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Test method of Ventilation filter
Test method Of Ventilation filter
Arrestance
The filter is installed in the standard test wind tunnel, and dust is continuously generated on the upwind side. At regular intervals, measure the weight of dust passing through the filter or the amount of dust collected on the filter to obtain the filter efficiency calculated by the weight of dust at this stage. The final weighting efficiency is the weighted average of the efficiency of each test stage according to the dust weight. The gravimetric method is used to measure low-efficiency filters, which are usually used for pre-filtration in central air-conditioning systems.
Related standards: American ANSI/ASHRAE52.1-1992, European EN779: 1993, China GB12218-89.
Dust-Spot
Sampling before and after the filter, there is a high-efficiency filter paper on the sampling head, so that the pollution degree of the high-efficiency filter paper at the sampling point before and after the filter is different. During the test, after a period of dust generation test, measure the light transmission of the high-efficiency filter paper at the sampling points before and after the filter under different dust generation conditions. By comparing the difference in the light transmission of the filter paper, the so-called "filtration efficiency" is obtained by the prescribed calculation method. The final colorimetric efficiency is the weighted average of the efficiency values at each stage of the test process according to the amount of dust generated. The colorimetric method is used to measure more efficient filters.
Related standards: American ANSI/ASHRAE52.1-1992, European EN779:1993.
Atmospheric dust counting
The dust source is "atmospheric dust" in the natural atmosphere. The "quantity" of dust is the total number of particles greater than or equal to a certain particle size. The instrument for measuring dust is ordinary optical or laser dust particle counter. The atmospheric dust counting method is used to measure the general ventilation filter, and its efficiency only represents the performance of the new filter.
Related standards: GB12218-89
Particle Efficiency
Before and after each dust test, a counting measurement is performed, and the filtration efficiency of the filter for various particle size particles is calculated. When the conditions for terminating the test are reached, the test is stopped. The typical efficiency value of the filter is within the specified particle size range, and the instantaneous efficiency of each stage is based on the weighted average of the amount of dust generated. The efficiency of counting method is replacing the efficiency of colorimetric method.
Standard: European Eurovent4/9-1993, American ASHRAE52.2-1999, European PREN779
Test method of high efficiency filter
Sodium FlameThe salt water splashes under the agitation of compressed air, and after drying, it forms a tiny salt mist and enters the air duct. Separate samples before and after the filter, and the salt mist gas samples make the color of the hydrogen flame blue and increase the brightness. The brightness of the flame is used to judge the concentration of salt fog in the air, and to determine the filtering efficiency of the filter on the salt fog. The average diameter of the salt spray particles specified by the national standard is 0.4μm.
Related standards: British BS3928-1969, Eurovent 4/4 in Europe, and GB6165-85 in China.
DOP method
The test dust source is 0.3μm monodisperse DOP (plasticizer commonly used in the plastics industry) droplets. "Amount" is the degree of turbidity of the air containing DOP. The instrument for measuring dust is a photometer, and the difference in turbidity of the gas sample is used to determine the filtration efficiency of the filter for DOP particles.
The DOP liquid is heated to steam, and the steam condenses into tiny droplets under certain conditions. After removing the excessively large and small droplets, particles of about 0.3μm are left. The foggy DOP enters the air duct, and the turbidity of the gas sample before and after the filter is measured. Degree, and judge the filtration efficiency of the filter 0.3μm dust.
Related standards: US military standard MIL-STD-282.
Counting scan
During the test, use a large-flow laser particle counter or condensation nucleus counter to scan and inspect the entire air outlet surface of the filter. The counter gives the number and particle size of each point of dust. This method can not only measure the average efficiency of the filter, but also compare the local efficiency of each point.
Related standards: European EN1882.1~1882.5-1998~2000, American IES-RP-CC007.1-1992.
Photometer scan
Dust is generally polydisperse phase droplets. Use a photometer to scan the entire surface of the filter for leak detection. This method can quickly and accurately find the leaking point of the filter. Because the dust is a polydisperse phase, and the photometer cannot determine the particle size of the dust, the "filtration efficiency" detected by this method has no practical significance. In addition, there is currently no corresponding standard to follow for this method.
Oil Mist
The dust source is oil mist, the "quantity" is the turbidity of the air containing oil mist, and the instrument is a turbidity meter. The turbidity difference of the gas sample is used to determine the filter efficiency of the oil mist particles.
Related standards: China GB6165-85, Germany DIN24184-1990.
Uranine
The test dust source is fluorescein sodium dust produced by the sprayer. In the experiment, samples were first taken before and after the filter, and then the sodium fluorescein on the sampling filter paper was dissolved with water, and then the fluorescence brightness of the aqueous solution containing sodium fluorescein under specific conditions was measured. This brightness indirectly reflects the weight of the dust. The efficiency of the filter is judged by the difference in fluorescence brightness of the samples before and after the filter (this method is limited to the test of nuclear industry filters).
Related standards: France NFX44-011-1972.
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