What are the replacement steps for the high-efficiency filter of a laminar flow sampling vehicle?

The replacement of the high-efficiency filter of the laminar flow sampling vehicle is a key step in maintaining the cleanliness performance of the equipment. Improper operation may affect the filtration effect or cause secondary pollution. The following are the detailed replacement steps and precautions for your reference:
I. Preparations Before Replacement
Confirm the replacement timing
When the pressure difference gauge of the high-efficiency filter shows that the pressure difference exceeds 1.5 to 2 times the initial value (or reaches the resistance threshold specified by the manufacturer).
The service life of the equipment has reached its rated lifespan (usually 10,000 to 20,000 hours, or according to the cycle recommended by the manufacturer).
The cleanliness test result does not meet the standard, and the primary filter has been cleaned or replaced, but there is still no improvement.
Prepare tools and materials.
New high-efficiency filters (consistent with the original model to ensure a filtration efficiency of ≥99.97%@0.3μm), sealants (silicone sealants, etc.), screwdrivers, wrenches, and other tools.
Disinfection supplies (75% alcohol, disinfectant wipes), dust-proof cloths, and garbage bags.
Protective equipment: Disposable gloves, masks, hats. Protective clothing should be worn when necessary.
Environmental and equipment handling
Turn off the power supply of the laminar flow sampling vehicle, cut off the main power supply, and ensure that the equipment is completely shut down.
Move the equipment to a relatively clean area (or cover the surrounding area with a dust-proof cloth to reduce the spread of dust during replacement).
Disinfect and wipe the equipment casing, filter door, and surrounding areas.
2. Disassemble the old filter
Open the filter door.
Locate the installation position of the high-efficiency filter (usually in the sealed compartment at the top or back of the equipment), use a tool to unscrew the compartment door screws, and slowly open the compartment door to prevent dust from falling.
Fix the old filter
Observe the fixing method of the old filter (such as slots, bolts, pressure strips, etc.), record the fixing position and sequence (photos can be taken for record, which is convenient for restoring when installing the new filter).
Disassemble the old filter.
First, loosen the fixing device and gently remove the old filter (be sure to keep it level to avoid tilting, which may cause dust to spill).
If there is sealant between the filter and the frame, use tools to carefully remove the old sealant, clean the residual sealant and dust on the frame surface, and ensure that the installation surface is flat and clean.
Deal with the old filter.
Put the old filter into a sealed bag, mark it as "contaminated", and dispose of it according to the standards for medical waste or industrial waste (if it is a filter containing dust or potentially contaminated, it needs to be disinfected before disposal).
Iii. Install the new high-efficiency filter
Check the new filter.
Before opening a new filter, make sure the packaging is intact and undamaged, and the label information (model, specification, date of manufacture, test report) is complete.
Gently shake the filter to ensure that the internal filter paper is not loose or damaged and the frame is not deformed.
Disinfection before installation
Wipe the frame edge and installation surface of the new filter with alcohol, and wait for it to dry before installation.
Fix the new filter
Place the filter steadily into the installation compartment, paying attention to the air flow direction indicator (usually the arrow points downward or towards the working area, which should be consistent with the air flow direction of the equipment), and avoid installing it in reverse.
Fix the filter with pressure strips, bolts, or slots to ensure that the frame is closely attached to the installation surface without any gap (the gap can be checked with a feeler gauge, ≤0.5mm).
Sealing treatment
Apply sealant evenly at the joint between the filter frame and the installation surface (in a continuous straight line or triangle), with a thickness of about 2-3mm. Ensure a tight seal without any leakage or air bubbles.
Wait for the sealant to cure (for the time specified in the adhesive manual, usually 24 hours), and avoid touching or vibrating the equipment during this period.
Iv. Inspection and Testing after Installation
Appearance and sealing performance inspection
Close the filter door, tighten the screws, and check whether the seal between the door and the main body of the equipment is good.
Observe whether there are any gaps or glue stains overflowing around the filter, and ensure that it is firmly installed without any looseness.
Trial operation of the equipment
Connect the power supply, start the fan, and observe whether the equipment operates normally and if there are any abnormal noises or vibrations.
Wind speed detection: Use an anemometer to measure at different positions in the working area. The wind speed should reach 0.3-0.6m/s (or meet the manufacturer's set value), and the uniformity should be good (deviation ≤±20%).
Cleanliness verification
Use a dust particle counter to test the cleanliness of the working area (such as ISO level 5 standard, the number of particles ≥0.5μm ≤3520 /m³).
If conditions permit, aerosol scanning tests (such as PAO tests) can be conducted to check for any leakage at the edge of the filter and the installation site.
Records and Identifications
Record the replacement date, filter model, batch number, operator, and other information in the equipment ledger, and update the initial value of the differential pressure gauge.
Stick a replacement label on the filter door, indicating the replacement time, to facilitate subsequent tracking of the maintenance cycle.
V. Precautions
Personnel protection
During the replacement process, avoid touching the filter paper of the filter directly with your hands to prevent contamination or damage.
If the old filter may have come into contact with harmful contaminants (such as biological samples or chemical reagents), a protective mask should be worn and the operation area should be thoroughly disinfected after replacement.
Installation details
Incorrect installation direction of the filter can cause a short circuit in the airflow, affecting the cleaning effect. It is essential to install it correctly according to the markings.
The sealant should be of the type that is heat-resistant and corrosion-resistant, and applied evenly to avoid air leakage due to poor sealing.
After-sales support
If it is your first replacement or you are not familiar with the operation, you can contact the technical personnel of the equipment manufacturer for guidance or have a professional maintenance team carry it out to ensure the quality of the replacement.
Through standardized replacement procedures and tests, it can be ensured that the performance of the high-efficiency filter meets the standards, maintaining a clean environment for the laminar flow sampling vehicle. After replacement, it is necessary to regularly monitor the pressure difference and cleanliness, and promptly detect and handle any abnormalities.