1, high efficiency filter
1) HEPA filter (HEPAFilter)
HEPA: HighEfficiencyParticulateAir is the meaning of "high efficiency air particle filtration". HEPA stands for high efficiency, defined as: the filtration efficiency of particles with a particle size of 0.3 μm is greater than or equal to 99.97%. As mentioned above, when using high-efficiency filters, it is necessary to express the efficiency and experimental methods together, such as : 99.97% (0.3 μm, DOP), indicating that it is highly efficient by the DOP experimental method.
2) ULPA filter (ULPAFilter)
ULPA: UltraLowPenetrationAir is a filter with a higher efficiency than HEPA filtration, defined as a 0.1-0.2μm filter with a particle filtration efficiency of 99.999% or more. The filter is used in pharmaceutical factories, electronics factories, chip factories, etc., and is not used in home appliances.
The principle of leak detection for high efficiency filters:
On the upper side of the detected high-efficiency filter, DOP aerosol is emitted as a dust source, and the leeward side is sampled and detected by a photometer. The scattered light generated by the dusty gas through the photometric time is converted into electric quantity by photoelectric effect and linear amplification, and is micro-ampere meter. Quickly appearing, the collected air sample passes through the diffuser of the photometer. The difference in light intensity is caused by particle diffusion. After measuring the light intensity, the photometer can measure the relative concentration of the aerosol.
5, testing procedures:
5.1 Introducing aerosol on the upwind side of the high efficiency filter:
5.1.1 When the system is leaked, the DOP smoke can be directly put into the air conditioner.
5.1.2 When the DOP episode is small, it can be placed in the static pressure box of the high efficiency filter.
5.2 Immediately scan the outlet side of the filter with the sampling head of the aerosol photometer. The sampling head is spaced about 2 cm from the filter and is inspected along the inner frame of the filter. The scanning speed should be less than 5 cm/s.
5.3 When the photometer reading exceeds 0.03%, it indicates that the amount of leakage exceeds the standard and the demand is repaired or changed.
5.4 After plugging or tightening the bolt with epoxy resin silica gel, stop the scanning inspection.
The company specializes in the consumption of high-efficiency filters, air-conditioning filters, air showers, transfer windows, ultra-clean workbench, high-efficiency air supply, FFU and air purification engineering design and construction.
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Leak test method for high efficiency filter
1) Sodium Flame Method SodiumFlame
Originated in the United Kingdom, China is popular, and some European countries were implemented in the 1970s and 1990s.
The experimental dust source is a monodisperse phase sodium chloride salt spray. The "quantity" is the light intensity of the characteristic light of the hydrogen flame when the salt spray is contained. The main test instrument is a photometer.
The salt water splashes under the agitation of the tight air, and it is boring to form a tiny salt spray and enter the air passage. Sampling separately before and after the filter, the salt mist sample makes the color of the hydrogen flame blue and the brightness increases. The salt spray concentration of the air is discriminated by the brightness of the flame, and the filtration efficiency of the filter to the salt spray is confirmed.
Relevant specifications: China has GB6165-85. At present, relevant domestic departments are revising the specification, whether it is abolished or continues to be inconclusive. This approach is no longer used in Europe.
2) Oil mist method OilMist
The original West Germany, the former Soviet Union, and China have adopted this method.
The dust source is oil mist. The "amount" is the turbidity of the air containing oil mist. The instrument is a turbidimeter. The filter efficiency of the oil mist particles is determined by the difference in turbidity of the gas sample.
The oil mist method has been a history in Germany. Only a small number of military units in China still use the oil mist method, because the former Soviet Union used the oil mist method to help China filter.
Related specifications: China has GB6165-85.
3) DOP method
Originated in the United States, it was internationally popular.
The experimental dust source is a droplet of 0.3 μm monodisperse phase DOP (dioctyl phthalate, a plasticizer commonly used in the plastics industry). The "amount" is the level of turbidity of the air containing DOP. The instrument for measuring dust is a photometer. The filtration efficiency of the filter to the DOP particles was determined by the difference in turbidity of the gas sample.
The DOP liquid is heated to steam, and the steam is condensed into minute droplets of about 0.3 μm under specific conditions, and the misty DOP enters the air passage. The turbidity of the gas sample before and after the filter was measured, and the filtration efficiency of the filter to 0.3 μm dust was discriminated.
The DOP method has a history of more than 50 years. This method was once the most commonly used method for measuring high-efficiency filters in the world. In the early days, people thought that the filter was the most difficult to filter for 0.3μm dust, so the 0.3μm dust was used to measure the high efficiency filter.
The phenyl ring in the DOP is suspected to be carcinogenic, and many laboratories have switched to alternatives that do not contain benzene rings, such as DOS, but the experimental method is still called the "DOP method."
The DOP method for measuring high-efficiency filters is also called "hot DOP method". Corresponding to this, "cold DOP" means that the nozzle blows air bubbles in the DOP liquid with the contracted air, and the splash generates foggy artificial dust.
Related specifications: US military specification MIL-STD-282.
4) MPPS method (MostPenetratiableParticulateSize)
European air-conditioning filters are used, except for the defense industry in the United States, which is implemented by individual Chinese companies. The ability to measure almost all HEPA and ULPA filters has a major trend to replace traditional methods.
It has been thought that the filter has the lowest filtration efficiency for 0.3 μm dust, so the filtration efficiency of 0.3 μm dust is taken as a typical value when evaluating the high efficiency filter. There are many ways to generate and measure 0.3μm dust, so there are ways such as DOP, oil mist, and sodium flame.
After research and experiments, it was found that a laser particle counter capable of measuring 0.1 μm particle size dust can not only measure the dust concentration, but also measure the particle size of each dust, so that the lowest efficiency typical value can be measured locally. The dust particle size corresponding to that typical value is MPPS (MostPenetratiableParticulateSize, the most easy to penetrate particle size), and the lowest efficiency value corresponding to MPPS is MPPS efficiency.
Related specifications: US IEST-RP-CC-007.1-1992, European EN1822-5:2000
5) Resistance Resistance
1. Definition: When the airflow passes through the filter, the filter will resist the airflow and the air volume will decrease.
2. The composition of the resistance. The resistance of the filter consists of the resistance of the filter material itself and the structural resistance of the filter. We hope that the smaller the resistance of the filter, the better. Because the resistance is higher, the air volume to reach the rated output is increased. The power of a large motor, if the motor power is too small, will produce a howling sound. These must be solved together, to choose the appropriate filter material.
3. Initial resistance: The resistance of the new filter is called the initial resistance.
4. Final resistance: The resistance when the filter is to be scrapped is called the final resistance. The choice of the final resistance is directly related to the service life of the filter, the range of air quality and the energy consumption of the system.
5. Unit of resistance: Pa Pa 1 Pa = 1 N / m 2
Inch units: inWG inches of water (WaterGauge)
Metric unit: mmH2O mm water column 1mmH2O=9.8Pa
inWG=250Pa
OBJECTIVE: After detecting the leakage of the high-efficiency filter, the defects of the high-efficiency filter and its device, such as small pinholes in the filter material and the gaps in the sealing part, were found to make timely compensation measures.
Scope: Inspection of the company's clean plant high efficiency filter leaks.
Responsibilities: The Equipment Engineering Department and the Quality Management Department shall act as the implementation of this Code.
content:
1, test method: DOP method
2. Test range:
2.1 filter material
2.2 The connection between the filter material and its frame
2.3 Connection between the seal of the filter frame and the support frame of the filter set
2.4 The connection between the support frame and the wall or ceiling.
3. Testing data and instruments:
3.1 Dust source: DOP solvent
3.2 Instruments: DOP episode, aerosol photometer
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