Compressed Air Quality and ISO 8573-1 Purity Classes

Airborne particles surround us everywhere.   In a general work environment, nearly four million particles per cubic foot is floating around us at any given time.  When a compressor compresses this air, the concentration increases substantially.  So, compressed air is not only expensive to make, but very dirty.  As the air exits your air compressor and travels into your pneumatic system, there is so much contamination that the International Standard Organization, ISO, created an Air Quality chart with Purity Classes.

ISO8573-1-2010

This chart is easy to follow and can be found in the ISO8573-1 standard for Air Quality.  It is used to select a cleanliness level for your compressed air system.  The contamination is categorized into three areas; Particles, Water, and Oil (reference above).  A Class is associated with a number for each category ranging from 0 (most stringent) to 9 (most relaxed).  As an example, an Air Quality value of ISO8573-1:2010 [1.2.4] has a Class 1 for Particles, Class 2 for Water, and Class 4 for Oil.  These Class values will show the maximum value in each category.

To define the categories in more detail, I will separate the three to discuss the origins and solutions.

  • Particles: For solid particles, this part comes from many different areas.  The surrounding ambient air that is being drawn into the air compressor is filtered; but the intake filter will only remove large diameter particles.  The smaller diameter particles will go through the filter and into the compressed air system.  Another part is rust particles that occur from steel air pipes and receiver tanks.  Over time, rust will flake off and create particles that can affect pneumatic equipment.  Other particles can come from components inside the air compressor, valves, etc., that wear and breakdown.  In the ISO column for Particles, it is separated into three different micron ranges and concentrations.  The removal of particles from the compressed air is done by traps and compressed air filters.  EXAIR offers two types; Filter Separators with 5-micron filtration and Oil Removal Filters with 0.03-micron filtration.  There are other types of filtration systems depending on your ISO requirement.
  • Water:  Humidity is a natural occurrence as water vapor in the surrounding air.  It can be measured as a dew point temperature.  This is the temperature at which water will condense and make rain.  Inside an air compressor, the air is ‘squeezed”, and the amount of space for water vapor is reduced.  So, it will condense into liquid form as “rain” inside the pipes.  Air that comes out from an air compressor will always be saturated with water.  To remove liquid water, a mechanical device can be used.  Inside a Filter Separator, a centrifugal separator will spin the air and remove the liquid water.  To remove water vapor, a compressed air dryer is required like a refrigerant, desiccant, deliquescent, or membrane type.  Each type will have a dew point range that they can reach.  As an example, a refrigerant type will reduce the dew point near 37 oF (3 oC).  That means that water will not condense until the temperature reaches below 37 oF (3 oC).
  • Oil: This category can be found as a liquid, aerosol or vapor, and it includes more than just oil. It contains small hydrocarbons, CO, CO2, SO2, and NOX.  Oil mainly comes from inside an oil-flooded air compressor.  As the air passes through the compressor, it will pick up remnants of oil aerosols and carry it downstream.  With high temperatures inside the air compressor, some of the oil will vaporize.  Even with oil-less type air compressors, carbon vapor can still be an issue.  Small hydrocarbons can come through the air intake and condense inside the system like water vapor above.  To remove the liquid and aerosol type of oil, Oil Removal Filters can be used.  They are designed to “coalesce” the small particles into larger particles for gravity to remove.  Oil vapor requires an activated carbon to remove.  These types of filter units will adsorb the vapor.  This helps to remove odors as well as dangerous chemical vapors that may be in the compressed air line.

There are a variety of pneumatic systems that use the ISO8573-1 standard.  This will include breathing air operations, food and beverage, pharmaceutical, and the electronic industries.  If you need stringent requirement for your compressed air system, the Air Quality standard should be used by referring to the Class numbers above.  This helps to dictate the types of filtration and air dryers that should be used within your pneumatic system.  If you have any questions about your compressed air system, an Application Engineer at EXAIR can help.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

ISO 8573-1 Chart by Compressed Air Best Practice.

Air – What Is It?

Air… We all breathe it, we live in it, we even compress it to use it as a utility.  What is it though?  Well, read through the next to learn some valuable points that aren’t easy to see with your eyes, just like air molecules.

Air – It surrounds us – (Yosuke,1)
  1. Air is mostly a gas.
    • Comprised of roughly 78% Nitrogen and 21% Oxygen.  Air also contains a lot of other gases in minute amounts.  Those gases include carbon dioxide, neon, and hydrogen.
  2. Air is more than just gas.
    • While the vast majority is gas, air also holds lots of microscopic particulate.
    • These range from pollen, soot, dust, salt, and debris.
    • All of these items that are not Nitrogen or Oxygen contribute to pollution.
  3. Not all the Carbon Dioxide in the air is bad.
    • Carbon Dioxide as mentioned above is what humans and most animals exhale when they breathe.  This gas is taken in by plants and vegetation to convert their off gas which is oxygen.
    • Think back to elementary school now.   Remember photosynthesis?
      • If you don’t remember that, maybe you remember Billy Madison, “Chlorophyll, more like Bore-a-fil.”
    • Carbon dioxide is however one of the leading causes of global warming.

      Moisture In The Air – (Grant)2
  4. Air holds water.
    • That’s right, high quality H2O gets suspended within the air molecules causing humidity.  This humidity ultimately reaches a point where the air can simply not hold anymore and it starts to rain.  The lack of humidity in the air leads to static, while lots of moisture in the air when it gets compressed causes moisture in compressed air systems.
  5. Air changes relative to altitude.
    • Air all pushes down on the Earth’s surface.  This is known as atmospheric pressure.
    • The closer you are to sea level the higher the level of pressure because the air molecules are more densely placed.
    • The higher you are from sea level the lower the density of air molecules.  This causes the pressure to be less.  This is also why people say the air is getting a little thin.

Hopefully this helps to better explain what air is and give some insight into the gas that is being compressed by an air compressor and then turned into a working utility within a production environment.  If you would like to discuss how any of these items effects the compressed air quality within a facility please reach out to any Application Engineer at EXAIR.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 – Air – Creative Commons – Tsurutea Yosuke – https://www.flickr.com/photos/tsurutayosuke/47732716442/in/photolist-2fHYDBG-dd5e5z-5snidD-oaU8fm-68kqiz-8sMG3P-fnqYx7-9bkTrx-5P2BDv-6R75dG-9vi5xL-5yADR-8EAFci-9NQvER-8sMGoR-4Uybwo-9bNqfB-6N9qf8-6LZyG-7MF4aZ-dehz3-5h1wXk-6uJWNq-7eQCUU-6qoUm6-8sQHxo-uqDdE-6NDHW3-8sQMDQ-7wyCsV-dd5io5-5yAwX-ZmCdh2-BMZCW-agSno-bQ8UFK-6d8Pkz-ars544-novykD-3PF1FT-W13jE9-3GSRLj-7r9Msu-6yn1Ne-32iJKf-7CPqWv-8qhcn-4Eicvh-LLgb4-54ixko

2 – DSC_0750 – Creative Commons – David Grant – https://www.flickr.com/photos/zub/24340293/in/photolist-39Kwe-2cZxjuw-6ywctR-26b7Z2F-84vqJN-bpjRN3-6aDzQR-i84BUr-xbu1Us-fxyvn-5UPDBh-VDz7nD-8Be4fP-a6MVGC-nP4end-PA5nb9-3ddwtq-nRF2yr-j4XPzo-cd5CvJ-eoGFTQ-rYNapy-pKAJpQ-pVrbq6-21hFhHB-n8hpva-7uMwPs-4EZ9ok-jGahK-foR798-JP9rcG-cMRjhu-i74Qo-2d1nE-7nXj3e-9tMib1-6JrXP-9tMdnd-4o5ZCx-6uk2LG-9Gt8K4-5xksdV-9tJgMa-9tMh8b-kkZNy5-c8oM8C-8reqky-4KXe87-aFt7kn-MNNDwU

About Compressed Air Dryers – What Are They and Why Use Them

All atmospheric air contains some amount of water vapor.  When air is then cooled to saturation point, the vapor will begin to condense into liquid water. The saturation point is the condition where the the air can hold no more water vapor. The temperature at which this occurs is knows as the dew point.

When ambient air is compressed, heat is generated and the air becomes warmer. In industrial compressed air systems, the air is then routed to an aftercooler, and condensation  begins to take place. To remove the condensation, the air then goes into separator which traps the liquid water. The air leaving the aftercooler is typically saturated at the temperature of the discharge, and any additional cooling that occurs as the air is piped further downstream will cause more liquid to condense out of the air. To address this condensation, compressed air dryers are used.

It is important to dry the air and prevent condensation in the air. Many usages of the compressed air are impacted by liquid water being present. Rust and corrosion can occur in the compressed air piping, leading to scale and contamination at point -of -use processes. Processes such as drying operations and painting would see lower quality if water was deposited onto the parts.

dryers.png

There are many types of dryers – (see recent blogs for more information)

  • Refrigerant Dryer – most commonly used type, air is cooled in an air-to-refrigerant heat exchanger.
  • Regenerative-Desiccant Type – use a porous desiccant that adsorbs (adsorb means the moisture adheres to the desiccant, the desiccant does not change, and the moisture can then be driven off during a regeneration process).
  • Deliquescent Type – use a hygroscopic desiccant medium that absorbs (as opposed to adsorbs) moisture. The desiccant is dissolved into the liquid that is drawn out. Desiccant is used up, and needs to be replaced periodically.
  • Heat of Compression Type – are regenerative desiccant dryers that use the heat generated during compression to accomplish the desiccant regeneration.
  • Membrane Type– use special membranes that allow the water vapor to pass through faster than the dry air, reducing the amount water vapor in air stream.

The air should not be dried any more than is needed for the most stringent application, to reduce the costs associated with the drying process. A pressure dew point of 35°F to 38°F (1.7°C to 3.3°C) often is adequate for many industrial applications.  Lower dew points result in higher operating costs.

If you have questions about compressed air systems and dryers or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
Send me an email
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Atomizing Nozzles – No Drip Deflected Flat Fan and 360° Hollow Circular

EXAIR manufactures three types of Atomizing Nozzles – Internal Mix, External Mix, and Siphon Fed.  Within the Internal Mix family, there are two specialty nozzles, the Deflected Flat Fan and the 360° Hollow Circular patterns.

Internal Mix nozzles are for pressure fed applications not requiring independent air and liquid control.

The model AD2010SS is the No Drip version of the Deflected Flat Fan and is shown below. Our patented No Drip design prevents unwanted post spray drips from wasting expensive fluids or ruining product finishes. The benefit to this design is that no secondary compressed air line is necessary to activate the on/off valve for the liquid, which is the case for competitive nozzles.

ad2010
Model AD2010SS – No Drip Internal Mix Deflected Flat Atomizing Nozzle

The Deflected Flat Fan patterned nozzle is designed for applications where space is a limited.  The spray pattern is at a right angle to the orientation of the nozzle, allowing the spray to be placed precisely where it is needed in tight quarters.  They are ideal for coating the insides of enclosures and ductwork.

NoDripIMDF

The model AT2010SS is the No Drip version of the 360° Hollow Circular and is shown below.

AT2010SS
AT2010SS – No Drip Internal Mix 360° Hollow Circular Atomizing Nozzle

The 360° Hollow Circular patterned nozzle is designed for applications where the spray pattern is to be orientated away form the nozzle in all directions.  They are ideal where a smooth and even coating is needed on the internal surface of a pipe or duct.  They are also good for processed where a mist is needed over a large area, including dust suppression, humidification, and cooling.

NoDripIM360HC-Pattern

The No Drip feature is a patented† design that has the added benefit of positively stopping the liquid flow when the compressed air is shut off. Post spray liquid flow can cause quality issues from unwanted drips on painted or coated surfaces.  Also, the No Drip feature helps to conserve and save on liquid use, reducing costs of expensive coatings or chemicals.

When the compressed air supply is shut off, the No Drip nozzle positively seals off the flow of liquid, eliminating over spray and drips. The design allows for just one compressed air line, there is no need for an additional to control the No Drip mechanism.

If you have questions about Atomizing Spray Nozzles, or would like to talk about any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

Send me an email
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† Patent #9156045

 

No Drip Internal Mix Atomizing Nozzles

Eliminate drips to conserve valuable liquids and improve product finishes!  EXAIR’s patented No Drip Atomizing Nozzle provides the same great performance as the the standard atomizing nozzles with the added benefit of positive liquid flow stoppage when the compressed air is shut off.

The No Drip option eliminates the occurrence of post spray liquid flow that results in unwanted drips that can mar a finish on painted or coated surfaces.  Also, excess liquid loss is minimized saving on expensive materials like chemicals or coatings.  When the compressed air is shut-off, the No Drip nozzle positively seals off the flow, eliminating the chance for a drip or lost liquid. Only one compressed air line is needed, as the line to combine and atomize the liquid also provides the no drip operation and control.

The No Drip Atomizing Nozzles are available in (3) types – Internal Mix, External Mix, and Siphon Fed.

The Internal Mix type operates under the principle that the air and liquid come together and mix ‘internal’ to the nozzle.  This type provides the finest atomization and smallest droplet size. The Internal Mix type of nozzle can be used with liquids up to 300 cP in viscosity.  Both the air and liquid sides are pressure fed.  The No drip Internal Mix Atomizing Nozzles are best for pressure fed applications not requiring independent air and liquid control.

ndAF_qtrin_anticorrsion
A No Drip Internal Mix Flat Fan Nozzle applying anti-corrosion fluid to stamped parts

The No Drip Atomizing Nozzles are available in (3) sizes – 1/8, 1/4, and 1/2 NPT – to provide a wide range of flow rates and pattern sizes.  The No Drip feature does not impact the flow rates compared to the standard models.  Minimum air pressure operation is 30 PSIG for the 1/4 and 1/2 NPT, and just 20 PSIG for the 1/8 NPT models.

Like the standard Internal Mix Atomizing  Nozzles, spray patterns include narrow and wide angle round, flat fan, deflected flat fan and a 360° hollow circular pattern offering a wide selection to best meet the application needs.

Operation at up to 180 spray cycles per minute is possible.  Air and Liquid Caps can be switched out to change the pattern and flow rates.

Typical Applications

  • Painting
  • Coating
  • Rinsing
  • Cooling
  • Quenching
  • Wetting
  • Humidification
  • Dust Control

Advantages

  • No post spray drip
  • Adjustable
  • Easily used with EFC
  • Minimizes air and liquid consumption
  • All stainless steel construction
  • Fine atomization
  • Interchangeable liquid and air caps
  • Compact

If you need an Atomizing Spray Nozzle or any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Intelligent Compressed Air: Refrigerant Dryers and How They Work

We’ve seen in recent blogs that Compressed Air Dryers are an important part of a compressed air system, to remove water and moisture to prevent condensation further downstream in the system.  Moisture laden compressed air can cause issues such as increased wear of moving parts due to lubrication removal, formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates.  The three main types of dryers are – Refrigerant, Desiccant, and Membrane. For this blog, we will review the basics of the Refrigerant type of dryer.

All atmospheric air that a compressed air system takes in contains water vapor, which is naturally present in the air.  At 75°F and 75% relative humidity, 20 gallons of water will enter a typical 25 hp compressor in a 24 hour period of operation.  When the the air is compressed, the water becomes concentrated and because the air is heated due to the compression, the water remains in vapor form.  Warmer air is able to hold more water vapor, and generally an increase in temperature of 20°F results in a doubling of amount of moisture the air can hold. The problem is that further downstream in the system, the air cools, and the vapor begins to condense into water droplets. To avoid this issue, a dryer is used.

Refrigerated Dryer
Fundamental Schematic of Refrigerant-Type Dryer

Refrigerant Type dryers cool the air to remove the condensed moisture and then the air is reheated and discharged.  When the air leaves the compressor aftercooler and moisture separator (which removes the initial condensed moisture) the air is typically saturated, meaning it cannot hold anymore water vapor.  Any further cooling of the air will cause the moisture to condense and drop out.  The Refrigerant drying process is to cool the air to 35-40°F and then remove the condensed moisture.  The air is then reheated via an air to air heat exchanger (which utilizes the heat of the incoming compressed air) and then discharged.  The dewpoint of the air is 35-40°F which is sufficient for most general industrial plant air applications.  As long as the compressed air stays above the 35-40°F temperature, no further condensation will occur.

The typical advantages of Refrigerated Dryers are-

  1.  – Low initial capital cost
  2.  – Relatively low operating cost
  3.  – Low maintenance costs

If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Will Water Move Through EXAIR Air Knives and Air Wipes? (Images included)

Today, I would like to discuss a question that comes up time and time again over the years.  “What happens when I put water through a Super Air Knife?” That raised another question from myself of what about a Super Air Wipe?

The answer is quite simple, it will come out, just not as good as compressed air does.   The engineering and design for Super Air Knives were all based around compressed air use.  With any good product of course comes the question in time, how else can we use this?   A number of applications for the Super Air Knife is blowing moisture off a part that has been applied through a series of wash/rinse nozzles.  What if the knife could apply the liquid and then a second knife could remove the liquid.  Below are some images from testing that was done on a Stainless Steel Super Air Knife at various gap sizes and various pressures.    The “best” performance visually was from operating the air knife with .004″ gap and approximately  a 17 PSIG inlet pressure (this is for a 12″ Super Air Knife).

Water flowing through a 12" Stainless Steel Super Air Knife
Water flowing through a 12″ Stainless Steel Super Air Knife

As you can see in the photos, the water does flow fairly well immediately out of the knife, and becomes more turbulent as it gets further away from the knife.   The stream actually begins to break up and thus the effective distance of the knife may be reduced when using it to flow liquids.   This is not going to perform like a pressure washer, the maximum distance for the stream of liquid before it completely fell off was around 10′ from the discharge point.   If this were to be used to remove loose debris or to cover a part in water to help cool the part the stream would be more than enough to perform.

As noted above the operating pressure was fairly low, and the gap was at a .004″ thickness.  I recently tested a 1″ Stainless Steel Super Air Wipe as well.  The shim gap was once again set to .004″ thick to permit a better flow and a low pressure, approximately 10-12 psig inlet pressure.  As you can see the flow of water is not as smooth as the air flow out of a Super Air Wipe but if a light rinsing process was needed, or a water cooling process, this would work well.

1" Stainless Steel Super Air Wipe w/ Water
1″ Stainless Steel Super Air Wipe w/ Water

 

So the answer to the main question at hand is yes, a Super Air Knife and Super Air Wipe will both operate with a pressurized liquid source under the correct circumstances.   While they do not operate exactly like they do with compressed air, the results still prove useful in certain applications.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF