Patent ID: 7410456

Claim:
A method of purifying contaminated oil from particles suspended there in by means of a liquid separation aid having a density larger than that of the oil and being dispersed in the contaminated oil in order to make the particles more easily separable from the oil, the method comprising supplying said contaminated oil and said liquid separation aid into a separation chamber of a rotating centrifugal rotor, separating in said separation chamber the particles and the liquid separation aid from the oil by centrifugal force, discharging purified oil from the separation chamber through a central light phase outlet thereof and discharging separated particles together with separated liquid separation aid from the separation chamber through a heavy phase outlet of the separation chamber, situated radially outside said central light phase outlet, pre-charging the separation chamber, before supplying a substantial amount of contaminated oil thereinto, with a starting liquid, which is heavier than the oil and insoluble therein, in an amount such that a layer of the starting liquid forms a liquid seal in the centrifugal rotor, covering said heavy phase outlet, supplying thereafter said contaminated oil and said liquid separation aid into the separation chamber, and discharging from the separation chamber through said heavy phase outlet at least part of said starting liquid and particles together with liquid separation aid, separated from the oil.