PAO-DOP high efficiency filter leak detection method flow
DOP-liquid trough high efficiency filter for leak detection purposes:
1. The material of the high efficiency air filter is not damaged;
2. Properly installed - sealed and airtight.
Foreword:
The filtration efficiency of the tank-type high-efficiency filter itself is generally detected by the manufacturer, and is accompanied by a filter filtration efficiency report and a certificate of conformity. For the user, the leak detection of the liquid trough high-efficiency filter refers to the on-site leak detection after the high-efficiency filter installation, mainly to check the small pinholes and other damages in the filter media, such as frame seal, gasket seal and filtration. Slots on the frame of the device, etc. The purpose of the leak detection is to check the high-efficiency filter itself and the defects in the installation by checking the sealing performance of the high-efficiency filter and its connection with the mounting frame, and take corresponding remedial measures to ensure the cleanliness of the area.
High efficiency filter leak detection method:
The high-efficiency filter for the DOP tank-type high-efficiency air supply port is itself a liquid tank high-efficiency filter. The leak test of this high-efficiency filter basically applies the challenge particles upstream of the high-efficiency air filter and then on the surface of the high-efficiency air filter. Use the particle detection instrument with the frame to search for leaks. There are several different ways of leak testing, which can be applied to different situations.
Efficient filter testing methods are:
1. Glue photometer test method
2. Particle counter test method
3. Full efficiency test method
4. External gas test method
The specific instructions are as follows:
PAO or DOP leak detection is an aerosol photometer test method
Aerosol photometer:
The gas gel photometer test method is the early test method of Zui, but because the effect is very good, it is still used today.
Aerosol Photometer is a type of particle counter that uses laser technology, but after scanning the particles of the air sample, it gives the total intensity of the particles, not the number of particles. DOP is an oily chemical that, when pressurized or heated to atomize, produces submicron-sized particles that can be used to simulate clean room particles and are therefore used as verification particles. Leakage is defined as one ten-thousandth of the upstream concentration. Since the gas gel photometer can directly display the ratio of the upstream and downstream particle concentrations, it is very convenient to scan the high-efficiency air filter. Because of its accuracy and reliability, the US Food and Drug Administration (FDA) stipulates that all high-efficiency air filter leak tests must use DOP and gas gel photometers within its jurisdiction (food processing facilities and medical and pharmaceutical sites). .
For some time, due to suspected carcinogenic effects, it is often replaced by DOS (Dioctylsebaeate dioctyl dicarboxylate), also known as DEHS [di (2-ethylexyl) sebacate] and PAO or DOP (polyaphaolefin polya olefin). However, the experimental method is still called "DOP method".
Atmospheric dust is sometimes large and sometimes low due to changes in its concentration with location and time, and is generally not used for leak detection. The FDA pointed out that in the case of leak detection, the selected aerosol should meet certain physical and chemical requirements, and aerosols that cause microbial contamination and microbial growth should not be used.
The DOP generator can be divided into two types: heat generation and cold generation. The heat generator uses the principle of evaporative condensation. The atomized aerosol particles are evaporated by a heater and condensed into tiny droplets under certain conditions to remove excessively large sum. After too small droplets, a fog-like DOP of about 0.3 um is left into the air passage, and the particle size distribution is 0.1 to 0.3 um. The cold generator refers to a polydisperse DOP aerosol which is made by using compressed air to bubble bubbles in a liquid and splashing through a laskin nozzle. The large distribution particle size of Zui is about 0.65 um. At present, there are many hot DOPs commonly used, so the efficiency of the filter should be guaranteed.
PAO-DOP high efficiency filter leak test equipment:
The instrument used was an Aerosol Photometer and an Aerosol Generator. The display version of the gas gel photometer is available in both analog and digital versions and must be calibrated once a year. There are two types of particle generators, one is a common particle generator, which only requires high-pressure air, and the other is a heated particle generator. For high-pressure air and power, the particle generator does not need to be calibrated.
DOP high efficiency filter leak detection equipment
DOP high efficiency filter leak detection instrument
PAO-DOP high efficiency filter leak test procedure:
1. Record the number of high efficiency air filters on the drawing and number them.
2. Make sure that the air conditioning system is running normally and ready for testing. The wind speed and air volume must be adjusted and balanced.
3. Use the gas gel generator to apply the challenge particles upstream, and drive the PAO or DOP upstream of the high efficiency air filter. The particle concentration is about 10 to 20 micrograms of PAO or DOP per liter of air. The more particles there are, the easier it is to find the leak, but after 50 micrograms, the difference is not big, and less than 10 is difficult to use. The particle concentration can be roughly calculated by the air volume and confirmed by a gas gel photometer.
4. After the upstream particle concentration is confirmed, it can be scanned on the surface of the high-efficiency air filter to find the leak. If necessary, the high-efficiency air filter can be covered with a plastic curtain to ensure the accuracy of the test.
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