1. No damage to the material of the HEPA filter; 2. Proper installation.
The filtration efficiency of the high-efficiency filter itself is generally tested by the manufacturer, and the filter filtration efficiency report card and certificate of conformity are attached to the filter when it leaves the factory. For pharmaceutical companies, high-efficiency filter leakage detection refers to the high-efficiency filter and its system after the installation of the site leakage detection, mainly to check the filter filter material in the small pinhole and other damage, such as frame seals, gasket seals and leakage seams on the filter frame, etc.. The purpose of the leakage check is to discover the defects in the high-efficiency filter itself and in the installation in time by checking the sealing of the high-efficiency filter and its connecting parts with the installation frame, etc., and to take corresponding remedial measures to ensure the cleanliness of the area.
High-efficiency filter leakage detection methods
The leakage test of high-efficiency air filters is basically to put the challenge particles in the upstream of the high-efficiency air filters, and then search for leakage on the surface of the high-efficiency air filters and borders with the particulate detection instruments. There are several different ways of leakage testing, which are applicable to different occasions. Test methods are: 1. aerosol photometer test method 2. particle counter test method 3. full efficiency test method 4. outside air test method Description is as follows.
PAO leak detection belongs to the aerosol photometer test method Aerosol photometer:
Aerosol photometer test method is the earliest test method, but because of the effect is very good, and still used today.
The Aerosol Photometer is a type of particle counter that also uses laser technology, but it scans an air sample for particles and gives the overall intensity of the particles, not the number of particles. DOP is an oily chemical that, when pressurized or heated and atomized, produces sub-micron particles that can be used to mimic clean room particles. particles and is therefore treated as a validation particle. Leakage is defined as leakage out of the upstream concentration of one part in 10,000. Scanning for HEPA filters is very convenient because the aerogel photometer directly displays the ratio of the upstream and downstream particle concentrations. Because of its accuracy and reliability, the U.S. Food and Drug Administration (FDA) requires that all leakage tests of HEPA filters within its jurisdiction (food processing sites and medical and pharmaceutical sites) must be performed using a DOP and an aerosol photometer.
For a period of time, because it is suspected of having a carcinogenic effect on people, is now often DOS (Dioctylsebaeate decanedioic acid dioctyl ester), also known as DEHS [di (2-ethylexyl) sebacate] and PAO (polyaphaolefin poly a olefin) and so on instead of the experimental method is still called. But the experimental method is still called "DOP method". Atmospheric dust is generally not used for leak detection because its concentration varies with location and time, sometimes large and sometimes low. FDA pointed out that in the leak detection, the selected aerosol should meet certain physical and chemical requirements, and should not be used to cause microbial contamination, resulting in microbial growth of the aerosol. DOP generator can be divided into hot generation and cold generation of two kinds, hot generator is the use of the principle of evaporation and condensation, the atomized aerosol particles with a heater to evaporate, and condense into tiny droplets under specific conditions, remove the oversized and small droplets left behind after the 0.3um mist DOP into the air ducts, the size distribution of the particles in the range of 0.1 ~ 0.3um. Cold generator refers to the use of compressed air bubbles in the liquid, through the laskin nozzle splash to produce the material state of the polydisperse phase DOP aerosol, the maximum distribution of particle size of about 0.65um. There are many hot DOPs in common use, so the efficiency of the filter should be guaranteed. Testing Instruments:
The instruments used are an Aerosol Photometer and an Aerosol Generator. The Aerosol Photometer has both analog and digital displays and must be calibrated once a year. There are two types of Aerosol Generators, one is an ordinary Aerosol Generator, which requires only high pressure air, and the other is a heated Aerosol Generator, which requires high pressure air and a power supply, and does not require calibration. Tools / raw materials
Aerosol Photometer (Aerosol Photometer) ? Particle generator (Aerosol Generator). High Efficiency Air Filter (HEAF)Clean Suit
Methodology/Steps
1. 1
. Record the number of HEPA filters on the drawing and number them.
Make sure that the air conditioning system is functioning properly and is available for testing, and that the air speed and air volume must be adjusted and balanced.
2. 3
Using an aerosol generator to apply challenge particles upstream, the PAO is pumped upstream of the HEPA filter at a concentration of about 10 to 20 micrograms of PAO per liter of air. the more particles, the easier it is to find leaks, but there is little difference after 50 micrograms, and it's difficult to use the filter with less than 10 micrograms. The concentration of particles can be roughly calculated using the air volume, and then confirmed using an aerosol photometer.
3. 4
After the upstream particle concentration is confirmed, the surface of the HEPA filter can be scanned for leaks, and the HEPA filter can be surrounded by a plastic curtain to ensure the accuracy of the test.
4. 5
Scanning the surface of the HEPA filter, the scanning path can be from the outside to the inside or along the long/short edges of the meander detection, in the following ways: a. Each HEPA filter and its frame should be tested. b. Each HEPA filter and its frame should be tested. c. Each HEPA filter and its frame should be tested. d. Each HEPA filter should be tested.
b. When scanning the surface of the HEPA filter, set up the leak detector as shown in Figure (b), and move forward in the short side direction to cover the whole HEPA filter. c. When scanning the edges of the HEPA filter, especially between the HEPA filter and the Ceiling Grid, the leak detector can be positioned as shown in (a) or (b) above, covering the entire joint.
d. Use the square cone-shaped (10mm*60mm) sampler of the particle counter to place it about 25mm under the HEPA filter and move it at 50mm/sec.
e. The reading on the aerosol photometer is the upstream and downstream percentage value, so if the value is greater than 0.01, it can be suspected of leakage, and can be returned to about 100mm to repeat the test, if there is no sustained high readings, you can continue to test, and vice versa, that is to say, there is leakage, which needs to be documented and repaired or replaced in the future. If the HEPA filter is damaged, it should be repaired or renewed, and then re-tested. If there is any leakage in the border, it should be re-installed and adjusted until there is no leakage. 8 The scanning result, the leakage condition and the treatment must be registered in the record.
Note: For HEPA in HVAC systems, to achieve uniformity of concentration when the aerosol reaches the HEPA, introduce the aerosol directly from the negative pressure side of the system fan, or from the duct at least 10 times the diameter of the duct from the HEPA, with as few turns as possible (American Academy of Environmental Science and Technology). In general, it is sufficient to keep the upstream aerosol at the required concentration and the concentration fluctuating within a certain range. For HEPA on laminar flow hoods and ultra-clean benches, aerosols are introduced directly from the negative pressure side of the system fan.
Precautions
Acceptance criteria
1. Any continuity reading exceeding 0.01% is considered to be a leak, and there shall be no leakage from each HEPA filter after testing and replacement, and there shall be no leakage from the border.
2. The repair area of each HEPA filter shall not be greater than 3% of the area of the HEPA filter. 3. The length of any repair shall not be greater than 38㎜.