The cleanliness of high-efficiency filters and cleanrooms is the technical correlation between "core equipment" and "final results". Efficient filters are one of the most critical technical means to ensure that cleanrooms achieve and maintain the designed cleanliness level. Specifically reflected in the following aspects:
Final barrier: determines the cleanliness of the incoming air
High efficiency filters are usually installed at the end of the purification air conditioning system, which is the last gateway for air to enter the workshop. Its core function is to filter out micron or even submicron sized particles in the air.
Filter object: mainly targeting small dust particles of 0.5 μ m and below, while also effectively filtering bacteria in the air, making the colony count of the outlet airflow close to zero.
Efficiency level: Filters with different efficiencies will be selected according to different cleanliness requirements. For example, for clean areas with ISO level 5 (formerly level 100) and above, it is usually necessary to use H13/H14 high-efficiency filters (with a filtration efficiency of ≥ 99.95% for the most easily penetrable particle size MPPS) or even U15 ultra high efficiency filters (with an efficiency of ≥ 99.9995%).
Core logic: If the efficiency of the high-efficiency filter itself does not meet the standard, is installed improperly, or leaks, then the air sent into the room is unclean, and the cleanliness cannot be discussed.
Synergistic effect: Maintaining cleanliness together with other factors
The cleanliness of a cleanroom is a systematic engineering, and efficient filters are the core link, but they need to work together with other elements to achieve the best results.
| influencing factors |
Technical association with high-efficiency filters | The impact of failure on cleanliness |
| air filtration |
The high-efficiency filter is the last stage of the three-stage filtration, and the initial and intermediate filters in the previous stage protect the high-efficiency filter and extend its lifespan. | The cleanliness directly decreases, and the concentration of dust particles sent into the air exceeds the standard. |
air distribution |
High efficiency filters are usually combined with laminar flow hoods or FFUs (fan filtration units), which are evenly arranged to form unidirectional or non unidirectional flow, effectively discharging pollutants generated indoors. | Even if the air supply is clean, pollutants cannot be discharged, which may result in poor indoor cleanliness. |
Static pressure difference |
Efficient filters need to overcome their own resistance and maintain positive pressure in the room by supplying air through the air conditioning system to prevent external pollution from infiltrating. | External pollution may enter the room through gaps, affecting cleanliness. |
Dynamic impact: the entire process of installation, operation, and maintenance
The impact of high-efficiency filters on cleanliness runs through their entire lifecycle, and any problem at any stage can damage the final cleanliness.
Installation process:
Environmental requirements: The system must be cleaned by air blowing and the clean room must be thoroughly cleaned before unpacking and installing at the installation site to avoid contamination.
Installation leak detection: PAO/DOP leak detection must be carried out after installation, with a focus on checking whether the filter itself is damaged and the sealing quality of the frame. For A/B-grade sterile areas or cleanrooms that are stricter than level 5, this is a mandatory requirement. Any small leakage point can lead to inadequate local cleanliness.
Resistance adjustment: Multiple high-efficiency filters installed in the same room should have similar resistance. If the difference in resistance is too large, it will cause an imbalance in air flow and affect the uniformity of the airflow.
Operation phase:
Wind speed and efficiency: For small particles mainly based on diffusion mechanism (such as 0.1-0.3 μ m MPPS), the lower the wind speed passing through the filter material, the longer the particle stays in the filter material, the higher the probability of being captured, and the higher the filtration efficiency. Experience has shown that halving the wind speed may reduce the dust transmission rate by an order of magnitude.
Resistance change: As the usage time increases, the filter accumulates dust and the resistance gradually increases. The final resistance is usually set at 1.5 to 2.0 times the initial resistance. When the resistance is too high, the air supply volume will significantly decrease, resulting in insufficient ventilation and affecting cleanliness.
Special requirements:
Chemical pollution control: In industries such as semiconductors, in addition to particulate matter, molecular level chemical pollutants (AMCs) can also seriously affect product yield. At this point, it is necessary to install chemical filters in the purification air conditioning system.
Microbial control: For the pharmaceutical and food industries, efficient filters not only need to control particles, but also the number of live microorganisms. Therefore, the selection of filters also needs to consider their antibacterial and sterilization capabilities.
summary
The high-efficiency filter provides the most essential clean air source for the dust-free workshop through its extremely high filtration efficiency. But it does not exist in isolation, and its technical performance depends on correct selection, installation, coordination with airflow organization, and maintenance management throughout its entire lifecycle. Negligence in any aspect can lead to the malfunction of the high-efficiency filter, ultimately resulting in an unsatisfactory cleanliness of the workshop.