Method for cleaning aircraft tanks

Abstract

The invention relates to a method for cleaning aircraft tanks (92), wherein the aircraft tank (92) is emptied, the method comprising the steps of: a) opening at least one access opening (93) to the interior of the aircraft tank (92); b) introducing a hand-held cleaning gun (20) which is connected to a cleaning device (1) via a hose (10) and has a steam outlet nozzle (21) and a suction nozzle (22), wherein the steam outlet nozzle (21) is designed for targetedly letting out steam provided by the cleaning device (1) and the suction nozzle (22) is designed for suction using a negative pressure generated by the cleaning device (1), wherein the steam outlet and the suction are coordinated with one another such that a locally limited cleaning space (50) for the steam is formed in front of the cleaning gun (20); and c) guiding the cleaning gun (20) along surfaces to be cleaned in the interior of the aircraft tank (92) when the steam outlet and suction are activated such that the cleaning gun (20) and the surface do not touch and at least parts of the surface are in the local cleaning space (50).

Description

Procedure for cleaning aircraft tanks

[0001] The invention relates to a method for cleaning aircraft tanks.

[0002] Contamination can occur in aircraft fuel tanks. In addition to contaminants introduced into the tank through openings, for example during refueling or maintenance, bacteria, mold, and fungi can form in the tank, particularly when aircraft are idle for extended periods. These can also result in fuel contamination - at least unless they adhere firmly to the interior surfaces of the tank. At the latest when microbial contamination of the interior of the tank is treated with suitable, toxic biocides known from the state of the art, the fuel is contaminated by biomass - in the form of killed microbes. Excretions from living microbes can also lead to fuel contamination.

[0003] To prevent fuel contaminants from reaching the aircraft's engine, fuel filters are known that filter out solids above a specified size from the fuel during operation. A disadvantage of this state-of-the-art technology is that, particularly in cases of intensive fuel contamination, the fuel filter can become clogged during operation, which poses a safety risk.

[0004] If there is significant contamination of the tank or the fuel contained therein, particularly by microbes, it is therefore known and intended - in particular to avoid the risk of clogging of the filter - to clean the affected tank by opening the tank and conducting a so-called "tank inspection". complex, which is why they can only be carried out by specially qualified and trained personnel, and usually take several days, also due to the preceding defuelling and ventilation steps, during which the aircraft with the tank to be cleaned usually occupies a space in a hangar.

[0005] To clean an aircraft tank according to the state of the art, the tank must be emptied, opened, ventilated, and measured to ensure that no hazardous substances, etc., remain in the tank. A skilled worker then enters the interior of the aircraft tank through one or more manholes and manually cleans the accessible surfaces using a rag and brush with a solvent mixture. This process is complex and may not be thorough enough, as, for example, a biofilm is often only partially smeared and not completely removed.

[0006] Furthermore, for aircraft with sufficiently stable fuel tanks, tank cleaning is performed using a high-pressure cleaner that sprays hot water. The resulting contaminated water then collects at the lowest point of the fuel tank and must be vacuumed out from there.

[0007] The object of the present invention is to provide a method for cleaning aircraft tanks which is improved over the known prior art.

[0008] This object is achieved by a method according to claim 1. Advantageous further developments are the subject of the dependent claims.

[0009] The invention accordingly relates to a method for cleaning aircraft tanks, the aircraft tank being emptied, comprising the steps of: a) opening at least one access opening to the interior of the aircraft tank; b) introducing a hand-held cleaning gun, which is connected to a cleaning device via a hose and has a steam outlet nozzle and a suction nozzle, the steam outlet nozzle being designed for the directed discharge of steam provided by the cleaning device and the suction nozzle being designed for suction by means of a negative pressure generated by the cleaning device, the steam being discharged and the suction being coordinated with one another in such a way that a locally limited cleaning space for the steam is formed in front of the cleaning gun;c) guiding the cleaning gun along the surfaces to be cleaned in the interior of the aircraft tank with the steam outlet and suction activated in such a way that the cleaning gun and the surface do not touch and at least parts of the surface are in the local cleaning space;

[0010] Starting from an emptied aircraft tank, in which all the fuel has been removed from the tank, e.g. pumped out or drained, according to a method known from the prior art, the method according to the invention is intended to clean the aircraft tank using steam. However, not only is steam directed towards the contamination through a steam outlet nozzle in order to loosen the contamination, but there is also direct suction, with which not only the detached contamination Not only is any fuel residue or other foreign matter extracted, but the previously introduced steam is also extracted again. This prevents the interior of the tank from filling with steam or condensed water – although it cannot be ruled out that, for example, small amounts of the steam may not be completely extracted due to deflection of the supplied steam by surfaces and components within the tank.

[0011] Basically, according to the invention the steam is limited to an area in front of the cleaning gun which is determined by the configuration of the steam outlet nozzle and extraction nozzle as well as the operating parameters for steam outlet and extraction. The steam escaping from the cleaning gun is therefore basically extracted again by the cleaning gun itself after it has moved into the space in front of the cleaning gun. The area into which the steam escaping from the cleaning gun spreads before it is extracted again by the cleaning gun is referred to as the “locally limited cleaning space”. As will be clear to a person skilled in the art, the extent of the locally limited cleaning space is determined by the outlet pressure of the steam at the steam outlet nozzle and the suction power of the extraction nozzle, which must be suitably coordinated with one another.For example, pressure and suction power can be coordinated in such a way that the locally limited cleaning space extends from the steam outlet nozzle in the direction of steam outlet, for example, over at least 5 cm or at least 10 cm.

[0012] The steam can loosen dirt adhering to the tank, especially biofilms. Thanks to the suction, the loosened dirt particles are immediately removed, preventing the dirt particles from splashing around, as can happen, for example, when cleaning with a high-pressure cleaner. occurs - is avoided. Recontamination of previously cleaned areas can thus be prevented.

[0013] The actual implementation of the method according to the invention is easily possible for sufficiently trained personnel. As is also known in the prior art for cleaning aircraft tanks, after the aircraft tank has been emptied, the access openings regularly provided for cleaning (so-called "manholes") are opened. Even if aircraft tanks are generally not dimensioned in such a way that one can climb completely into the tank, all interior surfaces of an aircraft tank can be reached for cleaning purposes through the - usually - multiple access openings of a tank.

[0014] In the method according to the invention, the cleaning gun is guided along the surfaces to be cleaned with activated steam and the suction is guided along the surfaces to be cleaned in such a way that the surface in question or successively different parts of the surface are each located in the locally limited cleaning area so that they are exposed to steam and any dirt loosened by this and other residues on the surface, such as possible fuel residues, are suctioned off. The cleaning gun is guided along the surface at such a distance that the cleaning gun and the surface do not touch each other in order to avoid possible damage from mechanical contact. The distance is to be selected so that it is greater than zero, but the surface still intersects the locally limited cleaning area.The locally limited cleaning space must therefore be designed so that it extends this distance from the outlet nozzle toward the surface. For example, the cleaning gun can be guided along the surface at a distance of at least 1 cm.

[0015] It is preferred if liquid and solid components are separated and / or filtered out from the fluid extracted via the cleaning gun in the cleaning device. Through separation, larger contaminants and other substances, such as fuel residues, as well as water condensed from the extracted vapor, can be separated from the fluid flow of the extraction and ultimately disposed of. Of course, a further, usually downstream, material separation process can also be provided in order to separate, for example, biological contamination from hazardous substances such as fuel and dispose of them properly. In order to prevent residual substances that could not be removed from the fluid flow by separation, for example, from being released into the environment in an uncontrolled manner, a suitable filter for the fluid flow can be provided after separation has taken place.It is also possible to rely exclusively on suitable filtration instead of separation, for which filter cascades are usually provided.

[0016] It is preferable that the temperature of the surface to be cleaned does not exceed 80°C, preferably 70°C, when the process is carried out properly. Adhering to appropriate temperature limits is advantageous to avoid possible damage to the aircraft fuel tank or the surface to be cleaned. At the same time, it has been shown that excellent cleaning results can be achieved even with appropriate temperature specifications.

[0017] As a helpful measure to comply with the above temperature limit, in addition to appropriate training, where in particular the dwell time of the cleaning gun on a surface area is to be taught as an essential parameter for the surface temperature, it is preferred that the temperature of the steam at the outlet from the steam outlet nozzle is between 80°C and 120°C, preferably 100°C. With appropriate steam outlet temperatures, an increase in the Surface temperatures exceeding 80°C are practically impossible, even if the process is carried out slightly differently than intended. At the same time, it has been shown that good cleaning results can be achieved with an appropriate steam outlet temperature. In order to achieve an appropriate steam outlet temperature, the steam can have a significantly higher temperature (e.g. 180°C) when it is generated, as it regularly exits the steam outlet nozzle at increased pressure (e.g. 10 bar) and expands to ambient pressure (approx. 1 bar), which also causes it to cool down.

[0018] The steam is preferably dry steam, i.e. steam which no longer contains any liquid components. If wet steam is used, its steam content is at least 90%, preferably at least 95%. The steam content is determined from the masses of the actual steam and the masses of the liquid components contained therein according to the formula

[0019] In principle, steam can be generated from any type of water. However, it is preferred if the steam is generated from softened or even demineralized water. By using appropriate water qualities, the maintenance and cleaning intervals of the cleaning device can be extended, as, for example, limescale deposits need to be removed less frequently. The cleaning device can also include a suitable softening or desalination device, with which the supplied water is first softened or desalinated before it is fed to the steam generator or a possible water tank for intermediate storage.

[0020] It is preferred to use a steam outlet nozzle suitably designed to generate a mechanical cleaning effect through the steam emitted through it. Although it may be sufficient to achieve a cleaning effect through the action of the steam alone, combined with the mechanical action of the suction, it has been shown that a kinetic effect on the soiling achieved through suitably applied steam can significantly increase the cleaning effect.

[0021] The steam outlet nozzle and / or the extraction nozzle can generally be interchangeable on the cleaning gun. It is preferable if the steam outlet nozzle and / or the extraction nozzle are selected appropriately for a specific cleaning task and attached to the cleaning gun. For example, for cleaning larger, smooth surfaces, different steam outlet nozzles and / or the extraction nozzles may be advantageous in terms of cleaning results or efficiency than steam outlet nozzles and / or the extraction nozzles used to effectively clean surfaces with rivets.

[0022] The hose preferably has a material-friendly outer surface and / or is conductive. Even if the cleaning gun is positioned at a distance from the surface to be cleaned, the hose connecting the cleaning gun to the cleaning device will come into contact with various edges and surfaces of the aircraft tank. To prevent damage, the outer surface of the hose can be designed to be suitable for material protection. Conductive hose capability is preferred to prevent the buildup of static charges.

[0023] The invention will now be described by way of example using an advantageous embodiment with reference to the accompanying drawing. It shows: Figure 1: a schematic representation for carrying out the method according to the invention.

[0024] Figure 1 schematically shows the method according to the invention for cleaning a fuel tank 92 of an aircraft 90 using a cleaning device 1 designed for this purpose. The tank 92 is integrated into the wing 91 of the aircraft 90 and emptied. An access opening 93, shown as an example, is already open.

[0025] The cleaning device 1 is connected to a generally hand-held cleaning gun 20 via a hose 10. The hose 10 has a material-protecting outer surface and is conductive.

[0026] The cleaning device 1 comprises a steam generator 2, which can be used to generate dry steam at a temperature of 180°C at 10 bar from demineralized water. The steam thus generated is conveyed via hose 10 to the cleaning gun 20 and exits through the replaceable steam outlet nozzle 21, where the steam then has a temperature of 100°C. Even if the steam is no longer completely dry in this state, the steam content is still 95% or more.

[0027] A replaceable suction nozzle 22 is also provided on the cleaning gun 20. For suction through this suction nozzle 22, the cleaning device 1 comprises a suction pump 3. A separator 4 is provided on the suction side of the suction pump 3, and a filter 5 is provided on the other side.

[0028] The steam generator 2 and the suction pump 3 are coordinated with each other, taking into account the steam outlet nozzle 21 and the suction nozzle 22, in such a way that a locally limited cleaning space 50 is created in front of the cleaning gun 20: Steam emerging from the steam outlet nozzle 21 is generally limited to this cleaning space 50 and is sucked out of this cleaning space 50 through the suction nozzle 22.

[0029] The cleaning gun 20 is guided by suitably trained personnel with the steam outlet and suction activated over the surfaces of the fuel tank 22 to be cleaned in such a way that a part of the surface is in the cleaning chamber 50 at any one time, without the cleaning gun 20 and the surface in question coming into contact. The steam emerging from the steam outlet nozzle 21 loosens any dirt adhering to the surface - depending on the design of the steam outlet nozzle 21, also with a mechanical cleaning effect - which is then immediately sucked away by the suction. Other residual substances, such as fuel residues, are also removed by the suction.

[0030] The fluid ultimately extracted by the suction pump 3 first enters the separator 4, where detached contaminants, fuel residues, etc., are separated from the fluid flow. The separator is designed to remove all solid and liquid components from the fluid flow. Any residues remaining in the fluid flow are filtered out by the filter 5 to prevent contamination of the surrounding area.

[0031] Both the steam outlet nozzle 21 and the suction nozzle 22 are interchangeable and arranged on the cleaning gun. They can be selected to suit the specific cleaning task.

Claims

Patent claims 1. A method for cleaning aircraft tanks (92), wherein the aircraft tank (92) is emptied, comprising the steps of: a) opening at least one access opening (93) to the interior of the aircraft tank (92); b) introducing a hand-held cleaning gun (20) which is connected to a cleaning device (1) via a hose (10) and has a steam outlet nozzle (21) and a suction nozzle (22), wherein the steam outlet nozzle (21) is designed for the directed discharge of steam provided by the cleaning device (1) and the suction nozzle (22) is designed for suction with the aid of a negative pressure generated by the cleaning device (1), wherein the steam discharges and the suction are coordinated with one another in such a way that a locally limited cleaning space (50) for the steam is formed in front of the cleaning gun (20);c) guiding the cleaning gun (20) along surfaces to be cleaned in the interior of the aircraft tank (92) with activated steam exit and suction in such a way that the cleaning gun (20) and the surface do not touch and at least parts of the surface are in the local cleaning space (50); 2. Method according to claim 1, characterized in that liquid and solid components are separated and / or filtered out from the extracted fluid in the cleaning device (1).

3. Method according to one of the preceding claims, characterized in that the temperature of the surface to be cleaned remains between 40°C and 80°C when the process is carried out correctly, preferably not exceeding 70°C.

4. Method according to one of the preceding claims, characterized in that the temperature of the steam when exiting the steam outlet nozzle (21) is between 80°C and 120°C, preferably 100°C.

5. Method according to one of the preceding claims, characterized in that the steam is dry steam or wet steam with a steam content of at least 90%, preferably of at least 95%.

6. Method according to one of the preceding claims, characterized in that the steam is generated from softened or demineralized water.

7. Method according to one of the preceding claims, characterized in that a steam outlet nozzle (21) is used which is designed to produce a mechanical cleaning effect by means of the steam emerging therethrough.

8. Method according to one of the preceding claims, characterized in that the steam outlet nozzle (21) and / or the suction nozzle (22) is interchangeable and is suitably selected.

9. Method according to one of the preceding claims, characterized in that the hose (10) has a material-protecting outer side and / or is conductive.

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