Backwashable filtering apparatus and novel filter element therefor

Abstract

A plurality of filter housing are arranged around a hollow hub section the interior of which is divided into an inlet chamber for receiving fluid under pressure to be filtered, an outlet chamber for receiving filtered fluid, and a backwash chamber that is connected to a waste line. Each filter housing contains an inverted, frustoconically shaped filter element having a closed lower end, and an open upper end connected to the outlet chamber of the hub section. Fluid that is to be filtered normally flows from the inlet chamber through a first series of valves to the lower ends of the filter housings, and then radially inwardly through the walls of the filter elements and out of the upper ends thereof and through a second series of valves to the outlet chamber. Because of its configuration, the pressure gradient across a respective filter element is substantially uniform throughout the entire axial length of the element, so that fluid is caused to flow through the entire useful surface of the element throughout its axial length. The lower ends of the filter housings can be selectively connected by a third series of valves with the backwash chamber. The first and third valves for each housing are interconnected, so that when a backwashing operation becomes necessary, the first valve is automatically closed at the time that the third valve opens, thereby causing a portion of the previously filtered fluid to flow in a reverse direction through the associated filter housing to the backwash chamber.