Abstract:
An insertion shoe for retrofitting an undersea pipeline to permit passage therethrough of a scraper includes a plate sized to cover an opening in a branch connection of the pipeline and an inner surface structured to match the inner surface surrounding the opening. The insertion shoe can be installed in the branch connection to protect the opening without lifting the pipeline above water, so that the scraper may pass through without becoming jammed.

Description:
FIELD OF THE INVENTION 
   The present invention relates to the maintenance of underwater pipelines, and more particularly relates to the repair and retrofitting of branch connections to permit the passage of a pipeline scraper or the like through the pipeline without impediment. 
   BACKGROUND OF THE INVENTION 
   Underwater pipelines for oil, gas and other fluids require maintenance to keep their interior passageways clear, and for this purpose a robotic internal pipeline scraper is often used. Such a scraper is inserted at one entrance to the pipeline and is propelled to pass along the pipeline to an exit, scraping the interior sides of the passageway free from buildup as it goes. 
   Necessarily, in order to scrape the sides, the scraper must contact the sides with an appropriate degree of force. This operation creates a problem when the pipeline contains a branch connection, as most pipelines do. The branch connection may be in the form of a Y or T connection, but in any case the connection fitting makes an opening in the main passageway. A scraper making its way along the main passageway may turn into the opening at the branch connection and become jammed. 
     FIG. 1  illustrates this problem in the context of a typical pipeline scraping operation. As shown therein, a 30 inch pipeline  10  has a 24 inch tie-in T-section  12  connected therein with a corresponding opening  14  to permit passage of the conveyed liquid. An auxiliary pipeline  16  is connected to the T-section  12  by a conventional bolted flange  18 . The direction of flow of the conveyed liquid is indicated by the arrow A inside the pipeline  10 . 
   In  FIG. 1 , a pipeline scraper  20  has been introduced into the main pipeline  10  from the upstream direction indicated by arrow B at the left of the figure and is traveling downstream, toward the right of the figure. At a first position  22  within the pipeline  10 , the scraper  20  is in contact with all interior sides of the pipeline  10  with sufficient force to be scraping those sides free of accumulated debris. However, when the scraper  20  reaches position  24 , it encounters the opening  14  and may tilt into it, with the lead end  26  of the scraper  20  entering the T-section  12  and becoming jammed against the far corner  28 . As a result, the pipeline  10  goes out of service and must be repaired. 
   The only way to repair the pipeline  10  under these conditions is to flush the pipeline  10  and then send one or more divers underwater to locate the jammed connection and lift the pipeline  10  itself onto a work barge, where the jammed scraper  20  can be removed by cutting out the section containing the fouled fitting and putting an appropriately configured new branch fitting in its place. The pipeline  10  can then be reclosed and deposited back under the sea. Needless to say, this is a very expensive operation and has considerable associated environmental risks. 
   Other robotic devices, such as monitoring devices, are also used to traverse the pipelines and may similarly become jammed at the branch openings. 
   The use of scrapers and such other devices is a relatively new development as compared with the age of certain existing pipelines that are still in service. Their use can enhance and extend the useful life of older pipelines, but this was not contemplated when the older pipelines were put in place. 
   Now that the use of scrapers has become more common, pipeline fittings are provided with the necessary guards or longitudinally extending bars that will preclude the entry of the scraper into the opening into the branch line. It would be highly desirable to retrofit the existing pipelines with such guard bars over the branch openings, but the only way currently known for doing so involves the pipeline lifting operation described above, making it prohibitively expensive to engage in any general overhaul. 
   Moreover, in many cases trunk lines cross under or over other trunk lines, flow lines, power lines and/or communication cables, so that individual trunk lines often cannot be lifted to the surface without wholesale disruption of the entire pipeline system. 
   Consequently, while retrofitting is highly advantageous, it is possible in accordance with conventional techniques only in limited circumstances and only at great expense. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a method for repairing pipeline branch connections that avoids the above-described difficulties of the prior art. 
   It is a further object of the present invention to provide a method that avoids the prior art difficulties in retrofitting pipeline branch connections to avoid future pipeline jams requiring repair. 
   It is another object of the present invention to provide a structure that may be used for such repair and retrofitting that may be connected in the pipeline without requiring the pipeline to be raised to the surface. 
   In accordance with these and other objects, a method is provided for retrofitting an undersea pipeline to permit passage therethrough of a device, wherein the pipeline includes a main pipeline having an interior first passageway through which the device is intended to pass and a branch fitting defining an interior second passageway in fluid communication with the first passageway through a first opening in the branch fitting, the branch fitting having a second opening from the second passageway spaced from the first passageway. The branch fitting further has a first inner surface defining a continuation of the first passageway surrounding the first opening at which the device may become jammed, and a connecting structure initially connecting the branch fitting to a branch pipeline through the second opening. 
   The method then comprises the steps of, without lifting the main pipeline above water, disconnecting the branch pipeline from the connecting structure of the branch fitting to expose the second opening, inserting an insertion shoe through the second opening into the first opening, the insertion shoe including a plate sized to cover the first opening and having a second inner surface structured to match the first inner surface when the insertion shoe is installed, and installing the insertion shoe in the first opening such that the plate covers the first opening and the second inner surface matches the first inner surface so that the device may pass through the first passageway and past the installed insertion shoe without becoming jammed. 
   In one embodiment, when it is desired to seal off the first opening permanently and no longer use the branch pipeline, the plate of the insertion shoe is without openings, so that fluid conveyed through the first passageway cannot pass out of the main pipeline past the insertion shoe. 
   In another embodiment, when the branch pipeline is to continue in use but it is desired to protect the first opening against jamming, the plate of the insertion shoe is provided with openings, so that fluid conveyed through the first passageway can pass out of the main pipeline past the insertion shoe into the second passageway, and the method further comprises the step of attaching either the original branch pipeline or a new one to the connecting structure after the insertion shoe is installed. 
   These and other objects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments, taken together with the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of a scraper becoming jammed in an undersea pipeline having an unprotected branch connection opening. 
       FIG. 2  is a schematic illustration of a scraper passing successfully past a branch connection opening protected by an underwater pipeline branch insertion shoe in accordance with a preferred embodiment of the present invention. 
       FIG. 3  is a partial cross-section/cutaway view of a preferred embodiment of an insertion shoe in accordance with the present invention. 
       FIG. 4  is a schematic view of the connection of the main pipeline to an auxiliary pipeline through a dropout spool. 
       FIG. 5  is a schematic view of the arrangement of  FIG. 4  after the dropout spool has been disconnected. 
       FIG. 6  is a semi-schematic side cross-sectional view of the insertion shoe of  FIG. 3 . 
       FIG. 7  is a partial cross-section/cutaway view of another preferred embodiment of an insertion shoe in accordance with the present invention. 
       FIG. 8  is a perspective view of the insertion shoe of  FIG. 3  and its accompanying insertion sleeve and lock bar. 
       FIG. 9  is a partial cutaway view showing the insertion shoe of  FIG. 3  in a first position. 
       FIG. 10  is a partial cutaway view showing the insertion shoe of  FIG. 3  in a final position. 
       FIG. 11  is a perspective view of the insertion shoe of  FIG. 3  being inserted into a model of the branch connection. 
       FIG. 12  is a top perspective view of the insertion shoe of  FIG. 3  as installed in the model of the branch connection. 
       FIG. 13  is a side perspective view of the insertion shoe of  FIG. 3  as installed in the model of the branch connection. 
       FIG. 14  is a schematic view of the arrangement of  FIG. 4  after the insertion shoe has been installed and a dropout spool reconnected. 
       FIG. 15  is a partial cross-section/cutaway view of yet another preferred embodiment of an insertion shoe in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2  illustrates the successful passage of a scraper  20  through a pipeline  100  that has been retrofitted in accordance with the present invention. 
   Pipeline  100  is a conventional 30 inch diameter pipeline and has a conventional 24 inch diameter branch connection tee fitting  102 , with an opening  106  into the vertical portion of the fitting  102  and a flange  118  connecting the fitting  102  to an auxiliary pipeline  16 , just as in  FIG. 1 . Now, however, an insertion shoe  104  in accordance with a preferred embodiment of the present invention has been installed to protect the opening  106  and permit passage of the scraper  20  from a first, upstream position  108  to a second position  110  past the opening  106  without jamming. 
   In accordance with an advantageous aspect of the present invention, it is possible to install the insertion shoe  104  without lifting the pipeline  100  above the surface. 
   A preferred embodiment of such an insertion shoe is illustrated in  FIG. 3 , which is a partial cross-section/cutaway view of a so-called “open” insertion shoe  112  installed to protect the main pipeline  100 . As shown in cutaway in  FIG. 3 , the pipeline  100  has an open interior passageway  114  through which the gas or oil is intended to flow and whose inner surface is to be scraped. In this example, a branch connection or fitting in the form of a T-section  120  is used although other branch connections such as Y-sections may also be employed within the scope of the present invention. 
   As is conventional, the opposed ends  101 ,  103  of the horizontal portion  113  of the T-section  120  are welded at respective seams  105 ,  107  to first and second portions  109 ,  111  of the main pipeline  100  to define a continuous passageway. Thus, the passageway  114  of the pipeline  100  proper leads into and is continuous with the horizontal portion  113  of the T-section  120 . 
   It will of course be understood that the terms “horizontal” and “vertical” as used herein are intended merely to define two different directions of flow through a main pipeline and out to a branch pipeline, and that different, or even non-perpendicular, orientations may occur within the scope of the present invention. 
   In the absence of the insertion shoe  112 , the horizontal portion  113  is open at an opening  116  to a second interior passageway  122  in the vertical section  123  of the T-section  120 . This second passageway  122  has a second opening  115  spaced from the first passageway  114 . The T-section  120  further has a conventional flange  142  that surrounds the second opening  115  and functions as a connecting structure for connecting the T-section  120  to feed into an auxiliary pipeline  144 . 
   In conventional practice, the T-section  120  does not attach directly to the auxiliary pipeline  144 . Rather, as shown in  FIG. 4 , the auxiliary pipeline  144  extends from, for example, a remote well platform  117  and is connected by a conventional link  119  to a dropout spool  121  which in turn is connected to the flange  142 . In the illustrated structure, the dropout spool  121  includes a conventional flange that can be bolted to the flange  142 . It is well known that the dropout spool  121  can be readily disconnected (unbolted) from the link  117  and/or the flange  142  by divers under water without having to raise this section of pipeline to the surface.  FIG. 5  shows the setup of  FIG. 4  with the dropout spool  121  disconnected from the flange  144  to permit installation of an insertion shoe in accordance with the present invention through the opening  115 . 
   In the present application, the term “branch pipeline” will refer to whatever pipe element extends from the branch fitting, whether it be a dropout spool, an auxiliary pipeline or other element. 
   Referring back to  FIG. 3 , the insertion shoe  112  includes a curved plate  124  sized to cover the opening  116 . In this embodiment, the outer perimeter  126  of the plate  124  fits tightly into the opening  116  against the inner surface  127  of the horizontal portion  113  of the T-section  120  at the opening  116  to block the flow of the conveyed liquid at the circumference  126 . Thus, the insertion shoe  112  fits into the opening  116  like a liquid-tight plug. 
   This feature is shown semi-schematically in cross-section in  FIG. 6 , which also illustrates that the horizontal portion  113  of the T-section  120  is circular in cross-section, matching a corresponding cross-section of the main pipeline  100 . The scraping device  20  will have a matching circumference, so that it can scrape off debris along the inner surface  127  and along the inner surface of the main pipeline  100 . To permit passage of the scraping device  20 , the plate  124  of the insertion shoe  112  has an inner surface  129  that matches the inner surface  127  of the T-section  120 . In this example, the inner surface  127  is circular and the inner surface  129  of the plate  124  completes the circle. It will be understood, however, that the relevant inner surface of any insertion shoe in accordance with the present invention can have whatever shape is appropriate in order to match the shape of the branch connection and the main pipeline in use so as to accommodate the scraper  20  or other traveling device. 
   Because the insertion shoe  112  is an open insertion shoe, it includes one or more openings, such as side opening  128   a  and top opening  128   b , through which the conveyed liquid may flow from the main pipeline  100  to the auxiliary pipeline  144 . Therefore the open insertion shoe  112  is suitable for use when the auxiliary pipeline  144  is to remain in use after the retrofitting operation. 
   As discussed below, the present operation also contemplates so-called “closed” embodiments wherein the insertion shoe is without openings, so that the opening  116  to the auxiliary pipeline  144  is completely blocked. Upon installation of such a closed insertion shoe, the auxiliary pipeline  144  may be scraped. In general, the only difference between an open insertion shoe and a closed insertion shoe in accordance with the present invention will be the presence or absence of such openings, and an example of such a closed insertion shoe  212  is illustrated in  FIG. 7  as being identical to the open insertion shoe  112  except for having no openings in the plate  234 . Therefore the description of any features in the various openings in the plate  234 . Therefore the description of any features in the various embodiments other than such openings is applicable to both types of insertion shoe. 
   The insertion shoe  112  of  FIG. 3  includes a structure for connecting the insertion shoe  112  to the T-section  120 , including a main guide rod  150 , and insertion sleeve  152  and a lock bar  154 .  FIG. 8  is a perspective view of the insertion shoe  112 , the insertion sleeve  152  and the lock bar  154 , and  FIGS. 9 and 10  are elevational views of the insertion shoe  112  in first and final positions for installation. As shown in  FIGS. 9 and 10 , the insertion shoe  112  includes opposed side panels  156 ,  158  that extend upwardly from the plate  124  and are sized to fit in the vertical portion  123  of the T-section  120 . The lower end  160  of the guide rod  150  is connected between the side panels  156 ,  158  on a pivot pin  162 , so that the plate  124  can pivot.  FIG. 9  illustrates the insertion shoe  112  with the plate  124  pivoted to a vertical first position in which it may be inserted through the opening  115  into the vertical portion  123  and then through the opening  116  into the horizontal portion  113 .  FIG. 10  illustrates the insertion shoe  112  with the plate  124  pivoted to the final horizontal position, also shown in  FIG. 3 , for fitting as a plug into the opening  116 . 
   The top end  164  of the guide rod  150  includes a lifting eye  166  for manipulating the guide rod  150  to lower the insertion shoe  112  into position. The guide rod  150  also has an external threading  168  for receiving a locking nut  170 . 
   The lock bar  154  includes a central opening  169  through which the guide rod  150  extends, with the central opening  169  being small enough to block passage of the locking nut  170 . The opposed ends  172 ,  174  of the lock bar  154  are shaped to fit into respective depressions  176 ,  178  in the insertion sleeve  152 . As shown in  FIG. 9 , the depressions  176 ,  178  have a defined depth and the lock bar  154  is generally uniform in thickness to match the depth of the depressions  176 ,  178 . The insertion sleeve  152  is shaped with a lower external surface  180  (see  FIG. 10 ) to fit onto the flange  142  of the T-section  120 . 
   To install the insertion shoe  112 , the plate  124  is pivoted into its first (vertical) position and is lowered, using the guide rod  150  as a handle, through the opening  115  and the opening  116  into the horizontal portion  113  of the T-section  120 .  FIG. 11  is a perspective view of the insertion shoe  112  being inserted into the T-section  120 . First the flange  142  and then the walls of the vertical portion  123  will keep the plate  124  from pivoting to horizontal during this process. However, once the plate  124  is in the horizontal portion  113 , it will naturally return to a horizontal position and can be drawn upwardly by the guide rod  150  to fit into the opening  116 . The insertion sleeve  152  is then fitted onto the flange  142  and the central opening  168  of the lock bar  154  slipped over the top end of the guide bar  154 , so that the ends  172 ,  174  fit into the depressions  176 ,  178 . Finally, the locking nut  170  is screwed down the guide bar  150  as far as possible to bring the plate  124  into its tightly fitting position in the opening  116 . The plate  124  pressing against the inner surface  127  of the T-section  120  prevents the insertion shoe  112  from moving upwardly, and the locking nut  170  pressing against the lock bar  154  prevents the insertion shoe  112  from moving downwardly.  FIGS. 12 and 13  are respectively top and side perspective views of the insertion shoe  112  after it has been installed. Thus, the insertion shoe  112  is quickly and easily installed. 
   In order to install an insertion shoe in accordance with any of the embodiments of the present invention, the following procedure is effected. First the pipeline as shown in  FIG. 4  is shut down and flushed to remove any residual oil or other conveyed fluid. Then one or more divers descend to the branch point in place to unbolt and remove the dropout spool connected to the branch connection of the main pipeline, as shown in  FIG. 5 . If a closed insertion shoe is desired, the divers install the shoe into the branch connection and the site is demobilized. 
   After installing an open insertion shoe, on the other hand, the divers reconnect the dropout spool (or connect a new one) as shown in  FIG. 14 , so that flow within the main and auxiliary pipelines can be resumed with the insertion shoe in place. 
   In either case, the main pipeline can now be scraped without the possibility of fouling. 
   It will of course be apparent to those of ordinary skill in the art that other types of connection structures for connecting the insertion shoe to the branch connection and/or main pipeline may be employed as appropriate for a particular application within the scope of the present invention. 
   For example, the plate of the insertion shoe might be connected to a T-section by one or more connection bars.  FIG. 15  illustrates an embodiment  300  using four such connection bars  302  fixed to the plate  304  and welded to brackets  306  on the T-section  308 . In an alternative embodiment, the connection bars can be welded onto the T-section itself or other structure. 
   While the disclosed method and apparatus have been particularly shown and described with respect to the preferred embodiments, it is understood by those skilled in the art that various modifications in form and detail may be made therein without departing from the scope and spirit of the invention. Accordingly, modifications such as those suggested above, but not limited thereto are to be considered within the scope of the invention, which is to be determined by reference to the appended claims.