Vacuum assisted air separation module operation

A method of fuel tank inerting comprises:

• regulating a flow of process air with an actuated valve;
• separating the flow of process air into nitrogen-enriched air and oxygen-enriched air with an air separation membrane which is oxygen permeable;
• applying, with a variable vacuum source, a vacuum to the air separation membrane to produce a pressure differential across the air separation membrane by permeating the oxygen-enriched air across the air separation membrane;
• sensing, with an oxygen sensor in a nitrogen-enriched air line downstream of the air separation membrane, a concentration of oxygen in the nitrogen-enriched air;
• adjusting, with a controller and a variable speed motor drive, the rate of flow of process air through the actuated valve, based on a concentration of oxygen in the nitrogen-enriched air detected by the oxygen sensor and data from at least one fuel tank;
• and
• manipulating the vacuum with the controller, based on the concentration of oxygen in the nitrogen-enriched air detected by the oxygen sensor and the data from the at least one fuel tank sufficient to adjust the concentration of oxygen in the nitrogen-enriched air, to vary the pressure differential and produce a varying purity of the nitrogen-enriched air for fuel tank inerting.