Abstract:
A process for testing the tightness of containers includes making available a first fluid in the container interior space that is different from a second fluid surrounding the container, creating a negative pressure in the container interior space, testing the interior surfaces of the container side wall for traces of second fluid penetration, and possibly localizing any entry points.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This application claims the priority of German Application 10 2004 058 606.3, filed Dec. 3, 2004, the disclosure of which is expressly incorporated by reference herein. 
     This invention is concerned with a process for testing the tightness of a container. Additionally, the invention provides for a process for sealing a container after a test of its tightness has been made, as well as a device for sealing the container. 
     The lack of tightness of fuel tanks and other containers in aircraft is a problem with far reaching effects on flight safety and operational safety on the ground. This problem also affects work safety and environmental protection. If aircraft fuel tanks are lacking in tightness, substantial repair costs can result, and the operational readiness of an aircraft fleet could be impaired. During a delivery of a new or overhauled aircraft to a customer, all systems are given a final testing. Tightnesses of the tank installations are also tested. During the operation of the aircraft on the ground, as well as during air operations, leaks may occur over the aircraft life-cycle, typically more than 25 years. The leaks may be the result of mechanical damage of the tank walls due to improper handling of the aircraft or due to unplanned stresses caused by flight operations such as overloads or vibrations. In military aircraft especially, such leaks may occur when the aircraft is being fired upon. 
     It is in the interest of an airline operator to restore flight worthiness of the aircraft at as little expense in time and personnel as possible without having the aircraft spend time in the repair hangar of the manufacturer. Especially in integral tanks, that is to say tanks which are fitted in their spatial design to the external contour of the aircraft and/or to the internal contour of the aircraft, the tank inner walls have multiple joint locations at which leakages can occur, even though the state of the art of sealing technology is very high both with respect to manufacture and testing quality. 
     In spite of all the measures taken, leaks that must be located and sealed can spring up in the tank walls during operation of an aircraft. 
     It is one object this invention to provide a process for testing the tightnesses of containers which can be carried out without a great expense even when the containers have complex internal and/or external contours, such as, for example, in the case of integral aircraft tanks, and to permit rapid determination of leak locations. Furthermore, it must be possible to seal leaks quickly and without great cost. 
     Testing for leakage of a container according to the invention includes separating a first fluid in an interior space of the container from a second fluid surrounding the container, producing a negative pressure in the interior space, testing interior surfaces of container walls for traces of second fluid penetration, and localizing any points of entry of the second fluid. 
     According to the invention, a partial vacuum is created in the tank and subsequently tested to determine whether a fluid has penetrated the internal space of the container. This makes it possible to locate in a simple way the exact entry point of the fluid entering the inner space of the container. This reversal of the principle, known as such, of creating high pressure in the interior space of a container and observing at which point fluid exits the container, avoids disadvantages of this known solution, since the fluid escaping from the container frequently is not visible at its point of exit but rather at some distance from it. 
     The localization of the entry point can also be observed through a window provided in the container, and it can be observed, from the outside, where the second fluid enters the interior space of the container. Nevertheless, it is especially advantageous when a probe is or several probes are brought into the interior space of the container. Such probes can be designed so as to be stationary within the internal container space or movable along the container internal wall. 
     Advantageous additional improvements are additionally provided. 
     After completion of the process of testing the containers for leakage, that is to say, after the localization of the entry point, a sealing compound can be applied with the help of a probe from the inside of the container at the point of leakage. This probe can be either independent of the camera or a combined probe which, in addition to the camera and, as the case may be, a gas supply, can also include at least one suitable repair tool such as, for example, an injector or an extruder for the sealing compound. 
     A device according to the invention for testing for container leakage and for repair of leaks allows for a fast repair immediately after identification of a leakage point. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An example of the invention will be explained in greater detail with reference to the drawings. 
         FIG. 1  shows a cross-section of an integrated aircraft tank, 
         FIG. 2  is a cross-sectional representation of an integrated tank showing locations of the joints, 
         FIG. 3  shows sealing of an integrated tank at a joint location, and 
         FIG. 4  shows inspection of an integrated tank with a camera probe. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic view of a cross-section of a jet aircraft fuselage  1 . The wings  2  and  3 , of which only the wing roots are shown, are attached sideways in the lower area of the fuselage  1 . As shown in the upper internal section of the fuselage  1 , two air conduction channels  4  and  5  through which ram air is conducted to the engines are provided. 
     An integrated tank  10 , which has several chambers, is shown within the fuselage. The chambers include an upper chamber  12 , a left chamber  14 , a right chamber  16 , and a lower chamber  18 . The fluid in the chambers can either be cross-connected or they each can have a separate refueling opening. 
     The upper chamber  12  of the integral tank  10  is limited by (not shown here) front and rear face walls, a section of the fuselage external skin  20 , a section of the wall  22  of the left air conduction channel  4 , a section of the wall  24  of the right air conduction channel  5 , a left upper vertical bulkhead wall  26 , a right upper vertical bulkhead wall  28 , and a middle horizontal bulkhead wall  30 . 
     The left chamber  14  of the integrated tank  10  is limited by a section of the fuselage external skin  20 , a section of the wall  22  of the left air conduction channel  4 , the upper left vertical bulkhead wall  26 , as well as a left horizontal bulkhead wall  32  and the (not shown here) front and rear face walls. 
     The right chamber  16  of the integrated tank  10  is limited by a section of the fuselage external skin  20 , a section of the wall  24  of the right air conduction channel  5 , the upper right vertical bulkhead wall  28 , as well as a right horizontal bulkhead wall  34  and the (not shown here) front and rear face walls. 
     The lower chamber  18  of the integrated tank  10  is limited by the middle horizontal bulkhead wall  30 , a section of the wall  22  of the left air conduction channel  4 , a section of the wall  24  of the right air conduction channel  5 , a lower left bulkhead wall  36 , a lower right bulkhead wall  38 ,as well as a lower horizontal bulkhead wall  40  and (not shown here) front and rear face walls. 
     The interior of the integrated tanks is accessible through a tank lid  11  lockable in or over an opening in the fuselage external skin  20 . 
     Corresponding sealing measures must be undertaken in order to seal reliably the integrated tank  10  everywhere the previously mentioned bulkhead walls or face walls push against the fuselage skin  20  and each of the walls  22  and  24  of the air conduction channels  4  and  5 .  FIG. 2  shows an example of such attachment of a bulkhead wall  50  on the corresponding side walls  52  and  54 . 
     The bulkhead wall  50  is composed of multiple types of profiles or profile sections, which are fastened together by rivets  56 . One of these profile sections is fastened by rivets  57  to the left wall  52 , and others of these profile sections are fastened with rivets  58  to the right wall  54 . Shown above the bulkhead wall  50  and between the left side wall  52  and the right side wall  54  is a chamber  60  of the integrated tanks. The individual profile sections of the bulkhead wall  50  are sealed together with a track sealant  62  on the side facing the chamber  60 . In the area in which the profile sections of the bulkhead wall  50  are secured to the left side wall  52 , a track sealant  64  is provided on the side of the chamber  60 . Similarly, in the area in which the profile sections of the bulkhead  50  are secured to the right side wall  54 , a track sealant  66  is also provided on the side of the chamber  60 . 
     Spray sealants  68  and  69  overlying the securing area are additionally provided on the side of the chamber  60  of the integrated tanks where the bulkhead  50  is pushed against the left side wall  52  and against the right side wall  54 . 
     The mounting and sealing of one bulkhead wall against another wall is represented in  FIG. 3 . 
     A bulkhead wall  70 , which has a cross-section in the form of an “I,” pushes with its bottom surface against the interior surface of a side wall  72 . The lower section of the bulkhead  70  has a left horizontal leg  70 ′ and a right horizontal leg  70 ″. A surface seal  74  is disposed between the bottom surface of the left horizontal leg  70 ′ and the bottom surface of the right horizontal leg  70 ″ of the bulkhead wall  70  as well as the interior surface of the side wall  72 . The surface seal  74 , for example, may consist of a polytetrafluoroethylene. 
     In its lower area at the side facing the side wall  72 , the bulkhead wall  70  is provided with a groove  71  at a location where the left horizontal leg  70 ′ and the right horizontal leg  70 ″ push against each other. The groove  71  is also filled with sealant  75 . 
     The bulkhead wall  70  and the side wall  72  are connected by rivets  73 ,  73 ′, which also penetrate the side wall  72 , the left horizontal leg  70 ′, and the right horizontal leg  70 ″. 
     Track sealants  76  and  77  are preferably provided, on the free rims of the left horizontal legs  70 ′ as well as the right horizontal leg  70 ″, between the legs  70 ′,  70 ″ and the side wall  72 . 
     The entire connection arrangement between the bulkhead wall  70  and the side wall  72  described above is additionally sealed on each side of the bulkhead wall  70  by sealant coatings  78  and  79  which, at the least, overlap a surface section of the bulkhead wall  70 , the interior head of the respective rivets  73 ,  73 ′, each of the track sealants  76 ,  77 , and at least one area of the internal side wall  72 . 
     In this way, a seal with three barriers between the bulkhead wall  70  and the side wall  72  is achieved. This sealing of the joint locations provides for reliable sealing of the interior spaces  80  and  82  from the external surroundings  84 . 
     During manufacture, each of these barriers is individually tested, during the assembly of the structure, in order to find any leaks as early as during the formation process. Here a differentiation is made between the dry tests in which gaseous test substances are used and the wet tests which take place with liquids such as, for example, water, fuel, or fuel substitute liquids. Customarily, these tests are carried out using high pressure in the tank space while simultaneously looking for leakage. In the process according to this invention, however, the interior space of the container or integral tank  10  is put under pressure lower than the prevalent pressure of the external environment. This causes leakage, in contrast to a process according to the state of the art, to proceed in the reverse direction along a track which terminates at the source of leakage, and thus the point of entry. Using this process, leakage can be both reliably located and perfectly pinpointed. 
     When a tank has a simple geometry, a transparent tank cover can be used in order to observe and locate the entry of the leakage through the transparent tank lid. When a more complicated tank geometry with especially difficult access to individual chambers of a tank or, as in the example of  FIG. 1 , an integral tank is present, it is preferable to insert controllable camera probes through the special sealable openings provided for such purpose in the tank covers of the individual chambers. 
       FIG. 4  shows an example of such a camera probe inserted into an integral tank. 
     The tank cover  11  of  FIG. 1  has been replaced in the example of  FIG. 4  by a tank cover  11 ′. A swiveling and axially adjustable probe  90  can be guided through a guiding tube  91  into the integral tank  10 . The guiding tube  91  is provided at its external end with a handle  92 , with the help of which the guiding tube  91  swivels about the transition point through the tank cover  11 ′ and can then be axially shifted. The guiding tube  91  is inserted through an opening  31  in the middle horizontal bulkhead wall  30  into the lower chamber  18  of the integrated tank  10 . A camera head  93  is provided at the lower end of the guiding tube  91 , which is linked by outside controlled optical or electrical wiring  94  through the guiding tube  91  to an image reproduction device (not shown here). 
     In addition to the camera head  93 , a device  95 , such as a spray nozzle, for emission of a sealant is located at the end of the guiding tube  91 . This device is also linked by a tube  96  extending through the conducting tube  91  outside to a feed line (not shown here) for a sealing compound. Sealant can be transported through the tube  96  into the nozzle  95  and then delivered under pressure through the nozzle  95 . 
     In place of a camera head  93 , or in addition thereto, a different type of sensor, for example a gas sensor, can also be used. This makes it possible to detect and recognize a point of entry of a gas entering into the chamber  18  of the integrated tank  10  from the outside. 
     With the shown probe  90 , it is possible to test the interior of a container, especially the shown integral tank  10 , for leakage when the container interior space is under lower pressure than the surrounding environment. It is thus possible to locate and identify the points of leakage and, using the nozzle  95 , to bring up sealing compound from the inside to the corresponding points of leakage of the chamber  18  and thus seal off and eliminate the leakage. If necessary, lighting (not shown here) can Also be planned to be added to the camera head  93 . As a probe  90 , for example, a conventional commercial borescope can be used. 
     The invention is not limited to the aforementioned examples, which have only been used for a general description of the invention. Within the scope of legal protection, a device according to this invention can take on other than the above-described forms. In this connection, the device can also include features which constitute a combination of the individual characteristics of the claims. 
     The reference characters in the claims and the drawings serve only for better understanding of the invention and are not to be considered to limit the scope of protection.