# US 8,539,818 B2 · Methods and systems for evaporative cooling infrared thermographic leak detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,539,818 B2 - Document ID: US8539818B2 - Status: Granted - Kind: B2 - Application number: 12/697,411 - Filed: 2010-02-01 - Published: 2011-08-04 - Granted: 2013-09-24 - Earliest claimed: 2010-02-01 - Assignees: The Boeing Company - Applicants: Paul van Staden - Inventors: Paul van Staden - Web page: https://patentgrep.com/patent/US8539818B2 ## CPC - G01M 3/002: {by using thermal means} - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract A method for leak testing a vessel is described. The method includes providing an environment within the vessel that is at a lower humidity than the environment surrounding the vessel, and using a thermographic imaging system to identify any leaks associated with the vessel. The leaks are identified based on evaporative cooling that occurs when a portion of the lower humidity environment escapes from the vessel and mixes with the higher humidity environment surrounding the vessel. ## Claims ### Claim 1 A method for leak testing a commercial aircraft fuel tank, said method comprising: providing an environment within the fuel tank that is at a lower humidity than the environment surrounding the fuel tank, and that is at a pressure less than about 4 psi greater than a pressure of the environment surrounding the fuel tank by at least forming a quasi-closed loop in which air is drawn from the fuel tank, routed to a dehumidifier, and pumped back into the fuel tank; and using a thermographic imaging system to identify any leaks associated with the fuel tank by detecting any areas of decreased temperature resulting from evaporative cooling that occurs when a portion of the lower humidity environment escapes from the fuel tank and mixes with the higher humidity environment surrounding the fuel tank. ### Claim 2 (depends on 1) The method according to claim 1 wherein providing an environment within the fuel tank further comprises: increasing humidity of the air in the area surrounding the fuel tank. ### Claim 3 (depends on 2) The method according to claim 2 wherein increasing humidity of the air in the area surrounding the fuel tank comprises applying water to an exterior of the fuel tank. ### Claim 4 (depends on 1) The method according to claim 1 wherein providing an environment within the fuel tank comprises providing an environment within the fuel tank that is at a greater pressure than a pressure of the environment surrounding the fuel tank. ### Claim 5 (depends on 4) The method according to claim 4 wherein the pressure within the fuel tank is at least 0.25 psi greater than the pressure of the environment surrounding the fuel tank. ### Claim 6 (depends on 1) The method according to claim 1 wherein using a thermographic imaging system to identify any leaks within the fuel tank comprises identifying areas of lower temperature within a thermal image of a portion of the fuel tank. ### Claim 7 (depends on 1) The method according to claim 1 wherein using a thermographic imaging system to identify any leaks associated with the fuel tank comprises sensing a temperature drop caused by localized evaporation of moisture from external air proximate the leakage area. ### Claim 8 A leak testing method comprising: pressurizing a commercial aircraft fuel tank to be leak tested to a pressure less than about 4 psi greater than a pressure of the environment surrounding the fuel tank with a gas having a humidity less than a gas surrounding the fuel tank by at least forming a quasi-closed loop in which air is drawn from the fuel tank, routed to a dehumidifier, and pumped back into the fuel tank; sensing any temperature drops proximate the fuel tank caused by localized evaporation of moisture from external gas using thermographic imaging; and identifying the temperature drops as leakages associated with the fuel tank. ### Claim 9 (depends on 8) The method according to claim 8 wherein sensing any temperature drops proximate the fuel tank caused by localized evaporation comprises sensing evaporative cooling that occurs when a portion of the lower humidity gas escapes from the fuel tank and mixes with the higher humidity gas surrounding the fuel tank. ### Claim 10 (depends on 8) The method according to claim 8 further comprising: increasing humidity of a gas in the area surrounding the fuel tank. ### Claim 11 (depends on 10) The method according to claim 10 wherein increasing humidity of a gas in the area surrounding the fuel tank comprises applying water to an exterior of the fuel tank. ### Claim 12 (depends on 8) The method according to claim 8 wherein pressurizing a fuel tank to be leak tested comprises providing at least one of: an environment within the fuel tank that is at a greater pressure than a pressure of the environment surrounding the vessel; and an environment within the fuel tank that is at a lower pressure than a pressure of the environment surrounding the fuel tank. ### Claim 13 (depends on 12) The method according to claim 12 wherein the pressure differential between the pressure of the fuel tank and the pressure of the environment surrounding the fuel tank is at least 0.25 psi. ### Claim 14 (depends on 8) The method according to claim 8 further comprising identifying areas of lower temperature within a thermal image of a portion of the fuel tank. ### Claim 15 A system for testing a commercial aircraft fuel tank for leakages, said system comprising: at least one device for providing a humidity differential between an inside of the fuel tank and the exterior of the fuel tank; a pump operable to provide a pressure differential of less than about 4 psi between the interior of the fuel tank and the exterior of the fuel tank; and a thermographic imaging system operable to identify any leaks associated with the fuel tank when the fuel tank is pressurized to less than about 4 psi, the leaks identifiable with said imaging system based on evaporative cooling that occurs when a portion of the lower humidity environment mixes with the higher humidity environment, wherein said at least one device, said pump, and said fuel tank are configured in a quasi-closed loop in which air is drawn from the fuel tank, routed to said at least one device, and pumped back into the fuel tank. ### Claim 16 (depends on 15) The system according to claim 15 wherein said thermographic imaging system comprises an infrared camera. ### Claim 17 (depends on 15) The system according to claim 15 wherein said thermographic imaging system comprises an image processing system operable for at least one of display and storage of images acquired by said thermographic imaging system. ### Claim 18 (depends on 15) The system according to claim 15 wherein said at least one device comprises a dehumidifier operable to reduce humidity either inside the fuel tank or surrounding the fuel tank. ### Claim 19 (depends on 15) The system according to claim 15 wherein said pump is operable for at least one of: increasing a pressure inside the fuel tank to provide the pressure differential between the interior of the fuel tank and the exterior of the vessel; and decreasing a pressure inside the fuel tank to provide the pressure differential between the interior of the fuel tank and the exterior of the fuel tank. ### Claim 20 (depends on 19) The system according to claim 19 wherein said pump is operable to create a pressure differential of at least 0.25 psi between the interior of the fuel tank and the exterior of the fuel tank.