It is important to note that not every application (or industry) requires the same level of protection. Therefore, as a first step, you should find out the level of air quality you need.
You can do so by consulting the table on this page, which defines air quality in accordance with ISO 8573-1 (ed. 2010). Divided into seven air quality classes and the three main types of contaminants, it is the most important internationally recognized air quality standard. ISO 8573-1 will serve as your essential guide to determine how clean your air must be. Essentially, it defines how many contaminants your air is still allowed to contain at a specific point in your compressed air system after it has been treated.
You will see that the determining factor for moisture in your compressed air is the pressure dew point (PDP). What is that?
Atmospheric air contains more water vapor at high temperatures and less at lower temperatures. This affects the water concentration in the air when it is compressed. For example, a compressor with a working pressure of 7 bar and a capacity of 200 l/s that compresses air at 20˚C with a relative humidity of 80% will release 10 liters/hour of water in the compressed air line.
The PDP is used to define that water content in the compressed air. Essentially, it is the temperature at which water vapor condenses into water at the current working pressure. Low PDP values indicate small amounts of water vapor in the compressed air.
So, what can you do to get that moisture out of your system? In the following pages, we will more closely examine the two main technologies – dryers and filters – and help you figure out which ones are best for you.
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Class
Solid Particle
Maximum number of particles per m²
Water
Pressure dew point (°C)
Oil
(Incl. vapor mg/m²)
≤ 20,000
≤ 400
≤ 10
≤ -70 (-94 °F)
≤0.01
≤ 400,000
≤ 6,000
≤ 100
≤ -40 (-40 °F)
≤ 0.1
Not specified
≤ 90,000
≤ 1,000
≤ -20 (-4 °F)
≤ 1
≤ 10,000
≤ 3 (38 °F)
≤ 5
≤ 100,000
≤ 7 (45 °F)
≤ 10 (50 °F)