What’s in compressed air? It’s not empty space inside a tank, but it contain water droplets, oil vapor, and solid particles that can injures a patient, clog a valve, or otherwise ruin product. That’s where ISO 8573 comes in.
The standard describe the minimum level of cleanliness required from your air for any particular job. For example, the industry-standard code are a matrix containing limits on three contaminants… Oil, water and particulates.
Each contaminant have a cleanliness class. Your process requirement is match to the appropriate class. No need to overfilter and waste money but no need to take risks by underfiltering and running into problems down the road.
Understanding ISO 8573 Compressed Air Quality Standards
What ISO 8573 Standard Covers
ISO 8573 covers solid contaminants such as rust and dust in its first half. They has classes that runs from 1-6 (larger particles) and 1-5 (small particle). Class 1 is super clean.
That’s basically nothing on air. Class 5 will allows some particles. If you’re inflating a truck tire you don’t need Class 1.
For general workshop usage Class 4 or 5 should of suffice. What matter is what amount and size of particle causes an issue within your system.
Solid Particulate Contaminants
Another major contaminant are water.
Water and Moisture Removal
It corrodes thing. When you compress air, it cools down and turns back into liquid. This corrode your metal part.
ISO 8573 does test for this, but uses the term Pressure Dew Point (PDP) as its measurement. The lower the PDP, the drier the air. Very low dew point mean class 1.
This is needed if you have chemicals reacting to moisture or there’s a chance of freezing. Class 2-6 allow higher dew points, i.e. It means there is more water. If you’re just doing some pneumatic nailing in your garage, you may be able to get by with Class 3.
For paint jobs on your car where moisture will cause blistering, you really want super-dry air. That’ll be Class 1 in a humid climate.
Oil Vapor and Liquid Filtration
There are also two types of oil.
Vapor and liquid. While you can see liquid oil and remove it with filtration, oil vapor cannot be seen and needs activated carbon. Both oil vapors and liquid aerosols has four classes.
Class 1 for oil vapor is considered oil free. That’s required for medical applications and food or pharmaceutical use. Often class 2 will work for automotive spray painting where some very slight amount of vapor is acceptable as long as it doesn’t impact the paint finish.
Reading ISO Class Codes
For example, a common spec would be ISO 8573-1 Class 2.3.4. Each number represent particles, water, than oil vapor. So if you read Class 1.2.1, that’s really low particle count, fairly dry air, with little or no oil present.
Why does it matter? Each of these is an independent spec. Mixing them create filters purchased for the wrong issue, as though you bought a rain coat instead of a winter jacket.
It provides the wrong kind of protection from your intended application. It is not just about picking the right compressor for the application, but also picking the proper class.
Selecting the Right Filtration System
A new rotary screw compressor can provides clean compressed air requiring minimal filtration.
An old piston compressor may require a lot of treatment. Begin by understanding what the air will be used for. The device that use the air may have a minimum requirement.
If there is a spec for Class 2.3.2 then that is your starting point. Everything above that is gravy; everything below that is risky business. Return to the process and select the best dryer and filter based off those requirements.
Give compressed air the same consideration that you give water or electricity. Don’t blow dirty air through delicate machine. With ISO 8573, you have the language to define clean.
You can turn a vague idea into something you can prove. After you learn the classes, you engineer instead of guessing. Your equipment runs longer, your air becomes predictable and your product stays perfect.
It keeps the air invisible, but the quality very visible.
