REPRODUCIBILITY OF FILTER TEST STANDS ALSO ACCORDING TO STANDARDS

摘要

Depending upon application, the nonwoven aerosol separators are classified and/or compared according to different standards. Thereby, not only the respectively prescribed measuring methods are crucial, but also the test aerosols to be used according to the respective specification. The fractional separation efficiency forms usually the basis of the evaluation of a separator according to the above mentioned standards. The more accurately and more reliably is measured the particle quantity as a function of the particle size, the more reliably can be determined the fractional separation efficiency. For this, it is recommended to use so-called aerosol spectrometers which - depending upon the measuring method - measure optically or aerodynamically. In addition to the particle measuring technology, the use of the correct as well as constant and homogeneous test aerosol is also important for the testing of separators. Due to the different applications of the nonwoven filters different test aerosols are specified in the respective standards. Occasionally, for the each other corresponding standards on national and international level different test aerosols are prescribed for the same application - e.g. EN779 in Germany and ASHRAE in the USA for the testing of room air filters. The negative effect is test results which deviate from each other and which are therefore not directly comparable. Not only due to such differences it must be pointed out that it can be appropriate - depending upon objective - to test not according to standard but according to objective, e.g. at the new development or optimisation of a separator. In the years 1999 and 2004 round-robin tests were accomplished according to standard with different test stands. The results were disillusioning: Depending upon comparative measurement, there were result deviations of up to 73%. In the paper we will show that the fractional separation efficiency determination of filters can be accomplished on different test stands also in close tolerance.