PURPOSE: To facilitate the extraction work of insulating oil in the maintenance and diagnosis of sealed oiled insulating equipment and shorten the time required for stoppage of the equipment.

CONSTITUTION: This oil extractor comprises a current transformer 1 coupled with an extracted oil vessel 2, an oil tank 11, a cylinder 15, a vacuum pump 9, and accessories such as a gauge 10, stop valves 3, 5, 6, 7, 8 and 12, a cross joint 4, and flanges used for connection of each pipe. The cross joint positioned at the center has four communication holes to which stop valves 5, 6, 7 and 8 are attacked. The line from the current transformer 1 is connected to the stop valve 5, and the line from the vacuum pump 9 is connected to the stop valve 6, and the line from the oil tank 11, which stores insulating oil for replenishment, is connected to the stop valve 7, and the line from the cylinder, which contains flexible bellows one end of which is fixed airtightly to the inner face of the cylinder cover 13, is connected to the stop valve 8. What is more, the cylinder is provided, on the other side, with a piston rod, with which one can move the bellows 14 manually from outside.