Designing advanced filtration media through metal additive manufacturing

Burns, Neil and Burns, Mark and Travis, Darren and Geekie, Louise and Rennie, Allan (2015) Designing advanced filtration media through metal additive manufacturing. In: FILTECH: The Filtration Event, Conference and Exhibition, 2015-02-24 - 2015-02-26, KoelnMesse, Cologne.

Abstract

Traditional metal filters are manufactured from perforated plate and one or more layers of woven wire mesh. The perforated plate forms the support portion of the filter, and delivers the overall strength of the filter to withstand operational pressures. The woven wire mesh forms the filter portion with the aperture size chosen to suit the required level of filtration. An ideal filter would have the maximum open area possible to minimise the filters’ resistance when in situ in the conduit. However maximising the open area decreases the overall strength of the filter and so open area must be compromised to deliver the required strength. The design freedoms and capabilities of Additive Manufacturing (AM) technology provides the opportunity to design novel filter media that are depth filters with x-, y- and z- planes with integrated support portion and filter portion. This filter mesh has a defined aperture size and by reducing the equivalent wire diameter, these novel filter media have a greater open area compared to the equivalent woven wire mesh. This potentially reduces the pressure drop across the filter and so reduces pumping energy requirements. In preliminary studies AM filter media have been designed using a repeating node unit to form the latticework of the AM filters. Previous test samples demonstrated that this AM integrated filter support and filter portion design decreased the pressure drop across the filter compared to conventional filter design. The aim is to develop the integrated support and filter AM design to incorporate different sizes of repeating nodes, with a larger node providing strength and the smaller node providing the filtration level. It has been possible to develop two node structures to deliver two latticeworks, one with a 1000μm aperture and the other with 500 μm aperture. Filter disks comprising of 1, 2 and 3 layers of the individual nodes were tested for strength by collapse pressure. Conical filters were designed and tested for each individual node and for combination of nodes, i.e. layer of 500μm and1000μm. These AM integrated filter supports and filter portion conical filters were tested for strength: collapse pressure and their pressure drop. The pressure drop across these novel AM integrated filters was largest for the AM 500μm aperture filter alone and least in the AM 1000μm filter. Combination of repeating nodes of both 1000μm and 500μm in one single filter delivered a decreased pressure drop across the filter compared to the AM 500μm filter with 500μm apertures alone. The integrated filter support and filter support portion AM design filters shown here have the potential to decrease the end users pumping energy requirements and so reduce energy costs and the end users carbon footprint.