PURPOSE: To exactly identify the kind of oil in order to prevent the oil contamination by providing a valve opening sensor for a bottom valve-opening and closing handle of each hatch, an opening and closing valve at the end of a common hatch discharge pipe, a pressure sensor for an air hose connected to an oil kind-identifying air pressure pipe at the oil supply opening of each oil storage tank, an oil kind identifying means and a control device for sending a valve opening signal to the opening and closing valve.

CONSTITUTION: Couplings 15 and 7 are connected together, a coupling 9 is connected to a coupling 2a and an air hose 22 is connected from an air tank 20 on a tank lorry R, for example, to an orifice 3a, one of the orifices 3 having the mouth diameter varying according to the kind of oil in an oil storage tank T. A pressure sensor 21 detects and outputs the back pressure of the orifice 3a varying according to the air bleed amount. When a bottom valve 4a is opened by its opening and closing handle 37, a valve opening sensor 5a outputs a hatch bottom valve opening signal. A control device 40 selects the kind of oil in a hatch from the hatch bottom valve opening signal and stored loading data and compares it with the oil kind signal from the pressure sensor 21 and, when they agree with each other, energizes a solenoid clutch to open the valve by the valve opening and closing handle.