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Purpose of DOP leak detection for high-efficiency filters on laminar flow cabinet

日期:2024-07-21 00:19
浏览次数:69
摘要: 1. Purification effect and installation replacement of laminar flow ultra clean workbench: If there are defects in the installation of high-efficiency filters, such as small holes in the filter itself or small cracks formed by loose installation, it can lead to the failure to achieve the desired purification effect. Therefore, after the installation or replacement of the high-efficiency filter, it is necessary to perform a leak detection on the filter and the installation connection.
1. Purification effect and installation replacement of laminar flow ultra clean workbench:
If there are defects in the installation of high-efficiency filters, such as small holes in the filter itself or small cracks formed by loose installation, it can lead to the failure to achieve the desired purification effect. Therefore, after the installation or replacement of the high-efficiency filter, it is necessary to perform a leak detection on the filter and the installation connection.
2. Purpose of leak detection
By testing the leakage rate of the high-efficiency filter, identify the defects in the high-efficiency filter and its installation, in order to take remedial measures.
Ultra clean workbench
3. Leakage detection range
Clean areas, laminar flow ultra clean workstations, and high-efficiency filters on equipment.
4. Leak detection method
The commonly used methods for leak detection are DOP method (using DOP solvent as the dust source and cooperating with aerosol photometer for leak detection), or dust particle counter scanning method (using atmospheric dust as the dust source and cooperating with particle counter for leak detection). Due to the cumulative reading of the particle counter, it is not conducive to scanning and the inspection speed is slow; In addition, on the windward side of the tested high-efficiency filter, the atmospheric dust concentration is often low, and it is necessary to supplement smoke to easily detect leaks. The particle counter method can make up for these shortcomings in leak detection, so the DOP method is widely used in foreign countries for leak detection.
5. DOP leak detection method
5.1. Working principle
The DOP aerosol is generated on the windward side of the detected HEPA filter as the dust source (DOP is dioctyl phthalate, with molecular weight of 390.57, and the particles are spherical after spray), and the photometer is used for sampling on the downwind side. The collected air sample passes through the diffusion chamber of the photometer, and the scattered light generated by the dust containing gas through the photometer is converted from photoelectric effect and linear amplification to electricity, and quickly displayed by the microammeter, then the relative concentration of the aerosol can be measured. The DOP test actually measured the penetration rate of the high-efficiency filter.
Ultra clean workbench
5.2 Materials and Instruments
① Dust source (DOP solvent);
② DOP generator [is a device that produces smoke. After pouring DOP solvent into the generator container, under certain pressure or heating conditions, the aerosol smoke is generated and sent to the upwind side of the high-efficiency filter (heating DOP liquid to form DOP steam, which condenses into small droplets under specific conditions, removing both too large and too small droplets, leaving only 0.3 μ Particles around m, misty DOP entering the air duct;
③ Aerosol spectrophotometer (an instrument for measuring and displaying aerosol concentration, with a calibration validity period indicated, must be qualified and within the validity period before use);
④ Nitrogen gas;
⑤ Epoxy resin silicone;
⑥ Spare high-efficiency filters of the required model
5.3. Procedure for leak testing
5.3.1 Leak detection preparation
Prepare the necessary equipment for leak detection and the layout plan of the air supply duct for the purification air conditioning system in the area to be inspected, and notify the purification air conditioning equipment company to be present on the day of leak detection for gluing and replacing high-efficiency filters.
5.3.2. Leak detection operation
① Check if the liquid level of DOP solvent in the aerosol generator is higher than the low liquid level. If it is insufficient, it should be added.
② Connect the nitrogen cylinder to the aerosol generator, turn on the temperature switch of the aerosol generator, and turn the red light to green light, which indicates reaching the temperature (about 390-420 ℃).
③ Place one end of the testing hose at the upstream concentration testing port of the aerosol photometer, and the other end on the inlet side (upstream side) of the tested high-efficiency filter. For system leak detection, DOP smoke can be directly placed into the air conditioner (be careful not to be adsorbed by the filter inside the air conditioner). If the DOP generator is small and cannot reach the specified concentration, it can be placed in the static pressure box of the tested high-efficiency filter, and the laminar flow workbench can be directly placed into the fan inlet. Turn on the photometer switch and adjust the test value to "100".
④ Turn on the nitrogen switch, control the pressure between 0.05 and 0.15 Mpa, slowly open the oil valve of the aerosol generator, and control the test value of the photometer to be between 10 and 20. After the test value stabilizes, input the concentration measured upstream to proceed with subsequent scanning and inspection operations.