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Compressed Air System Equipment – What You Need To Know

Published on by Russ BowmanLeave a comment

The use of compressed air in industry is so widespread that it’s long been called “the fourth utility” (along with electricity, water, and natural gas). As a function of energy consumption (running an air compressor) to energy generated (operation of pneumatic equipment), only 10-15% of the energy consumed is converted to usable energy stored as compressed air. Its “bang for the buck”, however, comes when you consider the total cost of ownership – yes, it costs a lot to generate, but:

  • It’s relatively safe, when compared to the risks of electrocution, combustion, and explosion associated with electricity & natural gas.
  • Air operated tools, equipment, and products are generally much cheaper than their electric, gas, or hydraulic powered counterparts.
  • Air operated products, like anything, require periodic maintenance, but oftentimes, that maintenance simply comes down to keeping the air supply clean and moisture free, unlike the extensive (and expensive) maintenance requirements of other industrial machinery.

Even with these advantages, though, it’s still critical to get all you can out of that 10-15% of the energy you’re consuming to make that compressed air, and that starts with having the right stuff in the right place. Now, all of the following “stuff” might not apply to every compressed air system. I once worked in a repair shop, for example, with a small compressor that was used for a couple of blow off guns, impact drivers, and a sidearm grinder. I’ve also done field service in facilities with hundreds of pneumatic cylinders & air motors that operated their machinery. Those places had even more “stuff” than I’m devoting space to in this blog, but here’s a list of the “usual suspects” that you’ll encounter in a properly designed compressed air system:

  • Air compressor. I mean, of course you need a compressor, but the size and type will be determined by how you’re going to use your air. The small repair shop I worked in had a 5HP reciprocating positive displacement compressor with a 50 gallon tank, and that was fine. The larger facilities I visited often had several 100 + HP dynamic centrifugal or axial compressors, which get more efficient with size.
  • Air preparation. This includes a number of components that can be used to cool, clean, and dry the air your compressor is generating:
    • Pressurizing a gas raises its temperature as well. Hot compressed air could cause unsafe surface temperatures and can damage gaskets, seals, and other components in the system. Smaller compressors might not have this problem, as the heat of compression is often dissipated through the wall of the receiver tank and the piping at a rate sufficient to keep the relatively low (and often intermittent) flow at a reasonable temperature. Larger compressors usually come with an aftercooler.
    • The air you compress likely has a certain amount of moisture in it…after nitrogen and oxygen, water vapor usually makes up more of the content of atmospheric air than all other trace gases combined. There are a number of air dryer types; selection will be dictated by the specifics of your facility.
    • Your air is going to have other contaminants in it too. We did welding & grinding in the repair shop where our compressor sat in the corner. We kept a few spare intake filters handy, and replaced them regularly. In conjunction with the aftercooler & dryer, larger industrial compressors will also have particulate filters for these solids. For extra protection, coalescing filters for oil vapor, and adsorption filters for other gases & liquid vapors, are specified.
  • Distribution. In the repair shop, we had a 3/4″ black iron pipe that ran across the ceiling, with a few tees & piping that brought the air down to the individual stations where we used it. The larger facilities I visited had larger variations of this “trunk and branch” type network, and some were even big enough to make use of a loop layout…these were especially popular when multiple air compressors were located throughout the facility. In addition to black iron, copper & aluminum pipe (but NEVER PVC) are commonly used too.
  • Condensate removal. The small repair shop compressor had a valve on the bottom of the tank with a small hose that we’d blow down into a plastic jug periodically. Larger systems will have more complex, and oftentimes automated condensate management systems.

So, that’s the system-wide “stuff” you’ll usually encounter in a properly designed compressed air system. After that, we’ll find a number of point-of-use components:

  • Air preparation, part 2. The compressor intake & discharge filtration mentioned above make sure that you’re putting clean air in the distribution piping. That’s fine if your distribution piping is corrosion resistant, like aluminum or copper, but black iron WILL corrode, and that’s why you need point-of-use filters. EXAIR Automatic Drain Filter Separators have 5 micron particulate elements, and centrifugal elements that ‘spin’ any moisture out. If oil is an issue, our Oil Removal Filters have coalescing elements for oil/oil vapor removal, and they provide additional particulate protection to 0.03 microns.
  • Pressure control. Your compressor’s discharge pressure needs to be high enough to operate your pneumatic device(s) with the highest pressure demand. Odds are, though, that not everything in your plant needs to be operated at that pressure. EXAIR Pressure Regulators are a quick & easy way to ‘dial in’ the precise supply pressure needed for specific products so they can get the job done, without wasting compressed air.
  • Storage. This could also be considered system “stuff”, but I’m including it under point-of-use because that’s oftentimes the reason for intermediate storage. Having a ready supply of compressed air near an intermittent and/or large consumption device can ensure proper operation of that device, as well as others in the system that might be “robbed” when that device is actuated. They’re good for the system, too, as they can eliminate the need for higher header pressures, which cause higher operating costs, and increased potential for leaks. EXAIR Model 9500-60 60 Gallon Receiver Tanks are an ideal solution for these situations.

For more information on proper installation and use of compressed air system “stuff” like this, the Compressed Air & Gas Institute’s Compressed Air and Gas Handbook has a good deal of detailed information. The Air Data section of EXAIR’s own Knowledge Base is a great resource as well.

Of course, all the attention you can pay to efficiency on the supply side doesn’t matter near as much if you’re not paying attention to HOW you’re using your compressed air. EXAIR Intelligent Compressed Air Products are designed with efficiency, safety, and noise reduction in mind. Among the other ways my fellow Application Engineers and I can help you get the most out of your compressed air system, we’re also here to make sure you get the right products for your job. To find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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How a Centrifugal Compressor Works

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Continuing our series on different types of air compressors, today’s blog will feature the centrifugal compressor.  The centrifugal compressor is classified as a dynamic compressor.  Dynamic compressors are designed to work with  a continuous flow of air that has its velocity increased by an impeller rotating at a very high speed.

The centrifugal compressor works by transforming the kinetic energy and velocity into pressure energy in the diffuser.  The air passes through the inlet guide vanes being drawn into the center of a rotating Impeller with radial blades and is then pushed outward from the center by centrifugal force. This radial movement of air results in a pressure rise and the generation of kinetic energy.  The kinetic energy is also converted into pressure by passing through the diffuser.

Centrifugal Pic 1
Sample Centrifugal Compressor

Multiple stages are required to raise the pressure to a sufficient level for typical industrial plant requirements.  Each stage takes up a part of the overall pressure rise of the compressor unit.  Depending on the pressure required for the application, a number of stages can be arranged in a series to achieve a higher pressure.

The most common centrifugal air compressor has two to four stages to generate pressures of 100 to 150 PSIG and incorporates a water cooled inter-cooler and separator between each stage to remove condensation and cool the air prior to entering the next stage.

Centrifugal compressors are the near middle of the road regarding efficiency, their typical operating cost is 16 to 20 kW/100 CFM.  The most efficient compressor type is the double-acting reciprocating and costs 15 to 16 kW/100 SCFM and the least is the Sliding Vane which costs 21 to 23 kW/100 SCFM.

Advantages of the centrifugal air compressor:

  • Up to 1500 HP systems are available
  • Price per HP drops as system size increases
  • Supplies lubricant-free air
  • Special installation pads are not required for installation

Disadvantages of the centrifugal air compressor

  • Costs more Initially
  • Requires specialized maintenance
  • Due to high rotational speeds (can exceed 50,000 RPM) precision high speed bearings and vibration monitoring are required

EXAIR recommends contacting a reputable air compressor dealer in your area to discuss your volume and pressure requirements to determine the best size & type air compressor for your needs.

Regardless of the type of air compressor you have, EXAIR’s Intelligent Compressed Air Products® can minimize your compressed air consumption, potentially reducing the size of compressor needed, reduce noise and still deliver powerful results!   If you would like to discuss highly efficient and quiet point of use compressed air products or any EXAIR product, we would enjoy hearing from you. 

Steve Harrison
Application Engineer
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Image Courtesy of  the Compressed Air Challenge

What’s The Big Deal About Clean Air?

Published on by Russ BowmanLeave a comment

Compressed air isn’t called manufacturing’s “Fourth Utility” (the first three being electricity, water, and natural gas) for nothing. Pneumatic tools are popular because they’re often so much lighter than their electric counterparts. Compressed air can be stored in receiver tanks for use when other power supplies are unavailable or not feasible. Many compressed air operated products can be made to withstand environmental factors (high/low temperature, corrosive elements, atmospheric dust, oil, other contaminants, etc.,) that would make electric devices very expensive, unwieldy, or impractical.

One of the most valuable considerations, though, is that your compressed air system is, by and large, under your control.  The type and capacity of your air compressor can be determined by your specific operational needs.  The header pressure in your supply lines is based on the applications that your air-operated devices are used for.  And the performance & lifespan of every single component in your compressed air system is determined by the care you take in maintaining it.

I covered the importance of compressed air system maintenance in a blog a while back…today, I want to focus on clean air.  And, like the title (hopefully) makes you think, it’s a REALLY big deal.  Consider the effects of the following:

Debris: solid particulates can enter your air system through the compressor intake, during maintenance, or if lines are undone and remade.  If you have moisture in your air (more on that in a minute,) that can promote corrosion inside your pipes, and rust can flake off in there.  Almost all of your air operated products have moving parts, tight passages, or both…debris is just plain bad for them.  And if you use air for blow off (cleaning, drying, etc.,) keep in mind that anything in your compressed air system will almost certainly get on your product.

Your compressed air system may be equipped with a main filter at the compressor discharge.  This is fine, but since there is indeed potential for downstream ingress (as mentioned above,) point-of-use filtration is good engineering practice.  EXAIR recommends particulate filtration to 5 microns for most of our products.

Water: moisture is almost always a product of condensation, but it can also be introduced through faulty maintenance, or by failure of the compressor’s drying or cooling systems.  Any way it happens, it’s also easy to combat with point-of-use filtration.

EXAIR includes an Automatic Drain Filter Separator in our product kits to address both of these concerns.  A particulate filter element traps solids, and a centrifugal element “spins” any moisture out, collecting it in the bowl, which is periodically drained (automatically, as the name implies) by a float.

Point of use filtration is key to the performance of your compressed air products, and their effectiveness. Regardless of your application, EXAIR has Filter Separators to meet most any need.

Oil: many pneumatic tools require oil for proper operation, so, instead of removing it, there’s going to be a dedicated lubricator, putting oil in the air on purpose.  Optimally, this will be as close to the tool as possible, because not all of your compressed air loads need oil…especially your blow offs.  If, however, a blow off device is installed downstream of a lubricator (perhaps due to convenience or necessity,) you’ll want to do something about that oil. Remember, anything in your system will get blown onto your product.

If this is the case, or you just want to have the cleanest air possible (keep in mind there is no downside to that,) consider an EXAIR Oil Removal Filter.  They come in a range of capacities, up to 310 SCFM (8,773 SLPM,) and the coalescing element also offers additional particulate filtration to 0.03 microns.

In closing, here’s a video that shows you, up close and personal, the difference that proper filtration can make:

If you’d like to discuss or debate (spoiler alert: I’ll win) the importance of clean air, and how EXAIR can help, give me a call.

Russ Bowman
Application Engineer
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What Makes A Compressed Air System “Complete”?

Published on by Lee EvansLeave a comment

It’s a good question.  When do you know that your compressed air system is complete?  And, really, when do you know, with confidence, that it is ready for use?

A typical compressed air system. Image courtesy of Compressed Air Challenge.

Any compressed air system has the basic components shown above.  A compressed air source, a receiver, dryer, filter, and end points of use.   But, what do all these terms mean?

A compressor or compressed air source, is just as it sounds.  It is the device which supplies air (or another gas) at an increased pressure.  This increase in pressure is accomplished through a reduction in volume, and this conversion is achieved through compressing the air.  So, the compressor, well, compresses (the air).

A control receiver (wet receiver) is the storage vessel or tank placed immediately after the compressor.  This tank is referred to as a “wet” receiver because the air has not yet been dried, thus it is “wet”.  This tank helps to cool the compressed air by having a large surface area, and reduces pulsations in the compressed air flow which occur naturally.

The dryer, like the compressor, is just as the name implies.  This device dries the compressed air, removing liquid from the compressed air system.  Prior to this device the air is full of moisture which can damage downstream components and devices.  After drying, the air is almost ready for use.

To be truly ready for use, the compressed air must also be clean.  Dirt and particulates must be removed from the compressed air so that they do not cause damage to the system and the devices which connect to the system.  This task is accomplished through the filter, after which the system is almost ready for use.

To really be ready for use, the system must have a continuous system pressure and flow.  End-use devices are specified to perform with a required compressed air supply, and when this supply is compromised, performance is as well.  This is where the dry receiver comes into play.  The dry receiver is provides pneumatic capacitance for the system, alleviating pressure changes with varying demand loads.  The dry receiver helps to maintain constant pressure and flow.

In addition to this, the diagram above shows an optional device – a pressure/flow control valve.  A flow control valve will regulate the volume (flow) of compressed air in a system in response to changes in flow (or pressure).  These devices further stabilize the compressed air system, providing increased reliability in the supply of compressed air for end user devices.

Now, at long last, the system is ready for use.  But, what will it do?  What are the points of use?

Points of use in a compressed air system are referred to by their end use.  These are the components around which the entire system is built.  This can be a pneumatic drill, an impact wrench, a blow off nozzle, a pneumatic pump, or any other device which requires compressed air to operate.

If your end use devices are for coating, cleaning, cooling, conveying or static elimination, EXAIR Application Engineers can help with engineered solutions to maximize the efficiency and use of your compressed air.  After placing so much effort into creating a proper system, having engineered solutions is a must.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE