Abstract:
A method for preparing a fuel tank for repairs and verifying the repair work using an apparatus is presented. The apparatus is connected to the fuel tank. The fuel tank is purged of oxygen to a certain level using a gas provided by the apparatus until a level of the oxygen in the fuel tank reaches that level. Openings on the fuel tank are closed to the environment. The fuel tank is repaired while the level of oxygen is maintained in the fuel tank. The gas provided by the apparatus pressurizes the fuel tank to a certain pressure level. The pressure level is maintained for a specified period of time. An inspection of the repaired area of the fuel tank is then performed.

Description:
This application claims the benefit of priority from provisional U.S. patent application Ser. No. 60/161,372, filed in the. U.S. Patent and Trademark Office on Oct. 26, 1999, herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     Aspects of the present invention generally relate to a method and apparatus for facilitating the repair of a fuel tank and testing of repair work. More specifically, aspects of the invention relate to a system and related method for preparing a fuel tank for repair by hotwork by rendering the tank non-reactive and testing the repair work upon completion by pressurizing the tank. 
     2. Description of Background Information 
     On occasion, fuel tanks acquire tears, cracks, and holes that require repair. Some repairs require the use of so-called hotwork, i.e., welding. However, when such repair work is to be completed on a fuel tank, there is always concern for the potential of a fire or explosion. 
     In order for a fire or an explosion to occur, three elements are required—an ignition source, fuel, and oxygen. Since welding is necessary to repair the tank, in order to avoid a fire or an explosion, elimination of either an oxygen source or a fuel source during such repair is necessary. 
     In the marine and petroleum industries, welding on tanks containing combustible or flammable substances is sometimes achieved by inerting the tank&#39;s atmosphere. Inertion of a tank involves blowing gas, such as carbon dioxide or nitrogen, into the tank, rendering the tank environment inactive by reducing the oxygen content by replacing it with an inert gas. To verify the repair work, the tank is ventilated and a localized air or fire hose test is performed on the repaired area. In this industry, these methods of testing repair work involve placing a human inside the tank to look for air or water leaking into the tank during such air or fire hose tests. Due to the size of these fuel tanks, it is not practical to test the entire tank. 
     Unlike the marine industry, the common method of repairing a fuel tank using hotwork involves draining the fuel from the tank and steaming the inside of the fuel tank, reducing the fuel hydrocarbon levels to below a lower explosive limit. This renders the tank safe for repair by hotwork. 
     Verifying tank repairs in the locomotive industry also differs from the marine industry. Locomotive fuel tanks are not large enough to place a human within to test repair work. One common method to verify repair work in the industry is to use a standing water test, where the repaired tank is filled with water above the repaired area and the repaired area is inspected externally for any leaking water. 
     In the locomotive industry, as with any industry, there is always an ongoing need to develop new methods and techniques for procedures. Thus, there remains a need in the locomotive industry to develop a method for preparing a tank for hotwork repair and testing the repair work. 
     In addition, each of these processes—preparing a fuel tank for repair by welding and testing the repair work—requires the use of different equipment. Currently, there is no comprehensive equipment capable of performing both of these processes to repair work. Thus, there remains a need for such equipment in the locomotive industry, as well as in other industries. 
     U.S. Pat. No. 3,590,559 (Bragg et al), herein incorporated by reference in its entirety, discloses an inerting system to prevent fires and explosions in fuel tanks by removing dissolved oxygen in the fuel when pressure changes within the fuel tank. 
     U.S. Pat. No. 5,668,308 (Denby), herein incorporated by reference in its entirety, describes a method of detecting leaks in storage tanks by pressurizing the tank and measuring the drop in pressure over a specified time period. Similar U.S. patents exist for testing motor vehicle&#39;s evaporative fuel systems by pressuring the tank and measuring the change in pressure over time. 
     Currently, there remains a need for improved effective methods to prepare a locomotive fuel tank for hotwork repairs and to test the repair work. Also, there is a need for comprehensive equipment that performs both of these functions. In addition, there remains a need for an apparatus and method that allow repairs to be performed and verified back-to-back until the repair is, in fact, complete. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention includes an apparatus for preparing a fuel tank for repairs and verifying repair work upon completion. The apparatus includes a supply system constructed and arranged to be coupled to the fuel tank for providing a supply of inert gas into the fuel tank, for purging the fuel tank of oxygen to a certain level and for making inert the fuel tank with the gas. The supply system includes a gas release system constructed and arranged to provide the supply of inert gas. The supply system further includes an arrangement for connecting and facilitating transport of the inert gas. A supply mechanism is configured and positioned to facilitate and regulate a transfer of gas from the gas release system to the fuel tank. A connector mechanism is for coupling the supply mechanism to the gas release system. A relief system is constructed and arranged to be coupled to the fuel tank to regulate and relieve pressure in the fuel tank. A plurality of connectors is for connecting the apparatus system to the fuel tank. The plurality of connectors include a first of the plurality of connectors constructed and arranged to couple the supply system to the fuel tank, and a second of the plurality of connectors constructed and arranged to couple the relief system to the fuel tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features, and advantages of the present invention are further described in the detailed description that follows, with reference to the following drawings wherein: 
     FIG. 1 is a system diagram of one embodiment of the fuel tank repair apparatus; 
     FIG. 2 is an operational flow diagram corresponding to the method implementing the fuel tank repair apparatus during both repair and testing of the repair work; and 
     FIG. 3 is an operational flow diagram corresponding to the method implementing the fuel tank repair apparatus during the testing of the repair work. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates an embodiment of an apparatus for locomotive tank repair preparation and testing in accordance with the present invention, designated generally by the reference character  10 . As shown, apparatus  10  comprises a supply system, generally indicated at  30 , a relief system, generally indicated at  70 , and a plurality of connectors. 
     In this embodiment, the plurality of connectors comprises two connectors, supply side connector  12  and relief side connector  14 . Supply side connector  12  and relief side connector  14  couple a fuel tank  20  to supply system  30  and relief system  70 , respectively. In the illustrated embodiment, each of supply side connector  12  and relief side connector  14 , is a four-foot length of hose, although other lengths can be used. One end of each hose thereof is connected to a respective fuel filler tank adapter (not shown). The fuel filler tank adapters attached to one end of each of supply side connector  12  and relief side connector  14  connect to fuel fixtures on fuel tank  20 . The other end of each of supply side connector  12  and relief side connector  14  are coupled to passages on the supply system  30  and the relief system  70 , respectively. 
     Supply system  30  comprises a connecting mechanism  36 , a gas release system  40 , and a supply mechanism  50 . Connecting mechanism  36  in the form of a hose couples gas release system  40  to supply mechanism  50 . In the illustrated embodiment, gas release system  40  comprises a gas supply  42  and a gas supply arrangement  44 . To render the fuel tank&#39;s  20  environment safe for repair by hotwork, gas supply  42  is a supply of gas capable of rendering the environment of fuel tank  20  non-reactive. Gas supply  42  in this embodiment includes four full 50-lb. cylinders of nitrogen gas, but may include additional or fewer cylinders of different sizes. While nitrogen gas is used in this embodiment, other gases capable of inerting fuel tank&#39;s  20  environment are also appropriate. 
     Gas supply arrangement  44  includes an arrangement of valves and passages for transporting gas from gas supply  42  to fuel tank  20 . Gas supply arrangement  44 , in the illustrated embodiment, is a four cylinder manifold stand system for attaching four cylinders  42  of nitrogen gas to its four outlets, each cylinder and outlet having its own valve  41 , with a master valve  46 . 
     High pressure regulating mechanism  32  is coupled to gas supply arrangement  44  and high pressure relief mechanism  34 . High pressure regulating mechanism  32  regulates the flow of gas passing from gas supply arrangement  44  to supply mechanism  50 . High pressure relief mechanism  34  relieves pressure in supply system  30  if the pressure exceeds a particular level. In the illustrated embodiment, high pressure regulating mechanism  32  and high pressure relief mechanism  34  are a high pressure regulator and a high pressure relief valve set for 200 psi, respectively. 
     Supply mechanism  50  is coupled to high pressure regulating mechanism  32  with high pressure relief mechanism  34 . In the illustrated embodiment, the coupling of these elements is achieved using a length of hose, such as a 15-foot long air duct hose. 
     In the illustrated embodiment, supply mechanism  50  comprises an arrangement of a plurality of flow control mechanisms, a plurality of passages, a supply side pressure regulating mechanism  52 , a supply side pressure measuring mechanism  54 , and a flow meter valve  56 , as shown in FIG.  1 . In the illustrated embodiment, the plurality of flow control mechanisms comprises nine valves  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 , and  29 . Supply side pressure regulating mechanism  52  is a low pressure regulator. Supply side pressure measuring mechanism  54  measures the gas pressure entering fuel tank  20 . In this embodiment, supply side measuring mechanism  54  is a pressure gauge and is considered the primary gauge. 
     In the illustrated embodiment, the plurality of passages comprises three passages  61 ,  62 , and  63 . The plurality of passages may include an arrangement of pipes, hoses, and structures that facilitate the transfer of gas to fuel tank  20 . Passage  61  is coupled to high pressure relief mechanism  34 , and to supply side connector  12 . Passage  62  is coupled to passage  61  such that gas may flow between passage  61  and passage  62 . In a similar manner, ends of passage  63  are coupled to passage  61 . 
     As shown in FIG. 1, valves  22 ,  23 ,  24 ,  25 , and  27  are connected in a serial configuration along passage  61 . Pressure regulating mechanism  52  is also coupled to passage  61 , interposed between valves  62  and  63 . In this embodiment, a first end of passage  62  is connected to passage  61  between valve  22  and the end of passage  61  coupled to connecting mechanism  36 . A second end of passage  62  is connected to passage  61 , interposed between valves  23  and  24 . Pressure measuring mechanism  54  is also coupled to passage  61  between valves  25  and  27 , wherein valve  26  is coupled to pressure measuring mechanism  54  in such a way that valve  26  can regulate a flow of gas to pressure measuring mechanism  54 . Passage  63  is coupled to passage  61 , wherein a first end is interposed between pressure measuring mechanism  54  and valve  27  and a second end is interposed between valve  27  and an end of passage  61  attached to connector  12 . 
     Valve  21  is coupled to passage  62 . Flow meter valve  56  is coupled to passage  63 . On each side of flow meter valve  56 , valves  28  and  29  are coupled to passage  63 . 
     Valves  21  along with passage  62  can prevent the movement of gas through passage  61  by being used as a bypass line around pressure regulating mechanism  52  in the illustrated embodiment. The use of this bypass feature is required during the purging process to permit flow meter valve  56  to operate at its design supply pressure. Valves  22  and  23  may be operated to isolate pressure regulating mechanism  52  from the flow of gas. Valve  26  can isolate pressure measuring mechanism  54 . Valve  27  may be operated to ensure that the flow of gas travels through passage  63  and past flow meter valve  56 . Meanwhile, valves  28  and  29  may be operated to isolate flow meter valve  56 . 
     Relief system  70  comprises a pressure measuring mechanism  72 , a plurality of pressure relief mechanisms  74 , a flow control mechanism  76 , and passage  64 . Pressure measuring mechanism  72  measures the gas pressure leaving fuel tank  20 . In the illustrated embodiment, pressure measuring mechanism  72  is a pressure gauge. In the illustrated embodiment, pressure measuring mechanism  72  is a secondary pressure measuring device. Pressure relief mechanism  74  comprises two low pressure relief valve in this embodiment, although more or less than two low pressure relief valves may be used. Pressure relief mechanism  74  relieves pressure in relief system  70  from fuel tank  20 . It is recommended that each of pressure relief mechanism  74  be capable of relieving the full capacity of apparatus  10 . Flow control mechanism  76  is a single valve  80  in this embodiment. Flow control mechanism  76  may comprise other valve or flow control configurations appropriate for controlling the pressure in fuel tank  20 . Valve  80  can be operated to prevent the release of gas through passage  64  and assist apparatus  10  with pressurizing fuel tank  20 . 
     Passage  64 , in this embodiment, may include an arrangement of pipes, hoses and structures that facilitate the movement of gas from fuel tank  20 . In the illustrated embodiment, one end of passage  64  is coupled to a hose end of connector  14 . In this embodiment, pressure measuring mechanism  72 , pressure relief means  74 , and flow control mechanism  76  are coupled to passage  64  in a serial configuration wherein pressure measuring mechanism  72  is closest to the end of passage  64  connected to connector  14 . 
     FIG. 2 generally depicts one embodiment of the method that prepares a tank for repair by hotwork and tests the repair work upon completion. This method is particularly applicable to fuel tank repair work involving small holes and cracks. However, this method can repair long tears and splits. When using this method, the remaining fuel in fuel tank  20  need not be drained prior to repair by hotwork. 
     In a first act A 1 , apparatus  10  is connected, via connectors  12  and  14 , to fuel tank  20 , which requires hotwork repair. In a second act A 2 , apparatus  10  purges the oxygen and inerts the environment of fuel tank  20 , rendering the environment non-reactive by entering nitrogen gas into fuel tank  20 . The fuel tank vents and/or fuel return lines must be blocked by appropriate means before inerting the environment of fuel tank  20 . In the illustrated embodiment, pipe plugs, cover plates, or a combination thereof, are used to close off the fuel tank vents and return lines on fuel tank  20 . Other appropriate materials for closing off the vents and fuel return lines to fuel tank  20  include a blanking plate and duct tape. Valve  80  is in an open position to allow the flow of gas to pass through supply system  30  and fuel tank  20  and out passage  64 . 
     To complete act A 2 , the valve to one bottle of gas supply  42  attached to gas release system  40  and the corresponding valve on gas release system  40  are opened. Master valve  46  is then opened. The valve to high pressure regulating mechanism  32  is adjusted until the outlet pressure reads between 50-80 psig. Valves  22 ,  24 ,  25  and  27  are opened along passage  61 . Valve  23  is then slowly opened. Valve  26  is opened to measure the flow of gas to fuel tank  20 . This process inerts the environment of fuel tank  20  with inert gas supply  42  and purges oxygen from the same. 
     Once the oxygen content in the gas escaping from valve  80  measures less than six percent, valve  80  is closed during the remainder of the inertion and purging process. Oxygen content levels are measured using oxygen detecting devices; such as a cannonball gas detector. Oxygen levels within fuel tank  20  are also measured at the drain holes. The drain holes are closed after the oxygen content of the escaping gas is below six percent. 
     In some instances, a hole is drilled into fuel tank  20  above the remaining fuel line to assist with monitoring of oxygen levels. In the illustrated embodiment, a cannonball probe is fed through the drilled hole to measure the oxygen content of the environment of fuel tank  20 . In these instances, the oxygen content measured at this hole must also register below six percent before hotwork repair may begin. 
     Once the oxygen levels at all gas escape points measure below six percent, valves  24 ,  26 , and  27  are closed. Meanwhile, valves  21 ,  28 , and  29  are opened. Valve  24  is then opened allowing inert gas to pass through passage  61  and past flow meter valve  56 . In the illustrated embodiment, flow meter valve  56  is set to 80 Standard Cubic Feet/hour (SCFH). The flow of gas from inert gas supply  42  should be reduced to between 80 and 40 SCFH on flow meter valve  56 . This completes act A 2 . 
     Purged of most oxygen and inerted by gas supply  42 , fuel tank  20  is ready for repair work by hotwork. Such repair work is conducted by conventional methods in a next act A 3 . It is recommended that gas flow from gas supply  42  should be kept at a minimum, but at a level sufficient to maintain the inert and purged environment of fuel tank  20 . In the illustrated embodiment, tank pressure in fuel tank  20  is maintained at 0.0 to 0.4 psig using flow meter valve  56 . For purposes of safety, it is also recommended that the oxygen content nearest the repair site be tested periodically during the repair to ensure the oxygen level remains below six percent. 
     Upon completion of the repair work in act A 3 , fuel tank  20  is pressurized to test the repair work in a next act A 4 . Act A 4  also involves preparing to pressurize fuel tank  20  by adjusting the appropriate flow control mechanisms. In the illustrated embodiment, valves  21  and  25  are closed. If a hole was drilled in fuel tank  20  above the fuel line during act A 2 , this hole is also closed. In the illustrated embodiment, the drilled hole is closed using a threaded plug inserted into a spud fitting welded to the top of fuel tank  20 . Valves  23 ,  28 , and  29  are also closed. Valves  24 ,  25 , and  27  are then opened. Next, valves  23  and  26  are slowly opened. To complete the preparation for pressurizing fuel tank  20 , valve  80  is closed. 
     Upon closing valve  80 , fuel tank  20  is being pressurized. In the illustrated embodiment, fuel tank  20  is pressurized to between 1.8 and 2.0 psig and held at this pressure for at least ten minutes before testing the repair work. To assist in regulating the pressure in fuel tank  20 , valve  24  is adjusted appropriately. 
     Once fuel tank  20  reaches and maintains the appropriate pressure level, personnel can verify the tank repairs by testing the repair work in a next act A 5 . In the illustrated embodiment, the inspector of the repair work conducts a visual and audible inspection. The visual inspection involves the use of a “snoop” or equivalent soap bubble solution to wet the repaired area, wherein the inspector would look for bubbles that indicate a leak in the repaired area. During an audible inspection, the inspector checks for leaking gas using the back of his or her hand. Other appropriate conventional inspection methods may be used to verify the repair work. 
     If a leak is found during act A 5 , corrective repair work can immediately follow in a further act A 5   a  upon closing valves  25  and  26  and opening valve  80 . When the corrective repair work is complete, valves  25  and  26  are reopened and valve  80  is closed to repressurize fuel tank  20 , as described in act A 4 . The corrective repair work can be tested in an appropriate manner, such as those methods suggested in act A 5 . This corrective repair process can be repeated iteratively until the repair work is complete. An advantage to this method is the repeated ability to verify repair work and immediately take corrective action, if necessary, until the repair is complete. 
     In a next act A 6 , repaired fuel tank  20  is vented, allowing the gas to escape from fuel tank  20 . In the illustrated embodiment, valve  24  is slowly closed and valve  80  is opened. Valves to the bottles of gas supply  42  are then closed; valves  21 ,  22 ,  23 ,  24 ,  25 ,  27 , and  80  are open; valves  26 ,  28 , and  29  are closed; high pressure regulating mechanism  32  is set for 50 psig; and pressure regulating mechanism  52  is set to 2-3 psig. After apparatus  10  is appropriately adjusted, the fuel tank plugs and tank vent cover are removed. Then, apparatus  10  may be disconnected from fuel tank  20 , and fuel tank  20  is assembled appropriately for normal use. 
     A user of the above described method may also opt to implement only one aspect of the invention, namely the preparation of fuel tank  20  for repair by hotwork or testing of repair work. FIG. 3 generally depicts one embodiment of a user employing apparatus  80  and the method for testing repair work. In a first act B 1 , fuel tank  20  is repaired by conventional methods, such as draining the remaining fuel and steaming fuel tank  20  to reduce hydrocarbon levels in fuel tank  20  to less than the lower explosive limit. In a second act B 2 , apparatus  10  is attached to repaired fuel tank  20  as in act A 1  in FIG.  2 . With apparatus  10  connected to repaired fuel tank  20 , repaired fuel tank  20  is pressurized in a next act B 3 , in a manner in accordance with act A 4 . In a next act B 3 , the repair work on fuel tank  20  is tested in the same manner as act A 5 . If a leak is found, corrective repair work may be undertaken immediately and retested in act B 4   a , as described above in act A 5   a . Upon completion of the repair and verification of the repair work, apparatus  80  should be disconnected in act B 5  in the same manner as set forth above in act A 6  above. 
     While the detailed description relates to a locomotive fuel tank repair work, the present invention is relevant to all fuel tank repair work. While the invention has been described by way of an example embodiment, it is understood that the words that have been used herein are words of description, rather than words of limitation. Changes may be made, within the purview of the appended claims, without departing from the scope and spirit of the invention in its broader aspects. Although the invention has been described herein with reference to particular structures, materials, and embodiments, it is understood that the invention is not limited to the particulars disclosed. The invention extends to all equivalent structures, mechanisms, acts and uses, as are within the scope of the appended claims.