Dependence of filtration properties on stainless steel medium structure

Abstract

Filtration properties including porosity, air permeability, minimum bubble point, pore size distribution, latex bead filtration efficiency and dirt-holding capacity were investigated for woven wire meshes and sintered nonwoven metallic fibre media, in order to understand the effect of their structural differences. When 165×1400 mesh and Fibermet® 20A0 fibre medium were compared, it was found that the basis weight and air permeability of the woven mesh and the nonwoven fibre medium were similar. The porosity of 165×1400 (36.7%) was lower than that of 20A0 (84.7%). However, the wire mesh had a much higher minimum bubble point than the fibre medium (3553 Pa versus 1845 Pa). The 165×1400 had a narrower pore size distribution than 20A0. Between 5 and 20 μ, the latex bead filtration efficiency of 165×1400 was lower than that of 20A0. At 20 μm, both 165×1400 and 20A0 had a latex bead filtration efficiency of 98%. The lower latex bead filtration efficiency of 165×1400 compared to 20A0 did not correlate with a higher minimum bubble point. A similar difference was also observed between 325×2300 wire mesh and Fibermet® 10A0, and both of them had a filtration efficiency of 98% at a latex bead diameter of 9 μm. Analysis of the structure of all four filter media showed that there were multiple filtration layers through the thickness in the depth filtration fibre media, and only a single filtration layer in the surface filtration wire meshes. The multiple filtration layers of interconnected pores and tortuous pore paths in the fibre media were more effective in catching rigid latex bead particles than the single filtration layer, and a nearly linear pore path in the wire meshes. The fibre media also had higher dirt-holding capacities than the wire meshes.