Fuel tank safety system

An inerting apparatus connected to a storage tank containing a combustible liquid and having an ullage region containing nitrogen and oxygen, the apparatus comprising:

• a nitrogen-scavenging molecular sieve zone which selectively removes nitrogen from a gas flowed through it and having an inlet connected by an inlet line in gas-flow communication to the ullage region, and an outlet;
• a purge gas line connected in gas flow communication from a source of purge gas to the molecular sieve zone and thence to the ullage region;
• a first gas-flow control valve in the inlet line is movable between a closed position and an open position;
• a second gas-flow control valve in the purge gas line is movable between a closed position and an open position;
• a pressurizing mechanism operably connected to the apparatus
• (a) to flow ullage gas from the ullage region to and through the molecular sieve zone to load the molecular sieve zone with adsorbed nitrogen when the first gas-flow control valve is in its open position and the second control valve is in its closed position;
• and
• (b) to flow purge gas through the molecular sieve zone to desorb nitrogen from the molecular sieve and thereby form a nitrogen-rich gas and flow the nitrogen-rich gas to the ullage zone when the second control valve is positioned to permit such flow and the first control valve is positioned to preclude flow of the ullage gas through the molecular sieve zone.

An inerting apparatus for a storage tank containing a combustible liquid and having an ullage region containing oxygen, the apparatus comprising:

• an oxygen-scavenging molecular sieve zone comprising at least first and second regenerable oxygen-scavenging sub-zones, the first sub-zone having one end to which is connected a first gas-flow line and a second end to which is connected a second gas-flow line, the second sub-zone having a first end to which is connected a third gas-flow line and a second end to which is connected a fourth gas-flow line;
• a first control valve member to which the first and third gas-flow lines are connected in gas-flow communication;
• an ullage gas inlet connected in gas-flow communication to the first control valve member;
• a second control valve member to which the second and fourth gas-flow lines are connected in gas-flow communication;
• an ullage gas return line connected in gas-flow communication between the second control valve member and the oxygen-scavenging zone;
• a purge gas line connected in gas-flow communication between a purge gas source and the second control valve member;
• and
• a pressurizing mechanism connected to the apparatus to flow gas therethrough, the first and second control valve members being operable to flow a stream of ullage gas through at least one of the oxygen-scavenging sub-zones and the resulting oxygen-depleted ullage gas from that sub-zone to the storage tank ullage region as return ullage gas.

An inerting apparatus for a storage tank containing a combustible liquid and having an ullage region containing nitrogen and oxygen, the apparatus comprising:

• a nitrogen-scavenging molecular sieve zone comprising at least first and second regenerable nitrogen-scavenging molecular sieve sub-zones, the first sub-zone having one end to which is connected a first gas-flow line and a second end to which is connected a second gas-flow line, the second sub-zone having a first end to which is connected a third gas-flow line and a second end to which is connected a fourth gas-flow line;
• a first control valve member to which the first and third gas-flow lines are connected in gas-flow communication;
• an ullage gas inlet connected in gas-flow communication to the first control valve member;
• a second control valve member to which the second and fourth gas-flow lines are connected in gas-flow communication;
• an ullage gas return line connected in gas-flow communication between the first control valve member and the molecular sieve;
• a purge gas line connected in gas-flow communication between a purge gas source and the second control valve member to flow a purge gas through, and thereby desorb nitrogen from, the molecular sieve zone to provide a nitrogen-enriched gas;
• a pressurizing mechanism connected to the apparatus to flow gas therethrough;
• the first and second control valve members being operable to contemporaneously flow a stream of ullage gas through one of the molecular sieve sub-zones to provide a stream of nitrogen-depleted gas, and to flow the nitrogen-enriched gas from the other molecular sieve sub-zone to the storage tank ullage region.

A method of inerting a storage tank containing a combustible liquid and having an ullage region containing nitrogen and oxygen, the method comprising the steps of:

• withdrawing from the ullage region a stream of ullage gas;
• flowing the ullage gas through a nitrogen-scavenging molecular sieve zone to remove nitrogen from the gas and adsorb it in the molecular sieve zone, to form a nitrogen-depleted gas;
• regenerating the molecular sieve zone by desorbing nitrogen therefrom and flowing a purge gas therethrough to thereby provide a nitrogen-enriched gas;
• and
• flowing the nitrogen-enriched gas into the ullage region.