PAO-DOP TEST PROCESS

PAO-DOP HEPA integrity test process.

The purpose of DOP-liquid tank type HEPA leak detection:

1. The material of the high-efficiency air filter is not damaged;

2. Proper installation - the seal is intact and there is no air leakage.

The filtration efficiency of the liquid tank type HEPA is generally tested by the manufacturer, and the filter filtration efficiency report and qualification certificate are attached when leaving the factory. For the user, the leak detection of the liquid tank type high efficiency filter refers to the on-site leak detection after the high efficiency filter is installed, mainly to check the small pinholes and other damages in the filter material of the filter, such as frame seal, gasket seal and filter Slots in the frame of the device, etc. The purpose of leak detection is to detect the defects of the high-efficiency filter itself and its installation in time by checking the sealing of the high-efficiency filter and its connection with the installation frame, and take corresponding remedial measures to ensure the cleanliness of the area.

The method of high efficiency filter leak detection:

The high-efficiency filter matched with the DOP liquid tank type high-efficiency air supply port is itself a liquid tank type high-efficiency filter. The leakage test of this high-efficiency filter is basically to place the challenging particles upstream of the high-efficiency air filter, and then on the surface of the high-efficiency air filter. Use a particle detector with the frame to search for leaks. There are several different ways of leak testing, suitable for different occasions.

HEPA filter test methods are:

1. Digital Aerosol photometer test method

2. Particle counter test method

3. Full efficiency test method

4. Outside air test method

The specific instructions are as follows:

PAO or DOP leak detection belongs to the aerosol photometer test method

Aerosol Photometer:

The digital aerosol photometer test method was the earliest test method, but because of its very good effect, it is still used today.

The Aerosol Photometer is a type of cleanroom particle count that also uses laser technology, but after scanning the air sample for particles, it gives the overall intensity of the particles, not the number of particles. DOP is an oily chemical that, after being atomized by pressure or heat, can generate sub-micron particles, which can be used to simulate particles in a clean room, so it is used as a verification particle. The definition of leakage is the leakage of one ten thousandth of the upstream concentration. Since the aerosol photometer can directly display the ratio of the upstream and downstream particle concentrations, it is very convenient to scan the high-efficiency air filter. It is precisely because of its accuracy and reliability that the US Food and Drug Administration (FDA) stipulates that within its jurisdiction (food processing sites and medical and pharmaceutical sites), all high-efficiency air filter leak tests must use DOP and digital aerosol photometers .

 For some time, because it is suspected to have carcinogenic effects on humans, DOS (Dioctylsebaeate dioctyl sebacate), also known as DEHS [di(2-ethylexyl) sebacate] and PAO or DOP (polyaphaolefin) are often used instead of, but the experimental method is still called "DOP test".

Because the concentration of atmospheric dust varies with location and time, sometimes it is larger and sometimes lower, and it is generally not used for leak detection. The FDA pointed out that when conducting leak detection, the selected aerosols should meet certain physical and chemical requirements, and aerosols that would cause microbial contamination and microbial growth should not be used.

DOP aerosol generators 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 specific conditions to remove excessive and after the droplets are too small, a misty DOP of about 0.3um is left into the air duct, and the particle size distribution is 0.1-0.3um.

The cold generator refers to the use of compressed air to bubble bubbles in the liquid, and splashing through the Laskin-Nozzle to generate a polydisperse phase DOP aerosol in the physical state. The maximum distribution particle size is about 0.65um. At present, there are many thermal DOPs commonly used, so the efficiency of the filter must be guaranteed.

PAO-DOP high efficiency filter leak detection test instrument:

The instruments are Digital Aerosol Photometer and Aerosol Generator. The display version of the aerosol photometer has two kinds of analog and digital, which must be calibrated once a year. There are two kinds of particle generators, one is the ordinary particle generator, which only requires high-pressure air, and the other is the heated particle generator, which requires high-pressure air and power supply, and the particle generator does not need to be calibrated.

DOP high efficiency filter leak detection instrument

PAO-DOP high efficiency filter leak detection test steps:

1. Record the number and number of HEPA filters on the drawing.

2. Make sure that the air conditioning system is operating normally and available for testing, and the air speed and air volume must be adjusted and balanced.

3. Use an aerosol generator to cast challenge particles upstream, and inject PAO or DOP into the 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 the particles, the easier it is to find the leak, but after more than 50 micrograms, there is little difference, and less than 10 is difficult to use. The particle concentration can be roughly calculated by the air volume and confirmed by the aerosol photometer.

4. After the upstream particle concentration is confirmed, you can scan the surface of the high-efficiency air filter to find leaks. If necessary, the high-efficiency air filter can be covered with plastic curtains to ensure the accuracy of the test.