Abstract: An apparatus and method for inerting the gas present in the ullage region of a storage tank for combustible liquids, e.g., a fuel tank containing a hydrocarbon liquid fuel, utilizes a molecular sieve zone (2, beds 12/14) which either (a) selectively adsorbs oxygen from the ullage gas to provide an oxygen-depleted return ullage gas, or (b) selectively adsorbs nitrogen from the ullage gas, which nitrogen is desorbed and conveyed by a purge gas to provide a nitrogen-enriched gas. The return ullage gas or the nitrogen-enriched gas is flowed to the ullage region (30, 130) in quantity sufficient to render the overall composition of gas in the ullage region (30, 130) non-combustible and non-explosive. The apparatus may include a compressor (22) or a vacuum pump to flow the ullage gas through the system, and a valving arrangement (16, 18) is used to control the flow of gases.

Abstract: An apparatus and method for inerting the gas present in the ullage region of a storage tank for combustible liquids, e.g., a fuel tank containing a hydrocarbon liquid fuel, utilizes a molecular sieve zone (2, beds 12/14) which either (a) selectively adsorbs oxygen from the ullage gas to provide an oxygen-depleted return ullage gas, or (b) selectively adsorbs nitrogen from the ullage gas, which nitrogen is desorbed and conveyed by a purge gas to provide a nitrogen-enriched gas. The return ullage gas or the nitrogen-enriched gas is flowed to the ullage region (30, 130) in quantity sufficient to render the overall composition of gas in the ullage region (30, 130) non-combustible and non-explosive. The apparatus may include a compressor (22) or a vacuum pump to flow the ullage gas through the system, and a valving arrangement (16, 18) is used to control the flow of gases.