Image Number 3 for United States Patent #5285745.
A slight, 13.2 psia, underpressure is created, and dynamically maintained, in the ullage space of the oil tanks of an unmanned barge in order to prevent or reduce the spillage of oil due to any rupture of the tanks. The underpressure is created by ejecting a high pressure gas, preferably 500 psia inert nitrogen gas in a 16 ft.sup.3 storage bottle, through an ejector that is also flow-connected to the ullage spaces of the barge's tanks. The gaseous mixture within the ullage space is preferably inerted so as to prevent combustion or explosion by mixing with the same high pressure inert gas that is otherwise used to energize the ejection. All flow connections are controlled by electric valves managed by a control computer that responds to tank level, pressure, and/or gaseous mixture sensors.