A Book of Test Methods for Filtering Efficiency of High Performance Air Filters in Junior High School
1 Weighing Arrestance
(1) Weighing is generally used to measure inefficient filters as pre-filters in central air conditioning systems.
(2) The filter is installed in a standard test wind hole, the upper wind end is continuously dusted, and the weight of dust passing through the filter(or the amount of dust collected on the filter) is measured at regular intervals, The filter efficiency calculated by dust weight at this stage is the weighted average of each test stage.
The dust source used in the test is large particle size and high concentration standard dust.
The final resistance value agreed with the user, or the final resistance value specified by the tester.
The weight-measuring test is a destructive test and can not be used as a performance test in product production.
(6) Relevant criteria for weight-measuring tests:
American Standard: ANSI/ASHRAE 52.1 -1992
British Standard: EN 779-1993
Chinese Standard: GB 12218-1989
2 Color method Dust-spot
The colorimetric method is used to measure more efficient general ventilation filters.
The test bed and test dust are the same as the weight method.
(3) Sampling before and after the filter with a sampling head containing a high-efficiency filter paper. After each dust test, the amount of light on the high-efficiency filter paper on the sampling head of the front and rear sampling point of the filter is measured under the condition of non-dust, by comparing the difference in the amount of light on the filter paper. The so-called filtration efficiency is obtained by the prescribed calculation method. The final colorimetric efficiency is the weighted average of each test stage depending on the amount of dust.
(4) The termination test conditions are similar to the weighing method: the final resistance value agreed with the user, or the final resistance value specified by the tester.
The colorimetric test is a destructive test and can not be used as a performance test in product production.
(6) Relevant criteria for weight-measuring tests:
American Standard: ANSI/ASHRAE 52.1 -1992
British Standard: EN 779-1993
China has never used colorimetry, and there is no colorimetric test bench.
The colorimetric method, once a popular test method abroad, is gradually being replaced by the counting method.
3 Atmospheric dust-count method
(1) The efficiency classification of general ventilation filters in China is based on the atmospheric dust count method. The Chinese counting standard is earlier than in Europe and the United States, but it should be based on domestic counters and corresponding measurements in the 1980s.
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The source of dust is atmospheric dust.
The instrument for measuring dust particle count is ordinary optical or laser particle counter.
The efficiency of the atmospheric dust-count method represents only the initial efficiency of the new filter.
(5) Standard: GB 12218-1989
4 Counting Method Part Effect
The high concentration test dust used for test stand and dust is similar to that used for weighing and colorimetry.
The amount of dust is the number of particles in small particle size.
(3) In the course of the test, counting is performed before and after each dust test, and the filtration efficiency of various 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. The instantaneous efficiency at each stage depends on the weighted average of the amount of dust produced.
(4) The counting efficiency is no longer a single data, but a filtration efficiency curve along different sizes. European tests show that when the final resistance of the test is 450 Pa, 0.4 μm
The count efficiency value is similar to the efficiency value of the traditional colorimetric method.
(5) European standards stipulate that specific multidispersion droplets are used for counting, such as DENS spray blown with a Laskin nozzle, or a Polystyrene latex ball(Latex). ** Latex is often used as a standard particle to calibrate a particle counter.
(6) The United States standard stipulates that bleach is used for counting. The efficiency values of different particle sizes are measured for different filters of different gears, and the final resistance of the test is also different depending on the efficiency grade.
A complete count efficiency test is a destructive test and can not be used for daily inspection of products.
(8) Relevant criteria for counting tests:
American Standard: ASHRAE 52.2-1999
European Standard: PREN 779
(CEN Draft, 1999, this standard will replace the colorimetric method stipulated by EN 779:1993)
The colorimetric method, once a popular foreign test method, is gradually being replaced by counting.
5 Oil Mist
(1) The oil fog method was used in the former Soviet Union, Federal Germany, and China. It has now ceased to be used abroad, and China has only used some filter factories.
(2) Dust source is oil mist. Germany stipulates the use of paraffin oil, the size of oil mist 0.3 μm -0.5 μm. The Chinese standard does not specify the type of oil, but stipulates that the average diameter of oil mist is 0.28 μm-0.34 μm. Quantity is the number of particles in small particle size.
The test instrument is a turbidimetric meter to determine the filtration efficiency of the filter(or filter material).
(4) Related Standards: Chinese Standard: GB 6165? 85
German Standard: DIN 24184? 1990
6 Sodium flame method Sodium Flame
(1) The sodium flame method originated in the United Kingdom and was adopted in some European countries in the 1970s and 1990s. With the popularity of the scanning method, the sodium flame method is no longer used internationally. There are still quite a few manufacturers of highly efficient filters in China. Use sodium flame method.
(2) Dust source single dispersed sodium chloride(Nacl) salt mist.
The aerosol size of sodium chloride solution is 0.2 μm-2.0 μm and the median particle size is about 0.6 μm.
(4) During the test, salt water splashes under the agitation of compressed air, and tiny test salt fog formed by drying enters the air duct. Sampling before and after the filter, the gas sample containing salt fog makes the hydrogen flame blue and the brightness increases. To determine the concentration of salt mist in the air by the brightness of the flame, The efficiency of filter on salt and alkali is determined.
(5) Related Standards: Chinese Standard: GB 6165? 85
British Standard: BS 3928? 1969
European Standard: Eurovents 4/4
7 DOP Method Dioctyl Phthalate
(1) DOP's Chinese translation is &;; Lt; Dioctyl phthalate & amp; Gt; , is a commonly used plasticizer in the plastics industry, and is also a common cleaning agent. The method of using 0.3 μm of DOP droplets as a dust source to test the efficiency of high-efficiency filter filtration is called DOP method, and the resulting filtration efficiency is called DOP. The test method originated in the United States and is internationally popular. The Chinese never practiced it.
(2) Heat the DOP liquid into steam, and the vapor condenses into tiny droplets under certain conditions. After removing too large and too small droplets, it leaves 0.3 μm * as a dust source. This method is also called "hot DOP method."
* The 0.3 μm dust particles were prescribed because early people thought that filters were the most difficult to filter 0.3 μm dust.
DOP liquid with compressed air bubbles, through the Laskin nozzle spatter to produce fog-like artificial dust called "cold DOP method." Cold DOP method produces DOP dust with a particle size of 0.1 μm-1.0 μm and ≥ 0.35 μm.
The filter efficiency measured by DOP is higher than that by single dispersion.
The filter filtration efficiency of 0.3 μm dust can be determined by measuring the turbidity of air sample before and after the filter.
(6) DOP has been used for the testing of efficient filters for nearly 40 years. In recent years, it has been suspected that the cyclobenzene contained in it is a carcinogen. It is now switched to a single dispersed DOS DEHS. These substances are harmful to the production of IC and disc drives. Therefore, single dispersed polystyrene latex spheres(SPLS) with a particle size of 0.1 μm-1.0 μm are commonly used.
(7) Related standards: United States military standards: MIL-STD-282
8 Count Scan Method(MPPS Method) Most Penetrate Partnership Size
(1) The current international high-efficiency filter mainstream test method.
(2) Continuous scanning of the entire air outlet of the filter with a counter, counter
The number and particle size of dust at each point are given. This method can not only measure the filter.
The average efficiency can also compare the local efficiency of each point.
(3) The MPPS method, as its name implies, is to measure the filtration efficiency of the most penetrable dust particle size. The European experience shows that the most penetrable dust particle size is at a certain point between 0.1 μm-0.25 μm, The U.S. standard simply stipulates that only 0.1 μm-0.2 μm is measured.
The source of dust used in the test is the DOP droplet produced by the Laskin nozzle, or solid dust with determined particle size.
If the condensing nuclear counter is used in the test, the single dispersed phase test dust with known particle size must be used.
MPPS is the strictest method to test high efficiency filters.
(7) Related standards: American standards: IES-RP? CC007.1-1992
European Standard: EN 1882.1? 1882.5? 1998-2000
9 photometer scan
(1) There is no corresponding standard for photometer scanning leakage detection.
(2) Scanning of the entire air outlet of the filter with a photometer. This method of scanning can quickly and accurately find the leakage point of the filter. Since the dust source is generally multi-dispersed, the photometer itself can not determine the particle size of the dust. Therefore, this scanning method gives no practical meaning to the "filtration efficiency".
(3) The photometer scanning method is very effective in the quality control of the production process, and the test equipment used is relatively simple. Some manufacturers believe that as long as the quality and specifications of the filter material are strictly controlled, The efficiency of the filter has been determined. Therefore, only a photometer scan for leak detection can guarantee the quality of the filter. However, this concept is not easily accepted by users.
10 Fluorescent Uranine
(1) Only French use is currently limited to the testing of some nuclear industry filters. In fact, the French filter factory used to use the DOP method more often than its own method of fluorescence. Now the French have set the European Standardization Association's counting method as a national standard. Fluorescence is less used.
(2) Fluorescent sodium dust produced by aerosol dispensers is the source of test dust.
(3) During the test, sample the filter before and after, then dissolve the Phosphor sodium on the sample filter paper with water, and then measure the fluorescence brightness of the aqueous solution containing Phosphor sodium under certain conditions, This brightness indirectly reflects the weight of dust.
(4) Related standards: French standards: NFX44-011-1972
10 Other methods of inspection
Ventilation leak. If the filter efficiency is reduced after reducing the wind volume, there must be leakage point.
Ventilation checks can only determine whether the filter is leaking, but can not locate the leakage point.
(2) smoke detection and leakage. In the darkroom, smoke is emitted upstream of the filter, and a strong light is used to illuminate the air surface of the filter. When the filter has a leak point, it can be clearly seen that there is a wisp of smoke at the leak point. This method can accurately locate the leak point.
(3) Non-pollution testing. Some users are concerned about dust contamination filters for testing. They often require filter manufacturers to use solid particle dust that they consider safe; Some laboratories require direct use of outdoor atmospheric dust.
Add: Chengdu Gaoxin West District Science and Technology Park