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Title: Flexible marine transport tank
Description: Description:
The present invention relates to a flexible marine transport tank. It is known to use for the transport of liquids, especially oil and fuels, flexible tanks consisting of a single element of revolution. These tanks have not possessed the stability and navigability characteristics desirable for increasing their employment. Also known are marine transport devices which comprise a plurality of flexible containers connected by elastic members and which are held immersed by means of a ballast system. Furthermore, devices are known which comprise a plurality of flexible containers for transporting liquids and which are connected fore and aft by a rigid body of hydrodynamic shape. However, because these devices are immersed or connected by rigid elements they do not permit satisfactory navigability or an acceptably efficient use of the tractive power required. According to the present invention there is provided a flexible marine tank for transport afloat, comprising at least two flexible elements of revolution longitudinally connected by flexible linking means, and means for maintaining an internal pressurisation within the elements during the various phases of utilisation thereof in order to maintain the geometric shape of the elements. The bi-lobed or multi-lobed structure of such a tank has satisfactory stability to rolling and for a given applied traction it has a minimum of drag while permitting accommodation of the disturbing forces caused by swell, and more particularly it tends to reduce the drag compared to what it would be for a similar sized tank of rigid geometry. The turning stability can be ensured by an underwater keel. Since the containers in use are always under pressure the geometry of the assembly is, however, virtually maintained. The tank may be towed or it may be self-propelling. By virtue of its very constitution the tank may be stored when empty, deflated and folded to a minimum volume, which is advantageous for maintenance, shipment and eventual letting out at the location of utilisation. Preferably the tank is provided with a settling arrangement which makes it possible to separate immiscible liquid phases of different densities during a filling operation. This feature is the more interesting since such separating means are useful for separating liquid having its origin in a pollution of water, especially by crude oil. This settling or separating arrangement also enables ballasting of the tank to be ensured, for example when it is to be floatingly conveyed in empty state, and facilitates post-utilisation cleaning operations by internal circulation of detergents. The invention will be better understood when reading the following description of several exemplary embodiments referring to the accompanying drawings, in which:- FIG. 1 is a plan view of a tank according to the invention; FIGS. 1a and 2 are elevational views of the same tank in floating position; FIG. 3 is a view in section of the tank, taken along line III--III of FIG. 1; FIG. 4 is a view similar to FIG. 3 of an alternative form of tank the flexible elements of which communicate with one another; FIG. 5 is a view in section similar to FIG. 3 of an alternative form of tank the separate flexible elements of which are linked by an intermediate member; FIG. 6 is a sectional detail view showing a flexible mode of linking a pair of coupled flexible elements; and FIG. 7 is a view in section taken along line VII--VII of FIG. 6. FIGS. 1, 2 and 3 show a tank according to the invention which comprises two flexible elements of revolution 1 and 1a each of which consists of a cylindrical portion 2 extended at either end by conical portions 4 and 5. The fore and aft conical portions 4 and 5 will preferably be identical for reasons of ease of manufacture. However the conical portions 4 and 5 may be so arranged, as shown, that one of the generatrices 6 and 8 of each portion respectively is perpendicular to the circular base of the oblique cone. It is thus possible to assemble these conical portions to the cylindrical bodies 2 of the reservoirs in such manner that, both fore and aft, the conical end portions provide desirable dynamic effects when the apparatus is moved through the liquid medium. More particularly, referring to the drawings, the planes of symmetry of the oblique cones 4 and 5 are vertical at the front and horizontal at the rear. Each element 1, 1a of the tank is divided into three compartments 44, 41, 42 by watertight bulkheads 45, 45a (FIG. 1a) so as to create a longitudinal compartmenting which imparts to the tank good floatation stability to pitching when the tank is only partly filled with liquid. The compartments 41 and 42 which may be limited to the conical portions 4 and 5 are inflated with a gas which represents a permanent buoyancy reserve, while the central compartment 44, which is also pressurised, is a reservoir intended to receive liquid 43 which may fill or partly fill the compartment 44 to any level as required without affecting to too large an extent the floatability stability to pitching. The walls of the elements are made of a resilient material, for example a fabric coated with elastomer. The elements maintain their geometry by virtue of the internal pressurisation kept up during the various phases of utilisation. To this end each element has an inflation orifice 9, 9a connected by a duct 39, 39a to a compressed air supply conduit 40. A calibrated pressure relief valve 10 is disposed on the conduit 40. The conical portions 4, 4a situated at the front of the tank are linked by a rigid bar 11 and each comprise an eyelet 12, 12a in which a sling 13, 13a is engaged. In the event of the tank being towed the slings 13, 13a are connected to a traction cable 14. At the rear of the tank there is provided a deck 15 capable of receiving a propulsion motor assembly, a pumping motor assembly for filling and emptying the tank and a compression motor assembly for maintaining the pressurisation. None of these assemblies is shown in the drawings. The stern deck 15 may also form a support element when the tank is being pushed rather than towed. Furthermore, this deck carries a support 16 to which the filling lines 17 and emptying lines 18 and an underwater keel 46 are secured. The filling line 17 is connected to two ducts 19, 19a directly opening via an orifice 20 into the flexible elements 1, 1a. The discharge line 18 on the other hand is connected to two ducts 21, 21a which are extended by a dip pipe 22 opening at its lower portion into a sump 23 adapted to the lower portion of each flexible element 1, 1a and capable of forming a bilge-keel for stabilising the assembly. For conveying in empty state the elements 1, 1a of the tank are inflated with air although in the event of strong winds they may be ballasted with water in order that the tank will float lower in the water. Furthermore, there is provided in the filling line at least one closure valve 24 and in the emptying line 18 at least one closure valve 25 (FIGS. 1 and 2). For filling the tank with a liquid, for example crude oil or a mixture of water and crude oil, the valve 24 is open so as to permit the entry via the ducts 19, 19a of the liquid. The air expelled by the arrival of the liquid escapes via the excess pressure valve 10. Where a mixture is admitted the valve 25 can be opened to allow the lower layer of water which settles to the bottom of the tank beneath the oil to escape under the effect of the pressurisation via the dip pipes 22; which makes it possible to evacuate the water to the exterior via the line 18. At the end of filling when the crude oil begins to be discharged via the line 18 the valve 25 is closed. For emptying the tank the valve 24 is closed and the valve 25 is opened, the crude oil is pumped via the tubing 18, the sump 23 and the dip pipe 22, the provision of the sump reducing to a minimum the amount of liquid left in the tank. The shape and the buoyancy of the tank are maintained by feeding air into the elements by means of the orifice 9 at the same time as the liquid is removed. FIG. 4 shows a further embodiment of the tank wherein the flexible elements 26, 26a are interconnected by a wall 27 having orifices 28 which permit communication between the two enclosures. Finally, according to a further embodiment shown in FIG. 5 the tank comprises two flexible elements 29, 29a which are linked by at least one intermediate member 30 which may be rigid. In FIGS. 6 and 7 there is shown a special mode of linking the two elements 1, 1a of the tank when they are coupled as in FIGS. 1, 2 and 3. For this purpose hoops 31a and b are respectively attached to the elements 1, 1a and have loops 32 in which are engaged rods 33 integral with the hoops and engaged in plates 34, 35 held together by a bolt 36; the said plates being separated by an elastic sleeve 37 having fins 38 disposed between the elements 1, 1a and the hoops 31a, 31b. A plurality of these linking assemblies are distributed along the length of the tank. Although only two flexible elements have been shown to form the tank, it is evident that a much larger number of elements may be used. Other info: Inventors: Grihangne, Andre (Paris, FR) Application Number: 420315 Filing Date: 1973-11-29 Publication_date: 1976-04-27 Assignee: Ste Superflexit (Courbevoie, FR) Primary Class(es): 114/74T Other Classes: US Patent Ref:
Other Refs:
Primary Examiner: Blix, Trygve M. Assistant Examiner: Goldstein, Stuart M. Attorney: Stevens, Davis, Miller & Mosher |
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