The purpose of leak detection:
1. The material of the high efficiency air filter is not damaged;
2. The installation is appropriate.
The filtration efficiency of the 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 pharmaceutical companies, high-efficiency filter leak detection refers to on-site leak detection after installation of high-efficiency filters and their systems, mainly to check small pinholes and other damage in filter media, such as frame seals, gasket seals, 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 air filter leak test basically applies the challenge particles upstream of the high-efficiency air filter, and then uses the particle detection instrument on the high-efficiency air filter surface and the frame to search for leaks. There are several different ways of leak testing, which can be applied to different situations.
The test methods are:
1. Glue photometer test method
2. Particle counter test method
3. Full efficiency test method
4. External gas test method
described as follows.
PAO leak detection is an aerosol photometer test aerosol photometer:
The gas gel photometer test method was the earliest test method, but because it works very well, 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 sebacate), also known as DEHS [di(2-ethylexyl)sebacate] and PAO (polyaphaolefin polya olefin). The experimental method is still called the "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 a droplet, 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 maximum distribution particle size is about 0.65 um. At present, there are many hot DOPs commonly used, so the efficiency of the filter should be guaranteed.
test instrument:
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.
Tools/raw materials
- Aerosol Photometer Aerosol Generator High Efficiency Air Filter Cleanroom
Method / step
- Record the number of high efficiency air filters on the drawing and number them.
- 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. The challenge particles are applied upstream using a gas gel generator, and the PAO is driven upstream of the high efficiency air filter, which has a PAO of about 10 to 20 micrograms 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. 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. Scanning on the surface of a high-efficiency air filter, the path of the scan can be detected from the outside or within the long/short side, as follows:
a. Each high efficiency air filter and its bezel are tested.
b. When the surface of the high-efficiency air filter is used, place the leak detector as shown in Figure (b) and advance in the short side direction to cover the full-efficiency air filter.
c. When scanning the high efficiency air filter frame, especially between the high efficiency air filter and the Ceiling Grid, the leak detector can be placed as shown in (a) or (b) above, covering all seams.
d. Use a square cone (10mm*60mm) sampler of the particle counter to place it under the high efficiency air filter for about 25mm and rotate at a speed of 50mm/sec.
e. The reading on the gas gel photometer is the upper and lower percentage value. Therefore, if the value is greater than 0.01, it can be suspected to be leaking. It can be returned to about 100mm for repeated retesting. If there is no continuous high reading, the test can be continued. Otherwise, there is Leaks need to be recorded and repaired or replaced in the future.
- If the high efficiency air filter is damaged, it should be repaired or updated and then retested. If there is a leak in the frame, it should be reinstalled and adjusted until there is no leakage. Scan results, leak conditions and handling methods must be registered during recording.
The original text was transferred from Suzhou Changliu Purification Technology Co., Ltd. http://
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