Air Compressors

The introduction of rotary screw air compressors controlled by variable speed drives (VSDs) is one of the best energy efficiency innovations introduced to the industry in the past few years. This style of compressor control can significantly reduce the energy wasted by compressors running in the unloaded condition. But the type of VSD control offered by various manufacturers can differ, and some of these differences can affect the efficiency of the system. This article discusses some little known tweaks to VSD compressor control, including some using hidden features that can sometimes be implemented to enhance the savings gained by the installation of this type of compressors.

Compressed Air Best Practices® (CABP) Magazine recently caught up with the Compressed Air and Gas Institute (CAGI) to discuss variable inlet guide vanes (IGV). The following interview describes how centrifugal compressor efficiency can be improved thanks to recent developments in IGV technology.

Compressed Air Best Practices® (CABP) Magazine recently spoke with Rick Stasyshan, Compressed Air and Gas Institute’s (CAGI) Technical Consultant, and Mr. Neil Breedlove of CAGI's Centrifugal Compressor Section and member company, Atlas Copco Compressors, about centrifugal air compressors. Specifically, the discussion outlined how various inlet conditions can impact the performance of centrifugal air compressors.

In general, this article focuses on the operating principles of centrifugal air compressors, discussing them in simple terms to provide an understanding of application limitations and opportunities. One primary goal is to define often-confusing terminology, such as “rise to surge,” stonewall and surge,” “mass flow,” and “dynamic compression.” This article is not intended to be an engineering discussion of the various types and designs of centrifugal and other air compressors, but rather, a guideline for deciphering operating curves and understanding general performance.

In 1979 I received a call from a business friend that had just purchased his first single-stage base cup blow machine. He was surprised to find out that he actually needed something more than 100 psi of plant air to blow bottles. This was my entry into engineering a polyethylene terephthalate (PET) compressor system. Since then, I have engineered and delivered over 350 systems—from Tobago to Tibet—and many locations in between.

Acrylon Plastics located in Winkler, Manitoba, Canada manufactures an extensive variety of custom plastic parts for a wide range of end use applications. Years ago changes to their production volumes increased the compressed air flows to above what their compressed air system could deliver. As a result the plant pressure would fall to low levels during production peak demands, which negatively affected sensitive compressed air powered machines. In addition to this during light plant loading conditions the air compressors would run inefficiently. Plant personnel tried a variety of strategies to deal with the plant peaks, with the most efficient solution coming as a result of installing VSD style compressors and pressure/flow control.

The beverage industry has been using polyethylene terephthalate (PET) 2-liter plastic bottles primarily for packaging carbonated soft drinks since the 1970s. As that market has grown to encompass bottled drinking water, stretch blow-molding machines continue to produce those plastic bottles. The concept is simple: A pre-form plug is inserted into the blow molding machine heated, and compressed air is injected, “blowing” into the pre-form to create the bottle.

A culture change is in the air at Sullair, a pioneer in air compressor technology, as the company celebrates its 50th anniversary. A global manufacturer of rotary screw air compressors used to power air-driven industrial equipment and tools used in manufacturing as well as the energy, mining and chemicals industries, Sullair operates five manufacturing facilities worldwide.

QCAS provides service, sales, parts and rental solutions for plant air systems, medical air systems, compressed air treatment and nitrogen generating systems. The company prides itself on being client-focused with a commitment to respond to service needs 24/7. “Our relationship with clients involves more than us just selling equipment, parts and maintenance. We provide system auditing, training, testing and information about innovations in our industry,” says Michael McCulley, president.

Quite a number of worst-case compressed air scenarios have been encountered over the years but none may compare to the conditions that existed in a metal foundry somewhere in North America. For reasons you are about to discover, we will not reveal the name of this factory or its location, in order to protect the innocent from embarrassment.