Compressed Air Purity Classes & ISO 8573-1. What Does it Mean for You?

The compressed air coming directly from your air compressor will usually require further treatment & preparation before it can be used. It’ll contain particulate matter, moisture, and hydrocarbons that the intake filter won’t remove…remember, it’s there to protect the compressor itself against damage from larger particulate. Smaller particulate and other contaminants that can affect air operated products & tools will still need to be addressed, after compression. The degree to which this additional treatment is necessary is dictated by what you’re using your compressed air for.

ISO 8573-1:2010 – Compressed air – Part 1: Contaminants and Purity Classes quantifies the quality of the air according to three properties, into different classes:

Per the descriptions above, here are the criteria by which compressed air purity is classified in these three categories. Certain applications can call for different classes for these three categories (more on that in a minute).
  • Maximum particle size & concentration of solid contaminants. These can come from rust on the inside of the distribution piping, particulate generated by wear of air system components, and atmospheric contamination that the compressor’s intake filter doesn’t catch.
  • Maximum pressure dew point. No matter where your compressor is located, the air it pulls in contains some amount of water vapor. Dew point is the temperature at which it will condense at a given pressure. As long as the compressed air temperature is above that dew point, there won’t be any water (in liquid form) in it.
  • Maximum oil content. This most often is due to carryover from oil lubricated compressors, but can come from atmospheric oil (or other hydrocarbon) vapor drawn into the compressor’s intake.

So…what does this mean to you, relating to your use of compressed air? Well, it largely comes down to the nature of your application. Whatever is in your compressed air supply will be in contact with whatever the air comes in contact with. If a machinist is using a Safety Air Gun to blow chips & coolant from machined parts, they’re not going to be particularly concerned with this specification from a regulatory standpoint. If those parts are going straight from the machine shop to a paint booth, they’re certainly going to want to use air that’s free of particulate, moisture, and oil. All of those things will, quite noticeably, affect the quality of the painted finish. Filter Separators and Oil Removal Filters installed at the point of use will take care of that. A case could be made for a purity specification and regular testing of their compressed air, but this really just falls under the confines of good engineering practice.

Compressed air use in applications where it can come in contact with food or beverages intended for consumption (by people AND animals, according to the Federal Food, Drug, and Cosmetic Act) is considered a critical factor for cleanliness. They reference guidelines from the British Compressed Air Society (BCAS) to specify purity classes for both direct and indirect contact with food and beverage products:

Direct contact requires testing and compliance to Class 2:2:1 per the above table means:

  • Particulate Class 2 – particle concentration, by particle size, in concentrations no greater than:
    • 400,000 particles sized 0.1-0.5 microns, per cubic meter
    • 6,000 particles sized 0.5-1.0 microns, per cubic meter
    • 100 particles sizes 1.0-5.0 microns, per cubic meter
  • Maximum pressure dew point Class 2 – vapor pressure dew point must be less than 40°F (40°C) at the maximum pressure of the compressed air system.
  • Oil content Class 1 – concentration must be less that 0.001 milligrams per cubic meter

Examples of direct contact applicable to the use of EXAIR Engineered Compressed Air Products include blowing air for cooling, moisture removal, coating layer distribution, etc., of unpackaged food product.

EXAIR Stainless Steel Super Air Knives are popular in food processing applications (left to right): removing excess moisture prior to flash freezing of fish filets, preventing clumping while packaging shredded cheese, and (my personal favorite) ensuring a consistent and even glazing of fresh, delicious doughnuts.

Line Vac Air Operated Conveyors and Vortex Tubes are also used in direct contact applications in the food industry:

316SS Threaded Line Vac conveys bulk grain in a distillery (left). Vortex Tube rapidly sets melted chocolate in a mold (right).

Indirect contact is slightly (but JUST slightly) less restrictive: those are Class 2.4.2. Particulate and oil content classes remain the same, but dew point can be as high as 37°F (3°C). This is where the air the air is coming into contact not with the consumable product itself, but, for example, the packaging or container:

Atomizing Spray Nozzles rinse bottles prior to labeling (left), 1″ Flat Super Air Nozzle blows off label to ensure proper scanning by sensor (center), Line Vac conveys canned goods (right).

EXAIR Corporation is committed to helping you get the most out of our products – and your compressed air system. If you have questions, I can talk about compressed air all day – and oftentimes I do! Let’s talk.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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ISO 8573-1 Chart by Compressed Air Best Practice.

Common Compressed Air Symbols

When any product / system is designed drawings are made to assist in the production of the designed product. For example if a mechanical part is being machined you may see symbols like these to verify the part is made correctly:

GD&T
GD&T Symbol Examples

Same with an electrical panel, they use symbols like the ones below to note the type of equipment used in a location.

electronic.JPG
Electrical Symbol Examples

 

Then there’s the Piping & Instrumentation Diagram (P&ID)…it depicts an overall view of a system, showing the flow (usually fluid or electricity) through that system’s components, giving the viewer an understanding of the operation, and expected results from said operation.

Some examples of symbols you might find in a compressed air system are:

Compressors:

all-compressor
The one on the left can be used for any air compressor. The others denote specific types of air compressor (from left:) Centrifugal, Diaphragm, Piston, Rotary, and Screw.

 

Air preparation & handling:

filters-and-regulator-symbols-and-pic.jpg
The symbols on the left denote the EXAIR products on the right: Automatic Drain Filter Separator, Oil Removal Filter, and Pressure Regulator

Instrumentation and control:

instrumentation-and-controls1.jpg
The symbols on top denote the EXAIR products below (left to right): Flowmeter, Pressure Gauge, and Solenoid Valve

Occasionally, we’re asked if there are standard ANSI or ISO symbols for any of our  engineered Intelligent Compressed Air Products…and there aren’t.  Perhaps one day they might make the cut, but for now, their standard convention is to choose a shape and call it out by name.  It might look something like this:

sak-pid1
From top left, and then down: Automatic Drain Filter Separator, Oil Removal Filter, Pressure Regulator, and Super Air Knife

If you have questions about any of the quiet 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.

Jordan Shouse
Application Engineer
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Knowing Your Symbols Is Key To Understanding Your Drawings

There are all kinds of engineering drawings, used for all kinds of purposes:

  • Pipe fitters and millwrights use Plan & Elevation drawings to make sure fluid system flanges, elbows, tees, etc., line up with each other, and don’t run into anything.
  • Exploded view drawings help maintenance folks identify parts, and, when they need replaced, make sure the new ones go in the same way the old ones came out.
  • Fabrication and machining drawings (usually to scale) are used to ensure the part being made is the right size & shape, that mounting holes are in the right place, and that critical surfaces are as flat & smooth as they need to be.
  • Then there’s the Piping & Instrumentation Diagram (P&ID)…it depicts an overall view of a system, showing the flow (usually fluid or electricity) through that system’s components, giving the viewer an understanding of the operation, and expected results from said operation.  It should not be confused with its simpler cousin, the flow chart that is so dreaded by OTE-types (“Other Than Engineer”…you know who you are,) of which these are my favorite examples:

There’s a lot of “life lesson” in these two graphics.

The big difference between a flow chart and a P&ID is the symbols.  In fact, you can find ISO & ANSI standard symbols for many components you’ll find in fluid & electrical P&ID’s.  Some examples of symbols you might find in a compressed air system are:

Compressors:

The one on the left can be used for any air compressor. The others denote specific types of air compressor (from left:) Centrifugal, Diaphragm, Piston, Rotary, and Screw.

Air preparation & handling:

The symbols on the left denote the EXAIR products on the right: Automatic Drain Filter Separator, Oil Removal Filter, and Pressure Regulator

Instrumentation and control:

The symbols on top denote the EXAIR products below (left to right): Flowmeter, Pressure Gauge, and Solenoid Valve

Occasionally, we’re asked if there are standard ANSI or ISO symbols for any of our  engineered Intelligent Compressed Air Products…and there aren’t.  Perhaps one day they might make the cut, but for now, their standard convention is to choose a shape (user preference…you’re the one it’s gotta make sense to) and call it out by name.  It might look something like this:

From top left, and then down: Automatic Drain Filter Separator, Oil Removal Filter, Pressure Regulator, and Super Air Knife

Oh, and if you’ve ever got any questions about your compressed air system that you think looking at a drawing together could help us solve, you can send that drawing to us at techelp@exair.com, and one of us will be happy to help.

Russ Bowman
Application Engineer
EXAIR Corporation
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