Abstract: Apparatus for the continuous vacuum cleaning of oil operating on the principle of continuous alteration of a compression, and of a separating cycle, by utilizing a combined action of quasistationary processes instigated by reduced pressure and of non stationary processes generated by a hydrodynamic cavitator. Due to a repeated circulation of the oil filling through a non-stationary and a quasistationary separating process, a high purity of oil, which is subsequently forced back into the container of the oil system, or of an electric transformer, respectively, is achieved and simultaneously a safe removal of contaminations.