What is the replacement process for the high-efficiency filter in the laminar flow transfer window?

The replacement of high-efficiency filters in laminar flow transfer Windows must follow a strict process to ensure that the environment of the clean room is not contaminated and to guarantee the normal operation of the equipment. The following is the detailed replacement process and precautions:
I. Preparations before Replacement
Confirm the replacement timing
The high-efficiency filter needs to be replaced when the following situations occur:
The resistance reaches twice the initial resistance (monitored by a differential pressure gauge).
The appearance of the filter is damaged, deformed, or has air leakage.
The cleanliness test is not up to standard (such as excessive bacteria and dust particle count).
Check the equipment manual in advance to confirm the model, size, and installation method of the filter (such as liquid tank type, compression type, etc.).
Prepare tools and materials.
Tools: Screwdriver, wrench, sealant (such as silicone sealant), cleaner (alcohol or neutral detergent), tape measure, protective equipment (gloves, mask, clean suit).
Materials: New high-efficiency filters (confirm that the specifications are consistent with the original factory), sealing rubber strips (replace the original rubber strips if they age), non-woven fabric, or cleaning cloth.
Environmental preparation
Clean and disinfect the replacement area in advance (such as wiping the surrounding surface with 75% alcohol) to prevent the spread of dust.
Turn off the fan and power supply of the laminar flow transfer window, and hang the "Under Maintenance" warning sign to ensure operational safety.
If replacement is to be carried out in the clean area, the relevant department must be notified in advance to avoid cross-contamination (such as suspending operations in adjacent areas).
Ii. Steps for Replacing High-Efficiency Filters
1. Remove the old filter
Open the inspection door: According to the structure of the equipment, remove the sealing plate or inspection door of the filter chamber (usually fixed with screws or snap-on type).
Disconnect electrical connections (if any): If the filter is interlocked with the wind speed sensor, differential pressure gauge, etc., the power supply and signal lines must be disconnected first.
Remove the old filter.
Liquid tank installation: Loosen the clamping device and carefully remove the old filter (to prevent the liquid tank sealant from spilling).
Compression installation: Remove the fixing screws or pressure plate, and take out the old filter smoothly. Be careful to prevent the filter from toppling over or fragments from falling.
Clean the installation frame: Use a non-woven cloth dipped in alcohol to wipe the surface of the filter installation frame to remove dust, old glue stains, and debris, ensuring that the installation surface is flat and clean.
2. Install the new filter
Check the new filter:
Check if the model and size are correct, and inspect if the outer packaging is damaged. This should be done in a clean environment before opening the package.
Visually inspect the appearance of the filter to ensure there is no deformation or damage, and the filter material has no wrinkles or fractures.
Install the filter
Place the new filter steadily into the installation frame. Pay attention to the direction of the airflow (the arrow mark usually points to the air outlet side) to ensure it is installed properly.
Liquid tank installation: Adjust the position of the filter to align the liquid tank with the edge of the frame to ensure good sealing. Then install the pressing device (apply force evenly to avoid damaging the filter).
Compression installation: Fix the filter with screws or pressure plates to ensure that the sealing strips around are evenly compressed without any gaps.
Sealing treatment: Apply sealant (such as silicone sealant) at the joint between the edge of the filter and the frame to form a continuous sealing line and prevent air leakage.
3. Restore the equipment and conduct tests
Install the inspection door: Reset the sealing plate or inspection door, tighten the screws, or fasten the clips to ensure a tight closure.
Connect electrical components: Restore the power and signal lines of devices such as wind speed sensors and differential pressure gauges, and check if the wiring is secure.
Startup test
Connect the power supply, start the fan, and observe whether the operation is smooth and if there is any abnormal noise.
Check the reading of the differential pressure gauge to confirm that the resistance value is within the normal range (refer to the equipment manual or the initial record).
Conduct leakage tests (such as PAO tests): Use an aerosol generator and a particle counter to detect whether there is any leakage at the edge of the filter and the installation interface. If there are any leakage points, resealing or adjusting the installation is required.
Clean the site: Remove the waste generated during the replacement process (old filters should be treated as hazardous waste and must not be discarded at will), wipe the surface of the equipment with alcohol, and restore the clean area environment.
Iii. Precautions
Personnel Requirements
Operators should wear clean suits, masks, and gloves to prevent the dust they carry from contaminating the equipment.
Untrained personnel are not allowed to replace the filter at will to avoid equipment damage or contamination caused by improper operation.
Safe operation
Old filters may adsorb harmful particles (such as microorganisms and chemical contaminants). When replacing them, avoid direct contact with the filter material and wash your hands promptly after operation.
If the filter contains radioactive substances or biological hazard factors, it should be operated by a special waste treatment process (such as sealed and discarded after autoclaving).
Record and archive
After replacement, the "Equipment Maintenance Record" needs to be filled out, which includes: the replacement date, filter model/number, resistance value, operator's signature, etc., for traceability management.
Regularly conduct statistical analysis on the filter replacement cycle and optimize the maintenance plan (such as adjusting the replacement frequency according to the growth trend of resistance).
Other key points
During the replacement process, avoid excessive squeezing of the filter to prevent damage to the filter material.
If both the primary and medium efficiency filters (pre-filtration system) are replaced simultaneously, the primary and medium efficiency filters should be replaced first, followed by the high-efficiency filter, in order to extend the service life of the high-efficiency filter.
Iv. Common Problems and Solutions
Air leakage issue: If the leakage test fails, it might be due to the sealant not being applied evenly or the installation being uneven. It is necessary to disassemble and adjust the seal again.
Abnormal resistance: If the resistance is too high after replacement, it might be due to an incorrect filter model or overly tight installation. Low resistance may be due to a damaged filter or loose installation, and a recheck is required.
Insufficient wind speed: Check whether the fan is operating normally or if it is caused by a clogged filter (such as being exposed to a polluted environment for a long time before installation). Replace it if necessary.
Through standardized procedures and meticulous operations, the high-efficiency filter replacement process of the laminar flow transfer window can be ensured to be safe and reliable, maintaining the stability of the clean environment.