To adequately execute water spray cooling to molding sand and to urge the inspection and repair of a device in real time in the case of the abnormal state by constituting a microcomputer in such a manner as to compare and compute the actual flow rate measured by a flow rate sensor and a calculated water spray target flow rate.

The flow rate of the water flowing through the flow rate sensor 6 is compared and computed with the calculated water spray target flow rate in the microcomputer 8. When a flow rate difference of the water more than the prescribed quantity is admitted between both, an electric signal is immediately outputted to a display 9 and an alarm is emitted from the display 9. The water spray is stopped simultaneously with the alarm and immediately, the inspection for the water leakage of water feed piping 3, the foreign matter deposited in the water feed piping 3 or the formation of rust and further the trouble of a water pressure constant device 1, etc., is carried out. The abnormal state is then repaired and the device is restarted. The abnormal state of the actual water flowing through the flow rate sensor 6 is detected in such a manner and, therefore, the execution of the inspection and repair of the device in real time is made possible.