Summary of Test Methods for High Efficiency Air Filter

The high-efficiency air filter must be inspected when it leaves the factory, and the customer will purchase it back or take a sample for inspection, and then leave the factory or purchase it after reaching the standard. Since the detection of high-suction air filters is so important, what are the detection methods? The following summarizes the detection methods of high-efficiency air filters for you.

high-efficiency air filter.

Commonly used instruments for leak detection of high-efficiency filters are dust particle counters and 5C aerosol generators.

Dust Particle Counter:

It is used to measure the size and number of dust particles per unit volume of air in a clean environment, and can directly detect clean environments with a cleanliness level of 10 to 300,000. Small size, lightweight, high detection accuracy, simple and clear functional operation, microprocessor control, can store and print measurement results, and the test clean environment is very convenient.

5C Aerosol Generator:

The TDA-5C aerosol generator can produce aerosol particles with a consistent distribution of various diameters. When the TDA-5C aerosol generator is used in conjunction with an aerosol photometer such as the TDA-2G or TDA-2H, it can provide enough challenging particles to Measure high-efficiency filtration systems.

detection

Domestic high-efficiency air filter testing is mainly based on GB/T 13554-2008 "High-efficiency air filter", GB/T 14295-2008 "Air filter", JB/T 6417-1992 "Air filter for air conditioning", GB/T 6165-2008 "High-Efficiency Air Filter Performance Test Methods Filtration Efficiency and Resistance", the testing methods include sodium flame method, oil mist method, and counting method, with the sodium flame method as the benchmark method. It can be seen from the evolution of the international high-efficiency filter testing standards that the high-efficiency air filter testing methods mainly include the sodium flame method, oil mist method, DOP method, fluorescence method, and particle counting method.

(1) DOP method

The DOP method originated in the United States in 1956 and has been adopted by many countries. It has also been adopted in China's national standards. This method was once the most commonly used method for testing high-efficiency filters internationally. Its test dust source is 0.3?m monodisperse adjacent dioctyl phthalate (DOP) droplets, also known as "hot DOP", and the "amount" is the degree of turbidity of the air containing DOP. The DOP liquid is heated into steam, and the steam is condensed into tiny droplets under specific conditions. After removing the oversized and undersized droplets, particles of about 0.3 μm are left, which enter the air duct and measure the turbidity of the air samples before and after the filter. Degree, and thus judge the filtration efficiency of the filter for 0.3?m dust. The measuring instrument is mainly a light scattering photometer (photometer). Relevant standards are MIL-STD-282-1956.

(2) Fluorescence method

The fluorescence method is only used in France, and the test dust source of the fluorescence method is the sodium fluorescein dust generated by the nebulizer. The test method is to the first sample before and after the filter, then dissolve the sodium fluorescein on the sampling filter paper with water, and then measure the fluorescence brightness of the aqueous solution containing sodium fluorescein under specific conditions, the brightness reflects the weight of dust, and thus calculates the filtration efficiency of the filter. efficiency. France has not used the fluorescence method for a long time, and they also regard the counting method of the European Standardization Association as the national standard, and some nuclear industry systems also use the fluorescence method for on-site detection filters.

(3) Sodium flame method

The sodium flame method originated in the United Kingdom in 1969 and was implemented in some European countries from the 1970s to the 1990s. It is one of the current national standard methods in my country. Its test dust source is polydisperse sodium chloride salt mist, and the "amount" is the brightness of the hydrogen flame when the salt mist is burned. The saltwater is splashed under the agitation of compressed air, dried to form tiny salt crystal particles, and enters the air duct, and samples are taken before and after the filter. The salt mist gas sample makes the color of the hydrogen flame turn blue and the brightness increases and the brightness of the flame is used to judge the air. The concentration of salt mist is used to determine the filtration efficiency of the filter for salt mist. The main detection instrument is a flame photometer. The relevant standards of the sodium flame method are British BS3928-1969, European Eurovent 4/4, and Chinese GB6165-85. This method can only detect with low sensitivity, and cannot detect ultra-high efficiency filters.

(4) Oil mist method

The oil mist method originated in Germany and was also practiced in China and the former Soviet Union. The dust source of the test is oil mist, and the "quantity" is the turbidity of the air containing oil mist. The filtering efficiency of the filter for oil mist particles is judged by the difference in turbidity of the air samples before and after the filter. Germany stipulates the use of paraffin oil, and the oil mist particle size is 0.3~0.5μm. The Chinese standard stipulates that the average weight diameter of oil mist is 0.28~0.34?m, and there is no specific regulation on the type of oil. Relevant standards are China GB6165-85 and Germany DIN24184-1990. When the oil mist method detects the filter, it is easy to cause damage to the filter, and the value cannot be read directly, which is a waste of time. The German oil mist method has become history. In 1993, Germany took the lead in promulgating the national standard with the counting method as the detection method. The European standard EN-1822 was formulated on the basis of the German standard. Only a few military-industrial units in our country use this method.

(5) Particle counting method

This method is commonly used in Europe, and the U.S. ultra-high efficiency filter test method is similar, and it is the mainstream test method in the world. The dust source is polydisperse liquid droplets or solid dust with a certain particle size. Sometimes, filter manufacturers use atmospheric dust or other specific dust according to the special requirements of users. If a nuclei counter is used in the test, a single dispersed phase test dust source of known particle size must be used. The main measuring instruments are high-flow laser particle counters or condensation nuclei counters (CNC). Use a counter to scan and inspect the entire air outlet surface of the filter. The counter gives the number of dust at each point, and can also compare the local efficiency of each point.

The experience of Europeans shows that for high-efficiency filters, the most penetrable dust particle size is at a certain point between 0.1? The filter effect of the device on the particle size dust, Europeans call this method MPPS method [14]. The American standard stipulates that only particles in the range of 0.1~0.2μm are measured. The MPPS method is actually a particle counting method because the detection instrument used in it is a particle counter or a condensation nuclei particle counter. The relevant standards of this method are European EN1882-1998~2000 and American IES-RP-CC007.1-1992.

How to test the quality of high-efficiency filter with water:

Just lay the air filter flat on the floor or table and sprinkle some water on top of the filter paper:

(1) If the filter paper seeps into the water within 5 minutes, it is an air filter made of cotton pulp paper (fake and inferior filter paper), and it must not be used. This kind of air filter is mostly produced in Hebei, and it is widely used in the air compressor industry. A small number of people who are greedy for cheap are using it.

(2) If the filter paper seeps into water within 2-5 hours, it is made of low-grade wood pulp paper and can be used, but it will reduce the gas production efficiency of the air compressor (more power consumption and less gas production), resulting in Power consumption is high. Because the price of air filters made of this kind of filter paper is relatively low, and they can also be used, so the air filter of this kind of filter paper is the mainstream in the air compressor industry, and most of the air compressor shops are selling this kind of air filter.

(3) If the filter paper seeps in after 12-15 hours, it is a better filter paper (mid-grade filter paper). Usually, domestic manufacturers with better quality use this type of filter paper air filter as the original consumables.

(4) If the filter paper does not seep in for 24 hours, it is definitely a high-quality product (high-grade filter paper). Usually, high-end complete machine factories choose this type of filter paper air filter as the original consumables.

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