High efficiency filter leak detection standard operating procedures
High efficiency filter
leak detection standard operating procedures
High efficiency filter maintenance tips
Maintaining a high-efficiency filter is an important issue. How can we maintain a high-efficiency filter? Let's first understand what a high-efficiency filter is: high-efficiency filter is mainly used to collect dust and various suspended solids below 0.3um. . Ultra-fine glass fiber paper is used as the filter material, and offset paper, aluminum film and other materials are used as the split plate, and the high-efficiency filter frame is used. Each unit has been tested and has the characteristics of high filtration efficiency, low resistance and large dust holding capacity. How to maintain high efficiency filters?
1. The high-efficiency filter is not allowed to tear or open the bag or packaging film by hand before installation. The air filter should be stored in strict accordance with the direction marked on the high-efficiency filter package; during the handling of the high-efficiency air filter, It should be handled gently and gently to avoid violent vibration and collision.
2. The transportation and storage of high-efficiency filters should be placed in the direction of the manufacturer's logo. During transportation, it should be handled gently to prevent violent vibration and collision, and it is not allowed to load and unload.
3. Before the high-efficiency filter is installed, it must be unpacked at the installation site for visual inspection, including: filter paper, sealant and frame for damage; side length, diagonal and thickness dimensions meet the requirements; frame with or without burrs and Rust spots (metal frame); whether there is a product certificate, technical performance meets the design requirements. Then in accordance with the national standard "clean room construction and acceptance specifications" [JGJ71-90] method of inspection, qualified should be installed immediately.
4. For high-efficiency filters, the installation direction must be correct: when the corrugated plate combination filter is installed vertically, the corrugated plate must be perpendicular to the ground; the connection between the vertical direction and the frame of the filter is strictly prohibited from leakage, deformation and damage. And leaking glue, etc., after installation, the inner wall must be clean, free of dust, oil, rust and debris. .
5, inspection method: observe or wipe the white silk cloth.
6. Before the high-efficiency filter is installed, the clean room must be thoroughly cleaned and cleaned. If there is dust inside the air-conditioning system, it should be cleaned and wiped clean again to meet the cleaning requirements. If a high-efficiency filter is installed in the technical interlayer or ceiling, the technical layer or the ceiling should also be thoroughly cleaned and wiped clean.
7. High-efficiency filter with cleanliness level equal to or higher than Class 100 clean room. Before installation, it should be leaked according to the method specified in “Cleanhouse Construction and Acceptance Specification” [JGJ71-90] and meet the specified requirements.
8. For high-efficiency filters, when the resistance value of the filter is greater than 450Pa; or when the airflow velocity of the windward surface is reduced to a minimum, even if the coarse and medium-efficiency filter is replaced, the airflow speed cannot be increased; If there is an unrepairable leak on the surface of the filter, a new high-efficiency filter must be replaced. If the above conditions are not available, it can be replaced once every 1-2 years depending on the environmental conditions.
9. High-efficiency filter leak detection method, the particle counter sampling head must be inserted into the exhaust static pressure tank (or pipeline) connected to the exhaust high-efficiency filter (this is different from the scanning leak detection for the air supply high efficiency filter) Because the leak detection side of the air supply high-efficiency filter is exposed to the room, and the leak detection side of the exhaust air high-efficiency filter is deep in the static pressure box or the pipeline), the above-mentioned leak detection side of the exhaust high-efficiency filter can be pressed as described above. The prescribed method is used for scanning leak detection.
The PAO leak detection of the high-efficiency filter installed in the clean room confirms the integrity of the high-efficiency filter and the sealing of the installation.
1, testing requirements
1.1 Test method: PAO leak detection method
1.2 Test scope: For all cleanrooms installed in the company with high-efficiency filters, high-efficiency filters in clean areas such as production workshops and laboratories must be inspected and leaked on site.
1.3 Working principle: PAO aerosol is generated as the dust source on the windward side of the detected high-efficiency filter, and is sampled and detected by the photometer on the downwind side, and the scattered light generated by the dusty gas through the photometric time is converted into electric quantity by photoelectric effect and linear amplification, and Quickly displayed by the micro-ampere meter, the collected air sample passes through the diffusion chamber of the photometer. Due to the difference in light intensity caused by particle expansion, the photometer can measure the relative concentration of the aerosol by measuring the light intensity. The PAO leak detection method measures the penetration rate of the high-efficiency filter, that is, the photometer directly displays the transmittance reading.
1.4 Testing materials and instruments
Aerosol generator (TDA-5C), aerosol photometer (TDA-2H), nitrogen bottle, PAO
1.5, the scope of leak detection
1.5.1 filter material
1.5.2 The filter material of the filter is connected to the inside of the frame
1.5.3 Filter frame between the gasket and the filter group supporting the cradle
1.5.4 between the support frame and the wall or ceiling
2, test status and preconditions
2.2. The air volume/wind speed test has been completed and the results are in compliance with the regulations;
3. Eligibility Criteria: The maximum value of the penetration rate measured by the high-efficiency filter under inspection shall not exceed 2 times the “factory pass rate”. ("Factory pass rate" can be calculated from the filtration efficiency marked on the nameplate of the HEPA filter)
In the formula: k----factory qualified penetration rate.
α----The filtering efficiency marked on the nameplate.
3.2. Note: Before the test, you need to fill in the relevant records of the “High Efficiency Filter Leak Record”.
4. Detection method:
4.1 Preparation: Remove the diffuser plate of the high-efficiency filter and clean the cabinet and frame to avoid interference from the dust. Prepare the nitrogen bottle and associated connecting tube.
4.2 Occurrence of aerosol smoke: The inert gas inlet of the aerosol generator is linked to the outlet of the nitrogen cylinder equipped with a pressure regulating valve by a plastic tube having a 1/4 outer diameter. The nozzle of the aerosol generator is connected to the intermediate storage nozzle of the air cabinet of the air purification system by a plastic tube. Press “TDA-5C Aerosol Generator” to heat it to a temperature of 393.3°C-407.4°C. Open the nozzle regulator valve, open the nitrogen source and its regulating valve to adjust the output of the aerosol smoke.
4.3 Parameter setting: aerosol photometer initialization, 0% reference standard value setting. Before each high-efficiency filter scan, first check the 100% reference, and connect the DOP detection hole reserved on the sampling tube street, one end is connected to the upstream (high-efficiency filter inlet side) sampling port, and the other end is connected with the aerosol photometer. Turn on and measure the upstream aerosol concentration. Adjust the opening degree of the aerosol generator output valve until it is confirmed that the upstream concentration reaches 10-20 ug/L, and set this base to 100%.
4.4 Adjust the aerosol generator and aerosol photometer according to the “TDA-2H Aerosol Photometer Standard Operating Procedures” and “TDA-5C Aerosol Generator Operating Procedures”.
4.5 Photometer Scan: Scan the entire high-efficiency filter's working surface (including between the filter and the frame, between the frame and the frame, and between the frame and the static pressure box) with the sampling head of the photometer. When scanning, the sampling head is about 2-4 cm away from the filter, and the speed is about 3-5 cm/s. When scanning, the line is reciprocated back and forth, and the lines should overlap. During the test, always observe the readings on the recording head or photometer panel. Note: Avoid ash interference on the cabinet during scanning, especially if the sampling head cannot touch the frame of the high-efficiency tuyere or filter.
5. Test result record: Record the measured penetration rate data of each clean room high efficiency filter in "High Efficiency Filter Leak Detection Record"
6. Analysis of the results:
After the test is completed, the test should be summarized and analyzed to form the “High Efficiency Filter Leak Detection Result Report”, which must explain: This leak detection has a leak test for the installed high efficiency filter in each room of the workshop-level area, and the test data proves : The integrity of the installed high efficiency filter in this area and the tightness of the installation; enumerate the corresponding results of all tested high efficiency filters:
Meet the requirements of relevant standards and can be put into use;
Part of the high-efficiency filter leaks and needs to be replaced and retested;
The frame of the high-efficiency filter connected to the static pressure box leaks and needs to be disassembled and reinstalled or re-tested after taking appropriate sealing measures.
7, the frequency of detection
7.1 Detecting when installing or replacing a high efficiency filter
7.2 In normal use, test at least once a year.