These are air filtration equipment, also called Inertial Separators, that are self-cleaning wherein as the sands & other dust particles separated from the flow, are collected in a suitable duct and ejected continuously by a bleed fan.
The filter is defined “inertial” because, if an air flow containing the dust particles or other impurities undergoes a direction change, the particles are subject to the force of inertia which makes them follow the direction of the original motion. The difference of kinetic energy that the particles with different masses have, helps the separation of the impurities from the air flow. The filter is formed by one or more assembled modular inertial cells, through which the dusty air undergoes an acceleration and a sudden change of direction. The air is separated from the dust crossing special slots. The dusts highly accelerated, maintain a rectilinear direction, go inside the cell and are conveyed in a collecting duct. The dusts, are, then, sucked and ejected by a bleed fan. Such fan, duly designed, is usually supplied with the filter. The bleed fan has to be suitable to transport dusty air and must have an air flow of 10% (about) of the primary fan air flow.