Patent ID: 7658839

Claim:
A device having a flow arrangement for purifying a liquid comprising oil, said liquid contained in an oil reservoir of a transformer, said flow arrangement comprising: a vacuum chamber having an inflow opening and an outflow opening communicating with the liquid in the transformer oil reservoir through a feed conduit and a return conduit, respectively, a pump arranged in the return conduit for pumping the liquid out of the vacuum chamber through the outflow opening and returning the liquid to reservoir through the return conduit, a vacuum pump connected with the vacuum chamber for maintaining a predetermined low pressure in the vacuum chamber, a filter cartridge arranged in the vacuum chamber and provided with a plurality of filter elements, each of said filter elements having a flow side communicating with a central passage and a flow side opening into the periphery of the filter cartridge, the central passage of the filter cartridge communicating with the inflow opening of the vacuum chamber, the liquid traversing across an inner face to an outer face of the filter cartridge to allow a maximum amount of the liquid to be exposed to the pressure in the vacuum chamber to boil off a liquid contaminant of the liquid, a vessel in fluid communication with the vacuum chamber, adapted for receiving and containing a gas removed from the liquid, and a first sensor provided in the vacuum chamber and adapted for monitoring a liquid foam level in the vacuum chamber, and a pressure equalizing valve adapted for controlling a supply of the gas contained by the vessel to the vacuum chamber in response to the first sensor to counteract formation of liquid foam.