I. Core Value of the System
Compressed air generated by air compressors contains impurities such as water vapor, lubricating oil mist, and dust particles. Direct use of such air can cause equipment wear, frequent malfunctions, and even damage to precision instruments or product scrap (e.g., poor welding of electronic components, oil spots on painted workpieces). The compressed air purification system, through the collaboration of multiple modules, converts this "dirty air" into "clean air sources" that meet production requirements, ensuring stable production and product quality.
II. Details of the 5 Core Modules
(I) Pre-Filter
Core Function: As the "first line of defense" in the purification system, it filters solid particles (e.g., dust, metal debris) with a diameter of ≥10μm from compressed air, while separating part of the liquid water and oil droplets. This prevents large impurities from entering subsequent dryers and precision filters, which could otherwise cause blockages or wear of components.
Working Principle: Based on the principles of "inertial collision + gravity sedimentation". After compressed air enters the filter, the airflow moves tangentially along the outer circumference of the filter element, creating a rotating airflow. Due to high inertia, large particle impurities cannot follow the airflow’s direction changes; instead, they collide with the inner wall of the filter and settle at the bottom. Liquid water and oil droplets, under the action of gravity, converge into droplets and are discharged through the bottom drain valve.
Selection and Maintenance
Filtration Precision: Prioritize pre-filters with 10μm precision, which are compatible with the air compressor’s air intake filter (usually 5-20μm), forming a "coarse filtration + pre-filtration" dual protection system.
Material: The filter element should be made of glass fiber or polyester fiber (oil-resistant and temperature-resistant, suitable for the compressed air system’s operating temperature below 80°C), and the housing should be made of aluminum alloy or stainless steel (to prevent rust and air source contamination).
Maintenance: Check the filter element’s pressure difference every 3 months (replace if the pressure difference exceeds 0.05MPa); manually drain 1-2 times a week (or install an automatic drain valve) to prevent impurity accumulation and blockage.
(II) Dryer
Core Function: Reduces the "dew point" of compressed air (the temperature at which water vapor condenses into liquid water), typically controlling it below -20°C (below -40°C for high-demand scenarios). This prevents pipeline condensation and equipment rust.
Selection Points
Select Type Based on Dew Point Requirements: Choose refrigerated dryers for general scenarios and adsorption dryers for high-demand scenarios.
Match Specifications Based on Processing Capacity: The dryer’s rated processing capacity should be 10%-20% higher than the air compressor’s displacement (e.g., for an air compressor with a displacement of 1m³/min, select a dryer with 1.2m³/min capacity) to avoid reduced dehumidification efficiency due to overload.
(III) Precision Filter
Core Function: Filters residual oil mist (0.1-1μm in diameter) and fine particles (0.1-5μm in diameter) after pre-filtration and drying. It typically controls oil content below 0.1mg/m³ and achieves a particle filtration precision of 0.1μm.
Working Principle: Adopts a composite principle of "depth filtration + membrane filtration". The filter element is composed of multiple layers of glass fiber or PTFE (polytetrafluoroethylene) membrane. When airflow passes through the filter element, tiny oil mist and fine particles are intercepted and adsorbed by the fibers. Meanwhile, the hydrophobic coating on the filter element’s surface prevents oil mist adhesion, ensuring stable filtration efficiency.
Common Classifications and Applications
Class Q (Pre-Precision Filter): Filtration precision of 5μm; removes liquid oil and coarse particles, protecting subsequent high-precision filters.
Class P (Oil Mist Precision Filter): Filtration precision of 1μm; reduces oil content to below 1mg/m³, suitable for pneumatic tools and ordinary cylinders.
Class S (Ultra-Precision Filter): Filtration precision of 0.1μm; reduces oil content to below 0.1mg/m³, suitable for painting and printing equipment.
Class C (Activated Carbon Filter): Adsorbs residual oil vapor; reduces oil content to below 0.003mg/m³, suitable for electronics, food, and pharmaceutical scenarios.
Maintenance Points: Replace the filter element every 6 months for general scenarios and every 3 months for high-oil-content scenarios (e.g., piston air compressors). Shut down immediately if the dryer malfunctions to prevent filter element mold growth and air source contamination due to humid air.
(IV) Oil-Air Separator
Core Function: Designed for oil-lubricated air compressors (e.g., screw, piston types), which may have a small amount of lubricating oil mixed into compressed air (usually 5-15mg/m³). Direct entry of this oil-contaminated air into dryers and precision filters would contaminate adsorbents and block filter elements, leading to purification system failure. The oil-air separator separates over 80% of the lubricating oil, reducing oil content to 1-3mg/m³ and alleviating the load on subsequent purification equipment (not required for oil-free air compressors).
Working Principle: Combines "centrifugal separation + wire mesh filtration":
Compressed air enters the oil-air separator from the top and rotates at high speed along the inner wall. Due to centrifugal force, lubricating oil is thrown onto the inner wall, converges into droplets, and flows into the bottom oil chamber.
After centrifugal separation, the air passes through the internal wire mesh filter element to further filter residual tiny oil mist, then is discharged from the top outlet.
The separated lubricating oil flows back to the air compressor’s head through the oil return pipe for recycling.
Selection and Maintenance: Compatible with oil-lubricated air compressors; replace the wire mesh filter element every 6-12 months (based on air compressor operating hours). Regularly check for blockages in the oil return pipe to prevent air compressor oil shortage.
(V) Post-Filter
Core Function: Installed after the precision filter, it provides "terminal precision filtration" for special production scenarios (e.g., semiconductor packaging, aseptic food packaging) to ensure the air source fully meets industry standards (e.g., FDA certification for the food industry, Class 1 cleanliness for the electronics industry).
Common Types and Applications
Aseptic Filter: Uses a polyethersulfone (PES) membrane filter element with a filtration precision of 0.22μm; intercepts bacteria and microorganisms, suitable for pneumatic filling equipment in the food and pharmaceutical industries.
Ultra-Clean Filter: Uses a HEPA (High-Efficiency Particulate Air) filter material with a filtration precision of 0.3μm and a filtration efficiency of 99.97%; suitable for chip packaging equipment in the semiconductor industry.
Deodorizing Filter: Filled with activated carbon or molecular sieves; adsorbs odors (e.g., lubricating oil vapor odor) in compressed air, suitable for pneumatic coding equipment in the cosmetics and food industries.
Selection Points: Select types based on industry standards (aseptic filters for food and pharmaceuticals, ultra-clean filters for electronics). Sterilize aseptic filters every 3 months (using high-temperature steam or disinfectants) and replace ultra-clean filters every 6 months to ensure filtration effectiveness.
III. Typical Configuration Schemes by Scenario
Different scenarios have varying requirements for air source cleanliness, requiring combinations of the above modules to form suitable solutions:
General Scenarios (Auto Repair, Hardware Processing): Air Compressor → Oil-Air Separator → Pre-Filter → Refrigerated Dryer → Class P Precision Filter.
Painting, Printing Scenarios: Air Compressor → Oil-Air Separator → Pre-Filter → Refrigerated Dryer → Class S Precision Filter → Class C Activated Carbon Filter.
Electronics, Pharmaceutical Scenarios: Air Compressor → Oil-Air Separator → Pre-Filter → Adsorption Dryer → Class S Precision Filter → Aseptic/Ultra-Clean Post-Filter.
IV. Core Principles for System Configuration
Customization Based on Needs: Combine modules according to the air compressor type (oil-lubricated/oil-free), production scenario (general/precision/aseptic), and cleanliness requirements (dew point, oil content, particle precision).
Logical Sequence: Follow the principle of "coarse filtration before precision filtration, dehumidification before oil removal" to avoid excessive purification (which increases costs) or insufficient purification (which damages equipment).
Professional Consultation: If there are questions about maintenance or operation, consult professional technicians or equipment suppliers to ensure safety and reliability.