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Key Technology Research on In-situ Leak Detection of Hepa Filter in Biosafety Laboratory

Author: ZhangZongXing
Tutor: QiJianCheng；LvJing
School: PLA Military Academy of Medical Sciences
Course: Health Protection epidemic prevention technology and equipment
Keywords: High-grade bio- security laboratory High efficiency filter Efficient air filtration unit Situ Leak Full efficiency detection method Scan detection method
CLC: R115
Type: Master's thesis
Year: 2010
Downloads: 117
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Abstract

The operation of the high-level biosafety laboratories for high induced pathogen microorganisms, many conventional experimental operation will generate hazardous aerosols. If the lab is contaminated, poisonous indoor air pollution emissions to the atmosphere will be infected people and animals, causing a pandemic, a serious threat to human life and health, and even lead to a major public health events. Therefore, high-level biosafety laboratories disposal to ensure that laboratory biosafety key air pollution emissions. Currently, high efficiency air filter is still the primary means of protection of the biosafety laboratory air pollution. High efficiency air filters there is a leak and the surface of pathogenic microorganisms survive, multiply the risk, the WHO \our standard GB19489-2008 also provides for BSL-3 laboratory should be in place exhaust efficiency filter sterilization and leak detection. High-level biosafety laboratory construction started late, and disposal technologies currently used in laboratory exhaust is still very backward, and can not meet the requirements of in situ high efficiency filter leak detection and in situ disinfection. In order to solve through the transformation of our country has been built and some high-grade bio-security laboratory under construction in line with the GB19489-2008 technical problems, it is necessary in accordance with existing standards and other technical requirements, efficient air filtration unit filter situ leak detection technology research, and the research and development of high-grade bio-safety laboratory exhaust disposal equipment suitable for China's national conditions. For high-level biosafety laboratory exhaust efficient traps were installed in the actual situation, the general efficiency filter scan leak detection, full efficiency leak detection method, in combination with standard of high efficiency filter efficiency testing proposed performance requirements, as well as the actual situation in our country has been built, and in the construction of the high-level biosafety laboratory proposed biosafety laboratory exhaust efficiency filter situ leak detection technology research programs. This paper studies how full efficiency leak detection applied to the exhaust filter device technology, and theoretical analysis experimental contrast and CFD simulation, designed exhaust filtration device downstream mixing device, can guarantee downstream sampling representative , it is recommended that aerosols mixed performance of the downstream sampling points were evaluated according to the standards ASHERE52.2-1999 \9 downstream of the filter dust emission point to inject artificial occurred DOP aerosol downstream sampling port test results show that the particle size of 0.3 ~ 0.5μm particles collected downstream sampling port corresponding to the point of all of dust relative deviation of the aerosol concentration test results were less than 3%, to meet the standard of not more than 10% of the requirements. For efficient air filtration unit upstream of dust and sampling functions, according to the standard requirements, the need to ensure that the aerosol concentration immediately upstream of the filter with spatial coherence. In order to meet the requirements, usually on the upstream retrofitting mixing plate, but in some cases, still difficult to achieve mixing requirements, can be prevented by the conventional dust port changed annular hair dust inlet. Tested by experiment, that the ring dust port can effectively accelerate the aerosol mix, a good mix. Using TSI3160 hierarchical filter test bench tested with different aperture leak efficient filter paper, filter paper MPPS efficiency greater than 99.97% measured MPPS particle size of 0.1 μm. The test results show that when the leakage point diameter of less than 0.4mm, the overall efficiency of the filter paper has little effect, when the diameter is greater than 0.4mm, the efficiency of the filter paper decreased significantly. Therefore recommended when the test scanning probe leak to identify and locate the leakage point performance, make the leak diameter elected 0.4mm appropriate. Here leak diameter refers to the diameter of the circular needle bar drain the leak. Conventional sampling probe application problems exist in exhaust filtration devices automatically scanning system developed line scan sampling probe program. Firstly, according to the sampling probe sample breath flow velocity consistency in both the sampling probe of the line scan design test sampling airflow 28.3L/min, a preliminary choice of two programs according to the test results, the line scan of the selected sampling The probe sampling points value of the wind speed of the port are in the average range of ± 20%, to meet the requirements of the relevant standards. Identify leakage points in order to test the line scanning probe, filter leak identification comparison test with conventional scanning probe, filter into the test, artificially produced two diameters of 0.4mm leakage on the leeward side of the filter paper point, the two probes around the leak fixed sampling distance 25mm filter position. The test results show that the line scanning probe test fixture leak resulting transmittance of about 0.7 times that of the conventional scanning probe and identify the range of line scanning probe leak about 7mm transmittance distribution of a parabola-shaped, rectangular sampling probe leak identification range transmittance distribution of 11mm to a trapezoidal shape, and line scanning probe measured the difference is relatively small leakage point to different locations, that can be used to filter scan. The line scan sampling probe to identify the characteristics of the leak, the movement of the scanning probe set to intermittent operation, each running 5mm suspend 0.5s. The reason to take intermittent running, in order to provide time to the collection and processing of data, when the particle counter with the computer to transfer data, the counter is not at the same time collecting data, this operation mode can effectively prevent the leakage recognition. Taking into account the length of the sampling tube caused by the data acquisition delay, to set the correction of the sampling time during the scanning process. Tainted point filter line scan leak detection can accurately locate the leak area. Based on the performance requirements of the exhaust filter device, automatic leak detection system developed a line scan the entire scanning system also includes motion control systems, in addition to including the sampling probe, sample line switching systems as well as data acquisition and processing system. The system has a scan cycle is short, simple mechanical structure, ancillary equipment, high degree of automation and the advantages of a more humane, and automatically scan all the electrical components of the system are all installed on the outside of the device, and can be fully applied to the exhaust filtration devices filter situ leak detection. The high-level biosafety laboratory should select the appropriate exhaust filtration devices according to their structure, and in accordance with the installation of its high efficiency filter, select the applicable leak detection methods. Series biosafety laboratory exhaust efficiency air filtration devices successfully developed for the high-level biosafety laboratory construction provides important technical and equipment support, and product performance reached the level of similar foreign products in the domestic high-grade Biosafety promote the use of laboratory construction.

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