Industrial Utility Efficiency    


It is becoming a “best practice” to install a variable frequency drive (VFD) air compressor whenever one is replacing an old air compressor.  As a result, real systems have fixed-speed and VFD air compressors, mixed.  I have observed several VFD compressor sizing methods.  In my last article, I referred to a common method: size one VFD compressor for the whole system.  This can work.  However, if it doesn’t meet a higher peak demand, one or more of the old compressors will be started, and a mixed system results.   Another method is to replace a compressor with the same size, but with a VFD.  If the compressor that was replaced is large, a big VFD is installed.  If small, a small one.

Air Compressors

There are many choices of compressor technology and types of controls that can be used for variable demands. Some examples are rotary screw compressors with inlet valve control: variable speed drives: load/unload control; or centrifugal compressors with variable inlet guide vanes. However, in many cases, the efficiency of the overall compression process can be reduced significantly during lower flow demands, leading to more power per unit of air flow being delivered. It is very important to evaluate different available options and see how a plant can run most efficiently.

Air Treatment

Compressed air is dried to prevent condensation and corrosion which can disrupt manufacturing processes and contaminate products. Water is the primary promotor of chemical reactions and physical erosion in compressed air systems. A myriad of desiccant dryer designs have been devised to provide “commercially dry” air, air having a dew point of -40°F or less, to prevent corrosion.  Desiccant dryers use solid adsorbents in granule form to reduce the moisture content of compressed air.


High speed bearing technology is applicable for aeration blowers operating at much higher speeds than the typical 60Hz, 3600RPM for cast multistage units. High Speed Turbo (HST) units are usually single stage (though some utilize multiple cores) and rotate from 15,000 to 50,000RPM. At such high speeds, standard roller bearings cannot offer the industry standard L10 bearing life. Two types of bearing technologies have come to dominate the wastewater treatment market for these types of machines: airfoil and magnetically levitated. Often the two technologies are compared as equals, however, in many significant ways they are not.

Compressor Controls

Load-sharing is an important part of a multiple centrifugal-compressor master control system. It minimizes blow-off based on the available turn-down. In addition, remote start-stop saves more energy if load floats between different ranges. Finally, adding a screw compressor and implementing a hybrid control system might save the most energy and provide the best back-up. In any case, a well-instrumented system allows engineers and operators to assess, optimize and tune the system.


Compressed Air Best Practices® Magazine interviewed Mr. Warwick Rampley, the National Sales Manager for Sydney (Australia) based, Basil V.R. Greatrex Pty Ltd. It’s not every day one is asked to deliver a system able to provide both a reliable compressed air dew point of -80°C (-112°F) and high purity nitrogen.  We work with some excellent technology suppliers and have engineered a rather interesting system.  Although our firm was founded in 1919, this application is one of the most demanding we’ve encountered. Basil V.R. Greatrex is a unique company as we focus only on compressed air measurement, compressed air quality and compressed air efficiency.


The design of wastewater treatment plants is changing, and it has something to do with LEGO® bricks. More specifically, it has to do with how large and complex LEGO structures are built. If you follow the instructions carefully, you build module after module, eventually piecing them together to create a fully functional and cohesive unit.


It’s one thing to move materials during the production process, but when it’s a finished product on the packaging line, choosing the right material handling system is essential. Getting it wrong results in squandered production time when product loss occurs, and wasted raw materials.

Cooling Systems

As a result of compressed air awareness training and a focus on energy management, two facilities in different parts of the world have reduced their compressed air demand substantially by removing vortex style cabinet coolers from some of their electrical panels and reworking the cooling systems.  These facilities were previously unaware of the high cost of compressed air and how much could be saved if other methods of cooling were used. This article describes some of their efforts in demand reduction.
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.
As readers of this publication know, there are many ways to save energy in industrial compressed air systems. One common supply side technology is the variable frequency drive (VFD) of the compressor. It is well-documented that positive-displacement compressors with VFDs provide cost-effective savings in comparison to inlet modulating, load-unload, and variable displacement control.
Formaldehyde is an organic compound that can adopt several different forms. It can be used in solution form as formalin, as a free gas, or in a solid form as paraformaldehyde prills. Formaldehyde is highly toxic to humans, regardless of the method of intake. At room temperature it is a colorless gas characterized by a pungent odor. Even with very short-term exposure, formaldehyde will cause irritation to the eyes including pain, redness, blurred vision followed by sneezing, soreness, coughing, shortness of breath, headaches and nausea. Exposure to elevated levels can lead to accumulation of fluid in the lungs (pulmonary edema).
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.
The Department of Energy estimates that compressed air systems in the U.S. consume about 30 trillion Watt-hours of energy per year. Of all the energy used in manufacturing, compressed air systems have the greatest potential return for implementing energy efficiency practices, according to the DOE. One approach to access some of that return is to eliminate waste by producing compressed air efficiently and only in the amount demanded. Another approach is to leverage compressed air system data to assess the impact of any system changes on energy consumption and productivity.
During my forty years of involvement with distribution (companies that sell and service compressed air system products) as a Vice President of Sales and Marketing and Account Manager, I have witnessed a tremendous amount of change in the compressed air industry. As much as we like to reminisce about the good old days, it is quite apparent that the resources, capabilities and knowledge of distribution today are significantly better than ever before.
Sullair of Houston, one of the largest North American distributors of Sullair industrial and portable diesel compressors, loves a challenge. The company designs customized air compressor packages that fit the rough and rugged world outside the walls of an industrial plant. It builds air compressor solutions that operate efficiently in extreme, harsh environments around the globe. This includes offshore or marine environments, high or low ambient conditions—any environment where a standard air compressor will not operate safely or efficiently.
Production complains about frequent work stoppages due to air supply related problems. It wants a more reliable consistent source of compressed air. Maintenance says it will need to replace an older compressor with a new one to improve the reliability and stability of the system. Maybe purchase a bigger one than currently needed in anticipation of future increases in air demands. Management wants assurances a good return on the investment will be realized from the expenditure before making a financial commitment. For comparing and evaluating alternatives, a benchmark must be established to determine the cost to run the current system. An assessment must be performed to identify the saving’s opportunities and assign dollar values. Questions about the cost of the assessment and what is to be expected in return need to be answered.
As an industrial distributor for 65 years, C.H. Reed, Inc. has been providing ideas, concepts and sustainable solutions to help manage issues associated with three key areas of industrial plants: compressed air systems and equipment; assembly tools and ergonomic material handling; paint finishing and fluid handling equipment. Compressed air has always been a strong focus for C.H. Reed, and it’s a common thread running through all of its product families.
This metal fabrication and machining facility produces high-quality precision-built products. Over the years, the plant has grown and there have been several expansions to the current location. The company currently spends $227,043 annually on energy to operate the compressed air system. This figure will increase as electric rates are raised from their current average of 9.8 cents per kWh.