Abstract:
An underwater apparatus for servicing subsea pipelines provides a telescoping frame which can be lowered to the vicinity of the pipeline. The frame has an open section so that it can straddle the pipeline and outer jacket and fixate itself releasably so that it can be selectively repositioned. A cutting apparatus is secured to a telescoping sub frame. The cutting structure can be rotated about the longitudinal axis of the sub frame, as well as advanced along the direction of the longitudinal axis of the frame due to the telescoping feature of the sub frame. The cutting structure can also be moved pivotally about an axis of rotation which is outside and generally perpendicular to the longitudinal axis of the pipe. Thus, combining the telescoping feature with the pivoting feature and the feature of being able to rotate about the longitudinal axis, a variety of different cuts can be made. The principal advantage of the apparatus is to be able to cut through an outer jacket of a jacketed pipeline transversely and longitudinally to remove it in pieces without cutting through the pipeline.

Description:
FIELD OF THE INVENTION 
     The field of this invention relates to an apparatus which can be employed subsea to cut an outer jacket off of a subsea pipeline for access to the pipeline for repairs or, alternatively, the apparatus can cut through a pipe and its jacket or a bare pipe. 
     BACKGROUND OF THE INVENTION 
     Pipelines run subsea occasionally require repairs. In many installations, the pipeline is jacketed with a concentric jacket which leaves an annular space between the pipeline and the outside of the jacket. In the past, in order to service such pipelines using known subsea cutting devices, the entire pipeline had to be severed by a cutting apparatus. Generally, these devices would be lowered to the pipeline and use a frame-supported diamond wire as the cutting mechanism. The devices of the prior art oriented the diamond wire to make a cut perpendicular to the longitudinal axis of the pipeline, through the pipeline and the surrounding jacket. This step would be repeated at another location so that an entire segment, which is thought to have a leak, can be removed and replaced. 
     The devices previously known did not have the capability of cutting away the outer jacket without also cutting through the pipe. An advantage that is obtained from the present invention, which has the capability of independently cutting the outer jacket without cutting through the pipe, is that the pipeline can be exposed to confirm the precise location of any leak and to, perhaps, make any repairs without having to needlessly remove a complete section of the pipeline. The present invention is not limited to cuts in a single plane transverse to the longitudinal axis of the pipe. As a result, a multiplanar cut can reduce binding on the cutter since the cut piece remains in place at the end of the cut. 
     Typical of cutting devices available in the prior art are U.S. Pat. Nos. 5,685,996; 5,598,754; 5,361,748; 5,010,694; 4,777,723; 4,312,498; 4,143,862; 4,091,514; 3,578,233; 3,056,267; 2,762,621; U.S. Statutory Invention Registration H-45; European application 0540834A1; Russian patents 777146; 659,687; 150,377; and Japanese patent 2-59273. Yet other patents deal with cutting devices generally and components therefor, whether such devices are used subsea or to cut other structures. Typical of such devices are U.S. Pat. Nos. 4,936,284; 4,765,307; 4,007,705; 3,479,830; 2,795,222; 2,674,238; and 1,689,829. U.S. Pat. No. 4,109,480 shows an underwater crane that can be used for repair of pipelines underwater. 
     None of these prior art devices have the capability of selectively removing an outer jacket from a covered subsea pipeline, coupled with the versatility of being able to cut perpendicular to the longitudinal axis or in a multiplicity of planes if, for any reason, a section has to be severed from the pipeline for repair. One of the objects of the present invention is to provide a device which can be economical to build and which works efficiently to give flexibility to make a variety of different types of cuts to address any particular subsea situation. Another object of the device is to be able to remove a section of an outer jacket without cutting the actual pipeline to provide access to the pipeline for analysis of the location of a trouble spot and for possibly effecting a repair without cutting through the pipeline. These and other advantages of the apparatus of the present invention will become more apparent from a review of the detailed description below. 
     SUMMARY OF THE INVENTION 
     An underwater apparatus for servicing subsea pipelines provides a telescoping frame which can be lowered to the vicinity of the pipeline. The frame has an open section so that it can straddle the pipeline and outer jacket and fixate itself releasably so that it can be selectively repositioned. A cutting apparatus is secured to a telescoping sub frame. The cutting structure can be rotated about the longitudinal axis of the sub frame, as well as advanced along the direction of the longitudinal axis of the frame due to the telescoping feature of the sub frame. The cutting structure can also be moved pivotally about an axis of rotation which is outside and generally perpendicular to the longitudinal axis of the pipe. Thus, combining the telescoping feature with the pivoting feature and the feature of being able to rotate about the longitudinal axis, a variety of different cuts can be made. The principal advantage of the apparatus is to be able to cut through an outer jacket of a jacketed pipeline transversely and longitudinally to remove it in pieces without cutting through the pipeline. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the apparatus being lowered to a pipeline. 
     FIG. 2 shows the apparatus settled on the pipeline. 
     FIG. 3 shows the frame of the apparatus secured to the outer jacket on the pipeline. 
     FIG. 4 shows the initiation of a cut through the jacket. 
     FIG. 5 is the view of FIG. 4, with the cutting structure rotated with respect to the longitudinal axis of the pipeline. 
     FIG. 6 is the view of FIG. 5, showing the completion of an initial cut through the jacket of the pipeline. 
     FIG. 7 is the view of FIG. 6, showing the completion of the initial cut in the jacket. 
     FIG. 8 shows the frame relocated with respect to the initial cut in the jacket and the progression of a longitudinal cut from the initial cut through the outer jacket. 
     FIG. 9 shows the conclusion of the longitudinal cut in the outer jacket. 
     FIG. 10 shows the cutting structure removed from the outer jacket at the conclusion of a second cut perpendicular to the longitudinal axis of the jacket. 
     FIG. 11 shows that the two sections of the jacket can be removed while the underlying pipeline remains uncut. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus A is shown in FIG. 1 in the position that it would take as it is being lowered from a surface vessel, employing the crane mounted on such a vessel. The supporting cables and hydraulic lines from the vessel crane to the apparatus A are not shown for clarity in understanding the invention. The apparatus A contains a base frame  10 . Base frame  10  is a U-shaped structure having an open bottom so that the apparatus A can be lowered onto a jacketed pipeline  12 . The jacketed pipeline  12  is an assembly of the actual pipeline  14 , which through a series of extending supports  16 , located periodically along its longitudinal axis, supports the outer jacket  18 . The jacketed pipeline may have to be lifted before the base frame  10  can straddle it. 
     The base frame  10  includes a plurality of drive rollers  20 , each of which is motorized by a motor  22 . The rollers  20  are shown on one side of the base frame  10  and a mirror image arrangement occurs on the opposite side, which is not shown in the drawing of FIG. 1. A movable bar  24  is connected to an actuator  26  such that extension of a piston out of the cylinder in actuator  26  results in rotational movement of movable bar  24  to move the rollers  20  from the position shown in FIGS. 1 and 2 to the position shown in FIG.  3 . With the piston extended from the cylinder in actuator  26 , as shown in FIG. 3, the rollers  20  have moved under the jacket  18  to secure the position of base frame  10  to the jacket  18 . The drive rollers  20 , motor  22 , and moveable bar  24 , serve as a clamping and crawling mechanism that is capable of clamping the sub frame to a jacket and is further capable of allowing the apparatus frame and the sub frame to crawl along a jacket to which the apparatus frame is securable. 
     Those skilled in the art will appreciate that a similar layout occurs on the backside of the base frame  10  so that the rollers  20  essentially are pivoted to a position under the jacket  18  (or the bare pipeline  14 ) to secure the position of base frame  10  until it is desired to move the base frame  10  by driving rollers  20 , as illustrated in FIG.  8 . 
     Base frame  10  has within it telescoping sub frame  28 . Sub frame  28  is shown in FIG. 1 nested within base frame  10  but can be actuated to extend with respect to base frame  10  as shown in FIG.  8 . Sub frame  28  supports sprocket frame  30 . A drive motor  32  operates sprocket  34 . Rotationally mounted to the sub frame  28  is open gear  36 , which is generally U-shaped and has a series of exterior teeth  38 . Sprocket  34  meshes with teeth  38  so that operation of motor  32  will rotate open gear  36  about the longitudinal axis of the jacketed pipeline  12 , as shown, for example, by comparing FIG. 1 to FIGS. 5 and 6. Sprockets  40 ,  42 ,  44 , and  46  are supported by sprocket frame  30 , with each having teeth to mesh with teeth  38 . The driving is done directly through sprocket  34  and through a belt  50  using sprockets  40 ,  42 ,  44 , and  46 , while the open gear  36  is longitudinally retained to prevent its movement so as to keep sprocket  34  meshed with teeth  38  as rotation in either direction, clockwise or counterclockwise, can be accomplished with respect to the longitudinal axis of the jacketed pipeline  12 . Those skilled in the art will appreciate that a complete 360° cut can be accomplished as the open gear  36  can continue to be rotated, even though one of the sprockets  40  or  44  loses contact with the teeth  38 . This can be seen by looking at FIG. 6 where open gear  36  has been rotated to the point where sprocket  42  is no longer in contact with open gear  36 . However, the other sprockets still can continue to drive open gear  36 . FIG. 6 represents an extreme position in one direction for the open gear  36  with respect to sprocket  34 . The other extreme position can be reached when end  48  of open gear  36  comes near sprocket  34 . This position is not shown in the figures. The cut is made by rotating the open gear  36  clockwise for a little over 180° and then reversing and rotating counterclockwise for a little over 360° to complete the cut. Continuous rotation in one direction, while possible, could tangle up the hydraulic cables. 
     Also shown in FIG. 1 is a continuous belt  50  which can be used off motor  32  to power the sprockets  40 ,  42 ,  44 , and  46 , as opposed to leaving them as idlers and powering the open gear  36  strictly from sprocket  34 . 
     Also secured to open gear  36  for tandem movement therewith is wire cutter frame  52 , which has a drive motor  54  which powers a diamond wire  56  along a series of pulleys  58 ,  60 ,  62  and  64 . An actuator  66  mounted on opposing sides of the wire cutter frame  52  and the open gear frame  68  allows for pivotal movement of wire cutter frame  52  with respect to pivots  70  on the open gear frame  68 . Pivots  70  define an axis generally perpendicular to the longitudinal axis of the pipeline  14  to define an arcuate movement of wire  56  toward or away from the pipeline  14  or jacket  18 . 
     The essential components of the apparatus A having been described, the sequence of operation for removing a section of the outer jacket  18  without cutting the pipeline  14  using the figures will be described. As has previously been explained, the apparatus A is lowered over the jacketed pipeline  12  and the rollers  20  are moved on either side of base frame  10  by virtue of operation of actuator  26 . The apparatus A is now secured to the outer jacket  18  by rollers  20 , as shown in FIG.  3 . 
     As shown in FIGS. 4 and 5, the wire cutter frame  52  is at pivots  70  in an arcuate path rotated downwardly into contact with the outer jacket  18 . The pivotal motion of wire cutter frame  52  can be combined with the translational motion of the sub frame  28  with respect to base frame  10  so that the movement of wire  56  is purely perpendicular to the longitudinal axis of the jacketed pipeline  12 . Alternatively, the wire  56  can be advanced on an arcuate path by rotation of frame  52  to the point where a short chord is made by wire  56  as it penetrates through the wall of the outer jacket  18 . The wire  56  is rotated either continuously or sporadically to finish the cut. Thereafter, as shown in FIGS. 5 and 6, motor  32  is actuated to turn in one or two directions to complete a cut through the outer jacket  18 . Again, when this process is going on, as illustrated in FIGS. 5 and 6, it can be combined with longitudinal motion of the sub frame  28  with respect to the base frame  10  so that the entire cut all the way around the outer jacket  18  is in a plane perpendicular to the longitudinal axis of the jacketed pipeline  12 . However, it is not mandatory that the initial cut illustrated in FIGS. 5 and 6 be in the single plane. In fact, it may be preferable to have the cut in more than one plane such as when the cut  72  is undulating or curved. The advantage of cutting the outer jacket  18  outside of a single plane perpendicular to the longitudinal axis of the jacketed pipeline  12  is that at the conclusion of the cut, the stresses in the outer jacket  18  will not pinch or bind the wire  56  because the two cut segments of the outer jacket  18  will remain in place until the second cut is made, as well as a longitudinal cut so that two sections of the outer jacket  18  can be taken off the pipeline  14 . 
     Referring to FIGS. 7 and 8, it can be seen that the base frame  10  has shifted through the operation of rollers  20  away from the original cut  72 . A longitudinal cut  74  is made with the wire  56  driven by motor  54 , while the sub frame  28  is telescoped into the base frame  10 . Gear  36  is not rotated to make this cut straight. If an undulating cut is desired, then gear  36  can be rotated back and forth as the sub frame  28  is retracted into base frame  10 . FIGS.  9  and  10  illustrate the completion of cut  74  and the initiation of cut  76  which can be parallel to cut  72 . The wire  56  is shown in FIG. 10 as being pulled up and out of the outer jacket  18 . This occurs at the conclusion of cut  76 . Those skilled in the art will appreciate that at the conclusion of longitudinal cut  74 , motor  32  is actuated and the process for making cut  76  is a repetition of the process for making cut  72 . Cuts  72  and  76  can be identical or they can be different as long as they fully go around and through the outer jacket  18  without penetrating through the pipeline  14 . As shown in FIG. 11, at the conclusion of cut  76 , the two pieces  78  and  80  can be removed or they can be allowed to fall to the seabed. 
     The apparatus A can also be used to cut through pipeline  14  by a combination of the telescoping motion between the sub frame  28  and the base frame  10  while pivotal motion occurs with regard to wire cutter frame  52 , while at the same time motor  32  is actuated. The cutter frame  52  does not need to be pivotally mounted and can be fixed for movement in a single plane transverse to the longitudinal axis of the pipe  14 . It can be combined with the telescoping action of sub frame  28  to obtain cuts that are in more than one plane. The cut made by the apparatus A can go entirely through the pipeline  14 . The cut can be in a single plane perpendicular to the longitudinal axis of the pipe  14 , or it can have a curve or any other shape because of all the degrees of freedom provided by the various movements described above. 
     In the preferred embodiment, cuts through the outer jacket  18  or through the pipeline  14  itself are preferably made by opposed motions of approximately 180° in opposite directions so as to avoid entanglement of various hydraulic control lines which are used, for example, to power motor  54 . It should be noted that the open gear frame  68  and open gear  36  are guided to prevent their longitudinal movement from sub frame  28 . In this manner, the teeth  38  on open gear  36  remain in alignment with the various sprockets  34 ,  40 ,  42 ,  44  and  46 . 
     At the conclusion of the cutting, allowing pieces  78  and  80  to be separated, the underlying pipeline  14  is exposed so that repairs could be accomplished and the exact position of the problem with the pipeline can be pinpointed. The apparatus A can be used to make numerous cuts of different types, either going through the outer jacket  18  or through the pipeline  14  in a to variety of locations. Those skilled in the art will appreciate that the jacketed pipeline  12  is normally on the seabed or somewhat submerged and is necessarily picked up and supported above the seabed prior to lowering the apparatus A onto the segment of the jacket pipeline  12  which is to be cut, either through the jacket  18  or through the pipeline  14 . 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.