Liquid filtration system

Abstract

A filtration system for removing both large, bulky and small, compactible solid contaminants from a liquid, intended primarily for the collection of chips and purifying and recycling coolant liquids used in machining and other metal working operations. Contaminanted liquid which has been used in the machining operation transports metal chips and other contaminants to a tank divided into upper and lower compartments by a wedgewire strainer. The sub-atmospheric pressure which develops in the lower compartment due to pumping of clean liquid from the lower compartment and the build-up of small, compactible contaminants on the upper side of the strainer is measured and a signal commensurate with the magnitude of the pressure provides the input to a drive motor for a continuous loop drag conveyor which scrapes the chips and sludge from the surface of the strainer. Thus, the rate of chip and sludge removal and the degree of coolant clarity is continuously and directly proportional to the degree of contaminant build-up. Also, the input signal to the drive motor has a minimum value greater than zero which is established as a function of the volumetric rate at which large, bulky contaminants, such as curly metal trunings, are supplied to the upper compartment. Although these contaminants provide very little resistance to flow through the strainer, they are nonetheless removed from the tank even at times when little or no small, compactible contaminants are present to increase the pressure differential between the upper and lower compartments.