Detection principle and maintenance of particle filtration efficiency tester
The particle filtration efficiency tester produced by international standard is used to test the particle filtration efficiency of daily protective masks and medical masks, and to determine the blocking performance of ordinary fabrics and medical protective masks for constant flow of air. It is applicable to medical device inspection center, safety protection inspection center, labor protection inspection center, drug inspection center, disease prevention and control center, textile testing center, hospitals, mask manufacturers, etc.
Main detection principles of particle filtration efficiency tester:
The particle filtration efficiency is measured by an automatic filter material tester. Sodium chloride aerosol is used in the environment with relative humidity (30 ± 10)%, temperature (25 ± 5) ℃. The number median diameter of sodium chloride aerosol is (0.075 ± 0.020) μ m, and the geometric standard deviation of particle distribution is ≤ 1.86. For the same product, different test gas flows are used, and the results of filtration efficiency are different. After experimental research, the filtration efficiency will decrease with the increase of test gas flow. Therefore, for the filtration efficiency, it must be indicated under what test gas flow is obtained.
In GB 19083, when the gas flow is 85 L / min, the filtration efficiency of mask for non oily particles shall meet the following requirements: Level 1 ≥ 95%; Grade 2 ≥ 99%; Grade 3 ≥ 99.97%. The pretreatment condition of mask is to place it at (70 ± 3) ℃ for 24h, and then at (- 30 ± 3) ℃ for 24h.
In YY 0469, when the gas flow is 30 L / min, the filtration efficiency of the mask for non oily particles shall be ≥ 30%. The mask was pretreated for (25 ± 1) h in the environment of relative humidity (85 ± 5)%, temperature (38 ± 2.5) ℃.
Precautions for use and maintenance of dust particle counter at main parts of particle filtration efficiency tester:
During the long-term use of the on-line dust particle counter, due to the particularity of the use environment and the misoperation of employees, the instrument or equipment may inevitably contact with droplets, dust or other substances, resulting in inaccurate measurement or damage of the instrument and equipment, and some may even lead to the failure of the whole detection system. Sometimes, due to the lack of effective detection means, the production environment or production materials cannot be correctly evaluated, resulting in the normal production of the factory, which affects the production efficiency of the company.
Precautions for use
1. Please handle the instrument with care and do not hit the instrument violently.
2. The installation position of the instrument shall be far away from the vibration, liquid droplets or oil stains as far as possible.
3. Use the power supply correctly, and do not use more than the rated power supply voltage.
4. Do not let droplets and greasy dirt enter the instrument.
5. Keep the instrument and equipment in a dry state, and all interfaces of the instrument and equipment are well connected.
6. Online dust particle counter shall be calibrated every year according to relevant national standards.
Routine maintenance
1. Temporary particles such as isokinetic sampling head or sampling pipe, instrument and equipment port can be cleaned, and the problem of inaccurate measurement caused by temporary particles can be eliminated.
2. Check the power supply and circuit, and check whether the wiring or wiring terminal is loose, aging and short circuit, which can eliminate hidden dangers, reduce the failure rate, prolong the service life of instruments and equipment, spend a little money and save a lot of money.
3. Check the air pipe for blockage or air leakage.
4. Strengthen the training of employees and improve their knowledge of instrument and equipment use management.
Contents of after-sales maintenance
1. Instrument maintenance: repair of instrument damage and instrument cleaning.
2. Calibration of particle sensor: according to the national dust particle counter calibration specification (JJF 1191-2008), the dust particle counter needs to be calibrated once a year; Calibrate the dust particle counter, including cleaning the outer surface of the counter, electrical signal processing substrate, optical system lens (cylindrical mirror, condenser), cavity, diode, etc