Patent Publication Number: US-2004045178-A1

Title: Method and apparatus for aligning and cutting pipe

Description:
[0001] This application claims the benefit of U.S. Provisional Application No. 60/280,271 filed on Mar. 30, 2001. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] With the aging of industrial plants, many plants need to be rebuilt. A primary reason for failure of an industrial plant is a breakdown of its piping system owing to stress applied to the system. Stress results from heating and cooling of fluids in the pipes which causes them to expand and contract. Stress also results from improper fitting of pipes during initial construction. Sections of pipe are connected at their ends, generally by welding. For a proper fit, the end surface of a new or replacement pipe is cut and beveled to match the end surface of an existing pipe. For large pipes, i.e. those having a diameter on the order of 20 inches or more, a cutting tool is used either to cut a section of pipe to length or to trim the end surface thereof to match the end surface of the pipe with which it is to be connected. The cutting tool, which may weigh as much as 200 pounds, is positioned on the pipe, to cut the edge to a desired configuration. Unfortunately, much guesswork is involved in positioning the tool which is also cumbersome to adjust. Using trial and error, a pipe fitter cuts the pipe to as close an approximation of the proper end surface configuration as possible. Then the pipe sections are connected together.  
       [0003] The present invention relates to a method and apparatus for cutting and fitting pipes so that they are properly aligned for welding to create a stress-free piping system. The invention may also be used in the replacement of worn or damaged pipe sections under stress.  
       BRIEF DESCRIPTION OF THE PRIOR ART  
       [0004] Laser devices for centering pipes are well-known in the patented prior art as evidenced by the US patent to Davis U.S. Pat. No. 6,052,911. As disclosed therein, a laser is rotatably connected with a frame which is mounted on the pipe. The axis of the laser is aligned with the centerline of the pipe and is used to provide marks which assist in aligning a new pipe parallel to an old pipe.  
       [0005] While the prior devices operate satisfactorily, they are rather cumbersome and do not afford the opportunity for a pipefitter to both align and cut a section of pipe with a single instrument, which greatly reduces the time and increases the accuracy of the cutting process. The present invention was developed in order to overcome these and other drawbacks of the prior devices by providing an improved method and apparatus for efficiently aligning and cutting pipes, particularly metal pipes in the piping system of an industrial plant. It will greatly enhance the ability of a person of average pipe cutting and fitting skills to install or replace pipes in the piping system.  
       SUMMARY OF THE INVENTION  
       [0006] Accordingly, it is a primary object of the present invention to provide a method and apparatus for aligning and cutting a cylindrical pipe having a longitudinal axis in which a frame or ring is mounted on the periphery of the pipe and has a laser mounted thereon. The laser generates a linear laser beam and the frame is adjusted so that the beam is directed onto a fixed remote target corresponding with the end of another pipe. Once adjusted, the frame is secured in place and a cutting tool is used to cut the pipe in a configuration to match and mate with the end of the other pipe.  
       [0007] According to a further object of the invention, a plurality of lasers are provided on the frame in spaced relation. The lasers are preferably adjustably connected with the frame so that the beams therefrom can be directed at selected angles relative to the longitudinal axis of the pipe.  
       [0008] It is yet another object of the invention to align and cut a damaged section of pipe for removal and to align and cut both ends of a replacement section of pipe for a precise fit of the replacement section with minimal stress after welding the replacement section.  
       [0009] A further object of the invention is to provide a method and apparatus for aligning and cutting a cylindrical pipe adjacent to an elbow portion thereof by mounting a ring on the pipe about the pipe circumference before the elbow portion and establishing a pair of first reference points spaced 90° relative to a longitudinal axis of another pipe at a remote location beyond the elbow and establishing a pair of second reference points on the ring and spaced 90° relative to a longitudinal axis of the pipe. The ring is adjusted to a fixed position so that the pair of second reference points are oriented in a configuration corresponding to the pair of first reference points to define a cutting location so that after cutting, the cut end surface of the pipe will be in 90° alignment with the end of the first pipe.  
       [0010] According to another object of the invention, the ring is adjusted on the pipe via triangulation. 
     
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
     [0011] Other objects and advantages of the invention will become apparent from a study of the following specification, when viewed in the light of the accompanying drawing, in which:  
     [0012]FIGS. 1 and 2 are front and side plan views, respectively of an alignment ring having a laser thereon in accordance with the pipe cutting method and apparatus of the invention;  
     [0013]FIG. 3 is a side plan view of an alternate embodiment of the alignment ring of the invention having a plurality of adjustable lasers thereon;  
     [0014]FIGS. 4 and 5 are front plan views showing a pipe mounting frame having a cutting tool and a laser mounted thereon, respectively;  
     [0015]FIG. 6 is a side view of an alternate assembly for mounting an alignment tool on a pipe;  
     [0016]FIG. 7 is a side plan view of a cutting tool of the invention and illustrating an alignment beam used therewith;  
     [0017]FIGS. 8 and 9 are side plan views showing the use of two cutting tools for trimming and removing sections of pipe, respectively;  
     [0018]FIG. 10 is a front plan view showing a cutting tool frame having three laser devices mounted thereon;  
     [0019]FIGS. 11 and 12 are front and side views, respectively, of a mounting bracket for a laser according to the invention;  
     [0020]FIGS. 13 and 14 are front and side plan views, respectively, of an adjustable mounting bracket for a laser according to the invention;  
     [0021] FIGS.  15 - 17  are side plan views, respectively, showing alternate mounting arrangement for a laser on a cutting tool according to the invention.  
     [0022]FIGS. 18 and 19 are front and side views, respectively, of a laser target used with the invention;  
     [0023]FIGS. 20 a  and  20   b  are side plan and front views, respectively, showing a first technique for cutting pipe at an elbow;  
     [0024]FIG. 21 is a perspective view illustrating the alignment of the end faces of two pipes on opposite ends of an elbow portion;  
     [0025]FIGS. 22 a  and  22   b  are side plan and front views, respectively, showing a second technique for cutting pipe at an elbow; and  
     [0026]FIGS. 23 and 24 are top and side plan views showing the technique for replacing an elongated elbow section. 
    
    
     DETAILED DESCRIPTION  
     [0027] The pipe alignment and cutting technique according to a first embodiment of the invention will be described with reference to FIGS. 1 and 2. As shown therein, a generally cylindrical ring  2  includes a clamping device  4  for clamping the ring around a cylindrical pipe (not shown) having a longitudinal axis. Any suitable clamping device may be used such as a nut and bolt, a spring latch, or the like. A laser  6  is mounted on the ring and generates a linear laser beam  8  which extends parallel to the axis of the pipe.  
     [0028] In accordance with the inventive method, the ring is loosely positioned on the pipe whose end face is to be cut. The ring is adjusted so that the laser beam is dissected onto a remote target corresponding with the end of another pipe to be connected with the first pipe. The ring is then clamped into a fixed position, the pipe is marked in accordance with the fixed position, and the pipe is cut. Thus, the cut end surface has a configuration which will align with the end surface of the remote pipe so that the pipes can be joined together in mating fashion such as by welding without inducing any stress in the joined pipes.  
     [0029] A more accurate position of the cutting ring on the pipe for better alignment with the remote pipe end is achieved by rotating the ring 90° about the longitudinal pipe so that the laser beam strikes a second target. The first and second targets provide two reference points spaced by 90° to effectively “squareup” the ring on the pipe to be cut. That is, the ring is aligned in two planes, one for each target, to properly orient the ring to the required position for marking the cutting location on the pipe.  
     [0030] In addition to aiding with focusing on two targets, the laser of the invention can also be used to measure the distance from the ring to the target along the beam. The distance measurements are helpful in setting the position of the ring so that the distances along the beams to both targets are the same.  
     [0031] In FIG. 3 is shown an alternate embodiment of the ring of FIG. 1. A plurality of lasers  6  are connected with the ring  2 . The lasers are preferably equally spaced about the ring. Moreover, the lasers are adjustably connected with the ring so that the beams thereof are directed at an angle relative to the axis of the pipe having the ring arranged thereon. In the embodiment shown, the lasers are pivotally connected with brackets  10  on the ring via pivot pins  12 .  
     [0032] Referring now to FIGS. 4 and 5, there is shown a pipe cutting device  14  according to the invention. The device includes a ring  16  having a plurality of adjustable legs  18  for mounting the ring about the outer circumferential surface of a first cylindrical pipe having a longitudinal axis. The ring is adapted to rotate with respect to the pipe when driven by a motor  20 . A cutting tool  22  is connected with the ring by any suitable fasteners such as bolts. The cutting tool can be replaced by a laser  24  as shown in FIG. 5. The laser  24  generates a linear laser beam  26  as shown in FIG. 7 and can be used to align the ring on the pipe as described above. Once aligned, the laser can be replaced with the cutting tool  22  to cut the pipe.  
     [0033] In lieu of the clamping bolt (FIGS.  1 - 3 ) or adjustable legs (FIGS. 4 and 5), an alignment tool  27  can be adjustably mounted on a pipe using a separate ring  29  including a plurality of tumbuckles  31  connected with the tool as shown in FIG. 6. The ring  29  is secured to the pipe in coaxial relation therewith. By loosening or tightening selected turnbuckles, which extend around the pipe, the alignment tool is adjusted to align the tool on the pipe as set forth above.  
     [0034] In FIG. 7 is shown an embodiment for cutting the end of pipe  28  to match the end of pipe  30 . In this embodiment, the ring is mounted on an inner frame  32  which is mounted on the pipe. The ring  16  thus rotates with respect to the stationary frame. In addition, the cutting tool  14  is mounted on the ring to provide a combined alignment and cutting device for the pipe.  
     [0035] In order to connect the pipe  28  with a second cylindrical pipe  30  having a longitudinal axis, it is desirable to match the ends of the pipes so that when the pipes are welded together, there is a minimal amount of stress because the pipes are properly aligned. The invention is used to align, cut and bevel the end of a pipe so that it can be matched or mated with another pipe of the same diameter. Accordingly, with the frame  32  mounted on the pipe to be cut adjacent to an end thereof, the laser beam is directed toward the second pipe. By adjusting the orientation of the frame on the pipe  28 , the laser beam can be redirected so as to strike a target associated with the second pipe  30 . For example, the target can be at a distance d 1  from the second pipe corresponding with a distance d 1  from which the laser beam is offset from the outer surface of the first pipe. Once the frame is properly adjusted, the inner frame is fixed to the first pipe, such as for example, by adjusting the legs thereof. With the frame fixed on the pipe, the ring and cutting tool  22  are driven around the pipe by the motor  20  to cut an end portion off of the pipe to define a properly configured new end surface for the pipe  28 . Depending on the type of cutting tool used, the end surface of the pipe can be flush and/or beveled for mating with the second pipe.  
     [0036] For a more precise cut, after alignment with a first target, the ring is rotated 90° and aligned with a second target (not shown) also spaced at a distance d 1  from a corresponding portion of the remote pipe  30 . Alignment relative to two targets offset by 90° provides a very accurate cutting position for the tool.  
     [0037] Referring now to FIG. 8, there is shown the first and second pipes  28 ,  30 , each having alignment and cutting tools  14 ,  34  thereon. With this arrangement, the ends of the respective pipes can be aligned and cut in the same manner as with the single tool of FIG. 7 so that the pipes can be connected without introducing any stress thereto. Preferably, the laser  36  on the tool  34  mounted on the second pipe  30  is arranged 180° relative to the laser  24  on the first cutting tool  14  to provide a beam  38  spaced from the pipe surfaces by the same distance d 1  as the spacing of the first laser beam  26  from the pipe surfaces. The tools are each rotated 90° for alignment with second targets prior to cutting the pipe ends.  
     [0038]FIG. 9 is similar to FIG. 8 and illustrates the technique for removing a section  40  of pipe. The tool  34  cuts one end of the section  40  of pipe, which deflects downwardly from the original alignment of the pipe before cutting. The deflection is due to the stress in the original pipe (or from earlier pipe installation techniques) which occurs over time in the piping system of industrial plants. Next, the tool  14  is adjusted and then operated to cut the other end of the section  40  of pipe to be removed. A replacement section of pipe can have its ends cut with an orientation to match the ends of the original pipe using the same alignment and cutting tool and techniques described above so that the replacement section when welded to the original pipe will have minimal stress because of its alignment with the original pipe ends.  
     [0039]FIG. 10 shows an alignment and cutting tool  114  according to an alternate embodiment of the invention wherein three lasers  124   a - c  are mounted on the ring  116  which in turn is mounted on a pipe  128 . The lasers  124   a  and  124   c  are arranged 180° relative to each other around the frame, with the laser  124   b  being arranged at 90° therebetween. Thus, the beam  126   b  from the laser  124   b  is spaced the same distance d 2  between the beams  126   a  and  126   c  from the lasers  124   a  and  124   c.    
     [0040] Fixed lasers have a fixed orientation relative to the frame. Such lasers  24  (FIG. 5) are connected with the frame via a fixed mounting bracket  42  as shown in FIGS. 11 and 12. The bracket is connected with the frame by any suitable fasteners such as bolts  44 .  
     [0041] Alternatively, the lasers  124  (FIG. 10) can be mounted on adjustable brackets  142  such as shown in FIGS. 13 and 14. With adjustable brackets, the angle of the laser beam with respect to the longitudinal axis of the pipe can be adjusted as will be developed below.  
     [0042] It is preferred that the lasers be arranged beyond the outer perimeter or circumference of the frame as shown in FIGS. 15 and 16 which show forwardly and rearwardly directed laser beams, respectively. In some instances however, it is desirable to arrange the laser within the outer perimeter of the frame as shown in FIG. 17.  
     [0043] To facilitate alignment of the cutting tool, targets associated with the remote pipe whose end is being matched are provided. A preferred target is shown in FIGS. 18 and 19. The target  46  includes a base  48  which is preferably formed of a magnetic material for mounting on a pipe since most pipes in industrial plants are metal. Other materials for non-metal pipes may also be used. For example, an adhesive may be used to attach a target to a pipe. A plate  50  having indicia  52  printed on a surface thereof is adjustably connected with the base via a bolt  54  which passes through a slot (not shown) in an upper portion of the base. When the target  46  is mounted on a remote pipe, the plate  50  is adjusted so that the center thereof is a predetermined distance from the surface of the pipe. In FIGS. 7 and 8, for example, the target would be adjusted to the distance dl. Next, the ring  16  is adjusted so that the laser beam  26  is directed to the center of the target. This sets the orientation of the cutting tool for a properly aligned cut of the pipe  28 .  
     [0044] The embodiments and techniques described above are suitable for cutting linear pipe having a longitudinal axis. The tool and method of the invention can also be used on pipes having 90° elbows therein which are subject to failure from stress.  
     [0045] Referring now to FIGS.  20 - 24 , use of the alignment and cutting tool  214  of the invention for cutting a pipe prior to an elongated 90° elbow (shown in FIG. 24) will be described. In the embodiment of FIGS. 20 a  and  20   b , the tool has three lasers  224   a ,  224   b , and  224   c  arranged thereon as in the embodiment of FIG. 10, with the lasers including adjustable brackets so that the beams can be directed at an angle relative to the longitudinal axis of the portion of the pipe  228  being cut. A target  246   b  is mounted on a remote pipe  230  beyond the elbow and spaced therefrom by a distance d 3  which corresponds to the height of the inner curve of the elbow. The laser  224   b  is adjusted to direct its beam perpendicular to the axis of the pipe and the tool  214  is adjusted so that the beam  226   b  strikes the target  246   b . Next, the laser  224   b  is adjusted upwardly until its beam strikes the bottom of the remote pipe  230  at point  246   d . From that point, equal distances are measured upwardly about the circumference of the pipe  230  to lateral positions  224   a  and  224   c  as shown in FIG. 20 b  at which points or locations additional targets are set. The angles for the lasers  224   a  and  224   c  are set to the 3 same adjusted angle of laser  224   b , and the tool  214  is then positioned to align the beams from the lasers  224   a  and  224   c  onto the target positions  246   a  and  246   c . In FIG. 20 a , the laser  224   c  and target  246   c  are not visible since they are on the backside of the tool  214  and pipe  230 , respectively.  
     [0046] Referring to FIG. 21, there is shown a triangular wedge defined by the laser beams  226   b  (prior to adjustment),  226   a , and  226   c . The points  246   a ,  246   b , and  246   c  from FIG. 20 b  define a triangle parallel to the face of the remote pipe  230 .  
     [0047] Because the lasers  224   a, b , and c can be used to measure distance, final positioning of the tool  214  on the first pipe  228  can be determined using triangulation. That is, the distance d 4  from the point  246   b  to the center of the pipe  228  is measured as the sum of the length of the beam  226   b  and the outer radius of the pipe  228 . The distance d 5  from the point  246   b  to the center of the pipe  230  is measured as the sum of d 3  and the outer radius of the pipe  230 . The distance d 6  between the centers of the pipes can be calculated via triangulation in accordance with the formula  
     
       d 
       6 
       2 
       =d 
       4 
       2 
       +d 
       5 
       2  
     
     [0048] The diameter line  250  on the pipe  228  passes between the lasers  224   a  and  224   c  through the center of the pipe, and the diameter line  252  on the pipe  230  passes between the targets  246   a  and  246   c  through the center of the pipe. Thus, the distance d 6  between the centers of the pipe is also the distance between the laser  224   a  and target  246   a  and between the laser  224   c  and target  246   c . The tool  214  can thus be positioned so that the lasers  224   a  and  224   c  are the required distance from their targets. This positioning provides the final position for the alignment tool. The pipe  228  can then be marked in accordance with the final position and subsequently cut by a separate cutting tool. Alternatively, where a combined alignment and cutting tool is provided, the cutting tool can be driven about the pipe  228  to cut the pipe end as aligned.  
     [0049] It should be readily apparent that prior to cutting, the end faces of the pipes shown in FIGS. 20 a  and  21  need not be square. However, once the alignment tool is positioned and aligned on the tool  228 , the triangular wedge shown in FIG. 21 must be square. By square is meant that a rectangle is defined by the laser  224   a , the target location  246   a , the target location  246   c  and the laser  224   c . For a non-elongated elbow, a true square would be defined. The “squaring” is possible because of the 90°×90° orientation between lasers  224   a  and  224   b  and between lasers  224   b  and  224   c . This orientation is thus transposed to the target locations relative to the remote pipe.  
     [0050]FIGS. 22 a  and  22   b  show an alternate embodiment for cutting pipe adjacent to an elbow. There, a square target  346  is arranged relative to a pipe  330 . A cutting tool  314  having lasers  324   a  and  324   b  is mounted on a pipe  330 . A third laser (not shown) is mounted on the tool opposite the laser  324   a  and 90° from the laser  324   b . The laser  324   b  defines a location  346   b  in accordance with the height of the elbow and the lasers  324   a  and not visible are directed toward target locations  346   a  and  c  in the same manner as described above in connection with FIGS. 20 a  and  20   b . Using the same squaring method, the tool is locked in position on the pipe  330  for marking and/or cutting the pipe end so that it will match the end of pipe  328 . With square ends of the pipes  328  and  330 , an elongated elbow may be welded therebetween with no stress at the weld locations.  
     [0051]FIGS. 23 and 24 show the use of the alignment tool  414  for cutting a pipe  428  prior to an elbow  460  for removal of the elbow which may or may not include an elongated cylindrical portion  462 . The tool includes lasers  424   a, b , and c which are positioned as in the embodiments of FIGS. 20 and 22 to cut the pipe  428  so that its face will match that of a location on the pipe  430  at the far end of the elbow. In this manner, a damaged elbow section can be easily replaced without re-trimming or otherwise reconfiguring the pipe end faces after the damaged elbow section has been removed. This greatly reduces the time required for replacement of a damaged pipe section. Moreover, because of the squared ends, the replacement elbow can be installed without adding any stress to the piping system.  
     [0052] With the method and apparatus of the invention, the man hours required by a pipe fitter for repair and replacement of damaged pipes in an industrial plant are greatly reduced, thus resulting in substantial savings in maintaining and refurbishing a plant. The alignment and cutting tool is inexpensive and easy to use and requires little training of the pipe fitter.  
     [0053] While the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those of ordinary skill in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.