Abstract:
A splitter system and methods are shown. Examples of splitter systems provide limited possibility of damage to adjacent utilities in the ground. Further, examples of splitter systems relax a shape memory of split pipe, which in turn reduces friction in a splitting operation. Configurations are further shown that provide lubrication to splitting operations in a number of locations along a splitter system. Configurations are also shown that provide electrical isolation to cutting blades.

Description:
RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit of priority, under 35 U.S.C. Section 119(e), to U.S. Provisional Patent Application Ser. No. 61/127,606, filed on May 14, 2008, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Pipe splitting is useful for replacement of pipes without the need to excavate the length of the pipe to be replaced. An example of pipe splitting includes pulling a cutting blade with an expander through the pipe to be replaced, and attaching a new pipe behind the cutting blade. The pipe to be replaced is split, and pushed into the surrounding soil, and the new pipe, of equal or larger diameter is pulled into the new space within the split pipe. Splitter are commonly used for small diameter pipes, and for pipes of a material that lends itself to splitting. 
         [0003]    Gas lines are one example of pipes where splitting is useful in pipe replacement. An example includes high density polyethylene (HDPE) gas pipe. Large quantities of 2 inch diameter HDPE gas pipes are currently in need of replacement. 300 miles of gas pipe in a single city in need of replacement is not uncommon. Improved splitter systems are needed to address the large task of replacing old pipes such as HDPE gas lines and other pipe materials/utilities in need of replacement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows a splitting system in operation according to an embodiment of the invention. 
           [0005]      FIG. 2A  shows a side view of a portion of a splitting system and a portion of pipe according to an embodiment of the invention. 
           [0006]      FIG. 2B  shows an end view of  FIG. 2A . 
           [0007]      FIG. 3  shows an end view of a portion of a splitting system and a portion of pipe according to an embodiment of the invention. 
           [0008]      FIG. 4  shows a split pipe and a new pipe and an adjacent utility line according to an embodiment of the invention. 
           [0009]      FIG. 5  shows a side view of a portion of a splitting system according to an embodiment of the invention. 
           [0010]      FIG. 6  shows a close up view of a portion of a splitting system according to an embodiment of the invention. 
           [0011]      FIG. 7  shows a side view of a portion of another splitting system according to an embodiment of the invention. 
           [0012]      FIG. 8  shows a side view of a portion of another splitting system according to an embodiment of the invention. 
           [0013]      FIG. 9  shows a flow chart of an example method according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. In the following description, the term cable is defined to include metal cables, wire rope, or other lengths of flexible line of suitable strength to pull devices as described below through a section of pipe. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and mechanical, structural, or logical changes, etc. may be made without departing from the scope of the present invention. 
         [0015]      FIG. 1  shows a splitter system  100  in operation performing a split and replacement. An entry pit  102  and an exit pit  104  are shown, with a pipe  120  that is to be replaced by the splitting operation. A pulling system is shown with a puller  110  illustrated in block diagram form. A pulling member  116  is shown coupled to the puller  110  and to a splitter  112 . In operation, the puller  110  engages and advances the pulling member  116  to move the splitter  112  from the entry pit  102  to the exit pit  104 . An expander  114  is also shown coupled to the splitter  112 . The expander expands the pipe  120  after the splitter  112  weakens the pipe  120  as will be described in more detail below. A new pipe  122  is also shown coupled to the expander. In one embodiment, the new pipe  122  is pulled into the cavity formed by the expander as the splitter  112  and expander  114  combination is pulled. 
         [0016]    A number of puller  110  and pulling member  116  options are possible. In one example, the pulling member included a number of pulling rods that are joined together in sections, and the puller includes a rod puller. One example of a rod puller engages the rods in a number of notches or openings in the rods (not shown). In one embodiment, the rods are first pushed through the pipe to be replaced, then the splitter system is coupled to the rods and the splitter system is drawn back through the pipe, as described above. In one embodiment, a leading portion with a swivel joint such as a ball joint is attached to a front end of the rods prior to pushing the rods through the pipe to be replaced. A short leading portion, such as an approximately six inch long portion with an rounded nose, provides improved tracking of the rods within the pipe to be replaced. Improved tracking helps prevent the rods from accidentally pushing through a wall of the pipe to be replaced. 
         [0017]    Other examples of a puller  110  and pulling member  116  includes a cable, wire rope, etc. pulling member  116  that is pulled by a winch, cyclic cable puller, or other cable puling device. Other pullers  110  and pulling members  116  are also possible, such as directional drill stem sections, etc. 
         [0018]    In addition to pulling options, in one embodiment, a number of rods are used to push an embodiment of a splitter system. In one example, after the splitter system is pushed through the pipe to be replaced, at least portions of the splitter system are removed, and the new pipe is attached to an expander and pulled back by the same rod puller/pusher. 
         [0019]      FIG. 2A  shows a splitter system  200  that is used in one example of the splitting operation shown in  FIG. 1 . A shaping mandrel  210  is shown coupled to a splitter body  212 . A pulling member  220  such as rods, cables, etc. as described above is also shown. The shaping mandrel  210  is shown partially within a pipe  250 . The pipe is shown with a wall thickness  252 . In one example of pipe splitting, a polymeric pipe such as HDPE pipe is split. One example includes 2 inch outer diameter HDPE gas line splitting. One of ordinary skill in the art having the benefit of the present disclosure will recognize that other pipe materials such as other polymers, copper, other metals capable of being split, etc. are within the scope of the invention. 
         [0020]    Using HDPE gas line splitting as an example, it has been found, that old pipes are sometimes distorted in an out of round shape, however, the wall thickness is quite consistent. In one example, pulling the shaping mandrel  210  through the pipe  250  before splitting forms the pipe  250  into a predictable configuration prior to a splitting operation. Although a round cross section pipe  250  is used as an example, other shapes and corresponding shaping mandrels  210  are within the scope of the invention.  FIG. 2A  also illustrates a leading feature  211  such as a taper or similar configuration to aid in pulling the shaping mandrel  210  into the pipe  250 . 
         [0021]    One problem to be overcome in splitting pipes is that frequently there are adjacent utilities buried in close proximity to the pipe to be split. Some adjacent utilities are fragile, such as fiber optic cables. Other adjacent utilities are dangerous such as electrical lines. It is desirable to perform a splitting operation on pipes  250  with minimal impact and minimal danger to a splitting operator. A device and method are needed to reduce damage to adjacent utilities. 
         [0022]      FIG. 2A  shows a plurality of blades  216  attached to an external surface of the splitter body  212 . The end view of  FIG. 2B  shows the plurality of blades  216  located at a number of different angular locations around the surface of the splitter body  210 . The blades  216  are shown with a cutting depth  217  that is less than the wall thickness  252  of the pipe  250 . When the blades  216  are pulled through the pipe  250 , they will therefore not penetrate a surface of the pipe  250 . This configuration ensures that the blades  216  will not contact any adjacent utility lines. This configuration is most effective when there is a consistent wall thickness  252  of the pipe  250 . One application with very consistent wall thickness  252  includes HDPE gas line replacement. 
         [0023]    In one example, a primary blade  214  is included with the plurality of blades  214 . The primary blade  214  is shown with a primary cutting depth  215 . In one example the primary cutting depth  215  is deeper than the cutting depth  217  of the other blades  216 . Using a primary blade  214  provides a more consistent fracture line for the pipe  250  during a splitting operation. In one example the cutting depth  217  of the blades is set at approximately 75 percent of the wall thickness  252 . In one example the primary cutting depth  215  is set at approximately 90 percent of the wall thickness. Although eight blades  216 , including one primary blade  214  are shown, the invention is not so limited. Other numbers of blades and primary blades are possible without departing from the scope of the invention. Although regular angular blade spacing of 45 degrees apart is shown, other embodiments include different blade spacings. 
         [0024]      FIG. 3  shows an end view of the splitter body  212  and the blades  216  engaging the pipe  250 . As can be seen from the figure, the primary blade  214  is cutting a deeper score in the pipe  250 , but is still not penetrating a surface of the pipe  250 , thus ensuring no damage to an adjacent utility.  FIG. 4  illustrates the pipe  250  further after a splitting operation. The pipe  250  shows a number of sections  254  defined by a number of scores  256  such as a 75 percent wall thickness score, or other suitable depth. The pipe  250  in  FIG. 4  also shows a break  258  that corresponds to the location of the primary blade  214 . A new pipe  260  is shown pulled into the cavity formed after the splitting operation. An adjacent utility line  270  is shown to illustrate the safety in splitting with blades having a cutting depth less than a wall thickness of the pipe  250 . 
         [0025]    One problem with splitting pipe such as HDPE gas lines is that the split pipes can have a detrimental shape memory. After splitting with a single blade, the pipe  250  can curl up and tighten about the new pipe  260 . This causes increased friction when pulling the new pipe  260  into the split pipe  250 . By cutting the pipe  250  into a number of sections  254 , any shape memory of the pipe  250  is relaxed, and the new pipe  260  can be pulled into the cavity formed more easily. Additionally, by keeping the sections  254  loosely attached at the scores  256 , the pipe  250  is weakened, but still retains some axial integrity. This can help prevent the pipe  250  from bunching up into a number of fractured strands during a splitting operation. An advantage of using a primary blade  214  includes formation of a predictable break line  258 . 
         [0026]      FIG. 5  illustrates further aspects of one embodiment of a splitter system  500  in operation performing a split and replacement. When polymer pipe such as HDPE gas pipe is installed, it is often fused in sections using some form of heat source. Each fusion joint tends to form a bead  552 , which often protrudes into an interior of the pipe  250  as shown in the figure. 
         [0027]    In one embodiment, the bead  552  rides up over a shaping mandrel  510  similar to other embodiments described above. The bead  552  is shown in  FIG. 5  being forced outward over the shaping mandrel  510  along arrows  524 . As shown in  FIG. 5 , a splitter body  512  and a number of blades  514  are coupled behind the shaping mandrel  510 . In one embodiment an interior portion of the bead  552  is removed from the pipe  550  prior to splitting on the blades  514 . A cutting blade  522  is shown adjacent to a cavity  520  as one example of a device to remove a portion of the bead  552 . 
         [0028]    In  FIG. 6 , the bead  552  is shown after it passes over the shaping mandrel  510  and an interior portion  554  is sheared off the bead  552  by the cutting blade  522 . In one example a cavity  520  is included as illustrated. In one example, the cavity  520  is sized and shaped to accommodate multiple sheared portions  554  of beads  552 . Removal of interior portions of beads  552  contributes to a consistent cutting depth of the blades  514  in the wall thickness of the pipe  550  as described in embodiments above. 
         [0029]      FIG. 7  illustrates further aspects of one embodiment of a splitter system  700  in operation performing a split and replacement. Similar to embodiments described above, a shaping mandrel  710  is shown attached to a splitter body  712 , having a number of blades  714 . As in other embodiments, the blades are formed with a cutting depth that is less than a wall thickness of a pipe to be cut (not shown in  FIG. 7 ). A pulling member  742  such as a pulling rod, cable, directional drill stem, etc. is shown coupled to a front end of the splitter system  700 . 
         [0030]    In one embodiment, a non-conductive insert  740  is coupled between the shaping mandrel  710  and the pulling member  742 . When splitting an insulating material such as HDPE, if an adjacent electrical line were breached and came into contact with metal cutting blades, electricity could travel down the pulling member  742  towards a pulling device such as a winch, rod puller, etc. By inserting a non-conductive insert  740  between the splitter body  712  and the pulling member  742 , a potential for electrical shock is reduced. In one example, a non-conductive insert  740  includes a fiberglass insert. Other non-conductive inserts  740  of sufficient strength and toughness are also possible. 
         [0031]      FIG. 7  further illustrates an expander  720  coupled behind the splitter body  712 . A new pipe  730  is shown being pulled in behind the splitter system  700 . In one embodiment, a fluid is pumped into the new pipe  730  as shown along lines  732  and the fluid is expelled in front of the expander  720 . One or more ports  722  are shown on the expander in  FIG. 7  to expel fluid as shown by arrows  734 . Examples of fluids include water, slurries of clay and water, or other suitable fluids. In other embodiments, the fluid is pumped through a supply hose (not shown) that is pulled within the new pipe  730 . Using a supply hose eliminates contamination of the inside of the new pipe  730  with residue from the fluid. 
         [0032]    In one method of pipe installation, the new pipe  730  is used as a liner, and a replacement line such as a gas line is further introduced within the new pipe  730  for service. Using such a pipe within a pipe configuration, there are no contamination issues from pumping a fluid directly by flooding an interior of the new pipe  730 . 
         [0033]      FIG. 8  illustrates further aspects of one embodiment of a splitter system  800  in operation performing a split and replacement. Similar to embodiments described above, a shaping mandrel  810  is shown attached to a splitter body  812 , having a number of blades  814 . As in other embodiments, the blades are formed with a cutting depth that is less than a wall thickness of a pipe to be cut (not shown in  FIG. 8 ). In one embodiment, the splitter system  800  includes a non-conductive insert  840  between the shaping mandrel  810  and a pulling member  842 . 
         [0034]    In addition, the embodiment of  FIG. 8  illustrates a lubricant dispenser  850  located in front of the shaping mandrel  810 . In a further effort to reduce friction in the system, the lubricant dispenser helps the shaping mandrel  810  and other following components to slide within the pipe to be replaced. One example of a simple and effective lubricant dispenser includes a sponge soaked in lubricant, located in advance of the shaping mandrel  810  and other components. A number of advanced lubricants are available that could be soaked into a sponge or similar lubricant retaining material and refilled or otherwise recharged before a new splitting operation. Other lubricant dispensers such as a fluid reservoir and ports, or a supply through a line from an external source are also possible. 
         [0035]      FIG. 9  shows an example flow diagram of a method of splitting a pipe using one or more device configurations as described above. In operation  910 , a splitter body is pulled through a pipe. In operation  912 , a portion of a wall thickness in the pipe is cut in a plurality of angular locations around an inside diameter of the pipe using a plurality of blades, each with a cutting depth that is less than the wall thickness of the pipe. Operations  914  and  916  illustrate expanding the pipe, and pulling in a new pipe behind the expander. 
         [0036]    As described above, in one embodiment, a shape memory of the split pipe is relieved by multiple interior scores using such as configuration, and friction on any new pipe being pulled in is reduced. By cutting only a portion of the wall thickness, adjacent utilities such as fragile fiber optics, or electrical lines are protected. 
         [0037]    While a number of advantages of embodiments of the invention are described, any lists of above mentioned advantages are not intended to be exhaustive. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. It is to be understood that the above description is intended to be illustrative, and not restrictive. Combinations of the above embodiments, and other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention includes any other applications in which the above structures and methods are used. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.