Abstract:
A method of repairing or reinforcing underground pipes includes the steps of providing a flexible liner assembly having a first end and a second end, applying an internal pressure to the flexible liner assembly, inserting the first end of the liner assembly into a first end of a pipe section while maintaining the internal pressure, pushing the flexible liner assembly through the pipe section while maintaining the internal pressure, releasing the internal pressure from the flexible liner assembly, and connecting the first and second ends of the flexible liner assembly to the pipe section so that the flexible liner assembly provides a substantially leak-free conduit through the pipe section. The method addresses drawbacks associated with prior art methods by preventing or reducing contact between the flexible liner assembly and sharp inner corners of the pipe section, thereby reducing drag between the flexible liner assembly and the interior of the pipe section.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention is directed to a method for repairing and reinforcing underground pipes, which does not require excavation to reach the section of pipe requiring repair and/or reinforcement. 
       BACKGROUND OF THE INVENTION 
       [0002]    Underground pipes used for swimming pools, wells, sewers, other water systems and electrical cables can become cracked after many years of use. Such cracking can result from shifting of the earth, growth of roots, and placement of heavy objects on the ground above the pipes. If the pipe is a water supply or drain pipe, the cracking can cause water to leak from the pipe. If the pipe is used to house electrical cable, the cracking can cause water to leak into the pipe. In either case, the cracking can result in failure of the pipe for its intended purpose. 
         [0003]    Repair of the damaged pipe can be accomplished by excavating the surrounding ground and repairing and replacing the damaged pipe or damaged sections of it. This process can be expensive and time consuming. An improved system and method for repairing and reinforcing underground pipes are disclosed in U.S. Pat. Nos. 7,137,757 and 7,241,076, both issued to Cosban, which are incorporated by reference. The disclosed system and method involve pulling a liner assembly through a length of the pipe and anchoring and sealing the liner assembly at both ends. The liner assembly includes a smooth flexible bore liner and a semi-rigid reinforcing helix that prevents or inhibits collapse of the liner within the pipe. Once the liner assembly has been pulled through the pipe and sealed at both ends, it functions as a new inner pipe wall which isolates the interior of the pipe from the cracks in the original pipe wall. 
         [0004]    One drawback of the foregoing system and method is illustrated in  FIG. 1 . In  FIG. 1 , a liner assembly  10  including a smooth flexible bore liner  12  and a semi-rigid reinforcing helix  14  is being pulled through a pipe section  16  using a nylon cord  18  connected to a temporary liner head  20 . The pipe section  16  has a wall  22  that bends and defines a sharp inner corner  24 . As the liner assembly  10  is pulled through the pipe section  16 , the liner assembly  10  is urged against the sharp inner corner  24  of wall  22 . The semi-rigid helix  14  can become ensnared by the sharp inner corner  24 , causing the smooth flexible bore liner  12  to become punctured, torn or otherwise damaged, and sometimes causing at least a partial collapse of the liner assembly  10 . Even if the liner assembly  10  is not damaged, the sharp corner  24  can make it difficult or awkward to pull the liner assembly  10  through the pipe section  16 . The amount of drag or resistance when pulling the liner assembly  10  can become intolerable when there are multiple corners in the pipe being repaired and/or when the pipe and liner assembly are long. 
         [0005]    There is a need or desire for an improved system and method for repairing and reinforcing underground pipes which overcomes the foregoing difficulty. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is directed to an improved system and method for repairing and/or reinforcing underground pipes which minimizes and substantially reduces the resistance and drag encountered when moving the liner assembly through the pipe. The method includes the steps of providing a flexible liner assembly having a first end and a second end, applying an internal pressure to the liner assembly, inserting the first end of the liner assembly into a first end of a pipe section while maintaining the internal pressure, pushing the liner assembly through the pipe section while maintaining the internal pressure until the first end of the liner assembly reaches a second end of the pipe section, and releasing the internal pressure from the liner assembly. The method may include the steps of sealing the first and second ends of the liner assembly before pushing the liner assembly through the pipe section, to facilitate pressurization and maintain the internal pressure, and unsealing the first and second ends of the liner assembly to facilitate the release of internal pressure. The method may also include the step of connecting first and second ends of the installed liner assembly to the pipe section so that the liner assembly provides a substantially leak-free conduit through the pipe section. 
         [0007]    The flexible liner assembly can include a smooth flexible bore liner and a semi-rigid reinforcing helix, and can be closed at both ends to maintain internal pressure. The flexible liner assembly can alternatively include another flexible material, such as a corrugated plastic material, which can be closed at both ends. The closure device can include a screw-in pressure plug at one or both ends which connects to an air compressor and transmits pressurized air to the interior of the liner assembly. Other types of closure devices can also be used. 
         [0008]    The air pressure in the liner assembly should be high enough so that the liner assembly can be pushed through the interior or the pipe section without collapsing, and low enough that the liner assembly has sufficient flexibility to bend around the corners in the pipe section. 
         [0009]    By providing a liner assembly that can be pushed through a pipe section, instead of being pulled, contact between the liner assembly and sharp corners of the pipe section can be generally avoided. The liner assembly does not become ensnared at the sharp corners, and less resistance is encountered when moving the liner assembly through the pipe section. This facilitates the repair of longer pipe sections, and pipe sections having a greater number of turns, than can be accomplished by pulling the liner assemblies through the pipe sections. 
         [0010]    With the foregoing in mind, it is a feature and advantage of the invention to provide an improved method for repairing and reinforcing underground pipes which avoids or minimizes the problems associated with flexible liner assemblies becoming ensnared at the sharp corners of pipe sections. 
         [0011]    It is also a feature and advantage of the invention to provide an improved liner assembly which can maintain internal pressure, enabling the liner assembly to be pushed instead of pulled through the pipe section. 
         [0012]    The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the invention, read in conjunction with the accompanying drawings. The detailed description and drawings are intended to be illustrative rather than limiting, the scope of the invention being defined by the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  schematically illustrates a prior art method of repairing or reinforcing an underground pipe that includes the step of pulling a liner assembly through a pipe section. 
           [0014]      FIG. 2  schematically illustrates an inventive method of repairing or reinforcing an underground pipe that includes the step of pushing an internally pressurized liner assembly through a pipe section. 
           [0015]      FIG. 3  schematically illustrates the use of a pig and a tag line to measure the length of a pipe section and determine the design length of a liner assembly to be inserted. 
           [0016]      FIG. 4  is a perspective view of a screw-in end plug that can be attached to both ends of the liner assembly to maintain internal pressure during installation of the liner assembly into the pipe section. 
           [0017]      FIG. 5  is a perspective new of the liner assembly of  FIG. 4  with a gas injection nozzle attached, to inject pressurized gas such as air into the liner assembly. 
           [0018]      FIG. 6  is a perspective view of an end cap for the liner assembly of  FIG. 4 . 
           [0019]      FIG. 7  is a top view of the liner assembly of  FIG. 4 , further equipped with two small partial openings for receiving a special two-pronged tool. 
           [0020]      FIG. 8  is a perspective view of one embodiment of a retainer sleeve that can serve as an adapter between one or both ends of the installed liner assembly and corresponding one or both ends of the pipe section. 
           [0021]      FIG. 9  is a perspective view of an end of a pipe section with the retainer sleeve of  FIG. 8  attached, and equipped with a threaded connector sleeve for connecting the pipe section to a main pipe or pipe assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Referring to  FIG. 2 , a pipe section  100  is shown having a first end  102 , a second end  104 , and a wall  106  having two sharp inner corners  108 . A flexible liner assembly  110  is provided including a first end  112  covered by plug  114 , and a second end  116  covered by plug  118 . The illustrated flexible liner assembly  110  includes a smooth flexible liner bore  120  and a semi-rigid reinforcing helix  122 . In alternative embodiments, the flexible liner assembly  110  may be formed of a corrugated semi-rigid plastic material, or another suitable material. 
         [0023]    In order to repair or reinforce the pipe section  100  using the flexible liner assembly  110 , a selected pressure, such as air pressure, is applied internally in the liner assembly  110 . The internal pressure is large enough to maintain integrity and prevent collapse of the liner assembly  110 , but not so large as to prevent bending and flexing of the liner assembly  110 . The plugs  114  and  118  or other suitable means are employed to maintain the desired pressure inside the liner assembly  110 . The desired pressure inside the liner assembly  110  is generally about two (2) to about twenty (20) psi, suitably about three (3) to about six (6) psi. The optimum pressure may be different for different applications, depending on the length and diameter of the pipe section  100 , the length and diameter of the liner assembly  110 , the material of construction of the liner assembly  110 , the number of turns in the pipe section  100 , and other factors. 
         [0024]    While maintaining the internal pressure, the first end  116  of the liner assembly  110  is inserted into the first end  102  of the pipe section  100 . The liner assembly  110  is then pushed through the pipe section  100  in the direction of the arrow until the first end  116  of liner assembly  110  approaches or reaches the second end  104  of pipe section  100 . As shown in  FIG. 2 , because the pressurized liner assembly  110  is being pushed instead of pulled, the liner assembly  110  urges away from the sharp inner corners  108  of the wall  106  of pipe section  100 , and instead slides along the smoothly curved outer portions  109  of the wall  106 . There is little or no risk of liner assembly  110  becoming ensnared by the sharp inner corners  108 , and the liner assembly  110  passes through the pipe section  100  with minimal resistance. 
         [0025]    The liner assembly  110  suitably has a predetermined length that is approximately equal to the length of the pipe section  100  being repaired or reinforced. This way, when the first end  112  of the liner assembly  110  approaches the second end  104  of the pipe section  100 , the second end  116  of the liner assembly  110  will approach the first end  102  of the pipe section  100 . Because the liner assembly  110  is flexible, it may have a length that is slightly longer or slightly shorter than the length of pipe section  100 . Suitably, the length of the liner assembly  110 , while internally pressurized, is within about 20%, or within about 10% of the length of pipe section  100 . 
         [0026]    After the liner assembly  110  is fully inserted in the pipe section  100 , such that the first end  112  of the liner assembly  110  reaches the second end  104  of pipe section  100 , the internal pressure is released from the liner assembly  110 . This can be accomplished by removing the end plugs  114  and  118  from the liner assembly  110 . Before or after the internal pressure is released, the outer circumference of the first end  112  of the liner assembly  110  can be sealed to the inner circumference of the second end  104  of pipe section  100 , and the outer circumference of the second end  114  of the liner assembly  110  can be sealed to the inner circumference of the first end  102  of the liner assembly  110 . By virtue of the sealing, and the removal of end plugs  114  and  118 , the interior of the liner assembly  110  then functions as the interior of the pipe section  100  for purposes of passing fluids or storing electrical cable. The flexible liner assembly  110  provides a leak-free conduit, while the original pipe section  100  provides structural integrity. 
         [0027]    The desired length of the liner assembly  100  can be determined by initially measuring the length of the pipe section  110  using a pig  130  attached to a tag line  132  as shown in  FIG. 3 . Pig  130  can be made of polystyrene foam or another lightweight material, and has a cylindrical shape or other suitable shape that allows it to be transported through pipe section  100  using a blast of air from the first end  102  and/or vacuum from the second end  104 . The tag line  132  has a length at least as high as the length of pipe section  100  and can range from about 50 feet to several hundred feet. The pig  130  can be transported through the pipe section  100  in the direction of the arrow using a blow gun applied at the first end  102  and/or a wet/dry vacuum applied at the second end  104 . When the pig  130  reaches the second end  104 , the tag line  132  can be detached or left attached. The length of the tag line between the first end  102  and the second end  104  is then measured to determine the design length of the liner assembly  110 . 
         [0028]    The pig  130  can alternatively be in the form of a wooden sphere, a plastic bag containing foam pieces, or another suitable material. When the pig  130  is formed as a wooden sphere, a fluid such as water can alternatively be employed to transport the pig  130  through the pipe section  100 . The length of pipe section  100  is typically the underground length, measured from a convenient entry point upstream from where the pipe section  100  enters the ground to a convenient exit point downstream from where the pipe section  100  leaves the ground. 
         [0029]    When the liner assembly  110  is formed of a smooth flexible bore  120  and semi-rigid helix  122 , the smooth flexible bore  120  can be formed of polyamide, polypropylene, polyethylene, EPDM, nitrile, PVC/NBR (polyvinyl chloride/nitrile butadiene rubber) blends, or another suitable flexible material having good long-term stability during use. The semi-rigid helix  122  can be formed of polypropylene, polyethylene, wire reinforcement, or another suitable semi-rigid material. The semi-rigid helix  122  can be inside the flexible bore  120 , or may be external to the flexible bore  120 , in which case the flexible bore  120  is adhered to the semi-rigid helix  122  using heat or a suitable adhesive material. A commercially available material that combines the flexible bore  120  and semi-rigid helix  122  is sold by Kuryama of America, located in Schaumburg, Ill., under the trade name TIGERFLEX®. 
         [0030]    The liner assembly  110  may alternatively be formed using a semi-rigid corrugated plastic material. Suitable plastic materials include without limitation polypropylene, high density polyethylene, polyamides, polyvinyl chloride, PVC/NBR blends, and laminates thereof. Other suitable materials and structures may also function as the liner assembly  110 , provided that the liner assembly  110  has sufficient flexibility to pass around corners in the pipe section  100 , and sufficient rigidity to avoid collapse. 
         [0031]    The plugs  114  and  118  can be externally threaded plugs that screw into mating threads provided at the respective ends  112  and  116  of the liner assembly  110  to provide a substantially air-tight seal.  FIG. 4  illustrates one embodiment of plug  114  or  118 , designated as a threaded plug  140  having an internally threaded opening  142  and external threads  144 .  FIG. 5  illustrates the same plug  140  in which an injection nozzle  146  is connected to inlet  142  to permit the controlled injection of air from a pressurized air supply (not shown).  FIG. 6  illustrates the same plug  140  in which a top cap  148  having a threaded portion  150  is screwed, pressure fitted, or otherwise sealed in the opening  142 . The top cap  148  optionally has a hook or loop  152  which can be connected to a tag line, as further explained below. 
         [0032]    When the liner assembly  110  is being pressurized, prior to insertion into the pipe section  100 , a first plug  114  (represented by a combination of threaded plug  140  and end cap  148 ) can be screwed into the first end  112  of the liner assembly  110  with the aid of an epoxy or other sealant, if necessary, to provide a sealed fit. A second plug  118  (represented by a combination of threaded plug  140  and injection nozzle  146 ) can be screwed into the second end  116  of the liner assembly  110  with the aid of an epoxy or other sealant, if necessary. Air from a pressurized air supply (not shown) can be injected through nozzle  146  into the liner assembly  110  until a desired pressure is achieved. Then, the air supply is isolated and the injection nozzle  146  is removed from the second plug  118  and replaced with an end cap  148 . 
         [0033]    At this point, the pressure inside the liner assembly  110  is maintained, and the liner assembly  110  can be inserted into the pipe section  100  by pushing from the second end  116  as described above. Alternatively, the liner assembly  110  can be inserted into the pipe section  100  using a combination of pushing from the second end  116  and pulling from the first end  112 . In order to perform the combination of pushing and pulling, the trailing end  131  of the tag line  132  shown in  FIG. 3  can be tied or otherwise connected to the hook  152  of the end cap  148  on the first end plug  114  on the liner assembly  110 . This is accomplished before the liner assembly  110  is inserted into the pipe section  100 . Then, the liner assembly  110  can be inserted by pushing from the second end  116 , as explained above, and pulling from the first end  112  by pulling the leading edge  133  of the tag line  132  which can be connected to the pig  130 . Depending on the application, the pushing and pulling of the liner assembly  110  through pipe section  100  need not be performed simultaneously. In some applications, it may be desirable to perform an alternating sequence of pushing and pulling. In other applications, it may be desirable to continuously push from the second end  116  of the liner assembly and only occasionally pull from the first end  112  of the liner assembly. By designing the liner assembly  110  for both pushing and pulling, the user has the flexibility to perform whatever steps are necessary to successfully insert the liner assembly  110  into the pipe section  100 . 
         [0034]    The plugs  114  and  118  can be formed of any suitable material such as polyvinylchloride, polypropylene, high density polyethylene or the like. The end plugs  114  and  118  are not limited to the foregoing configurations. Also, the tag line  132  should be formed of a material that is sufficiently strong to accommodate the liner assembly  110 , but does not cut and groove any portion of the wall  106  of the pipe section  100 . If the material of the tag line  132  is too sharp, it may cut and groove the sharp inner corners  108 , causing unwanted drag. One particularly suitable material for the tag line  132  is a flat nylon tape having a width of at least about 0.5 inch. 
         [0035]    As illustrated in  FIG. 7 , the top of the plug  140  may be designed with two small partial openings  141  and  143  that do not extend all the way through the plug  140 . The partial openings  141  and  143  are intended to accommodate a special two-pronged tool which facilitates the screwing and unscrewing of the plug  140  from the liner assembly  110 . 
         [0036]    After the liner assembly  110  has been fully inserted into the pipe section  100 , the internal pressure is released by removing both end plugs  114  and  118 . If the threaded plugs  140  are used, they can be unscrewed with the aid of a two-prong tool that engages openings  141  and  143 . After the end plugs  114  and  118  are removed (or, in some instances, before), the outer surface of the end portions  112  and  116  of the liner assembly  110  can be fitted to the inner surface  109  of the pipe section  110 . Typically, the first end  112  of liner assembly  110  is fitted to the pipe section  100  near its second end  104 , and the second end  116  of liner assembly  110  is fitted to the pipe section  100  near its first end  102 . 
         [0037]    In order for the installed liner assembly  110  to serve as a conduit within the pipe section  100 , it is important to provide leak-proof seals between the ends of the liner assembly  110  and the pipe section  100 . In most instances, the outer diameter of liner assembly  100  is slightly smaller than the inner diameter of pipe section  100 . In order to accommodate the differences in diameter, a retainer sleeve  160 , such as shown in  FIG. 8 , can be provided at both ends  102  and  104  of pipe section  100  to serve as an adapter between liner assembly  110  and pipe section  100 . 
         [0038]    The retainer sleeve  160  has a first portion  162  of narrower outer diameter, a second portion  164  of intermediate outer diameter, and a third portion  166  of wider outer diameter. The first portion  162  may or may not be threaded, and is adapted to engage the inner surface of liner assembly  110  at either or both ends  112  and  116 . The outer diameter of first portion  162  is about equal to the inner diameter of liner assembly  110 . An epoxy or other sealant can be applied to form an air and water tight, pressure resistant seal. 
         [0039]    The second portion  164  may or may not be threaded, and is adapted to engage the inner surface of pipe section  100  at either or both ends  102  and  104 . The outer diameter of second portion  164  is about equal to the inner diameter of pipe section  100  at either or both ends. An epoxy or other sealant can be applied to form an air and water tight, pressure resistant seal. 
         [0040]    The third portion  166  may or may not be threaded, and has an outer diameter about equal to the outer diameter of pipe section  100  at either or both ends. As shown in  FIG. 9 , when the retainer sleeve  160  is fully installed, the third portion  166  may appear as a short extension of pipe section  100  at one or both ends  102  and  104 . The pipe section  100  can then be reconnected to the main pipeline or pipe assembly from which it was disconnected to initiate the repair or reinforcement. If the ends of the pipe section  100  are equipped with a standard threaded connector sleeve  170  having threads  172 , the connector sleeve  170  can be reconnected to a mating connector sleeve on the main pipeline or pipe assembly (not shown). The reconnection of mating connector sleeves further reinforces the position of retainer sleeve  160  at one or both ends of pipe section  100 . Sealing rings, such as O-rings, can also be used to reinforce the connection between connector sleeves  170  and mating connector sleeves. 
         [0041]    The embodiments of the invention described herein are exemplary. Various modifications and improvements can be made without departing from the sprit and scope of the invention. The scope of the invention is indicated by the appended claims, and all changes that fall within the meaning and range of equivalents are intended to be embraced therein.