Patent Publication Number: US-7581600-B1

Title: Method of forming a trenchless flowline

Description:
BACKGROUND OF THE INVENTION 
     Underground utilities, such as storm sewers and other fluid lines, require a flow line to be bored in the ground beneath the surface. Accuracy in the boring process is essential for proper flow through the line. Various methods have been utilized for boring the flow line and installing the pipes therein. These methods include open digging or trenching, tunneling and auger boring, and directional drilling. Each of these methods of boring the flow line has problems and limitations. 
     For example, open digging presents hazards for workers in the trench. Also, the large size of the trench created by open digging requires extensive time to dig and refill. Furthermore, the pipe in the trench must be backfilled with gravel or similar material to keep the pipe in place. The equipment used in tunneling is complex and expensive, and typically not cost effective for bores having a diameter of less than two to three feet. The tunnel equipment is also bulky and heavy. The pipes used in the tunnels are also expensive. Auger boring lacks guidance, and therefore presents difficulty in creating the proper grade and line. Also, the pipe in both tunneling and auger boring is installed within the bore by a jacking process, and thus must have sufficient strength to withstand the jacking forces. In both tunneling and auger boring, it is sometimes necessary to provide a carrier pipe within a larger pipe to prevent corrosion and provide proper grade. 
     The directional drilling process eliminates many of the problems associated with open trenching, tunneling and augering, but also has drawbacks, such as lack of accuracy in the electronic tracking components so as to provide proper line and grade for the flow line. Also, the pipes are subjected to substantial pressure from the slurry in the bored hole, and the pipe can float or deflect if the bored hole is too large. 
     Therefore, a primary objective of the present invention is the provision of an improved method of forming a trenchless flow line using directional drilling. 
     Another objective of the present invention is the provision of a method of pilot stem control during directional drilling of a flow line. 
     A further objective of the present invention is the provision of an improved method of back reaming a directionally drilled bore for a flow line. 
     Still another objective of the present invention is the provision of a method of supporting the boring tool during drilling so as to overcome gravity drop of the tool in vertical sight relief holes. 
     Another objective of the present invention is the provision of a method of forming a flow line using a minimum of steps. 
     A further objective of the present invention is the provision of a method of forming a flow line using directional drilling having close tolerance between the bore and the pipe. 
     Still another objective of the present invention is the provision of a method of forming a flow line using directional drilling wherein the slurry in the bored hole is pushed ahead of the pipe and is forced into vertical sight relief holes as the pipe is pulled through the bored hole. 
     Yet another objective of the present invention is the provision of an improved method of forming a trenchless flow line which is accurate and cost effective. 
     These and other objectives will become apparent from the following description of the invention. 
     BRIEF SUMMARY OF THE INVENTION 
     The improved method of directionally drilling a flow line involves the initial steps of making a series of substantially vertical sight relief holes, and then drilling a pilot hole in a first direction to each of the sight relief holes using a boring tool on a directional drilling machine. One aspect of the present invention is supporting the boring tool at each of the sight relief holes using a hook extending into the hole so as to overcome the force of gravity on the tool. The method also includes the step of back reaming the pilot hole in a second direction opposite the first direction using a back reaming tool so as to enlarge the diameter of the pilot hole. Another aspect of the present invention is attaching the flow line pipe to the reaming tool and pulling the tool and pipe together in the second direction through the enlarged hole in a single step, thereby eliminating two steps in the known, prior art directional drilling process. Liquid is supplied during the reaming step to form a slurry in the enlarged hole, with the slurry being forced ahead of the pipe and into the sight relief holes as the pipe is moved through the enlarged hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of the first aspect of the improved method of the present invention wherein the pilot stem is supported by hooks extending downwardly in the vertical sight relief holes. 
         FIG. 2  is a schematic view of a second aspect of the present invention wherein the back reaming tool and pipe are pulled through the reamed flow line hole together, in one step. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, the ground surface is generally designated by the reference numeral  10 . Multiple sight relief holes  12  are drilled substantially vertically in the ground to a distance slightly below the grade or level of the flow line pipe to be installed. A pilot stem or boring tool  14  of a directional boring machine located on the surface  10  creates a pilot hole under the surface  10  of the ground. As the pilot stem  14  reaches each sight relief hole  12 , the depth and line of the bore stem  14  is measured, preferably in the manner described in Applicant&#39;s prior U.S. Pat. No. 6,732,816, which is incorporated herein by reference. 
     The present invention is directed, in part, to a tool or hook  16  extending downwardly in each of the sight relief holes  12  to support and engage the pilot stem  14  as the stem passes through the holes  12 . Particularly in soft or sandy soil, there is a tendency for the pilot stem  14  to drop due to the force of gravity as it passes through the hole  12 , thereby deflecting from the proper line and grade of the flow line. The hooks  16  overcome the gravitational effect on the pilot stem  14 , thereby maintaining the correct line and grade for the pilot hole. The hooks  16  are each support above the ground in any convenient manner, such as by tripods  15 . A lifting device  17  is provided on each tripod to allow the vertical position of the hook  16  to be adjusted so as to provide the proper line and grade of the pilot stem  14  through the respective sight holes  12 . 
     After the pilot hole is completed, a reaming tool  18  is connected to the end of the pilot stem  14 . The new pipe  20  is connected to the reaming tool  18  via a swivel connector  22 , a mud paddle  24 , and a connecting rod  26 . The pilot stem  14  is then pulled backwardly through the pilot hole, thereby pulling the reaming tool  18  and the pipe  20  through the hole in a single step. The reaming tool  18  enlarges the pilot hole ahead of the pipe  20 . As the pilot hole is being reamed by the reaming tool  18 , drilling fluids are supplied in a conventional manner, thereby creating a slurry mixture of soil and fluids. The slurry mixture  30  flows in front of and around the pipe  20 , as well as upwardly into the vertical sight relief holes  12 . This improved method allows the pipe  20  to be installed in a reamed hole that is only ⅛-1 inch larger in diameter than the outside diameter of the pipe  20 , no matter what size pipe is being installed. The slurry mixture  30  prevents the pipe  20  from floating within the reamed hole, while the sight relief holes  12  also prevent excessive slurry pressure from damaging the pipe  20  and existing utilities. 
     The connecting rod  26  will preferably have a length equal to, or slightly greater than, the largest distance between adjacent sight relief holes  12  alone the line. The rod  26  may have one or more sections to get the desired length. Thus, the pipe pulling head  28  may be separated from the reaming tool  18  by a distance of 40 feet or more. The spacing between the pipe pulling head  28  and the reaming tool  18  allows the tool  18  to pass each of the relief holes  12 , with the pipe pulling head  28  forcing the slurry  30  ahead of the head  28  and up each relief hole  12 . The mud paddle  24  has a plurality of blades which minimize or eliminate rotation of the connecting rod  26 , thereby enhancing safety. 
     By connecting the pipe  20  to the reaming tool  18  and pulling them together through the reamed hole, two steps are eliminated from the prior art process described in Applicant&#39;s U.S. Pat. No. 6,732,816. In particular, the pre-reaming and push back steps are not necessary with the present invention. Therefore, the improvements of the present invention provide for drilling of a trenchless flow line with less time and cost. 
     The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. From the foregoing, it can be seen that the present invention accomplishes at least all of its stated objectives.