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Compressed Air Quality Classes | Air Compressor Guide
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Compressed Air Quality Classes

Compressed air must be clean and dry to prevent damage to equipment and ensure the safety of the end products.

Water, oil, and particulates, for example, can cause severe issues ranging from corroded equipment to compromised product quality. For instance, in the food and beverage industry, poor air quality can lead to contamination risks, violating health regulations and risking consumer safety.

Why Quality classes

Ensuring compressed air is free from contaminants requires adherence to stringent air quality standards, which are designed to classify air purity and guide industries in maintaining appropriate air quality levels. The quality of compressed air is not just about prolonging the life of the machinery and ensuring safety; it's also about efficiency. Cleaner air means fewer breakdowns and disruptions, translating directly to cost savings and more reliable production schedules.

By setting a clear understanding of compressed air’s critical role and the need for stringent quality checks, industries can pave the way for more detailed discussions on standards, monitoring, and purification methods, which are crucial for maintaining the high standards required in contemporary production environments.

ISO 8573

Air quality standards: the guidelines that ensure compressed air is suitable for specific uses. The most notable of these standards is ISO 8573-1:2010, which benchmarks the level of purity required in various industrial processes.

ISO 8573-1:2010 is the primary standard for compressed air quality. It outlines precise classifications for air purity, specifically addressing the levels of particulates, water, and oil in compressed air.

Structure of ISO 8573-1:2010

The standard is systematic and methodical. It divides air contamination into three major classes: particles, water, and oil. Each class has a range of purity levels, or quality classes, which define the concentration limits for these contaminants. This structured approach helps in categorizing the air quality requirements based on different industrial needs.

Classification and Quality Classes

In ISO 8573-1, each contaminant type has specific quality classes. For solid particles, the classes range from 0 to X, with Class 0 representing the highest level of air purity and Class X indicating a lower level, suitable for less critical applications. Water and oil contaminants are similarly classified.

This classification system enables users to choose a compressed air system that meets the specific requirements of their operational needs, allowing for customization and optimization based on the purity classes.

Explanation of Different Purity Classes

Purity classes are numerically rated within the standard. For example, for solid particulates, a typical rating might read as follows:

  • Class 2: Particle size > 1 micron and ≤ 5 microns
  • Class 1: Particle size > 0.1 micron and ≤ 0.5 microns
  • Class 0: Particle size ≤ 0.1 micron

Each step up in class represents cleaner air, with fewer and smaller particles permitted.

Specific Criteria for Solid Particulates, Water, and Oil Purity Levels

The ISO standard also sets exact criteria for the maximum concentration levels of water and oil:

  • Water is measured both in terms of humidity (pressure dew point) and liquid water content.
  • Oil is measured in terms of total oil content, which includes aerosols, vapors, and liquid oil.

For instance, for oil, the classes define limits such as:

  • Class 1: Total oil content must not exceed 0.1 mg/m³
  • Class 0: Total oil content must not exceed 0.01 mg/m³

This detailed classification helps ensure that the compressed air quality is not only compliant but also consistent with the specific needs of sensitive applications, such as in pharmaceuticals or food production, where any contamination could compromise product quality.

By adhering to these guidelines, industries can better protect their machinery, products, and processes from the adverse effects of contaminated compressed air, thus ensuring safety, efficiency, and regulatory compliance.

CLASS SOLID / DIRT Particle size in micron WATER @ 7 bar / 100 psiPressure Dewpoint OIL (including vapor)
0.10<d<0.5 0.5<d<1.0 1.0<d<5.0
Max number of particles per m3 ° C ° F Mg /m3 PPM
0 As specified As specified As specified
1 100 1 0 -70 -94 0.01 0.008
2 100.000 1.000 10 -40 -40 0.1 0.08
3 10.000 500 -20 -4 1 0.8
4 1.000 +3 +38 5 4
5 20.000 +7 +45 25 21
6 +10 +50
Tire pressure check check Check
Leakages in air, oil or fuel system check check check
Coolers ( engine, compressor oil and air) Clean Clean
Min and max rpm engine check check Check
Torque wheel nuts check check Check
Brake system Check/adjust Check/adjust Check/adjust
Safety valve (air receiver) Test
Door hinges grease Grease
Towbar and system grease grease
Safety switches grease
Oil separator Check pressure drop Replace separator
Tension of V-belts Adjust Adjust
Fuel tank Clean Clean
Oil compressor Change
Oil filter compressor Change
Air intake filter Change
Safety cartridge air intake filter (if installed) Change
Oil engine Change Change
Oil filter engine Change Change
Fuel filter Change
Fuel pre-filter Change Change
Intake and exhaust valves engine Adjust
Compressed air after filters (if installed) Change

How to use the table

The ISO standard gives quality ratings for solid particles, for water and for oil. To completely ‘belong' to a class, all requirements must be met (solids, water and oil).

For example, air with 2.000 particles of 2.0 um and a pressure dewpoint of -20 degrees Celsius will be class 5.

2.000 particles of 2.0 um will give us class 5 for solid particles/dirt. -20 degrees Celsius will give us class 3 for water. The overall class of the compressed air will be 5, although for water only it will be higher: class 3.

Again, use your commons sense.

You might not be interested in oil in your air, but dust and water might be disastrous for your equipment.

Here's a small list of general recommendations for air quality classes for different kinds of equipment / use.

Air tools with air motors (like grinders):

Dirt: 2
Water: 5
Oil: 4

Other hand tools:

Dirt: 5
Water: 5
Oil: 4

Machines with pneumatic cylinders:

Dirt: 4
Water: 4
Oil: 4

General workshop air:

Dirt: 4
Water: 5
Oil: 4