Manufacturer: Niikura Kogyo  Co., Ltd
Model: FCV Series: FCV-N-50 to 150, FCV-200 to 300

Purpose

The overflow pipe for fuel oil, lubricating oil and the other flammability oil will be led to overflow tank. The overflow pipe is set up with the operation of mutual circulation and backflow prevention.
Moreover, it has a rule that “if sea water flows into the tank when overflow pipe opened, it is possible that the sea water will backflow into the other tank through overflow pipe, it should be to set up with backflow prevention”…(NK Steel Vessel Rule Volume D 13. 7. 4-2)
This Float Check Valve is the device of backflow prevention.