What is a coalescing filter and how does it work?
In compressed air systems, maintaining air purity is critical - especially in industries like pharmaceuticals, food processing, and electronics. One of the most effective tools for achieving this is the coalescing filter. But what exactly is it, and how does it work?
A coalescing filter removes fine oil aerosols, water droplets, and solid particulates from compressed air. As contaminated air passes through the filter media, tiny liquid droplets coalesce—merge—into larger ones. These heavier droplets then fall into a moisture trap and are drained away, leaving behind cleaner air. This process is essential for protecting downstream equipment and ensuring product quality.
Atlas Copco’s coalescing filters use multi-layered synthetic media, often enhanced with nanofiber technology. The filter housing is typically made of anodized aluminum with stainless-steel inner cores, ensuring durability and corrosion resistance. The design also includes features like service indicators, bypass valves, and low-pressure drop elements to optimize performance and maintenance.
Coalescing filters are used in:
- Manufacturing: Protecting pneumatic tools and actuators.
- Food & Beverage: Ensuring air purity in contact with products.
- Pharmaceuticals: Preventing contamination in cleanroom environments.
- Automotive: Supporting paint booths and assembly lines.
The ISO 8573-1:2010 standard defines seven classes of compressed air purity, based on three key contaminants:
- Solid particles
- Water (humidity or dew point)
- Oil (aerosol, vapor, and liquid)
For example, Class 1 air quality allows:
- ≤ 20,000 particles/m³ (0.1–0.5 µm)
- Pressure dew point ≤ –70°C
- Total oil content ≤ 0.01 mg/m³
Atlas Copco’s coalescing filters—such as DD+, PD+, and UD+—are engineered to meet or exceed these standards, ensuring compliance for even the most sensitive applications.
Atlas Copco offers a wide range of coalescing filters, including:
- DD+ and PD+: For general and high-efficiency filtration.
- UD+: A two-in-one filter that combines DD+ and PD+ performance in a single unit, reducing pressure drop by 40% and saving energy
- QD/QDT: Activated carbon filters for removing oil vapors and odors.
These filters are tested and certified according to ISO 8573:2010, the international standard for compressed air purity.
- Energy Efficiency: Lower pressure drop means reduced energy consumption.
- Compact Design: UD+ filters reduce footprint and installation complexity.
- Extended Service Life: Durable materials and smart design reduce maintenance frequency.
Atlas Copco’s coalescing filters stand out due to their innovative Nautilus filter media, inPASS™ bypass system, and rigorous quality control. These features not only ensure superior air quality but also lower total cost of ownership - making them a smart investment for any compressed air system.
