German
French
Italian
Portuguese
Japanese
Korrean
Russian
Purpose of DOP leak detection for high-efficiency filters of laminar clean bench
Purpose of DOP leak detection for high-efficiency filters of laminar clean bench1. Purification effect and installation and replacement of laminar clean bench: If there are defects in the high-efficiency filter and its installation, such as small holes in the filter itself or small cracks caused by loose installation, the expected purification effect will not be achieved. Therefore, after the high-efficiency filter is installed or replaced, the filter and the installation joint must be leak-checked.2. Purpose of leak detection By testing the leakage of the high-efficiency filter, the defects of the high-efficiency filter and its installation can be found to take remedial measures. Clean bench 3. Leak detection scope Clean area, laminar clean bench high-efficiency filters on equipment, etc. 4. Leak detection method The commonly used method is DOP leak detection (i.e. using DOP solvent as the dust source and cooperating with aerosol photometer for leak detection), and the dust particle counter scanning method can also be used for leak detection (i.e. using atmospheric dust as the dust source and cooperating with particle counter for leak detection). Since the particle counter reading is cumulative, it is not conducive to scanning and the inspection speed is slow; in addition, on the upwind side of the high-efficiency filter being tested, the atmospheric dust concentration is often low, and additional smoke is required to easily detect leaks. The DOP method can make up for these shortcomings of the particle counter method, so the DOP method is widely used for leak detection abroad. 5. DOP method leak detection 5.1. Working principle DOP aerosol is emitted as a source on the upwind side of the high-efficiency filter being tested (D0 dioctyl dimethoxybenzene, molecular weight 390.57, village dry ball shape after spraying), and a photometer is used for sampling on the downwind side. The collected air sample passes through the diffusion chamber of the photometer. The scattered light generated by the dust-containing gas passing through the photometer is converted into electricity by photoelectric effect and linear amplification and is quickly displayed by the microammeter, so the relative concentration of the aerosol can be measured. The DOP test measures the penetration rate of the high-efficiency filter. Clean bench 5.2. Materials and instruments ① Dust source (DOP solvent); @ DOP generator! It is a device that produces smoke. After DOP solvent is poured into the generator container, aerosol smoke is generated under certain pressure or heating conditions and sent to the upwind side of the high-efficiency filter (heating DOP liquid to form DOP steam, the steam condenses into tiny droplets under specific conditions, removes oversized and undersized droplets, leaving only particles of about 0.34m, and mist DOP enters the air duct); ③ Aerosol photometer (an instrument for measuring and displaying aerosol concentration, the calibration validity period should be indicated, and it must be calibrated and within the validity period before it can be used); Fish Nitrogen; ⑤ Epoxy resin silica gel; ⑥ Spare high-efficiency filter of the required model 5.3. Leak test work procedures 5.3.1. Leak test preparation Prepare the equipment required for leak detection and the plane layout of the air supply duct of the purification air conditioning system in the area to be inspected, and notify the purification air conditioning equipment company to come to the site on the day of leak detection to perform operations such as glue application and replacement of high-efficiency filters. 5.3.2. Leak detection operation ①) Check whether the liquid level of the DOP solvent in the aerosol generator is higher than the low liquid level. If it is insufficient, add more. (②) Connect the nitrogen bottle to the aerosol generator, turn on the temperature switch of the aerosol generator, and wait until the red light turns green, indicating that the temperature has reached (about 390~420℃). ③ Connect one end of the test hose to the upstream concentration test port of the aerosol photometer, and the other end to the air inlet side (upstream side) of the high-efficiency filter to be tested [the system leak detection can directly put the DoP smoke into the air conditioner (be careful not to be adsorbed by the filter in the air conditioner); if the DOP generator is small and does not reach the specified concentration, it can be placed in the static pressure box of the high-efficiency filter to be tested, and the laminar flow workbench can be directly placed in the fan suction port], turn on the photometer switch, and adjust the test value to "100". ④ Turn on the nitrogen switch, control the pressure at 0.05~0.15Mp, slowly open the oil valve of the aerosol generator, control the test value of the photometer at 10~20, and input the upstream measured concentration after the test value stabilizes, and then you can perform the subsequent scanning and inspection operations. ⑤ Connect one end of the test hose to the downstream concentration test port of the aerosol photometer, and use the other end, i.e. the sampling head, to scan the air outlet side and the bracket of the filter. The sampling head is about 3~5cm away from the filter and scans back and forth along the inner frame of the filter. The inspection speed is below 5cm/. The test range includes the filter material of the filter, the connection between the filter material and its frame, the connection between the sealing gasket of the filter frame and the support frame of the filter group, and the connection between the support frame and the wall or ceiling to check for small pinholes and other damage in the filter medium, frame seal, gasket seal, and leaks on the filter frame. Laminar clean bench ⑥ The instrument indication value on the photometer is the penetration rate of the high-efficiency filter. When the efficiency of the high-efficiency filter is below the acceptable standard, use epoxy resin silicone to plug the leak or tighten the bolts (stop smoking and replace the high-efficiency filter if necessary), and then conduct scanning inspections until the instrument indication value is within the acceptable range. ⑦ Leak detection records should be filled in in time, and the plugging points should be marked with the application diagram of epoxy resin silicone plugging. 5.3.3. Acceptable standards The efficiency of the high-efficiency filter in the 100,000-level clean area should be >95% (the aerosol photometer instrument indication value is less than 5); the efficiency of the high-efficiency filter in the 10,000-level clean area should be >99.97% (that is, the aerosol photometer instrument indication value is less than 0.03). 6. Description 6.1. DOP powder leakage must be performed after the high-efficiency filter is installed or replaced; daily leakage detection of high-efficiency filters in clean areas above 10,000 is generally once a year (once every six months in sterile areas); when there are significant abnormalities in the number of dust particles, sedimentation bacteria, wind speed, etc. in the daily monitoring of the clean area, leakage detection should also be performed. 6.2. DOP, which is a dust source, contains benzene rings. Although the dust sources are different, the principles and methods of leak detection are the same. |
