Patent ID: 7338606

Claim:
A method of maintaining a minimum flow velocity in a return piping of a centralized machine tool coolant filtration system for a plurality of machine tools which each are supplied with coolant from a filtration apparatus and each of which collect contaminated coolant containing entrained solids which is directed under pressure into said return piping, said minimum flow velocity alone said return piping comprising that flow velocity which is sufficient to carry said entrained solids in the coolant from the machine tools, along said return piping comprising the steps of: diverting a make up flow of filtered coolant from a filtration apparatus included in said system into said return piping; and, controlling said make up flow of filtered coolant to be at a flow rate just sufficient to substantially maintain said minimum flow velocity therein so as to carry said solids with the flow of said coolant in said return piping, by sensing the pressure of contaminated coolant directed into said return piping and diverting a flow of filtered coolant from said filtration apparatus into said return piping so as to substantially maintain the pressure of said contaminated coolant introduced into said return piping to that pressure corresponding to said minimum flow velocity.