooling
Potential Alternatives: Fans, air conditioning
Reasoning: Using compressed air for personnel cooling is not only expen-sive, but can also be hazardous. Additional fans or an HVAC upgrade should be considered instead.

Existing Low-Pressure End Use: Parts cleaning
Potential Alternatives: Brushes, blowers, vacuum pumps
Reasoning: Low-pressure blowers, electric fans, brooms, and high-efficiency nozzles are more efficient for parts cleaning than using compressed air to accomplish such tasks.

Existing Low-Pressure End Use: Air motors and air pumps
Potential Alternatives: Electric motors, mechanical pumps
Reasoning: The tasks performed by air motors can usually be done more efficiently by an electric motor except in hazardous environ-ments. Similarly, mechanical pumps are more efficient than air-operated double diaphragm pumps. However, in an explosive atmosphere and/or the pumping of abrasive slurries, the application of a double diaphragm pump with appropriate pressure regulating and air shut-off controls may be appropriate.

Case Study: Low-Pressure End Uses are Replaced with Alternative Applications

A bottling plant was using compressed air in some applications that could be better supported with less energy-intensive methods. The plant was cooling and hardening bottlenecks by blowing cool, compressed air on them. Also, some of the blow mold machines were continuously blowing compressed air through air jets onto the pre-form feed lines to prevent them from jamming. Lastly, the plant’s stackers in the packaging area were using compressed air-operated venturi vacuum producers to pick up and position dividers between layers of bottles. To cool the bottlenecks, the application of a small blower that would blow cool air from chilled water was recommended. The installation of an electromechanical vibrator was identified as the best way to prevent the feed lines from jamming. Finally, a central vacuum system having energy costs that were 30% lower than that of the venturi devices was shown to be as effective as the existing system. The annual compressed air energy savings from implementing these simple modifications was $80,000.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air11.pdf

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