Patent Publication Number: US-6209474-B1

Title: Transporter for heavy objects at sea

Description:
This application is the National phase under 35 U.S.C. § 371 of PCT International Application No. PCT/NO97/00344 which has an International filing date of Dec. 17, 1997 
    
    
     FIELD OF THE INVENTION 
     The invention concerns a transporter for heavy objects at sea, comprising an oblong structure with a U-shaped cross section and a prismatic enveloping surface, comprising two long sides, an intermediate underside, an opposite open top side and two short sides. 
     DESCRIPTION OF THE BACKGROUND ART 
     Heavy objects, such as platform decks, platform jackets and bridge elements are transported by sea on ships or barges. The object is transferred from and to the ship or the barge by hoisting cranes, the object being pushed or pulled, or by means of rolling transport where wheels or rollers are employed. 
     Another known method is to transfer objects by ballasting the ship or the barge and moving it into a passage under the object, whereupon the ship or the barge is deballasted, thus causing it to be raised and leaving the object lying on the ship or the barge. The object may be unloaded in a similar manner by deballasting the ship or the barge, thus causing it to be lowered, with the object supported by lower-lying supports on the side of the ship or the barge. 
     These known methods of transporting heavy objects at sea work well as long as the object does not require to be turned, and as long as the level differences which have to be obtained by the ballasting/deballasting are relatively small. When using a ship or a barge, however, it is not possible to turn an object, such as a mast or a platform jacket, which is so large that it has to be transported horizontally, but which has to be turned into a vertical position before being installed in position. 
     U.S. Pat. No. 5,111,764 describes a method for recovering the substructure of an offshore platform. A floating barge is used comprising a ballastable hull having a deck suitable for receiving the substructure in a substantially horizontal position and including ballastable floats disposed above the deck to right and to left of the intended location for the substructure. The hull and the floats are ballasted so that although it does not sink, the barge moves down into the water and tilts into a position where its deck can be moved against one of the faces of the substructure. The barge is fixed to the substructure, the substructure is disconnected from the sea bed, ballast is removed from the barge to return it to a position where it is floating and carrying the substructure, and the barge is moved to the desired location for unloading the substructure. The invention is applicable to recovering substructures of large dimensions. With the method and barge according to U.S. Pat. No. 5,111,764 it is thereby possible to a certain extent to transport heavy objects at sea, and to turn the object in the water. The degree of attachment and rotational movement which are achieved, however, are limited to the attachment and rotation. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a transporter which compared with known devices for transport of heavy objects at sea has greater possibilities for securing the object, and which also has greater possibilities for turning the object in the water. 
     The object is further to provide a transporter which will also be able to be used for installation or removal of a deck on and from a platform jacket respectively, and installation or removal of a platform jacket on and from the seabed respectively. 
     The latter object is achieved with a transporter of the type mentioned in the introduction, which, is also characterized by the features which are stated in the claims in the applicant&#39;s copending Norwegian patent applications Nos. 973561 and 973562. 
     The invention therefore includes in a transporter for heavy objects at sea, comprising an oblong structure with a U-shaped cross section and a prismatic enveloping surface, comprising two long sides, an intermediate underside, an opposite open top side and two short sides. In the invention ballasting chambers are arranged in each of the structure&#39;s 8 corners which are formed by the points of intersection between the long sides, the undersides, the open top side and the short sides, whereby the structure can be rotated by means of ballasting into a desired position in the water. Moreover, the transporter is provided with attachment means for securing objects which have to be transported. 
     The ballasting and deballasting are performed in the known manner by pumping water in and out of the ballasting chambers by means of pumps, piping and valves. When the structure is rotated, those ballasting chambers which have to be moved downwards during rotation and after rotation will be located at the bottom are ballasted, while at the same time those ballasting chambers which have to be moved upwards during rotation and after rotation will be located at the top are deballasted. A computer calculates which ballasting chambers have to be ballasted and deballasted in order to achieve the desired rotation and final position of the transporter in the water, while simultaneously calculating the metacentric height and monitoring the progress of the ballasting/deballasting and the rotation. The computer communicates with an operator, who in turn gives orders concerning the execution of the necessary ballasting and deballasting. In this context the information on the metacentric height is very important, since a stable rotation of the transporter, without sudden movements, is dependent on the maintenance of a constant positive metacentric height. 
     The actual movement of the transporter will be conducted by tugs. 
     The transporter&#39;s ballasting chambers are preferably provided in longitudinal pontoons in the corner areas between the transporter&#39;s underside and long sides, and at the top of the long sides. The result is a structure which offers little resistance to movement in the water, and which is consequently suited for transport. 
     In a preferred embodiment the transporter has attachment means for securing objects, for example in the form of brackets or beams attached to the pontoons. 
     The above and further preferred embodiments of the invention will be seen in the detailed description. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be explained in more detail in association with a description of specific embodiments, and with reference to the drawings which are given by way of illustration only, and thus are not limitative of the present invention, and, in which: 
     FIG. 1 is a perspective view of a transporter according to the invention, 
     FIG. 2 illustrates the transporter in FIG. 1 viewed from a short side, 
     FIG. 3 is a perspective view of a second transporter according to the invention, 
     FIG. 4 illustrates a transporter according to the invention, viewed from the side, 
     FIG. 5 illustrates a tansporter according to the invention in use during a lifting/transport operation at sea, and 
     FIGS. 6 a-h  illustrate a sequence in which the transporter in FIG. 4 is used to install a bridge element. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2 elucidate the core of the invention. FIG. 1 illustrates a transporter according to the invention in perspective, and FIG. 2 illustrates the transporter viewed from a short side, in the direction shown by the arrow P in FIG.  1 . The transporter in FIGS. 1 and 2 consists of two long sides  2  and an intermediate underside  3 , which together form an oblong structure with a U-shaped cross section. The three sides which form the U-shaped cross section together with an open top side  4 , which is located opposite the underside  3 , and two short sides  23 , form a body with a prismatic enveloping surface. 
     Thus in the illustrated embodiments, the top side  4  and the short sides  23  are only imaginary surfaces or sides. Nor are the long sides  2  and the underside  3  real surfaces, and should be understood as planes which contain structural elements which constitute the transporter according to the invention. 
     The ballasting chambers  5  are provided in pontoons  6  in each of the transporter&#39;s 8 corners, i.e. the 8 corners which are formed by the points of intersection between the surfaces or the sides which form the prismatic enveloping surface. More correct, each of these 8 corners is defined by the intersection between three edgelines which in turn are intersecting lines between adjacent planes or sides in the prismatic body. A structure is thereby formed in which the ballasting chambers  5  are arranged in all the extremities, thereby permitting ballast or buoyancy to be brought to all these extremities. 
     The transporter in FIGS. 1 and 2 further consists of transverse connecting elements  7  and longitudinal connecting elements  13  which bind the pontoons  6  together. In addition, not shown, the transporter comprises piping, valves, pumps with motors and control equipment for performing the ballasting/deballasting. The ballasting/deballasting is remotely controlled by means of not shown communication equipment. Alternatively, the ballasting/deballasting may be performed with an umbilical which contains both pressurised water for ballasting and pressurised air for deballasting, together with pressurised fluid for operation and control of the valves. 
     By ballasting or deballasting the various ballasting chambers  5  it is possible to rotate the transporter in FIGS. 1 and 2 into any desired position in the water. Calculations and tests confirm this property of the transporter. 
     FIG. 3 illustrates a transporter which like the transporter in FIGS. 1 and 2 consists of two long sides  2  and an intermediate underside  3  which together form an oblong structure with a U-shaped cross section. Lower longitudinal pontoons  9  are arranged in the longitudinal corner areas between the underside  3  and the long sides  2 , and upper longitudinal pontoons  8  are arranged in the upper section of the long sides  2 , between the long sides and the imaginary top side. At each end of the longitudinal pontoons  8  and  9  there are arranged ballasting chambers, which are located in one of the corners in the imaginary prismatic enveloping surface around the transporter. In the same way as in FIGS. 1 and 2 the transporter in FIG. 3 forms a structure in which each of the extremities can be ballasted or deballasted, thus making it possible for the structure to be rotated into any desired position in the water. 
     In the embodiment in FIG. 3 the longitudinal pontoons  8 ,  9  extend in the entire transporter&#39;s longitudinal direction. The ballasting chambers in the transporter&#39;s corners may extend from the end of the longitudinal pontoons all the way into the area in the middle of the pontoon, but each pontoon is preferably divided into several chambers. This division into several chambers is performed both in order to achieve a simpler control of the ballasting/deballasting, and to increase the structure&#39;s stability in the event of a functional fault or damage to the structure which results in an uncontrolled ballasting or deballasting. 
     The longitudinal pontoons are preferably composed of tubes or have a tubular cross section, since this is advantageous both with regard to manufacture, internal volume and resistance to internal and external pressure. 
     Like the transporter illustrated in FIGS. 1 and 2 the transporter illustrated in FIG. 3 has transverse connecting elements  7  provided in the long sides  2  and the underside  3 , in order to bind the longitudinal pontoons together. These transverse connecting elements are preferably also composed of ballastable pontoons or tubes, thus enabling them to contribute to the ballasting/deballasting of the transporter. 
     During transport of the transporter, which is conducted by tugs, it is advantageous to deballast the transporter, so that it offers least possible resistance to motion. In most cases this means that it is advantageous to place the transporter in a position where it is lying with the underside  3  down, as high as possible in the water. 
     In order to increase the capacity during ballasting/deballasting, and to provide an area for placing objects which are to be transported, the transporter in FIG. 3 comprises two longitudinal pontoons  24  arranged in the transporter&#39;s underside  3 . In a preferred embodiment, as shown in FIG. 3, these two longitudinal pontoons together with their respective transverse connecting elements  7  are, compared to the surface forming the underside  3 , located closer to the transporter&#39;s central area. This placing of the longitudinal pontoons  24  and the respective transverse connecting elements  7  has the effect that they are at least partly located above the water when the transporter is lying deballasted in the water with the underside down, with the result that during transport they offer little or no resistance to the movement in the water. 
     The object which are to be transported can be placed in different locations on the transporter, especially on the underside  3  or the upper longitudinal pontoons  8 . In order to obtain easy access for inserting objects which have to be transported to the area above the underside  3 , the transporter&#39;s short sides are open. This is most clearly illustrated in FIG. 2, where the short side is indicated by reference numeral  23 . 
     In order to secure objects which are to be transported the transporter illustrated in FIG. 3 has attachment means in the form of beams  10  on the longitudinal pontoons in the transporter&#39;s underside, beams  20  on the upper longitudinal pontoons, and beams  21  on the lower longitudinal pontoons. The beams  10 ,  20 ,  21  may be provided with boltholes for attaching the object by bolting, eyes or lugs for attaching the objects by wives, or other appropriate attachment means. 
     In order to increase the transporter&#39;s usefulness, in the embodiment illustrated in FIG. 3 it has at one end a recess  11 , formed due to the fact that the undersides  3  in the longitudinal direction have a shorter extension than the long sides  2 . When the transporter is lying in the water with the underside  3  down, the long sides  2  can thereby be moved on the outside of a support for an object which has to be transferred to the transporter. This will be discussed below in more detail with reference to FIG.  5 . 
     Furthermore, in the transporter illustrated in FIG. 3 the lower longitudinal pontoons  9  are longer than the upper longitudinal pontoons  8  at the end in which the recess is located, with the result that the lower longitudinal pontoons have portions or sections  12  which in the longitudinal direction project past the underside  3  and the long sides  2 . The lower longitudinal pontoons&#39; outwardly projecting sections  12  contribute to keeping the transporter horizontal when it is lying in the water with the underside down, a ballasting or deballasting or these outwardly projecting sections providing a moment which can counteract the effect of the weight of an object which is placed on the underside  3  or the upper longitudinal pontoons  8 . 
     FIG. 4 illustrates a transporter according to the invention viewed from the side, located in the water  18 . This illustrates how an object  14  can be placed on the upper longitudinal pontoons  8  in an area which in the transporter&#39;s longitudinal direction is located opposite the outwardly projecting sections  12  of the lower longitudinal pontoons  9 . This placing of the object  14  will attempt to turn the transporter, thus raising the end where the outwardly projecting sections  12  are located. In order to counteract this the outwardly projecting sections  12  can be ballasted. Similarly, a placing of an object  15  at the end of the transporter where the outwardly projecting sections  12  are located will attempt to turn this end down into the water  18 , which can be counteracted by a deballasting of the outwardly projecting sections  12 . 
     FIG. 5 illustrates a transporter according to the invention in use during a lifting/transport operation at sea. Here the transporter is lying with the lower pontoons  9  under the water  18 , and the long sides have been moved on to the outside of a platform jacket  17  which is standing on the seabed  19 . The platform jacket is located in the recess  11  in the underside  3 , which is not shown, since the underside is located down in the water. Attachment means in the form of supporting sections on the transporter&#39;s long side have been brought into abutment against a platform deck  16  which rests on the jacket  17 . When the transporter is deballasted it will be raised in the water, thereby enabling the deck  16  to be lifted from the jacket  17 , and taken away by means of the transporter. 
     FIGS. 6 a-h  illustrate a sequence in which the transporter in FIG. 4 is used to transport and install a bridge element. In FIG. 6 a  a transporter  1  is lying horizontally in the water  18 , beside a bridge element  30 . The bridge element  30  is resting on two supports  31 , a front support and a rear support indicated by dotted lines. It should be understood that the rear support is located behind the front support, and that the bridge element  30  in the direction perpendicular to the transporter&#39;s longitudinal direction has an extension which is larger than the transporter&#39;s width. Further, between the supports  31  there is a recess which is sufficiently wide and deep to contain the transporter  1 . 
     FIG. 6 b  illustrates the transporter in a position where it is so ballasted that it has sunk down in the water under the bridge element  30 , and is partially rotated into a position where it can lift the bridge element. 
     FIG. 6 c  illustrates the transporter in a vertical position, where it has lifted the bridge element off the supports, so that the bridge element is resting on the outwardly projecting sections  12  of the lower pontoons  9  and a cross element  7 . 
     FIGS. 6 d  and  6   e  illustrate the transporter with the bridge element during and after rotation to a horizontal position in the water respectively, for transport to a destination. 
     FIG. 6 f  illustrates the transporter during rotation to a vertical position after arrival at the destination, and 
     FIG. 6 g  shows the transporter in a vertical position, raised to the correct height for transfer of the bridge element. 
     FIG. 6 h  illustrates the bridge element transferred from the transporter, as it should be understood that the bridge element is attached to not shown adjacent bridge elements or bridge foundations. After the transfer the transporter is lowered into the water and removed. 
     Compared to the introductory known device, represented by Norwegian patent application No. 91 0358, the transporter according to the invention therefore provides greater possibilities for securing the object, and greater possibilities for turning the object in the water. Thus the transporter according to the invention fulfils the object of the invention. 
     Further advantageous embodiments and applications of the transporter, associated with removal of a platform deck from a jacket, and removal of a jacket from the seabed, are illustrated and described in the applicant&#39;s copending Norwegian patent applications Nos. 973561 and 973562. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.