Свойства воздушных фильтров и их применение
Properties of air filters.
The classification stated in Charter no 2 makes comparison of performace for different types and designs of filters possible using the test conditions and standards valid nowadays. The test results differ from those achieved under the practical conditions for filter groups G and F. Charter no 1 contains recommendation for the application of various groups and classes of filters. On the base of a common application and typical particles separated in these filters we can usually state the suitable class of the filtration for the special application.
The important variations are as follows:
- The possible sedimentation of natural Middle European outside aerosols is from 0,4 to 3 times higher for the filters in the group G than it is for the synthetic test dust - measured according to EN 779. The figure for the filters of the group F is from 1,5 to 8. (6).
- The separation capacity may substantialy differ from natural Middle European outside aerosols regarding the average level diameter of particles, the filtration material, the level of filter blockage and the volume of the air. Before all the synthetic filtration material, which is eloctrostatic shows up to 4 times lower capacity of separation comparing to that measured by standard coarse synthetic test dust according to EN779. The lower capacity is due to loss of the electrical potential. (7, 8, 9, 10).
- When started, stopped or being dirty the filters with non stable material in the air flow (e.g. pocket filters) may release the old dust particles int the air flow (so called reentrainment or shedding) which causes the reduction of the capacity.(11, 12).
- The filters of the group G can have worse separation of the particles with larger diameter (from about 5 mm) and starting velocity ( so called particle bounce or shedding). (13, 14).
Application of air filters.
Charter no 1 contains recommendations for application of different groups and classes of filtration. On the base of a common aplication and typical particles separated in these filters we can usually state the suitable class of filtration. Besides there are standards and instructions which give the minimum class of the filtration for the special applicaton.
- High Efficiency Penetration Air
- Ultra Low Penetration Air
- Most Penetrating Particle Size