Abstract:
A system and method for storing and conveying (e.g. towing) fluids. The system includes a collapsible fluid container with an elongate shape and a first and a second end. A flexible fluid conduit is fixedly attached to the front end of the container. A towing/mooring device is attached to the conduit. A retarder/mooring device is attached to the container second end. The system also includes container retrieval, storage and deployment devices.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of storing and conveying fluids, and more particularly, to an improved system and method for storing and conveying fluids, such as potable water, by means of a collapsible, floating and towable container. Furthermore, this invention relates to methods for filling and/or emptying and retrieving and/or deploying such containers. 
     2. Description of the Related Art 
     Although approximately two thirds of the surface of the Earth is covered by water, many areas and regions around the world are severely affected by the lack of this fundamental natural resource. People living in regions in the Middle East and in Northern Africa are today in need of reliable water supply for nutrition (food and drink), irrigation (agriculture) and sanitation purposes. Also, large areas in Asia, China and the Americas are threatened by lack of water, due to high population density compared to the available local water resources. Furthermore, local water resources in several areas are unfit for human use, due to pollution and contamination. 
     In addition to the aforementioned uneven distribution of water as such, fresh water, i.e. water suitable for e.g. human and animal consumption and sanitary use, is even more scarce on a world wide basis. Only about 3.5% of the Earth&#39;s surface water is fresh water, and almost all of that fresh water is in the form of ice, predominantly in the Arctic and Antarctic regions. According to Philip Ball, author of “H 2 O: A Biography of Water” (Weinfelds and Nicolson, 1999, ISBN 0 297 64314 2), only approximately 0.01% of the Earth&#39;s fresh water is in a form available for human and animal use, in the form of lakes, streams, rivers and groundwater aquifers. However, only half of this amount is directly accessible. Scientists have estimated that the global population presently is using more than half of the accessible fresh water. If the current trends persist, scientists predict, the demand for water on a global basis might exceed the total available supply by around the year 2030. 
     Despite substantial wide efforts to improve fresh water accessibility, including e.g. water management programs and desalination, there is still a need for a redistribution of water supplies. Although solar power will contribute to lowering the cost of desalination, this process is still very energy demanding and thus prohibitively costly for many third world countries. 
     In one type of redistribution effort, water is transported by sea over considerable distances, by means of ocean going tankers and barges. This method is very expensive, however, and can only handle relatively small volumes. One other means of transporting fresh water, which is considerably less expensive, is the use of large bags which are towed in a semi-submersed state, by one or more tugs. Commercial operations using such bags have been established; one example being the ongoing shipment of fresh water from Turkey to Northern Cyprus, undertaken by the applicant for the present invention. 
     As the process of transporting water in floating and towable fabric bags is still fairly new, the associated technology is still not developed to a satisfactory state. Examples of shortcomings with the present water bag technology, are poor fabric rupture control, cumbersome hose pull in- and connection procedures, inadequate towing capabilities and retarding/mooring problems. 
     Prior art water bags have no means for controlling or limiting fabric rupturing. Thus, a tear occurring in prior art bags may very rapidly propagate along a substantial length of the bag, leaving no option for the operator but to discard the bag. Repairing extensive tears is prohibitively costly. 
     Prior art water bags are towed by the connector element, which is attached to the front end of the bag. Thus, the operation of connecting and/or disconnecting prior art water bags to water filling- and/or discharge facilities, involves the launching of a filler/discharge hose from the filling/discharge facility, and performing the connection/disconnection in the sea. This operation is cumbersome, time-consuming, labor demanding and unreliable. 
     Prior art water bags are, while on tow and due to their considerable mass, in certain situations difficult to maneuver and control. This is a particularly crucial problem when the water bag needs to be decelerated and brought to a complete stop prior to connection to the onshore facility. Prior art water bags lack adequate means for retarding prior to connection, and also for adequate mooring during fresh water filling or discharge. 
     It is therefore a long felt need for an improved system for transporting large quantities of water over considerable distances, at affordable costs. 
     The present invention solves that need, in that it provides a system and method for transporting fluids in towable, floating bags, which provides better rupture control, improved handling characteristics and quicker pull in- and connection operation. Additionally, the invention provides novel methods for filling and emptying such water bags in order to ensure that the water bags do not sink to the seabed before, during and after filling. 
     BRIEF SUMMARY OF THE INVENTION 
     These and other objects and features of the invention are provided by an improved system for storing and conveying fluids, where the system is adapted for towing by marine crafts in offshore conditions. In general, the system comprises: 
     a collapsible fluid container with an elongate shape and a first and a second end; 
     a fluid conduit fixedly attached to the front end of the container; 
     towing/mooring means fixedly attached to said conduit; 
     retarder/mooring means attached to said container second end; and 
     container retrieval, storage and deployment means. 
     Furthermore, an improved system and method for towing collapsible, floating, fluid containing containers is provided, where such system for towing comprises a fluid filling and emptying conduit attached to said container first end, and towing means attached to said conduit, and where the method comprising the towing of said container by means of pulling a fluid filling and emptying conduit attached to said container first end. 
     Furthermore, it is provided a method for emptying and retrieving a collapsible fluid container filled with a volume of fresh water, thus: 
     while the conduit is attached to an emptying facility, attaching the container second end to a container retrieval storage and deployment means removeably mountable on a vessel intended for the transportation of said container in an empty state; 
     coordinated with the discharge of said fresh water through said conduit, reeling said container onto said retrieval, storage and deployment means; 
     coordinated with the reeling of said container onto said retrieval, storage and deployment means, propelling said vessel in a direction generally towards said facility; and 
     when said container is sufficiently empty, releasing said hose from said facility, thereby enabling the part of said container and said hose still in the water to be completely retrieved onto said retrieval, storage and deployment means, 
     whereby said method effectively causes virtually said entire volume of fresh water to be emptied from said container. 
     Furthermore, it is provided a method for deploying of, and filling with an volume of fresh water, a collapsible fluid container, thus: 
     pulling the conduit off a container retrieval, storage and deployment means removeably mountable on a vessel intended for the transportation of said container in an empty state; 
     connecting said conduit to a filling facility and commencing a filling of fresh water through said conduit and into said container; 
     coordinated with the filling of said fresh water through said conduit, reeling said container off said retrieval, storage and deployment means; 
     coordinated with the reeling of said container off of said retrieval, storage and deployment means, propelling said vessel in a direction generally away from said facility; and 
     when said container is sufficiently filled with fresh water, releasing said container second end from said retrieval, storage and deployment means. 
     Preferred embodiments are contained within the accompanying claims. 
     Other features, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of a preferred embodiment which follows, when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B is a plan view and a cross sectional view, respectively, of the collapsible fluid container according to an embodiment of the present invention. 
     FIGS. 2A and 2B show the panels in one typical section of a fluid container according to an embodiment of the present invention, FIG. 2A being a perspective view and FIG. 2B being a cross sectional view. 
     FIG. 3 is a plan view of the fluid container of FIG. 1 in a towing configuration, also showing the sections joints, hose and ancillary equipment, according to an embodiment of the present invention. 
     FIGS. 4A and 4B show a typical bag section according to an embodiment of the present invention, FIG. 4A being a perspective view and FIG. 4B being a cross sectional view, where the section is equipped with buoyancy elements. 
     FIGS. 5A and 5B show plan- and cross-sectional views, respectively, of a bag according to embodiment of the present invention, where some of the bag sections are equipped with buoyancy elements. 
     FIGS. 6A and 6B are cross sectional views of the section seam joint of FIG. 3, according to an embodiment of the present invention where FIG. 6A shows a basic joint configuration and FIG. 6B shows a configuration where an additional sealing profile is provided. 
     FIGS. 7A,  7 B and  7 C are cross sectional views of the section rear joint of FIG. 3, according to various embodiments of the present invention. 
     FIG. 8 is a side view of the flexible hose, including the bag junction element, valve and towing gear, according to an embodiment of the present invention. 
     FIG. 9 is a schematic side view of a filling/discharge facility (shown partly), according to embodiment of the present invention. 
     FIG. 10 is a perspective illustration of the aft part of the tug, showing e.g. the bag storage drum and guide frame. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1-10, a preferred embodiment of the system according to the present invention comprises a bag  100  suitable for the storage and transportation of fluids such as potable water. The bag  100  is made up of a number of modules, or sections  110 ,  111 ,  112 ,  113 ,  114 ,  115 ,  116 . For a typical configuration, the total bag length may be around 160 meters, and each of the center sections may be approximately 30 meters long. The bag width in a filled state is approximately 35 meters, and the draft about 7 meters. FIG. 1A is a plan view of the water bag, and displays the general mavicular shape of the bag. FIG. 1B shows a bag cross section. 
     Each section may be comprised of a number of panels ( 1 - 30 ) which are generally rectangular in shape and oriented as shown in FIGS. 2A and 2B. The panels may e.g. be made of a fabric, suitably coated both internally and externally, and be joined as disclosed in International Patent Application Number PCT/NO97/00145 (“A lap joint between fabrics and a method of joining weldable fabrics”, Christensen, et al.). Alternatively, each section may be made as one integral, seamless piece. 
     The bag  100  according to the preferred embodiment, comprises the following sections joined consecutively: A front section  110  joined by a section seam joint  200  to a forward tapered section  111 , a first central section  112 , a second central section  113 , a central third section  114 , a rearward tapered section  115 , and an aft section  116 , terminating the bag at the second end. 
     All of the consecutively joined sections are joined by each one of section seam joints  200 , where the seam string  220  is indicated by the diagonal lines in FIG. 3, the exception being the rearward tapered section  115  and aft section  116 , which may be joined by a number of clamps  300 . Alternatively, the clamps may be replaced by individual pieces of string  220 , which will be described later. 
     In order to preventing the bag from sinking down into the sea after the bag has been emptied of, or before it has been properly filled with, fresh water, the bag sections may be equipped with rectangular buoyancy elements  120  (FIG.  4 ). FIG. 4A is a perspective view, and FIG. 4B a cross sectional view of a bag section comprising pairs of longitudinal plate elements  121 , between which rectangular buoyancy elements  120  are fitted and retained by a string arrangement  122 , For clarity of illustration, the elements are shown in sizes that are larger than the actual sizes. Also, only five elements are shown, while the actual number of elements my be increased or decreased. FIGS. 5A and 5B show plan- and cross sectional views, respectively, of the buoyancy element arrangement described above. 
     Each section seam joint  200 , which is shown in cross section in FIG. 6A, comprises a rope or wire  500  in each abutting section end, where the ropes may be fastened to the respective section edge by the edge being folded back and enclosing the rope, and may be fastened to the section fabric as e.g. disclosed in the aforementioned International Patent Application. Still referring to FIG. 6A, the two sections are joined by a string  220  running through holes in the section fabric and entwining the two ropes  500 . The string pulls the two sections ends together and creates a sealed joint. The string may run around the entire section or, alternatively, be terminated at regular intervals around the section circumference. The holes in the fabric, through which the string runs, may be circumferentially spaced in any suitable fashion. 
     As an alternative, an additional sealing means, a sealing profile  600  may be introduced between the two abutting sections edges, as shown in FIG.  6 B. In order to provide an additional seal, a sealing strip  210 , preferably made of the same material as the sections, is welded to the water bag interior side, completely covering the seam. 
     The section rear joints  300  are provided between the rearward tapered section  15  and the aft section  116 . FIGS. 7A and 7B show these joints as being clamp joints. The clamps act as rear attachment points for retarder- and/or mooring lines  310 . As indicated in FIG. 3, a number of lines  310 , uniformly distributed around the rear of the bag, is preferred in order to distribute the pulling loads as uniformly as possible around the section joint. The lines  310  converge to be attached to tug line  320 , which in turn may be releaseably connected to a tug  900  or a mooring point. 
     FIGS. 7A,  7 B and  7 C are cross sections of the rear joint  300 . As with the section seam joint  200 , the rear joint comprises a rope, wire or webbing  500  in each abutting section end, fastened to each section edge as described above. A sealing profile  600  is interposed between the two abutting sections edges, providing an additional sealing means. The two bag sections are joined by an exterior clamp half  302  and an interior clamp half  303 , held together by any mechanical fastener means  304  (FIGS. 7A,  7 B). The exterior clamp half is provided with a towing ring  301 , to which the aforementioned lines  310  are attached. As an alternative, the clamped connection may be replaced by strings terminated at regular intervals around the bag section circumference (FIG.  7 C). 
     Referring again to FIG. 3, the front section  110  connects to a flexible hose  400 , which—in addition to being used for filling into and discharging fluids from the bag—also possesses the structural integrity sufficient for serving as the towing device. The hose is connected to a valve/connector unit  410 , to which are connected a number (preferably 2) of towing lines  420 . The towing line connects to a tug line  440 , which is connected to the main tug  900  (or other propulsive means) for transportation, or may also be connected to a mooring point. 
     FIG. 8 shows the hose/towing device in better detail. A junction element  450 , comprising an adequate number of escape valves  455 , is connected to the front section  110  by means of a number of clamp assemblies  452 ,  453 ,  454 . Only two are shown. The rope  500 , fastened to the front edge of the front section  110  in a manner described in the foregoing, is received in a circumferential groove  451  on the junction element  450  and sealably fastened by means of the clamp assemblies. Still with reference to FIG. 8, the junction element is connected to the flexible hose  400  by e.g. a conventional flange connection  402 . The hose  400  which may be of any suitable length, comprises preferably an outer wall of a buoyant material, but may also and/or in addition be fitted with buoyancy elements. Only one such element  401  is indicated. 
     The hose is in its front end connected via an e.g. conventional flange connection  403 , to a valve and connector element  410 . This element comprises a valve (e.g. ball valve, butterfly valve, etc.) which serves as the water bag closure device. In addition, the valve/connector element  410  is equipped with a number of towing lines attachment points or towing rings  411 . Referring now to FIG. 9, upon connection to the filling/discharge facility  800 , the hose is pulled by the valve/connector element onto the facility platform, where the element  410 , via a pull-in and connection assembly  810 , is connected to filling/discharge lines. 
     When the water bag has been emptied, the full length of the bag is reeled onto a bag storage drum  910  mounted on the stem part of a vessel (e.g. the tug  900 ), as indicated in FIG.  10 . The bag is reeled onto the drum  910  (by conventional motor means), through the guide frame  911 , by the tug line  320 . The guide frame is positioned relative to the drum or reel such that it serves as a passive alignment device for the vessel during container deployment and retrieval, thus rendering other alignment devices or methods (e.g. use of lateral thrusters) superfluous. 
     When the empty bag is completely stored on the drum, the valve and connector element  410  is hanging off the guide frame as shown in FIG. 10, and the vessel may transport the bag to a filling facility. When the bag is to be filled, it is pulled off the drum by means of the element  410 , as described above, 
     It is thus advantageous to employ the system described above when emptying and retrieving (onto the drum) the water bag. While the bag is attached to an emptying facility and emptying may be in progress, the rear end of the bag is attached (via lines  310 ,  320 ) to the bag storage drum  910 . Coordinated with the discharge of fresh water through the hose, the bag is spooled onto the drum. Simultaneously, the tug will be backing up towards the facility. When the bag is sufficiently empty, the hose is released from the emptying facility and the part of the bag and said hose still in the water are completely retrieved onto the drum. This method ensures that the effectively entire volume of fresh water is emptied from the bag, and it prevents the bag from sinking down into the sea and onto the seabed where the bag may be damaged. 
     A generally reverse procedure is employed when the bag is to be deployed from the drum and refilled with fresh water. Again, an empty bag in the sea is difficult to control and is susceptible to damage as it (e.g.) may sink to the seabed Thus, to ensure a controlled deployment and filling method, the hose is pulled off the drum and connected to the filling facility. As the fresh water makes its way through the hose and into the bag, the bag is reeled off the drum by conventional motor means in a fashion that is coordinated with the fresh water filling. Simultaneously, the tug advances away from the filling facility by the time the bag is sufficiently filled with fresh water, it is fully deployed off the drum and into the sea. The rear attachment lines  310 ,  320  are cast off and the filled bag is floating in the sea. 
     For towing the filled bag to its destination, the connector element  410  is released from the filling facility as described above. A tug  900  connects via lines  440 ,  420  to the connector element  410 . Thus the bag is towed by the tug pulling the flexible hose  400 , which is attached to the bag first end. 
     The foregoing description of an embodiment of the system and method in accordance with the invention, thus illustrates a bag for the storage and/or transportation of fluids, such as e.g. fresh water; where the bag may be towed by means of the flexible filler/discharge hose. The bag is modularized, thus facilitating convenient and quick repair procedures, in that individual sections easily may be replaced. 
     The foregoing description and the embodiments of the present invention are to be construed as mere illustrations of the application of the principles of the invention. The system and methods in accordance with invention are equally applicable to any bag material, coatings, shape, size, volunme, number of sections, number of panels, panel joining means, and section joining means. Also, although the system and methods described in the preferred embodiment primarily is intended for the transport of fresh water, the present invention is equally applicable for any fluid. None of the foregoing is intended to limit the scope of the claims, but the true spirit and scope of present invention is defined by the claims.