Abstract:
A pipeline is constructed in steep terrain by digging a ditch on the incline, assembling pipe joints together adjacent a top of the incline and then lowering the assembled pipe joints down the incline through the ditch. A wheeled assembly at the lower end of the pipeline carries much of the load and rolls down the ditch as allowed by winch equipment at the top of the incline. Bearing supports are installed periodically in the ditch to support the pipeline, the supports being of a softer material than coatings on the pipe.

Description:
[0001]     This invention relates to an improved method and apparatus for laying pipe on inclined terrain and more particularly to laying pipe from adjacent the top of an incline toward the bottom.  
       BACKGROUND OF THE INVENTION  
       [0002]     The least expensive method of transporting large relatively constant quantities of liquids, slurries and gases is through pipelines buried in the earth. Once pipelines are built, operating costs are very small relative to the value of the contents being transported, safety concerns are much reduced and environmental impact from spills and leaks are very small. In other words, pipelines are the preferred method of transporting large quantities of liquids, slurries and gases. Unfortunately, initial capital costs are a very large proportion of the total cost of transporting fluids by pipeline meaning that very large sums are spent before any income is received. Accordingly, there is a large incentive to find less expensive techniques for installing or laying small and large diameter pipelines.  
         [0003]     Laying pipelines in relatively flat or moderately hilly country is done routinely and is not exorbitantly expensive. Pipelining in mountains or other steeply inclined terrain is difficult and exorbitantly expensive. The standard technique for laying pipeline on a steeply inclined area such as a mountain side or across a fault scarp, is to trench the route on the steepest and most direct route and then lay pipe from the bottom upwardly toward the top. Pipe joints are welded together, one joint at a time, in the ditch. After the welds are inspected and the bared ends field coated, the ditch is backfilled by pushing spoil back in the ditch.  
         [0004]     Installing pipelines on a steep incline is very slow, very dangerous and thus very expensive. There is always a danger of rocks, debris or equipment careening down the right-of-way, imperiling those below. It is difficult to stand on a steep incline, much less walk, weld or hold massive pipe joints in a position where they can be welded. There are many variables, of course, but it would not be surprising to learn that the cost per foot of laying pipe on a steep incline on any particular job may exceed $1000 per foot or be twenty five to thirty five times the cost per foot of laying comparable pipe in a conventional manner on flat ground or along a moderately hilly route where pipelining can be done in a normal manner.  
         [0005]     A moderately sized spread of men and equipment can lay pipe on flat or moderately hilly ground at a surprisingly rapid rate. A common speed would be several miles per day of pipe welded together, field coated, inspected, transferred to the ditch and backfilled. In contrast, pipelining on a steep slope is very slow. A common speed would be one to two lengths of pipe per day, totalling perhaps eighty feet per day but it could be much slower depending on the steepness of the slope, the material on the surface, the weather, and the diameter of the pipe being installed.  
         [0006]     Disclosures of interest relative to this invention are found in U.S. Pat. Nos. 2,991,974; 3,248,884; 5,197,713; 6,450,736 and 6,588,984.  
       SUMMARY OF THE INVENTION  
       [0007]     In this invention, pipelining on a steep slope is done by welding pipe joints together at or near the top of the slope, lowering the joined pipeline section into the ditch so the pipeline slides down the slope while in the ditch, welding additional joints to the upper end of the joined pipeline section and lowering the pipeline section again. This process is repeated until the lower end of the pipeline reaches the bottom of the slope where the lower end of the inclined pipeline is tied in to a pipeline section leading away from the slope.  
         [0008]     There are four major problems encountered when pipelining down a steep incline from the top: how does one safely hold the pipeline at the top of the incline so work can be done, how does one safely slide the pipeline in a controlled manner down the incline, how does one support the pipeline in its travel down the slope without irreparably damaging the coating on the exterior of the pipe and how does one steer the lower end of the pipeline if it attempts to curve into a side of the ditch, as it will almost surely do.  
         [0009]     One feature of this invention is the provision of a mechanism on the lowermost end of the pipeline that allows the pipeline to slide down the incline. This mechanism is typically wheeled and placed in the ditch so the pipeline follows the ditch down the incline. Downward movement of the mechanism is controlled in any suitable manner. One technique is to use cables attached to the mechanism which are slowly paid out. Another technique is to provide two sets of slips holding the upper end of the pipeline. Periodically, one of the slips is released and the other set of slips, connected by cables to a winch, is lowered by paying out the cable. In the latter technique, the pipe is used to transfer the load of the pipe to equipment at the top of the slope. The lower end of the pipeline can be steered in a variety of ways, one of which is to provide jacks pushing between the mechanism and the side of the ditch so the mechanism moves away from one side of the ditch.  
         [0010]     Another feature of this invention is the provision of bearings in the ditch to provide support for the pipeline during sliding movement down the incline. By selecting the material of the bearings to be softer than the material of the pipeline coatings, any wear that occurs is on the bearings and not on the pipeline coating. In addition, the bearings may be lubricated in a suitable manner to facilitate the pipe moving smoothly over the bearings.  
         [0011]     An important advantage of this invention is minimizing the number of people on the incline. Because all of the work done in joining pipeline sections together, in inspecting welds and in field coating bare pipe adjacent the welds is done at or near the top of the incline and almost no work is done on the incline, the number of people on the slope is minimized. This is extremely important for safety reasons. If there are fewer people on the slope, then fewer people can be hurt by rocks or debris careening down the incline. In addition, the fewer number of people on the slope provides fewer opportunities for people to be the cause of dislodging rocks or the like to imperil those below.  
         [0012]     An important advantage of this invention is minimizing of the width of the right-of-way that needs to be cleared. The right-of-way is usually an easement bought and used by the pipeline owner on which the pipeline is laid. A typical pipeline right-of-way is 50-100′ wide. Previously, the entire right-of-way would be cleared of trees, brush and debris. In the practice of this invention, a much narrower cleared right-of-way is sufficient because so few workmen and such little equipment is actually on the slope. A cursory investigation of the costs of pipelining, both financial and environmental, will reveal that the wider the cleared right-of-way, the higher the costs. In this invention, almost all of the work done in joining pipeline sections together is done at or near the top of the incline and almost no work is done on the incline. Thus, the right-of-way that needs to be cleared on the incline is no wider than necessary to accommodate the men and equipment needed to ditch a path down the incline. Whatever part of the right-of-way that needs to be cleared to make the ditch will necessarily be of sufficient width to accommodate men and equipment needed during laying of the pipeline. Minimizing the width of the cleared right-of-way is particularly important on a steep incline because it minimizes erosion after the pipeline is in the ground.  
         [0013]     Another important advantage of this invention is minimizing the amount of winch equipment needed to conduct operations. Heavy construction in mountainous areas is difficult because most equipment will not safely ascend or descend grades much greater than 27° without assistance from other stable stationary equipment. Heavy equipment safely moving on a steep hillside with an excessive grade depends on the nature of the soil. If the surface of the hill is loose material, heavy equipment cannot safely move or be safely operated. Under the best of soil and weather conditions with a 27° slope, most heavy equipment can operate, albeit very slowly. Of course, if the slope contains some rock, which is very common, the maximum safe slope is much less steep because moving equipment loses traction on rock. For example, if solid rock is on the surface, heavy equipment cannot safely negotiate a slope greater than about 9°. The only current solution is to winch the required equipment up and down the slope. If mobile equipment is not stable by itself, winching equipment is used to winch mobile equipment up the slope, hold the mobile equipment until the task is completed and then winch the mobile equipment down the slope. As will be more fully apparent hereinafter, very little equipment need be winched up and down the slope in the practice of this invention.  
         [0014]     It is an object of this invention to provide an improved technique for laying pipeline on inclined terrain.  
         [0015]     Another object of this invention is to provide an improved method and apparatus for laying pipeline in a ditch on inclined terrain that can be backfilled on completion.  
         [0016]     A further object of this invention is to provide an improved method and apparatus for lowering a long pipeline section from the top of an incline toward the bottom.  
         [0017]     Another object of this invention is to provide an improved method and apparatus for pipelining in steeply inclined terrain so fewer people are needed on the right-of-way so dangers and costs are substantially reduced.  
         [0018]     These and other objects of this invention will become more fully apparent as this description proceeds, reference being made to the accompanying drawings and appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a frontal view of a pipelining operation on a mountain side showing the ditch having been made;  
         [0020]      FIG. 2  is a pictorial view of a pipelining operation of this invention, showing the top of the incline and showing the ditch in longitudinal cross-section;  
         [0021]      FIG. 3  is a side view of the lower end of the pipeline showing the ditch in lateral cross-section and showing the wheeled assembly supporting the lower end of the pipeline;  
         [0022]      FIG. 4  is a front view of the wheeled assembly of  FIG. 3 ;  
         [0023]      FIG. 5  is a rear view of the wheeled assembly of  FIGS. 3 and 4 ;  
         [0024]      FIG. 6  is a side view of a lower set of slips to hold the pipeline stationary and then to release the pipeline for movement;  
         [0025]      FIG. 7  is a side view of an upper set of slips used to move the pipeline down the incline;  
         [0026]      FIG. 8  is a side view of an intermediate portion of the pipeline showing the ditch in longitudinal cross-section;  
         [0027]      FIG. 9  is a cross-sectional view of the pipeline and ditch taken along line  9 -- 9  in  FIG. 8  as viewed in the direction indicated by the arrows; and  
         [0028]      FIG. 10  is a view, similar to  FIG. 3 , of an alternative technique for lowering the pipeline down an incline. 
     
    
     DETAILED DESCRIPTION  
       [0029]     Referring to  FIGS. 1-8 , there is illustrated a pipelining method and apparatus for laying pipe from the top  10  of steep terrain  12  toward the bottom  14  along a cleared right-of-way  16  which has been trenched to provide a straight ditch  18  extending down the terrain  12 . In this invention, more than usual care is taken to make the ditch  18  relatively straight and of relatively constant slope because the pipeline  20  will move down the ditch  18 . Because the pipe is relatively stiff, any abrupt curves or changes in slope cannot be tolerated. Although the ditch  18  is illustrated as extending straight down the terrain  12 , it will be apparent that the ditch  18  may be slightly curved horizontally along the surface of the terrain or slightly bowed vertically to accommodate curvature of the slope. A general rule of thumb is the radius of curvature, in feet, has to be equal or greater than one hundred times the diameter of the pipe in inches. In other words, a 30″ diameter pipeline can safely be curved on a radius of 3000′ or greater.  
         [0030]     The pipeline method and apparatus of this invention has three distinct parts, i.e. what happens at or near the top  10  of the terrain  12 , what happens at or near the lower end of the pipeline  20  and what happens at an intermediate part of the pipeline  20 .  
         [0031]     After the ditch  18  has been cut and the necessary equipment and pipe have been assembled at or adjacent the top  10 , the first pipelining operation is to install an assembly  22  on the lowermost joint  24  of the pipeline  20  as shown best in  FIGS. 3-5 . The function of the assembly  22  is to facilitate movement of the pipeline  20  down the ditch  18 . The assembly  22  comprises a frame  26  having a lower frame member or yoke  28  secured, as by welding or the like, to the lowermost joint  24  in a stable manner. To this end, a pup joint  30  is provided which connects to the yoke  28  through a pair of pins  32  integral with the pup joint  30 . An axle  34  extends through the frame  26  and a large wheel  36  is mounted on the axle  34 .  
         [0032]     The frame  26  also includes an upper frame member  38  rigid with the lower frame member  28  at one end and connected at the other end by a connection  40  of adjustable length to a reinforcing pad  42  surrounding and secured to the pup joint  30  in a suitable manner, as by welding or the like. The adjustable connection  40  conveniently includes one or more telescoping braces  44  and a hydraulic cylinder  46  ( FIG. 5 ). Because the pup joint  30  is welded to the lowermost joint  24  of the pipeline  20 , adjusting the length of the braces  44  and cylinder  46  changes the angle between the lower frame member  28  and the pup joint  30 , thereby raising or lowering the free end of the pup joint  30  relative to the bottom of the ditch  18  and thereby raising or lowering the lower end of the pipeline  20 . The cylinder  46  is powered by a hydraulic system (not shown) mounted on the assembly  22  including an internal combustion engine driving a hydraulic pump, suitable hydraulic lines and suitable valves. The lowermost joint  24  and the assembly  22  are placed in the ditch  18 , as by the use of a crane  48 , so the wheel  36  is below a lower pipe roller assembly  50  ( FIG. 2 ).  
         [0033]     Referring to  FIG. 2 , the lower pipe roller assembly  50  cooperates with an upper pipe roller assembly  52  to start the pipeline  20  down the mountain side  12 . The assemblies  50 ,  52  are securely anchored in the earth and provide suitable rollers  54 , preferably of hour glass shape, engaging the pipeline  20  thereby facilitating sliding of the pipeline  20  down the incline of the ditch  18 .  
         [0034]     It is necessary to hold the pipeline  20  stationary so suitable pipeline operations can occur, such as welding additional joints to the open end of the uppermost joint  56 , inspecting the welds between adjacent joints and field coating the bare ends and welds of the previously coated pipe joints. To this end, a pair of expandable slips  58 ,  60  are provided. The lower slips  58  are installed in any suitable manner, as by using the crane  48  and suitable attachments (not shown). The lower slips  58  are held in place in the ditch  18  by chains or cables  59  attached to the upper pipe roller assembly  52  and manipulated between positions holding and releasing the pipeline  20  by a suitable control system (not shown). The upper slips  60  are manipulated between positions holding and releasing the pipeline  20  by a suitable control system (not shown) and move up and down the ditch  18  as allowed by a cable or other tension element  62  under the control of a winch system  64 .  
         [0035]     The slips  58 ,  60  and winch system  64  operate to hold the pipeline  20  stationary for work to be done on it and then lower the pipeline  20  for movement downward through the ditch  18 . To hold the pipeline  20 , both slips  58 ,  60  are in the holding position, preferably with the upper slips  60  raised to the position shown in  FIG. 2 . To lower the pipeline  20 , the lower slips  58  are manipulated to release the pipeline  20  and the upper slips  60  are allowed to move downwardly toward the lower pipe roller assembly  50  by paying out cable  62  from the winch system  64 . It will accordingly be seen that the lower slips  58  are relatively stationary and the upper slips  60  are movable.  
         [0036]     Details of the slips  58 ,  60  are shown in  FIGS. 6 and 7  and have much in common. The slips  58 ,  60  include a conical sleeve  66 ,  68  stiffened by a series of ribs  70 ,  72  and a series of wedge shaped slip segments  74 ,  76  received inside the sleeves  66 ,  68 . The slip segments  74 ,  76  are advanced and retracted by hydraulic cylinders  78 ,  80  acting between the slip segments  74 ,  76  and a frame member  82 ,  84  rigid with the sleeves  66 ,  68  and spaced axially by a series of struts  86 ,  88 . It will be seen that extension and retraction of the hydraulic cylinders  78 ,  80  causes the slip segments  74 ,  76  to advance and retract from the conical sleeves  66 ,  68  thereby gripping and releasing the pipeline  20  from the slips  58 ,  60 .  
         [0037]     The lower slips  58  are preferably relatively stationary, either by providing a separate foundation mounted in the ditch  18  or by securing the slips  58  to the upper pipe roller assembly  52  with the chains or cables  59 . The upper slips  60  are mounted for movement along an axis  90  parallel to the pipeline  20  and parallel to the ditch  18 . To this end, a frame member  92  is attached to the ribs  72  and provides hourglass shaped pipe rollers  94  for abutting and rolling on the pipeline  20  when the slips  60  are released from the pipeline  20 . The frame member  92  provides an eye  96  so it can conveniently be hoisted by the crane  48  when needed.  
         [0038]     The upper slips  60  include a pair of multiline sheaves  98  mounted for rotation on a frame  100  welded to the cone  68  and ribs  72 . The sheaves  98  receive multiple lines of the cable  62  hauled in and paid out by the winch system  64 . It will accordingly be seen that, when the pipeline  20  is to be held stationary, the lower and upper slips  58 ,  60  may both grip the pipeline  20 . When the pipeline  20  is to be lowered down the slope in the ditch  18 , the upper slips  60  grip the pipeline while the lower slips  58  are actuated to release the pipeline so paying out the cable  62  by the winch system  64  allows the pipeline  20  to slide down the ditch  18  as facilitated by the wheeled assembly  22 .  
         [0039]      FIGS. 3, 8  and  9  illustrate an important feature of this invention. Suitable bearings  102  are provided periodically along the length of the pipeline  20  to raise the pipeline  20  above the bottom of the ditch  18  to reduce friction on the pipeline  20  and to control wear of a coating  104  on the exterior of the pipeline  20 . Pipeline coatings have evolved substantially over the years so the current state-of-the-art coating is an epoxy based polymer concrete exemplified by POWERCRETE available from Tyco Adhesives of Norwood, Mass. Typically, the pipeline coating is applied at the pipe mill or at a plant long before the joints are delivered to the job location. A short length of metal pipe is left bare on each end so adjacent pipe joints can be welded without degrading the coating. Many permanent type current pipeline coatings are quite hard and tough, typically at least about 75 on the Shore D hardness scale after curing for twenty four hours.  
         [0040]     As will be more fully apparent hereinafter, after the joints are welded together, the previously uncoated bare ends of the pipe joints are coated. This occurs at a site in the ditch  18  above the lower slips where the welded joint is being held while an additional joint is being welded on the end of the pipeline. Modern materials for field coating cure quickly enough that there is no appreciable delay in the pipelining operation. For example, in large diameter pipe where this invention has greatest application, it may take an hour or two to weld joints together, leaving plenty of time to X-ray the field weld, prepare the bare ends of the pipe, coat the bare ends or field joint and allow the field coated sections to cure enough so as not to be damaged while the pipeline is sliding down the slope.  
         [0041]     An important feature of this invention is that the bearings  102  are considerably softer than the coating  104  so that any wear occasioned by sliding the pipeline  20  across the bearing  102  causes wear on the bearing  102  and not on the coating  104 . To this end, the bearing  102  is selected of a suitable plastic or polymeric material such as high or low density polyethylene having a Shore D hardness in the range of 40-60, such as is available from Performance Pipe, Plano, Tex., Maskill Robbins of Houston, Tex. or Forrester Supply of Green Bay, Wis. As shown best in  FIGS. 8 and 9 , the bearings  102  are generally upwardly concave providing one or more struts or cleats  106  extending away from the bearing  102  to prevent the bearings  102  from slipping off the foundation  108  while the weight of the pipeline  20  is gradually transferred from the wheel assembly  22  to the ditch  18 .  
         [0042]     As shown in  FIG. 3 , after passage of the wheel  36 , a suitable foundation  108  is placed on the bottom of the ditch  18  to receive the bearings  102 . In many instances, the foundation  108  may simply be bags  110  of sand or other particulate material. In some situations, the foundations  108  may need to be sturdier or more elaborate, depending on the slope of the ditch  18  and the available material in the bottom of the ditch. After construction of the foundation  108 , the bearing  102  is slid into place in any suitable manner, as by first laying the bearing  102  on top of the pipeline  20  as shown in  FIG. 3  and then sliding it downwardly under the pipeline  20  when the wheeled assembly  22  moves away from the last installed foundation  108 .  
         [0043]     An important feature of this invention is lubricating the bearings  102  with a liquid lubricant thereby promoting sliding movement between the bearings  102  and the pipeline  20  and minimizing tipping or movement of the bearings  102  relative to the ditch  18 . To this end, a suitable lubricant such as DYNA-BLUE available from American Polywater Corporation of Stillwater, Minn. is applied to the bearings  102 , preferably after each bearings  102  is placed on its foundation  108  and before the pipeline  20  advances into contact with the bearing  102 . The lubricant is applied in any suitable manner, as with a mop type applicator or by spraying.  
         [0044]     The method of this invention should now be apparent. After the ditch  18  is trenched down the slope  12  and the necessary equipment assembled at the top  10 , the lower most joint  24  is welded to the pup joint  30  of the assembly  22 . The assembly  22  is then placed in the ditch  18  below the lower pipe roller assembly  50 , as by use of the crane  48 . The lower slips  58  are manipulated to grip the pipeline  20  and the upper slips  60  are slipped over the inclined end of the upper most pipe joint. The upper slips  60  are actuated to grip the pipeline  20  so the upper end of the upper most pipe joint  56  is securely held in a stationary position.  
         [0045]     The crane  48  picks up a joint  112 , or a multiple joint, of pipe and holds it in the inclined position shown in dashed lines in  FIG. 2 . A double joint of pipe is the result of welding two joints of pipe together at a location away from the upper pipe roller  52  and coating the bare ends of the welded pipe to provide a continuous coating  104 . Double, or multiple, jointing is a conventional technique to increase the rate of pipe laying. Suitable pipe clamps (not shown) are used to clamp the lower end of the suspended pipe joint  112  coaxial with the uppermost joint  56  and the pipe joints  56 ,  112  are welded together at a location adjacent the upper pipe roller  52 . Upon completion of the weld, the pipeline  20  is lowered down the slope in the ditch, using the slips  58 ,  60  as previously described. When the most recent weld reaches a location  114  adjacent the lower pipe roller assembly  50 , other pipelining operations are conducted such as inspecting the weld with an suitable X-ray machine  116  and coating the bare ends of the newly welded joint with a coating assembly  118 , as previously discussed.  
         [0046]     At suitable intervals, the sand bags  110  are placed in the ditch behind the wheeled assembly  22  and the bearings  102  placed between the pipeline  20  and the sand bags  110 . In the event the pipeline  20  is slightly too low, the cylinder  46  may be manipulated to raise the end of the pipeline or the pipeline  20  may be raised by using a jack under the reinforcing pad  24 . When the pipeline  20  reaches the bottom  14  of the inclined terrain  12 , the pipeline  20  is stabilized in any suitable manner, the simplest way being simply to back fill the ditch  18  in a few locations spaced along the slope. Under some circumstances, it is feasible to leave the bearings  102  in place and in some situations it is desirable to remove them. If the bearings  102  are removed, a suitable inflatable air bag type jack is brought to the location of each bearing  102 , placed under the pipeline  20  near the bearing to be removed and then inflated to raise the pipeline  20  so the bearing  102  can be retrieved.  
         [0047]     After the pipeline  20  is stabilized, the wheeled assembly  22  is removed and the lower end of the pipeline is tied into a pipeline leading away from the steep terrain  12  in a conventional manner. At the top of the steep terrain  12 , the upper and lower roller assemblies  50 ,  52  and other equipment at the top  10  are disassembled and removed. The upper end of the pipeline is tied into a pipeline section leading away from the top  10  in a conventional manner.  
         [0048]     Referring to  FIGS. 4-5 , an important feature of this invention is illustrated to steer the assembly  22  in the event it is moving too close to one side or the other of the ditch  18 . To this end, a jack  120  is provided. The jack  120  is carried on the wheeled assembly  22  and connected to the hydraulic system powering the cylinder  46 . The jack  120  is placed in the ditch  18  and abuts, if necessary, a suitable backup  122 , such as a plate or beam, between the jack  120  and ditch  18  to provide additional bearing. Delivering high pressure hydraulic fluid through a hydraulic line  124  extends the jack  120  and pushes the wheel  36  away from the close side of the ditch  18  thereby steering the wheeled assembly along a central portion of the ditch  18 .  
         [0049]     Referring to  FIG. 10 , an alternative technique is illustrated to control the assembly  22  as it is lowered through the ditch  18 . Rather than using a pair of slips  58 ,  60  and moving the upper slips  60  with the cable  62 , a cable  126  extends from the winch system  64  down the pipeline  20  to adjacent the wheeled assembly  22  where it connects in any suitable fashion to the reinforcing pad  42 . It will be seen that the assembly  22  is directly connected to the cable  62  and the assembly  22  is allowed to move down the ditch  18  when cable  126  is paid out from the winch system  64 .  
         [0050]     Although this invention has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of construction and operation and in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.