Archive | Compressed Air Systems


4:07 pm
May 16, 2016
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Don’t Ignore Compressed Air Filters

Men during precision work on production line

By Ron Marshall, Compressed Air Challenge (CAC)

Compressed air filters are often-forgotten items that can affect the quality of your air supply and—surprisingly—the efficiency of your overall system. You can’t afford to overlook them.

Screen Shot 2016-05-16 at 11.02.07 AMAir compressors ingest atmospheric air from the compressor room, pass it through an inlet filter, and compress it to a space about 1/7th the original size. This process generates large amounts of heat that must be removed by some type of cooler. When this is done, moisture is squeezed and condensed out of the air and mostly eliminated by a water separator. While it’s inside the compressor, though, the air also picks up small amounts of the equipment’s lubricant. Any dust in the air as it passed the inlet filter remains, but in a denser form due to the reduction in volume.

Water, lubricant, and dust particles that aren’t filtered out before they reach the air dryer will travel to points unknown throughout the system. Among other things, such contaminants could then ruin your product or clog the internal pneumatic circuits of expensive production equipment. That’s why compressed air filtration is so important.

Fortunately, there are many different types and styles of filtering solutions in the marketplace, ranging from very coarse elements that remove large particles to very fine ones that remove tiny dust particles and minute traces of lubricant and water. Unfortunately, all filters present a restriction to the flow of air that leads to the development of pressure differential.

Contaminants, among other things, that aren’t filtered from your compressed air system could clog internal pneumatic circuits of expensive production equipment.

Contaminants, among other things, that aren’t filtered from your compressed air system could clog internal pneumatic circuits of expensive production equipment.

Pressure differential consumes energy in compressed air systems. About 1% of additional power is required for every 2 psi higher compressor-discharge pressure. Thus, filters need to be chosen wisely. Note, too, that there’s usually a balance between the need for clean air and the cost of compressor operation. In general, the finer your filtering, the higher your energy costs.

That said, who chooses your filters and why? Frequently it’s the compressor supplier—who might have somewhat of a vested interest in supplying your operations with filter elements for years to come. Often, you’ll find a train of multiple filters installed in a compressor room, from coarse to fine, sometimes in multiple groups before and after the air dryer. These types of units can represent the biggest pressure differential in a plant.

For more information on compressed air topics and related training through the Compressed Air Challenge (CAC), visit, or contact Ron Marshall directly at


3:58 pm
May 16, 2016
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Select The Right Pneumatic Tubing And Hose

Remember these important dimensions when specifying pneumatic tubing and hose.

Remember these important dimensions when specifying pneumatic tubing and hose.

When it comes to today’s pneumatic applications, industry has a variety of options for connecting air-preparation systems, valves, and cylinders. Most users turn to flexible pneumatic tubing or hose rather than rigid tubing—and many different types of both are available. A recently released eBook from Cumming, GA-based AutomationDirect ( offers the following advice on selecting the right tubing and hose solutions for your needs.

Tube or hose

Screen Shot 2016-05-16 at 10.50.05 AMFlexible tubing is the most common way to connect pneumatic valves to cylinders, actuators, and vacuum generators in modern automated equipment, with hose coming in a close second. Despite tubing type, be careful to not confuse outside diameter (OD) with inside diameter (ID), and be aware that flexible and rigid tubing reflect very different materials of construction. Remember, too, that tubing is specified by outside diameter and hose is specified by inside diameter.

Most tubing used in pneumatic systems is less than 1-in. OD with common pneumatic main supply circuits in the 1/4–in. to 1/2-in. tube OD range, and pneumatic control circuits in the 1/8-in. to 3/8-in. tube OD range. Pneumatic tubing is available in metric and English sizes, which, clearly, shouldn’t be mixed on the same machine.

In automated equipment and machine-shop applications, the outside diameter drives the selection and specification process, matching the tubing to the push lock or other fitting.

If more airflow is needed, larger diameter stock is the obvious choice. Keep in mind, however, that the inside diameter of tubing is affected by the tube-wall thickness, with thick walls reducing ID and airflow.

Hose is sometimes manufactured by adding a nylon braid between the inner and outer layers of tubing and attaching a rigid and a swivel fitting. Whether the hose is made of rubber or lighter-weight polyurethane or other materials, it is strong, flexible, and kink resistant—and, therefore, an easy way to connect shop air to blow-guns or other pneumatic tools.

Hoses are commonly available in diameters of 1/4-in., 3/8-in., and 1/2-in. with national pipe thread (NPT) or quick-disconnect fittings (QD). To ensure proper airflow for an application, check diameters carefully.

Material types

Several materials are used to produce extruded-plastic pneumatic tubing including:

Polyurethane tubing is strong and has excellent kink resistance compared to other types. With a working pressure of 150 psi or higher, it’s the most commonly used tubing material. It also has tight OD tolerance, and a wide range of available push-to-connect fittings. Note that a number of tubing colors and diameters are offered to help identify pneumatic circuits. UV stabilization is an option for outdoor use.

Polyurethane and PVC tubing are the most flexible materials available. Polyurethane tubing is very durable with outstanding memory, making it a good choice for coiled, portable, or self-storing pneumatic hose applications. PVC is not as tough as polyurethane, but can be specified for food-grade applications. It’s also a good choice when high flexibility and low cost are required.

Nylon and polyethylene tubing use harder plastics and, thus, are less flexible. This makes these material types a good choice for air distribution and straight-run piping applications. Notable nylon-tubing properties include high working-pressure capability (to 800 psi), a temperature range to 200 F, and excellent chemical resistance.

PTFE tubing has several notable properties of its own, including high heat resistance, excellent chemical resistance, and good dielectric properties. PTFE tubing can handle temperatures as high as 500 F, is chemically inert, and can be used in applications sensitive to static electricity. MT

To learn more about this topic and download a free copy of the referenced Practical Guide to Pneumatics eBook, as well as access a wealth other useful automation-related information, visit


2:47 am
March 9, 2016
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Kaeser Rolls Out New 20 – 500 SCFM Compressed-Air-Filter Offering

Screen Shot 2016-03-08 at 8.09.31 PMKaeser Compressors (Fredericksburg, VA and Coburg, Germany) has expanded its air-treatment offering with compressed-air filters in flows from 20 – 500 scfm. According to the manufacturer, these rugged products deliver reliable air quality with exceptionally low pressure drop that translates to year after year of energy savings.

This comprehensive line includes liquid separator, particulate, coalescing and oil vapor adsorbing filters to meet a wide range of air quality needs.

  • Particulate and coalescing filters incorporate deep-pleated filter elements wrapped in stainless steel cages for superior filtration and increased efficiency.
  • Vapor filters use high-efficiency carbon matting to prevent channeling, reduce pressure drop, and prevent particles from escaping.

Robust, aluminum housings feature treated interiors and powder-coated exteriors for extra durability and corrosion resistance.

Kaeser notes that the products are designed with larger flow areas to ensure the lowest pressure drop and provide easier installation, operation, and maintenance.

For more information on Kaeser Compressors’ complete portfolio, CLICK HERE.


9:12 pm
February 8, 2016
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If It’s Leaking, Think Before Tightening

Applying more compression on the sealing element is typically assumed to be the right solution to a leak.

Applying more compression on the sealing element is typically assumed to be the right solution to a leak.

Your natural inclination to stop a leak could lead to greater problems.

By Henri Azibert, Technical Director, Fluid Sealing Association

Whenever a piece of equipment is leaking, our natural inclination is to tighten whatever can be tightened. Applying more compression on the sealing element is typically assumed to be the solution. The expectation is that the tighter the fastener and the greater the clamping force, the higher the level of sealing performance. Unfortunately, this is not necessarily the case and, quite often, will make matters worse—much worse. Given the fact that safety should always be a primary concern, working on pressure-containing equipment requires careful thinking before any remediation is considered and implemented.


Flanges sealed with a gasket should have been tightened with a torque wrench according to the manufacturer’s specifications. The gasket compression loading must take into consideration, among other factors, the process pressure, process temperature, and the gasket material and style. This assumes using new bolts and an appropriate lubricant to achieve an accurate clamping stress from the torque level.

In case of a problem, tightening the bolts will often make conditions deteriorate. The gasket could be crushed and damaged. An elastomeric gasket could be extruded. The flange could become deformed. Further tightening will only exacerbate the leakage.

Compression packing

Personnel are expected to adjust compression packing on pumps to achieve desired leakage levels. While adjustments to reduce leakage are standard procedures, they should only be minor. If improvements aren’t quickly realized, you may have a significant problem on your hands. Extrusion, excessive sleeve wear, chemical attack, radial motion, and other factors can’t be remedied by increased compression. In those cases, increased tightening will aggravate the wear process.

Similar considerations apply to valve packing. Leakage levels are expected to be minimal. If those levels become excessive, only very small, incremental adjustments should be made—after first verifying that the originally specified torque levels are present on the gland packing bolts.

Mechanical seals

Mechanical seals typically aren’t subject to adjustments to reduce leakage. That said, there are some cases where tightening comes into play.

When the stationary seal ring is of a design that can be clamped, the clamping action can easily create distortion. A few millionths of an inch out of flatness will result in a leak. Any increased tightening of the gland bolts will worsen the condition.

Even when the seal ring isn’t clamped, it is often axially supported inside a gland plate. Deflection of the gland plate can be transmitted to the stationary seal face. In these cases, the only way to eliminate the leakage is to loosen the bolts.

The solution begins by confirming the specified torque requirements for the equipment—and verifying, with a torque wrench, whether those specifications had been met. If you don’t have time to research the situation, consider the possible implications of the leakage and what is most likely causing it. When it comes to leakage, your motto should be “Think twice, adjust once.” MT

Headquartered in Wayne, PA, the Fluid Sealing Association (FSA) is an international trade association of companies involved in the production and marketing of a wide range of fluid-sealing devices targeted mainly at industrial applications. Founded in 1933, the association continues to be recognized as, among other things, the primary source of technical information in the fluid-sealing area. For more information, visit For more information on technical topics, email


7:20 pm
January 12, 2016
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Air System Cuts Costs, Maintenance

The Sigma Air Utility system provides the consistent, high-quality compressed-air delivery Scholz manufacturing needs while cutting maintenance and energy costs.

The Sigma Air Utility system provides the consistent, high-quality compressed-air delivery Scholz manufacturing needs while cutting maintenance and energy costs.

German plastics manufacturer Scholz uses a compressed-air system/service to cut maintenance and energy costs while improving air delivery.

The German town of Kronach is home to a plastics manufacturer with a passion for precision.  Horst Scholz GmbH & Co. KG manufactures a wide range of customized components destined primarily for lifestyle products and the automotive and medical-technology industries. The medical sector in particular insists on stringent requirements to ensure high product quality and it’s no different when it comes to the quality standards for the compressed air the company relies on for control and process air.

  • When it came time to modernize their existing compressed-air system, the company’s management discussed three key concerns:
  • frequent fluctuations in demand that go hand in hand with supplying the automotive industry
  • limited space within their plant facility for a new compressed-air system
  • desire to take advantage of the latest technology and all the benefits Industry 4.0 has to offer.

These three key concerns led Scholz to Kaeser Compressors, Coburg, Germany/Fredricksburg, VA  (, a compressed-air systems provider well known for providing unique solutions.

Three concerns

Kaeser’s answer was a Sigma Air Utility (SAU). The SAU is a contracting model in which the compressed-air system remains the property of the air-system provider while the customer simply uses the compressed air as needed, just like power from an electrical socket, and always at the same fixed rate. From an accounting perspective, this approach addressed Scholz’s fluctuating-demand concern since the company would only be billed for the air needed to handle their varying production demands.

Space was Scholz’s second concern and being able to provide a suitable room or area for Kaeser to install the compressed-air system was problematic since space was at such a premium. To solve this problem, Kaeser’s engineering team designed a contained rooftop compressed-air system. This required design work down to the millimeter, but provided a “plug-and-play” compressed-air system after it was installed.

Scholz’s third concern was technology. SAU contracting models feature the latest in Kaeser’s compressor air treatment, system controls, and air-audit technology. First, Kaeser needed to understand the plant demand to build a custom system that would meet Scholz’s production and air-quality needs. They began with a detailed air-demand analysis (ADA) and measured the plant’s air, pressure, and other parameters to complete a detailed compressed-air audit. Based on the audit findings, the new compressed-air system was designed to not only incorporate the very latest in Industry 4.0 technology, but also reliability, quality, and efficiency, as well as impressive energy savings.

Kaeser engineers designed a contained system that delivered necessary compressed air while fitting in limited equipment space.

Kaeser engineers designed a contained system that delivered
necessary compressed air while fitting in limited equipment space.

A key part of the plant’s compressed-air system is Kaeser’s Sigma Air Manager (SAM) 2. SAM 2 is a master controller and the foundation for the highly efficient operation of the entire system. Since the compressors and compressed-air treatment components are equipped with integrated industrial PC technology, they are able to forward their data to the master controller. As a result, SAM 2 can monitor all components, as well as the environmental and production conditions, and can precisely adapt compressed-air production to match the company’s actual compressed-air requirement. Furthermore, SAM 2 optimizes pressure values, automatically adjusts compressor-system air delivery to accommodate fluctuating air demand, and optimizes system efficiency by constantly analyzing the relationship between control losses, switching losses, and pressure flexibility.

Thanks to SAM 2’s built in Kaeser Connect capabilities, Kaeser service personnel can remotely monitor the new system to ensure uptime. System data are easily viewed on HTML pages, allowing remote diagnostics and significantly reducing troubleshooting time. The alarm notifications alert Kaeser personnel of a possible problem and dispatch a technician right away if necessary. Scholz never has to worry about their supply of compressed air.

Additionally, long-term data storage capabilities mean energy and system data can be analyzed over longer periods of time. SAM 2 also generates reports to clearly show energy consumption and system trends, making it possible to perform energy management in compliance with ISO 50001.

Heat recovery reduces energy costs

Karl-Herbert Ebert, head of technology and development at Scholz, is more than happy with the compressed-air solution. “The entire compressed-air supply ran smoothly right from the outset,” he said. “The container was delivered and once connected, we had our air supply.” Additionally, as part of the agreement, Scholz is not responsible for any maintenance on the compressed-air system and they’ve benefited from the superior customer service.

Ebert is especially pleased that this contracting concept has also delivered significant energy savings. The system has provided Scholz the opportunity to take advantage of heat recovery for the first time. Scholz now uses the heat rejected by the compressors, as a result of the compressed-air production process, to heat the company’s facilities—a measure that has resulted in a 50% reduction in oil consumption in the first year alone. For more information, visit MT


6:28 pm
December 17, 2015
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Compressed Air Challenge: Re-commission Your System

By Ron Marshall, CET, CEM for the Compressed Air Challenge (CAC)

Once upon a time, your compressed air system was shiny and new. You proudly inspected the final installation, knowing that the supplier and installer had set things up so that the compressors and dryers would coordinate with each other and work properly.

Over time, however, things can change. Components wear and fail. Relays and sensors burn out and clog. Eventually, the system requires repairs and adjustment. Then, along comes Mr. Fixit, your handy compressor-repair guy. His tool chest includes a handy-dandy adjustment screwdriver that he promptly uses to “optimize” the settings of your system.

The bad news is that Mr. Fixit may not have been around when your equipment was new and set up correctly. He may never have attended a compressor-repair class, much less clearly understand the important aspects—and intricacies—of compressor control. That doesn’t stop him, though, as he happily twists an adjustment screw here and there, hoping to get your compressor purring like a kitten.

While your plant may not have dealt with this type of Mr. Fixit, data from many compressed-air assessments of relatively young, upgraded systems show that the situation is not uncommon. Often, the efficiency of a system depends on the careful adjustment of critical equipment settings. That said, adjustments must be made by qualified personnel who know how compressed-air systems should work.

It pays to have somebody look at your system from time to time to re-commission it, i.e., ensure nothing has happened that might be causing efficiency issues. Regular compressed-air assessments can pay for themselves quickly in energy savings. Items to examine include:

Compressor-pressure settings. Because it’s rather easy (physically) to adjust compressor settings, it’s also easy to misadjust them. Although adjustments may have been made since the system was installed, they could have been in response to a one-time, low-pressure event or other temporary system problem. Consequently, the pressure may be too high or pressure bands too narrow. Reviewing the appropriateness of your compressor settings is an important exercise.

Selection of lead compressor. Some compressors are more efficient than others. Some are more appropriate as lead compressors, others should trim, taking partial load. Efficiency can be maintained by choosing the correct order of operation.

Air-dryer settings. If you have desiccant dryers with dewpoint controls, they could have been bypassed, or might not be working due to a fouled sensor. Reviewing the operation of your dryers and repairing as needed could save a bundle.

Automatic drains. Airless drains, purchased to prevent wasted air, can wear out and fail (undetected). This situation affects dryer operation and the quality of the compressed air. Proper testing is important.

Monitoring systems. It’s important to monitor the efficiency of your system, especially if compressed air is a major part of your electric bill. Permanent monitoring of the system helps you assess the system on a daily basis to maintain efficiency.

Find more information about compressor efficiency on the CAC website ( or in the organization’s Best Practices for Compressed Air Systems Manual. Check the website calendar for scheduled training. MT


6:32 pm
June 12, 2015
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Compressed Air Challenge: Avoid VSD-Compressor Control Gap

04cacBy Ron Marshall, CET, CEM for the Compressed Air Challenge (CAC)

One of the hottest topics in the compressed-air energy-efficiency field is the variable-speed-drive (VSD) screw compressor. Since this unit’s acceptance in the industry several years ago, all major manufacturers have developed a line of compressors that control compressor output pressure by varying the speed of the compression element. This results in an almost linear reduction in power consumption between the compressor’s full load and minimum speed. Minimum speed is the slowest the compression element is allowed to spin while under variable-speed control.

There are other, less efficient, ways to control compressors so that they maintain a constant pressure under varying loads. Some compressors modulate, choking off the inlet flow to vary the compressor output.

Others load and unload to maintain pressure between two set points. Still others might use variable capacity, opening up ports in the compression element with a secondary control system to effectively vary compressor capacity. None of these modes of control is as efficient as variable speed through the full range of compressor output.

Setting up a VSD-controlled unit in a system with a single compressor is easy, but a VSD compressor, inserted into a multiple-compressor system, can generate problems. Most often, multiple fixed-speed compressors are set up in a cascaded arrangement where each successive compressor feeds varying air demand in a set order. On the other hand, a system using a combination of fixed-speed and VSD units must be carefully set up so each VSD always takes partial loads. This requires each VSD target set point to be within the overlap between the fixed-speed compressor set points. This is known as a nested arrangement.

There is also an important sizing rule when applying VSD compressors: The variable part of the VSD capacity must equal or exceed that of the fixed-speed compressors with which it must sequence. If the VSD variable range is smaller than the fixed-speed range, there will be a gap within which the compressors will inefficiently fight for control. This control gap is evident if the VSD is constantly ramping between minimum and full speed while another fixed-speed compressor is loading and unloading. This condition will exist only when the flow is within a control-gap region, defined as the difference between the fixed-speed capacity and the VSD control range (full load minus minimum speed).

Basically, when you mix compressor types, watch your control gaps.

More information about compressor efficiency can be found at the CAC website or in CAC’s Best Practices for Compressed Air Systems manual. Be sure to check the online calendar for scheduled training. MT

The Compressed Air Challenge® is a partner of the U.S. Department of Energy’s Industrial Technology programs. To learn more about its many offerings, log on to, or email


6:25 pm
March 13, 2015
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Compressed Air Challenge: Show Me the Money

04cacBy Ron Marshall, CET, CEM for the Compressed Air Challenge (CAC)

With compressed air system efficiency, ignorance is not bliss. Conditions can slowly develop over time that erode system efficiency. And because most compressed air systems have little in the way of monitoring instrumentation, key performance indicators that are important to keeping systems running in a cost-effective manner can’t be easily tracked. System operators rarely know how their system is performing or, more importantly, how it compares to a well-performing system.

Standard systems rarely come with energy-monitoring capabilities. Maybe this is because the feature is not requested or because system manufacturers have determined that its added price would make their systems uneconomical to purchase. It may also be that your compressors have these tools, but you haven’t discovered them. To get a handle on your system, you should make an effort in this area, and spend the time or money needed to track your system’s energy performance.

Initial monitoring need not be expensive; the investment depends on the accuracy you need. For example, if your compressors are running in load/unload mode, an adequate first-cut system of monitoring can be done simply by tracking the compressor’s loaded and run-time hours (this method is not appropriate for other control modes). Most compressors have hour meters built into the controller. To do this exercise, you will need to know the compressor’s power consumption when unloaded and loaded, and the rated output air flow. This can be obtained by asking the manufacturer and/or having an electrician take a measurement.

For example, let’s say you have a single 25 hp 100 cfm compressor that runs 168 hours per week feeding a small production area. The compressor consumes 22 kW when loaded and 7 kW unloaded. If the compressor was loaded for 80 hours out of 168, that duty cycle would calculate to 48% (80/168= 0.48). This corresponds roughly to an average flow within the running hours of 48 cfm. Compressor average power consumption can be roughly estimated by estimating and adding up the average power during loaded and unloaded hours:

Avg. loaded kW = 0.48 x 22 = 10.6 kW

Avg. unloaded kW = 0.52 x 7 = 3.6 kW

Total in period = 14.2 kW

Total annual cost (if compressor runs full time) =
14.2 kW x 8,760 hours per year x $0.10 per kWh =

Compressor specific power = 14.2 kW/48 cfm x 100 = 29.6 kW/100 cfm

The rated specific power of this compressor at full load is 22 kW/100 cfm. The difference between the rated and calculated suggests there may be room for improvement. For more accurate measurement, direct readings could be taken. Constant monitoring shows how the system changes over time.

More information about compressor efficiency can be found at the CAC Website or in CAC’s Best Practices for Compressed Air Systems Manual. Be sure to check the online calendar for scheduled training. MT