During long-term use, the increase in differential pressure is a key issue affecting the filtration efficiency and lifespan of paint mist filter boxes. The essence of increased differential pressure is the gradual blockage of the pores within the filter material by paint mist particles, leading to increased airflow resistance. This phenomenon not only reduces the efficiency of the ventilation system but may also cause increased equipment energy consumption and premature filter box failure, requiring comprehensive control from multiple dimensions, including material properties, operating environment, and maintenance strategies.
The pore structure and surface properties of the filter material directly affect differential pressure changes. Paint mist filter boxes typically use glass fiber, synthetic fiber, or composite filter media, and their initial differential pressure depends on the material's permeability and pore size distribution. With prolonged use, sticky particles and resin debris from the paint mist adhere to the filter media surface, forming a dense filter cake layer, while simultaneously penetrating deep into the fibers and blocking micropores. This dual blockage mechanism increases frictional resistance and localized eddies as air passes through the filter media, leading to a continuous increase in differential pressure. Using filter media with a gradually varying pore size structure can alleviate this problem—large pore layers trap large particles, while small pore layers filter fine particles, thereby extending the effective service life of the filter media.
Paint mist concentration and composition are the core causes of increased pressure differential. In high-concentration paint mist environments, a thick paint film quickly forms on the filter media surface, especially in scenarios with frequent spraying operations or high paint viscosity, significantly accelerating clogging. Furthermore, water in water-based paints and organic matter in solvent-based paints can cause filter media fiber swelling or leave sticky residues, further exacerbating pore clogging. To address these issues, a pre-filter layer can be added at the front end of the filter box to intercept most large paint mist particles, or a wet scrubbing system can be used to pre-treat high-concentration exhaust gas, reducing the paint mist load entering the filter box.
The matching of the ventilation system is crucial for pressure differential control. If the fan is too large, the filter box will operate at high wind speeds for extended periods, accelerating the impact and penetration of paint mist particles on the filter media and shortening its lifespan. If the fan is too small, insufficient airflow may cause paint mist to accumulate inside the filter box, leading to localized clogging. A reasonable approach is to select a fan model that matches the rated airflow and initial differential pressure of the filter cartridge, and ensure that the ventilation duct design is free of structural defects such as sharp bends or reduced diameters to minimize additional pressure loss caused by airflow turbulence.
Regular maintenance and replacement are crucial aspects of differential pressure management. By installing differential pressure sensors, the pressure difference between the filter cartridge's inlet and outlet can be monitored in real time. When the differential pressure exceeds twice the initial value, it indicates that the filter media is nearing saturation and needs timely replacement. For washable filter media, neutral detergent and low-pressure water can be used to rinse away surface paint residue, but care must be taken to avoid damaging the fiber structure. For disposable filter media, the replacement cycle must be strictly followed to prevent overuse from causing the differential pressure to exceed the equipment's safety limits.
The influence of ambient temperature and humidity on differential pressure is also significant. In high-temperature environments, volatile components in paint mist can easily solidify rapidly, forming hard particles that clog the filter media. In high-humidity environments, paint mist may combine with water vapor to form sticky substances that adhere to the filter media surface. Therefore, it is necessary to control the temperature and humidity in the painting workshop within a reasonable range and enhance the dehumidification function of the ventilation system to slow down the rate of pressure differential increase.
Optimizing the painting process can reduce paint mist generation at the source. Adopting automated technologies such as electrostatic spraying and robotic spraying can improve paint utilization and reduce paint mist emissions caused by excessive spraying; selecting environmentally friendly paints with low viscosity and high solids content can also reduce the particulate matter content in the paint mist. These measures not only reduce the load on the filter box but also improve the overall painting quality.
