Intelligent Compressed Air®: Compressor Motors And Controls

Use of compressed air has gone hand in hand with manufacturing for centuries. From manually operated bellows devices that stoked fires to generate the high temperatures needed for forging metals in ancient times, to the massive steam or oil driven compressors used in the 1800’s on projects like the Mont Cenis Tunnel drills, to the sophisticated electric-powered compressors used widely across modern industry, compressed air has actually been “the fourth utility” longer than the other three (electricity, gas, and water) have been in existence.

Diesel & gas powered compressors offer advantages like higher power ratings, portability, and freedom from reliance on local electric power grids, but most air compressors in industrial use are powered by electric motors. They’re plentiful, reliable, and easily adaptable to a range of control schemes that offer efficient operation across a wide variety of operations.

Which control method is right for you will depend on a number of factors specific to your operation. Here’s a brief run-down that may help you narrow down the selection:

  • Compressors in smaller facilities that supply intermittent loads like air guns, paint sprayers, tire inflators, etc. (like the one shown on the right) are oftentimes controlled via Start/Stop. This turns the compressor motor on and off, in response to a pressure signal. This is the simplest, least expensive method, and is just fine for smaller reciprocating compressors that aren’t adversely affected by cycling on & off.
  • Some compressors ARE adversely affected by Start/Stop control…like rotary screw models. These take a finite amount of time to start back up, which could allow header pressure to drop below usable levels. If they cycle too often, heat from the starting current can build up & overheat the motor. If that’s not bad enough, the screw elements & bearings of the compressor itself are oil lubricated…every time they start up, there’s a finite amount of time where metal-to-metal contact occurs before the oil flow is providing rated lubrication. With Load/Unload control, the motor turns continuously, while a valve on the intake of the compressor is cycled by the compressor discharge pressure: it opens (loads) to build or maintain pressure, and closes (unloads) when rated pressure is achieved. When unloaded, the motor uses about 1/3 of the energy it uses while loaded.
  • While turning down energy use to 1/3 of full load is a great way to cut operating cost while maintaining operational integrity of your compressed air system, and physical integrity of your compressor, it doesn’t necessarily make sense when demand may be low enough to be serviced by existing system storage over long periods of time. That’s where Dual/Auto Dual control comes in. It allows you to select between Start/Stop and Load /Unload control modes.  Automatic Dual Control incorporates an over-run timer, so that the motor is stopped after a certain period of time without a demand. This method is most often used in facilities where different shifts have substantially different compressed air load requirements.

When any of the above control schemes are used, they will necessarily rely on having an adequate storage capacity…the compressor’s receiver, and intermediate storage (like EXAIR’s Model 9500-60 60 Gallon Receiver Tank, shown on right) must be adequately sized (and strategically located) to ensure adequate point-of-use pressures are maintained while the compressor’s motor or intake valve cycle. Other methods use variable controls to “tighten up” the cycle bands…these don’t rely on as much storage volume, and in some (but not all) cases, result in higher energy efficiency:

  • A variation of Load/Unload control, called Modulation, throttles the intake valve instead of opening & closing it, to maintain a specific system pressure. This method is limited in range from 100% to 40% of rated capacity, though, so it’s fairly inefficient in many cases.
  • Slide, spiral, or turn valves are built in to certain compressor designs to control output by a method called Variable Displacement, which (as advertised) changes the physical displacement volume of the air end. When header pressure rises, it sends a signal which repositions the valve progressively, reducing the working length of the rotors. This allows some bypass at the inlet, limiting the volume of air that’s being compressed with each turn of the rotor. Since the inlet pressure & compression ratio remain constant, the power draw from the partial load is considerably lower…so it costs less to operate. The normal operating range for this method is from 100% to 40% of rated capacity, but when used in conjunction with inlet valve Modulation, it’s effective & efficient down to 20% of rated capacity.
  • Of course, the most significant advance in efficient control of rotating industrial equipment since Nikola Tesla invented 3-phase AC is the Variable Speed Drive. When the frequency of the AC power supplied to an electric motor is changed, the speed at which it rotates changes in direct proportion. By applying this type of control to an air compressor, the motor’s speed is continuously controlled to match the air demand. Energy costs can be greatly reduced, as this method allows efficient turn down to as low as 20% of rated capacity.

As mentioned a couple times above, multiple control schemes can be applied, depending on user specific needs. Adding accessories, of course, adds cost to your capital purchase, but discussions with your air compressor dealer will lay out the pros, cons, and return on investment. While we don’t sell, service, or even recommend specific air compressors, EXAIR Corporation is in the business of helping you get the most out of your compressed air system. If you’d like to talk more about it, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Take It All In – Just Filter It

The Nose – Only the Nose Knows

Take a nice deep breath as you read this. In through the nose. If you are like me right now, due to Fall allergies you’ll have a little bit of a restriction, hold it for just a second and then breathe out through the mouth. The body is an amazing thing, when we breathe in through our nose the body has some natural filtration built in that is also known as nose hair. While not the most attractive thing to most, it is important. The hairs in the nose help to filter out allergens and catch foreign debris.

An Improperly maintained Cabin Air Filter on a car makes a great bed for mice

Other items you interact with daily have similar air intake filtration. A car often has both an intake air filter and even an in-cabin air filter, these both protect various parts. The engine air filter is vital to prevent dust, debris and even excessive water from entering into the precision machined and assembled motor. The HVAC system in every business or home generally has an intake air filter in order to protect the coils and heater box.

There’s another system in most manufacturing facilities that should always have a filter on it, and that is the compressed air system. Properly maintaining and filtering the incoming ambient air feed before it is compressed starts the process of on the right foot to optimize performance and insure efficiency is maintained from the start of the entire process. These filters are like many others and can be part of a preventative maintenance program. The air compressor manufacturer will have a recommendation on frequency for the various types.

Old Piston driven air compressor intake air filter.

If these filters are left unchanged then the compressor begins to have restricted flow on the intake which then results in less air being pulled in or maybe the filter is removed and then the debris all gets pulled in and sent through to become foreign debris inside the compressor. Both of these will cause the compressor to wear or overheat and work harder to compress the air and send it into the storage tank. This results in premature maintenance needed on the compressors and or point of use devices.

Thus, always filter your incoming air. Whether for your air compressor, car engine, or house, start with a fresh intake and then keep it optimized from there. The payback will be longer lasting equipment that operates at a higher efficiency. And remember, breathe in through your nose.

If you would like to discuss your filtration setups, feel free to reach out to an Application Engineer.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

What’s So Great About Compressed Air?

Compressed air is commonly known as “the fourth utility” – along with electricity, water, and gas – due to its ubiquitous use in modern industry. But…why? If you compare the power required to make it, versus the work you can get out of it, it’s abysmally inefficient. And, while it won’t electrocute you, drown you, or blow you up (like the “first three” utilities, respectively), purposely depressurizing a compressed air line comes with its own particular set of risk factors.

Of course, benefits outweigh inefficiencies and risks in many things most of us do every day. Over half of the energy released in your car’s engine goes to heat & friction, instead of turning the wheels. Insurance companies say the typical American driver has a 77% chance of getting into an automobile accident EVERY YEAR, and that most of us will be in up to THREE traffic accidents in our lifetimes. Looking at the number of fellow commuters I saw on my way to work this morning, it’s clear, though, that most of us are ready to accept that inefficiency and risk. And that’s not so surprising, considering they’re mitigated greatly by ever improving technology in fuel efficiency, and safety.

It’s, of course, the same with compressed air use, and the “first three” utilities as well: regulation, training, and engineering lower the aforementioned risks to broadly accepted levels. These disciplines also provide for the most efficient use, in spite of the inherent inefficiencies (no engine is 100% efficient) – getting the most out of what you have is “the name of the game”. So, how does all of this apply to industrial use of compressed air?

SAFETY

  • Regulation: In the United States, the Occupational Health & Safety Administration (OSHA) limits the nozzle pressure or or opening of a gun, pipe, cleaning lance, etc., when used for cleaning to 30psi, to protect against dead-ending such a device against your skin, which can cause a deadly condition known as an air embolism. This same directive mandates “effective chip guarding” to keep the blown off debris from hitting the operator. EXAIR Corporation has been in the business of making engineered compressed air products that comply with this directive for almost forty years now.
  • Training: There are companies whose sole purpose is to train & certify personnel in both the management, and operation, of industrial equipment in a safe manner. At EXAIR Corporation, our Safety Manager maintains certification from such an agency, which qualifies him to conduct regular training to ensure safe operation of tools, equipment, and chemicals used in the manufacture of our engineered compressed air products.
  • Engineering: In the “Hierarchy of Controls” established by the National Institute of Occupational Safety & Health (NIOSH), “Engineering Controls” is considered to be less effective than “Elimination” or “Substitution” of the hazard, but more effective than “Administrative Controls” or “Personal Protective Equipment”. THAT’S why EXAIR Corporation has been doing what we do – and why we’re so successful at it – for all this time.
For more on this, I can’t recommend my colleague Jordan Shouse’s recent blog on the subject highly enough. Go read it now…this blog will wait.

EFFICIENCY

  • Regulation: Since the energy crisis of the 1970’s, the United States Department of Energy has implemented numerous initiatives directed at improving energy efficiency. If you’ve ever shopped for a home appliance, you’re likely familiar with EnergyStar ratings. They have a similar program for commercial and industrial air compressors. While they’re not a government body with powers to mandate regulations, the Compressed Air Challenge membership consists of manufacturers & distributors, users, research & development agencies, energy efficiency organizations, and utilities, with key focus on providing direction for the most efficient operation of compressed air systems…from generation to point of use.
  • Training: Speaking of the Compressed Air Challenge, they, and other organizations like the Compressed Air & Gas Institute (CAGI) conduct formal training sessions, in addition to the documented direction I mentioned above. CAGI also has a personnel certification program for those interested in developing credibility and confidence by demonstrating knowledge, understanding, and expertise in the design & operation of compressed air equipment. You can even get a cool logo to put on your business cards and in your signature line.
  • Engineering: While there are multiple avenues to engineer SAFE compressed air products, not all of them are necessarily efficient as well. At EXAIR Corporation, we set ourselves above the fray by maintaining focus on safety AND efficiency. In their discussion of controls that I mentioned above, NIOSH has this to add on the subject of Engineering Controls: “The initial cost of engineering controls can be higher than the cost of administrative controls or PPE, but over the longer term, operating costs are frequently lower, and in some instances, can provide a cost savings in other areas of the process.” (emphasis mine)

To answer the question I posed in this blog’s title, there are many considerations that make compressed air great to use…among them are:

  • Pneumatic tools are lighter, cheaper, more mobile, and lower maintenance than their electrical counterparts. The risk of electrocution is also avoided.
  • Compressed air distribution systems are easier and less costly to install than electrical grids or natural gas lines.
  • Compressed air doesn’t lose energy over distance like steam.
  • Compressed air leaks, while potentially costly, don’t present an inherent safety risk to plant personnel like gas leaks or electrical “leaks” (aka electrocution hazards).

Add in safety and efficiency, and THAT’S what’s so great about compressed air. If you’d like to find out how EXAIR Corporation can help YOU get the most out of our compressed air use, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Compressed Air Efficiency Results in Better Business!

Time and time again we write about how compressed air is considered the fourth utility in a manufacturing setting. Compressed air is a great resource to use, however it needs to be used responsibly!

How you use it in your business is important, for a couple of key considerations:

The Cost of Compressed Air

Compressed air isn’t free.  Heck, it isn’t even cheap.  According to a Tip Sheet on the U.S. Department of Energy’s website, some companies estimate the cost of generation at $0.18 – $0.30 per 1,000 cubic feet of air.  A typical industrial air compressor will make 4-5 Standard Cubic Feet per Minute per horsepower.  Let’s be generous and assume that our 100HP compressor puts out 500 SCFM and is fully loaded 85% of the time over two shifts per day, five days a week:

500 SCFM X $0.18/1,000 SCF X 60 min/hr X 16 hr/day X 5 days/week X 52 weeks/year =

$22,464.00 estimated annual compressed air cost

So to minimize the compressed air use and the over all generation costs there are six easy steps to follow!

  1. Measure: the air consumption You must create a baseline to understand your demand requirements. How can you measure your improvements if you do not understand your total demand or baseline? Installing an EXAIR Flow Meter to your main air lines will help identify the amount of compressed air demand you have and help identify areas of concern.
  2. Find and fix leaks in the system: The repair of compressed air leaks is one of easiest ways to gain energy savings. In most cases all you need is a keen sense of hearing to locate a leak. Once a you have confirmed a leak then the make the necessary repairs. Harder to find leaks may require tools such as EXAIR’s Ultrasonic Leak Detector. This is a hand held high quality instrument that can be used to locate costly air leaks.
  3. Upgrade your blow off, cooling and drying operations: Updating your compressed air process tooling can save you energy and help you comply with OSHA noise and safety regulations. An example would be to replace old blow off or open pipe systems with EXAIR Safety Air Nozzles. Replacing open copper tubes or pipes can amount up to 80% air savings. You achieve lower sound levels and significant energy savings.
  4. Turn off the compressed air when it isn’t in use: It sounds obvious but how many times has an operator left for a break or lunch and doesn’t shut off the compressed air for his/her station? The minutes add up to a significant amount of time annually meaning there is opportunity for energy savings. The use of solenoid valves will help but EXAIR’s Electronic Flow Control (EFC) will dramatically reduce compressed air costs with the use of a photoelectric sensor and timing control.
  5. Use intermediate storage of compressed air near the point of use: The use of storage receivers can improve your overall system efficiency in a number of ways. For example, using a main air receiver at the compressor room can make load/unload compressor control more efficient. Localizing receiver tanks such as EXAIR’s 9500-60 sixty gallon receiver tank by the point of use for a high demand process will stabilize the demand fluctuations allowing a more fluid operation.
  6. Control the air pressure at the point of use to minimize air consumption: The use of pressure regulators will resolve this issue. Using regulators you can control the amount of air being processed at each point of use. EXAIR offers different sized pressure regulators depending upon your air line and process requirements. Regulating the compressed air to the minimum amount required and will reduce your overall demand resulting in annual savings and a payback schedule.

Health & Safety

Injuries and illnesses can be big expenses for business as well. Inefficient use of compressed air can be downright unsafe.  Open ended blow offs present serious hazards, if dead-ended…the pressurized (energized) flow can break the skin and cause a deadly air embolism.  Even some air nozzles that can’t be dead ended (see examples of cross-drilled nozzles on right) cause a different safety hazard, hearing loss due to noise exposure.  This is another case where EXAIR can help.  Not only are our Intelligent Compressed Air Products fully OSHA compliant in regard to dead end pressure, their efficient design also makes them much quieter than other devices.

Efficient use of compressed air can make a big difference in the workplace – not only to your financial bottom line, but to everyone’s safety, health, and livelihood.  If you’d like to find out more about how EXAIR can help, give me a call.

Jordan Shouse
Application Engineer

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