Precision filters for air compressor systems are essential for downstream purification. How to choose the right one?

Filter Working Principle: Filter cartridges are composed of materials such as fiber media, filter screens, and sponges. 

Solid and liquid particles (droplets) in compressed air are intercepted by the filter media and accumulate on the surface of the filter cartridge (inner and outer sides). 

The accumulated droplets and impurities settle to the bottom of the filter under gravity and are then discharged automatically or manually.

Filter Materials:

1. Shell: Stainless steel or PP;

2. Filter Cartridge Material: B and C series environmentally friendly special fibers, non-woven fabric; D series, activated carbon.

Filter Classification: Filter classes are classified according to the size of solid contaminant particles, the content of liquid water, and the content of oil droplets, oil mist, and oil vapor after the filter cartridge processes compressed air, as defined by ISO 8573. 

Filter grades are classified according to the filter element (different suppliers may use different definitions for filter grades; here we use C/T/A/H to represent them):

Main Line Filter: Grade C main line filters remove large amounts of liquid and solid particles larger than 3μm, achieving a minimum residual oil content of only 5ppm, with trace amounts of moisture, dust, and oil mist. Used in air compressors, after the aftercooler and before other filters, 

for general protection; used before refrigerated dryers as a pre-treatment device.

Air Line Filter: Grade T air line filters remove liquid and solid particles as small as 1μm, achieving a minimum residual oil content of only 0.5ppm, with trace amounts of moisture, dust, and oil mist. 

Used before Grade A filters for pre-treatment; after refrigerated dryers and desiccant dryers to further improve air quality.

Ultra-High Efficiency Oil Removal Filter: Grade A ultra-high efficiency oil removal filters remove liquid and solid particles as small as 0.01μm, achieving a minimum residual oil content of only 0.01ppm, removing almost all moisture, dust, and oil. 

Used before H-class filters and desiccant dryers for protection, and after refrigerated dryers to ensure the air is oil-free.

Activated Carbon Filter: The H-class activated carbon filter removes oil mist and hydrocarbons as small as 0.01μm, achieving a minimum residual oil content of only 0.003ppm. It is free of moisture, dust, and oil, and odorless.

It serves as the final filtration step, supplying high-quality compressed air to industries such as food processing, respiratory systems, and aseptic packaging.

C-class Precision Filter: Suitable for pre-filters in general reciprocating air compressors. 

Multi-layer glass fiber filter element. 

Filtered impurities: 5 microns. 

Filtered oil content: 5 microns. 

Maximum pressure: 16 kg/cm². 

Maximum temperature: 65°C. 

General pressure differential: 0.2 kg/cm². 

Maximum pressure differential: 0.7 kg/cm². 

Function: Filters large amounts of oil and gas in compressed air to below 5 microns and removes impurity particles to 5 microns.

T-class Precision Filter: Suitable for pre-filters in general screw air compressors. Post-filter

Material: Multi-layer glass fiber filter element

Filtered impurities: 1 micron

Filtered oil content: 0.5 PPM

Maximum pressure: 16 kg/cm²

Maximum temperature: 65℃

Normal pressure differential: 0.17 kg/cm²

Maximum pressure differential: 0.7 kg/cm²

Function: Filters oil and gas in compressed air to 0.5 PPM and removes impurities to below 1 micron. Class A Precision Filter

General application: Post-filter for general air compressors

Material: Multi-layer glass fiber filter element

Filtered impurities: 0.5 PPM

01MICRON

Oil content: 0.01PPM

Maximum pressure: 16KG/CM

Maximum temperature: 65℃

Normal pressure difference: 0.275KG/CM

Maximum pressure difference: 0.7KG/CM

Function: Precisely filters trace amounts of oil and gas in compressed air to 0.01PPM, while simultaneously filtering out airborne impurities to 0.01MICRON, achieving high-quality compressed air with oil-free standards.

H-class precision filter

General application: Dedicated for high-precision filtration

Material: Activated carbon filter element

Impurities filtered: 0. 03MICRON

Oil content: 0.003PPM

Maximum pressure: 16KG/CM

Maximum temperature: 65℃

General pressure difference: 0.75KG/CM

Maximum pressure difference: 0.7KG/CM

Function: Generally used to filter ozone, very fine oil vapor, and ultrafine particles from compressed air.

Filter Installation Precautions

(1) The working pressure should not exceed the maximum pressure indicated on the filter.

(2) The filter should generally be installed after the aftercooler and air tank, as close as possible to the point of use and the lowest temperature.

(3) The filter should not be installed after a quick-opening valve to prevent backflow and impact.

(4) The filter should be installed vertically, with sufficient space below for filter element replacement.

(5) Larger filters should have appropriate support in the pipeline.