Method for replacing PCB containing coolants in electrical induction apparatus with substantially PCB-free dielectric coolants

Claim 1

A method for replacing a coolant containing PCB in an electrical induction apparatus having a tank containing said coolant, an electrical winding and porous solid cellulosic electrical insulation immersed in said PCB-containing coolant with a substantially PCB-free high boiling dielectric permanent coolant to convert said electrical apparatus into one in which the rate of elution of PCB into said coolant is below the maximum allowable rate of elution into the coolant of an electrical apparatus rated as non-PCB, said solid porous electrical insulation being impregnated with said PCB-containing coolant, said method comprising the steps of: (a) draining said PCB-containing coolant from said tank to remove a major portion of said PCB-containing coolant contained by it; (b) filling said tank with an interim dielectric cooling liquid that is miscible with said PCB, is sufficiently low in viscosity to circulate within said tank and penetrate the interstices of said porous solid electrical insulation, and is capable of being readily separated from said PCB; (c) electrically operating said electrical induction apparatus and continuing said electrical operation for a period sufficient to elute PCB contained in said PCB-containing coolant impregnated in said porous solid insulation therefrom into said interim dielectric cooling liquid; (d) thereafter draining said interim dielectric cooling liquid containing said eluted PCB from said tank; (e) repeating the cycle of steps (b), (c) and (d) when the rate of elution of PCB into said interim dielectric cooling liquid exceeds 0.55 ppm of PCB per day based on the weight of said permanent dielectric coolant; and (f) filling said tank with a substantially PCB-free permanent coolant selected from the group consisting of high boiling, high viscosity, silicone oils, synthetic ester fluids, poly-alpha-olefin oils and hydrocarbon oils so as to reclasify said electrical apparatus to non-PCB status.

Claim 2

A method for replacing a coolant containing PCB in an electrical induction apparatus having a tank containing said coolant, an electrical winding and porous solid cellulosic electrical insulation immersed in said PCB-containing coolant with a substantially PCB-free high boiling dielectric permanent coolant to convert said electrical apparatus into one in which the rate of elution of PCB into said coolant is below the maximum allowable rate of elution into the coolant of an electrical apparatus rated as non-PCB, said solid porous electrical insulation being impregnated with said PCB-containing coolant, said method comprising the steps of: (a) draining said PCB-containing coolant from said tank to remove a major portion of said PCB-containing coolant contained by it; (b) filling said tank with an interim dielectric cooling liquid that is miscible with said PCB, is sufficiently low in viscosity to circulate within said tank and penetrate the interstices of said porous solid electrical insulation, and is capable of being readily separated from said PCB; (c) electrically operating said electrical induction apparatus and continuing said electrical operation for a period sufficient to elute PCB contained in said PCB-containing coolant impregnated in said porous solid insulation therefrom into said interim dielectric cooling liquid; (d) thereafter draining said interim dielectric cooling liquid containing said eluted PCB from said tank; (e) repeating the cycle of steps (b), (c) and (d) when the rate of elution of PCB into said interim dielectric cooling liquid exceeds 0.55 ppm of PCB per day based on the weight of said permanent dielectric coolant; and (f) filling said tank with a substantially PCB-free permanent coolant selected from the group consisting of high boiling, high viscosity, silicone oils, synthetic ester fluids, poly-alpha-olefin oils and hydrocarbon oils so as to reclasify said electrical apparatus to non-PCB status.