Clogging process and related pressure drops in wire-wound filters: laboratory evidence.

The present work is aimed at analyzing the performance of the commercial filters used for the mechanical filtration of suspended solid particles. In particular, it is intended to evaluate the head losses due to the presence of the filter in the plant and how these losses vary depending on the circulating flow rate, the nominal porosity of the filter, and its clogging degree. Filters with interstices of different sizes, from 1 to 50 μm, were compared for the performance analysis. The polypropylene wire, in facts, wrapped around a windowed cylinder of the same material, allows the creation of meshes with the desired degree of compactness. The experiments were carried out at the Laboratory of Environmental and Maritime Hydraulics (LIDAM) in a hydraulic circuit reproducing a domestic piping system, where different water demand scenarios were analyzed. The clogging of the cartridge was made with the aid of sand particles, attached, with the help of a natural glue, to the external surface of the filter. More than 200 measurements were carried out, which showed a clear increasing trend of the head losses at the filter as the clogging degree and the circulating flow rate increase. In all cases, the trend of the pressure drop at the filter has a more than linear trend. Also, it was observed that head losses did not exhibit a marked dependence on the nominal porosity. Best performances in terms of minor head losses were obtained by the 50-μm filter.