About Rotary Screw Air Compressors

What is an air compressor? In simple terms it is a machine that increases fluid pressure, it works by changing the volume of air and storing it in a storage tank. Many industries use compressors to increase production and thus has led to the development of many new industries. There are a couple types of air compressors but today I will focus on the Rotary Compressor.

The Rotary Screw Compressor is a very common type of air compressor. This compressor uses dual rotors with meshing lobes that trap air while rotating. The rotation continues to push air toward a discharge port while decreasing the space the air take sup, thus increasing pressure. The rotary compressor has a simple structure with few components and has some clear advantages over other compressors:

  • Longevity
  • When operating, they are quiet
  • Low vibration
  • Continuous operation, or they can match demand

Some disadvantages include:

  • Skilled maintenance required compared to other compressors.
  • They are more expensive than other compressors

There are two types of rotary air compressors. They are oil-injected and oil-free rotary air compressors. Oil-injected rotary screw compressors as the name suggests has oil injected in the compressor element during the air compression. An insignificant amount of oil will escape into the compressed air system also known as “oil carryover”. The use of EXAIRs oil removing filters and filter separators will help remove the oil, moisture and other particulates from the compressed air lines resulting in clean compressed air.

Oil-free rotary screw compressors are similar to the oil-injected compressor but without the use of oil. The oil-free compressors use a two stage system with a cooling process between stages as the compressed air will become extremely hot if not for a cooling process between stages of compression. The oil-free compressors are commonly used in food and medical industries.

EXAIR is here to help with your “Intelligent Compressed Air Products” so please contact us with your compressed air tooling needs.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@EXAIR.com
Twitter: @EXAIR_EK

File:IngersollRand R-series-R110.jpg image is licensed under the Creative Commons Attribution 3.0 License.

What’s The Big Deal About Clean Air?

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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