Abstract: A method of reducing the effects of fluctuating fluid pressure differential between the inlet and the outlet of a filtering unit operating in a system for filtering metal contaminants from a lubricating coolant and for recycling a constant volume flow of filtered lubricating coolant to a workpiece to be subsequently machined by pumping metal-contaminated lubricating coolant from a holding vessel to a filtering unit-modulator valve combination, monitoring the pressure or flow rate of filtered lubricating coolant downstream of the filtering unit-modulator valve combination, and operating the modulator valve in response to any changes in the downstream monitored flow parameter so as to maintain a predetermined constant fluid pressure differential across the filtering unit-modulator valve combination, thus compensating for fluctuations across the filtering unit during filtering operation, resulting in the maintenance of constant head pressure at the outlet of the pump, as well as for maintenance of a constant vol

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.