Characterisation and modification of the porous metal foams used for the EN 15051-2 dustiness rotating drum test.

Abstract

Two approaches were used to evaluate the performance of the reticulated metal foams used to size select and collect dust generated in the dustiness rotating drum tester according to the EN 15051-2 standard "Workplace exposure-Measurement of the dustiness of bulk materials-Rotating drum test". Firstly, the detailed performance of the metal foams was measured in a calm air chamber using a polydisperse aerosol of glass particles and assessed against the respirable conventions described in the EN 481 standard "Workplace atmospheres-Size fraction definitions for measurement of airborne particles". Secondly, the performance of the EN 15051-2 metal foam size selection for the respirable fraction was compared using the rotating drum dustiness test, with that of a cyclone set-up, using 4 polydisperse glass powders of different size distribution and dustiness potential. The research discusses further improvements to the EN 15051-2 standard and an approach to more closely match the EN 481 convention. In general, for the respirable fraction, the tests in this study demonstrated a conservative oversampling by the current EN 15051-2 metal foam set-up in comparison with the EN 481 convention. Calculations and tests showed an improved fit was achieved by reducing the inner diameter of the flanges separating the metal foams and the filter. This study also showed the importance of sealing the circumference of the metal foams when testing highly dusty powders. A direct comparison of the respirable dustiness fraction, measured by the current EN 15051-2 metal foams set-up and by a cyclone set-up, showed broad agreement. However, for extremely dusty powders, the metal foams can clog, and dust can accumulate between the 20 and 80 pores per inch foams.