Test Method of High Efficiency Air Filter
Sodium Flame Method
It is fromUK,Chinaapplied, used in some countries in European in 70-90 years.
Test dust source is single dispersed phase sodium chloride salt fog,” quantity” is the luminance of the flame included salt fog hydrogen; the key test instrument is luminometer.
Salty water is spattered when stirring the depressed air, the tiny salt fog passed dried entered the wind tunnel, it is sampled in the front and back of air filter, the air sample included the salt fog made the hydrogen flame be blue and luminance increased, it can be judged the salt fog concentration in the air as per the luminance of flame and confirmed the Filter efficiency for the salt fog.
It is fromUSA, international applied except forChina.
Test dust is 0.3μm single disperse phase DOP(Plastic industry common plasticizer) liquid drop, “quantity” is turbidity of air included DOP air. The key test instrument is turbid meter; it can be judged the filter efficiency for DOP particle as per the difference of air sample’s turbidity.
It heated the DOP liquid to form the DOP steam, the steam can be condensate the tiny liquid drop in the specified condition, it got rid of the large and small drop and keep 0.3μm particle, and fog type DOP steam entered the wind tunnel. It used the turbid meter to measure the turbidity of air sample in the front and back of filter respectively to judge the efficiency of air filter fro the 0.3μm DOP particle.
DOP method have more than 50 years history, it is the most popular test method of testing the high efficiency air filter in foreign country for years, in the early time, it is thought the 0.3μm particle is the most difficult to be filtered, so it is specified to use the 0.3μm particle to test filter efficiency.
DOP is included the benzene ring, it is doubted to be carcinogenic, so some lab changed to use the similar substitution with similar performance and non-benzene ring, eg. DOP, but the test name is called the DOP all the time.
It can be got the other grain size liquid drop by changed the parameter of sending out the dust, so it appeared the 0.1μm DOP method for testing the ULPA filter in the European countries and USA more than 10 years ago, some companies marked the filter efficiency of 0.05μm or 0.03μm DOP, but it is only business unconventional-type and no science basis.
DOP test for testing the filter efficiency is also called the hot DOP method; to distinguish the cold DOP method by Laskin sprayer nozzle sprayed the multi disperse phase DOP dust.
The related standard：USA military standard MIL-STD-282.
Oil Mist Method
It is used in the EX-Soviet Union,China,West Germany,
Dust source is oil mist, “quantity” is the turbidity of the air included oil mist, the key test instrument is turbid meter, it can be judged the filter efficiency for the oil mist particle as per the difference of turbidity of gas sample.
Germanyspecified that the paroline oil mist grain size is 0.3~0.5μm,Chinaspecified the oil mist’s average weight grain size is 0.28~0.34μm, but it is not specified the oil mist type.
Although the Chinese standard specified to use oil mist, but the domestic companies specified another kind of Sodium Flame method,
It is only applied inFrance.
Dust source is 0.17μm single disperse phase soda salt fog. The air sample is absorbed by specific liquid, “quantity” is fluorescent luminance of the sample included salt in the specific condition. It is judged the filter efficient as per the fluorescent luminance difference of sampled in the front and back of air filter
Uranine is complex, when the test is started, it must be sampled in the front and back of air filter, and measured the fluorescent in the other side of filter. Actually,Franceused the DOP method usually, and is transited to MPPS method, when it is test the nuclear class filter, they will use Uranine method.
The related standard:FranceAFNOR X44-11
It is applied in European, similar to American’s, the other countries is following up it.
European thought that “the easiest penetrating grain size” is some point in the range of 0.1~0.25μm, it must be confirmed the position of this point, or compared after sampled some points (the general counter can be read many points at the same time).USAstandard specified to test the range of 0.1~0.2μm.
MSSP method can be scanned and tested for all the filter, not only test the average filter efficiency of all flat side of air filter, and also comparing the part efficiency of each point.
The dust of MSSP method used is DOS liquid drop generated by Laskin spraying nozzle; the more particular company used the LATEX ball. Sometimes, it is also used the atmosphere dust or other specific dust as per customer’s special requirement.
MPPS method is the strictest method for testing the high efficiency air filter. Using MSSP method instead of other test method is general trend.
The related standard: European CEN EN 1882, USA IES-RP-CC007.1-1992.
Turbid Meter Scanning
Dust source is general multi disperse phase liquid drop, e.g. DOS liquid drop generated by Laskin spraying nozzle. Using turbid meter scanned and tested the leakage for all flat side of Air filter. Scanning can find the leakage of filter quickly and accurately. But when the dust source is multi disperse phase, the “filter efficiency” which tested by turbid meter is meaningless.
Some companies and users thought that the filter efficiency is confirmed when controlled the filter paper’s quality and specification strictly, so only doing the qualitative scanning and testing leakage can guarantee the quality of filter.
There is no related standard to comply. This kind of method is very effective for quality controlling in the process of manufacturing, and the test equipment is simple, so some companies used it. In the near future, the large flux laser particle counter can be instead of turbid meter, because the scan and test platform of turbid is easy to change into the MSSP scan platform.
Other testing leakage method
Using standard test wind tunnel, if the filter efficiency decreased after decreased the air flow, it must be exist the leakage point. This test method of changing air flow is listed many standard. But the test method of changing air flow can only test there is leakage point or not, cannot test the position of leakage.
There is another effective method of sending out the smoke for testing leakage, it is not very particular. In the darkroom, firstly sending out the smock under the filter, then a powerful light exposure the above of filter, if the filter has the leakage point, it can see a cloud of blue smoke obviously at the test leakage point. This method can check the leakage point position to repair it conveniently.