Determine the efficiency of the last-stage air filter according to the clean purification standards required in the cleanroom, and reasonably select the combined stages of the air filter and the efficiency of each level.
If the room requires general purification, the primary effect filter can be used; if the room requires medium purification, the primary and medium-efficiency two-stage filter should be used; if the room requires ultra-clean purification, the primary, medium, and high-efficiency three filters should be used. Stage purification and filtration, and should match the efficiency of each level of filter reasonably and properly. If the efficiency of the adjacent two levels of filters is too different, the previous level of the air filter will not be able to affect the subsequent level of the HEPA air filter. Protection function, the standard efficiency expression method of the cleanroom air filter.
When the dust concentration in the filtered gas is expressed by weight concentration, the efficiency is the weight efficiency; when the count concentration is expressed, the efficiency is the efficiency; when other physical quantities are used as relative expressions, it is the colorimetric efficiency or Turbidity efficiency, etc. The most commonly used method of expression is the counting efficiency expressed by the concentration of dust particles in the airflow at the inlet and outlet of the air filter.
1. Under the rated air volume, according to the national standard GB/T14295-93 "Air Filter" and GB13554-92 "HEPA Air Filter", the efficiency ranges of different filters are as follows:
Primary efficiency filter, for particles ≥5 microns, filtration efficiency 80＞E≥20, initial resistance ≤50Pa
Medium-efficiency filter, for ≥1-micron particles, filtration efficiency 70＞E≥20, initial resistance ≤80Pa
High and medium efficiency filter, for ≥1-micron particles, filtration efficiency 99＞E≥70, initial resistance ≤100Pa
Sub-high efficiency filter, for ≥0.5-micron particles, filtration efficiency E≥95, initial resistance ≤120Pa
HEPA filter, for ≥0.5-micron particles, filtration efficiency E≥99.99, initial resistance ≤220Pa
Ultra-high efficiency filter, for ≥0.1-micron particles, filtration efficiency E≥99.999, initial resistance ≤280Pa
2. Since many companies now choose imported filters, and their methods of expressing efficiency are different from those in China, for ease of comparison, the conversion relationship between them is listed as follows:
According to European standards, coarse-efficiency filters are divided into four levels (G1~~G4):
G1 efficiency to particle size ≥5.0μm, filtration efficiency E≥20% (corresponding to American standard C1)
G2 efficiency to particle size ≥5.0μm, filtration efficiency 50＞E≥20% (corresponding to American standards C2~C4)
G3 efficiency to particle size ≥5.0μm, filtration efficiency 70＞E≥50% (corresponding to American standard L5)
G4 efficiency to particle size ≥5.0μm, filtration efficiency 90＞E≥70% (corresponding to American standard L6)
The medium efficiency filter is divided into two levels (F5~~F6):
F5 efficiency to particle size ≥1.0μm, filtration efficiency 50＞E≥30% (corresponding to American standards M9, M10)
F6 efficiency to particle size ≥1.0μm, filtration efficiency 80＞E≥50% (corresponding to American standards M11, M12)
High and medium efficiency filters are divided into three levels (F7~~F9):
F7 efficiency to particle size ≥1.0μm, filtration efficiency 99＞E≥70% (corresponding to American standard H13)
F8 efficiency to particle size ≥0.5μm, filtration efficiency 90＞E≥75% (corresponding to American standard H14)
F9 efficiency to particle size ≥0.5μm, filtration efficiency 99＞E≥90% (corresponding to American standard H15)
The sub-high efficiency filter is divided into two levels (H10, H11):
H10 efficiency to particle size ≥0.5μm, filtration efficiency 99＞E≥95% (corresponding to American standard H15)
H11 efficiency to particle size ≥0.5μm, SEO, filtration efficiency 99.9＞E≥99% (corresponding to American standard H16)
The HEPA filter is divided into two levels (H12, H13):
H12 efficiency to particle size ≥0.5μm, filtration efficiency E≥99.9% (corresponding to American standard H16)
H13 efficiency to particle size ≥0.5μm, filtration efficiency E≥99.99% (corresponding to American standard H17)
3. Correctly determine the filter characteristics. The characteristics of the air filter www.rfilter.com are mainly filtration efficiency, resistance, penetration rate, dust holding capacity, filtration wind speed, and processing air volume. When conditions permit, filters with high efficiency, low resistance, large dust holding capacity, moderate filtering wind speed, large air handling capacity, convenient manufacturing and installation, and low price should be selected as far as possible. This is the need for economic analysis that comprehensively considers one-time investment, secondary investment, and energy efficiency ratio when selecting air filters.
4. Analyze the nature of dusty gas. The nature of the dust-containing gas related to the selection of the air filter is mainly temperature, humidity, acid and alkali, and the number of organic solvents. Because some filters are allowed to be used at high temperatures, and some filters can only work at normal temperature and humidity, and the amount of acid, alkali, and organic solvents in the dust-containing gas have an impact on the performance and efficiency of the air filter.
5. The specifications and rated air volume of the air filter, some standard sizes, the air volume, and initial resistance of various filters are as follows:
Serial number name Overall dimensions Rated air volume Initial resistance
1. Coarse efficiency flat filter 595X595X202500m3/h≤50Pa
2. Coarse efficiency folding filter 595X595X463600m3/h≤50Pa
3. Medium-efficiency bag filter 595X595X5003600m3/h≤80Pa
4. W-type sub-high efficiency filter 610X610X2923200m3/h≤160Pa
5. HEPA filter with partition 610X610X1501000m3/h≤220Pa
6. HEPA filter without partition 610X610X691000m3/h≤160Pa
Under normal circumstances, the last-stage air filter determines the cleanliness of the air supply. The front-end air filters at all levels protect the last-stage air filter, prolong the service life of the last-stage air filter and ensure its normality. jobs. When choosing an air filter, we must consider comprehensively and choose a suitable air filter reasonably according to the specific situation. The selection principle is as follows: correctly determine the dust content and dust particle characteristics of the outdoor air. Because the filter filters and purifies the outdoor air and sends it indoors, the dust content of the outdoor air is a very important data. Especially in the multi-stage purification and filtration process, the use environment, spare parts cost, operating energy consumption, maintenance and supply, and other factors should be considered when choosing a pre-filter.