I. Before Installation: Foundation preparation is the prerequisite
The preparatory work before installation directly affects the quality of subsequent installation. It is necessary to strictly control the three major elements of “environment, equipment, and personnel”.
1. Pre-treatment of the installation environment
Cleanliness compliance: The installation of filters must be carried out after the basic completion of the civil construction, decoration and equipment installation of the clean room. Moreover, the installation area should be pre-cleaned (such as sweeping, vacuuming and wiping) in advance to prevent dust and debris from adhering to the surface of the filters or entering the air flow channels.
Primary filter: It can be installed in a generally clean environment, but construction dust should be avoided.
Medium-efficiency filters: Simple dust removal is required in the installation area (such as cleaning the inner walls of the air ducts and the installation frames with a vacuum cleaner).
High-efficiency/ultra-high-efficiency filters: The cleanroom must be in a “clean state” (for example, before installing high-efficiency filters in a 10,000-level cleanroom, it is necessary to run the medium-efficiency filtration system for 1-2 hours to remove dust first), and the installation process must be carried out under the protection of a “clean workbench” or “laminar flow hood”.
Installation surface inspection: Confirm the flatness and sealing performance of the filter installation frame (such as static pressure box, air duct flange, filter bracket) – the frame surface should be free of burrs, depressions, and rust, and the flange sealing surface should be smooth, with a deviation of no more than 2mm/m. For high-efficiency filters, the dimensions of the installation frame must precisely match the outer frame of the filter (with a gap of no more than 1mm) to prevent leakage caused by dimensional deviations.
2. Inspection of filters and accessories
The filter itself: Before opening the box, check if the packaging is intact. After opening the box, verify whether the filter model, specification, and efficiency grade (such as primary efficiency G4, medium efficiency F8, high efficiency H13) meet the design requirements. The key points to check are whether the filter paper is damaged or has creases, whether the sealant is cracked or has fallen off, and whether the outer frame is deformed. For high-efficiency filters, the factory “leak test report” and “Efficiency test certificate” need to be verified.
Sealing and fixing accessories: Prepare suitable sealing materials (such as polyurethane sponge strips, nitrile rubber gaskets, sealant) and fixing parts (such as stainless steel bolts, pressure strips, nuts) in advance. Ensure that the sealing materials are not aged and have good elasticity, and the fixing parts are not rusted (stainless steel material is preferred to avoid particle contamination).
3. Personnel and Tool Management
Personnel requirements: Installation personnel must wear work clothes that meet the cleanliness level (such as dust-free suits, dust-free caps, dust-free gloves, and shoe covers) and pass through the air shower room for dust removal before entering the clean area. High-efficiency filter installers need to receive specialized training, be familiar with the installation process, and key points of leakage control.
Tool preparation: All tools (such as wrenches, screwdrivers, tape measures, vacuum cleaners) need to be cleaned and degreased in advance to avoid bringing in impurities. Tools that are prone to generating debris (such as ordinary sandpaper and unclean cloths) are prohibited from being used.
Ii. Classification: Key Points for Installing Primary, Medium, and High-Efficiency Filters
The functions, installation positions, and precision requirements of filters of different levels vary greatly, and it is necessary to control the key links in a targeted manner.
|
Filter level |
Installation location |
Key points to note |
| Primary filter | Fresh air inlet, return air section of the air conditioning unit |
1. Installation direction: Install according to the arrow marking on the outer frame of the filter (airflow direction), and do not install in reverse. 2. Sealing and adhesion: It should be closely adhered to the filter bracket/slot. If there is a gap, sealing sponge can be filled. 3. Firm fixation: It is fixed with clips or bolts to prevent shaking due to air flow impact during operation. |
| Medium-efficiency filter | The middle and rear sections of air conditioning units and the front ends of clean room supply air ducts |
1. Frame adaptation: Prioritize the use of “bag-type medium-efficiency filters”. During installation, ensure that each filter bag is fully unfolded to avoid wrinkles that may affect air volume. 2. Sealing method: “Strip sealing” or “gasket sealing” is adopted. The strip should be evenly pressed to prevent short circuit of the airflow. 3. Pre-protection: It is necessary to ensure that the primary filter has been installed and is operating normally to prevent large particle impurities from directly impacting the medium-efficiency filter paper. |
| High-efficiency/ultra-high-efficiency filters | Cleanroom supply air terminals (such as inside ceiling diffusers, FFU units), local purification equipment (such as biosafety cabinets) |
Sealing is the core: – Common sealing methods: “Liquid tank sealing” (suitable for high cleanliness rooms such as Class 100 clean rooms, insert the outer frame of the filter into the liquid tank filled with sealing liquid, and the sealing liquid should cover the outer frame by ≥5mm), “compression sealing” (use closed-cell sponge pads, and evenly press them with bolts, with the compression amount controlled at 30%-50%). – Do not apply sealant directly to the filter paper to avoid chemical contamination. 2. Installation accuracy Use a “level” to calibrate the installation plane of the filter to ensure it is parallel to the air supply surface and avoid uneven air distribution. When multiple filters are installed side by side, the spacing should be consistent (usually ≥50mm), and the edges of the outer frames should be aligned. 3. Avoid damage: Do not touch the filter paper with your hands during installation. When handling, support the outer frame and do not lift the filter material. 4. Pre-confirmation: Before installation, the medium-efficiency filtration system should be run for at least 1 hour, and the air cleanliness of the installation area should be tested with a dust particle counter (for areas below grade 10,000, it should reach above grade 100,000). |
Regardless of the level of the filter, the installation process must follow the following common principles:
Eliminate “air flow short circuit” and “leakage”
Airflow short circuit is a “fatal defect” in cleanrooms: It is necessary to ensure that there is no gap between the filter and the installation frame. If the frame is found to be uneven, it should first be leveled with a gasket (ordinary foam gaskets cannot be used, but clean-grade sealing gaskets should be used).
After the high-efficiency filter is installed, on-site leak detection must be carried out (for example, by using the “aerosol photometer method”, PAO aerosol is used as the challenge particle to detect the leakage rate on the filter surface and at the sealing area, and the leakage rate should be ≤0.01%).
2. Protect the filter material from human damage
When installing, do not step on or press the filter, and do not allow tools or hard objects to collide with the filter paper.
The filter paper of the high-efficiency filter is made of glass fiber or PTFE membrane, which is extremely fragile. It should be handled with care during transportation and installation. If any damage to the filter paper is found, it must be replaced immediately and cannot be repaired for reuse.
3. Comply with the “dynamic management” requirements of cleanrooms
If a pause is needed during the installation process, the filter and the installation port should be covered with clean plastic sheeting to prevent dust from falling in.
Welding, cutting, and other operations that produce particles or odors are strictly prohibited in the installation area. If such operations must be carried out, the uninstalled filters must be removed first and the area thoroughly cleaned.
4. Adapt to airflow and pressure
Before installation, it is necessary to confirm that the system air volume matches the rated air volume of the filter (the actual operating air volume of the filter should be within the range of 70% to 120% of the rated air volume. Exceeding this range may cause damage to the filter material or a decrease in efficiency.
After the high-efficiency filter is installed, the fan should be started slowly to avoid sudden high-pressure impact on the filter material.
Iv. After installation: Acceptance and record-keeping are indispensable
1. Installation acceptance
Visual inspection: The filter is firmly installed without deformation, with no gaps at the sealing points and clear markings on the airflow direction.
Leakage detection: High-efficiency/ultra-high-efficiency filters must undergo aerosol leakage detection, while primary and medium-efficiency filters can be detected by the “smoke method” (using a smoke generator to check if there is smoke leakage at the seal).
Performance test: After running the system for 30 minutes, the number of dust particles and the uniformity of air velocity in the clean room should be tested. They must meet the designed cleanliness level (for example, in a Class 100 clean room, the number of particles ≥0.5μm ≤3520 per m³).
2. Record and archive
The following information needs to be recorded in detail as the basic data for the operation and maintenance of the cleanroom:
Filter model, specification, efficiency grade, factory serial number, installation date;
Type of sealing material and fixation method;
Leak detection results, test data (such as leakage rate, wind speed, cleanliness);
The installation personnel and the acceptance personnel sign.
Summary
The core logic of cleanroom filter installation is “preparation first, then adaptation, strong sealing, and strict acceptance” – primary filters focus on “pre-protection and firmness”, medium-efficiency filters focus on “filter material spreading and uniform airflow”, and high-efficiency filters focus on “sealing accuracy and undamaged installation”. Only by strictly controlling each link can the long-term stable operation of the filter be ensured and the core function of the clean room be maintained.
