PURPOSE: To prevent the ignition and explosion of residual fuel oil by a method wherein a hole is bored on a fuel tank by a hydraulic-driven drilling tool to which spark preventing process has been applied and the residual fuel oil in the fuel oil tank is sucked by a pneumatic-driven explosion-proof pump and led to an oil-water separator.

CONSTITUTION: A blade 1a, to which surface spark preventive process has been applied, strikes onto a fuel tank by means of the motion of a piston P equipped on a tool 1 to make a hole on the fuel tank. The residual fuel oil in the fuel tank is sucked by an explosion-proof pump 4 driven by compressed air from a compressor 5, and is collected into a tank 6t of an oil-water separator 6A through a bellow hose 2, a pipe 3, a pump 4 and a pipe 5. In the oil- water separator, water W accumulated under gasoline G is discharged through a drain cock 6c and a drain pipe 6d. Thereby, friction, spark and other hazards due to drilling of the fuel tank and transferring of residual fuel oil are prevented, and as the recovered fuel oil is stored underground, risk of ignition and explosion of residual fuel oil is avoided.