Abstract:
A pipe repair fitting comprising a mating pair of generally semi-circular segments, each formed by an arcuate wall having arcuate ends, the segment walls carrying compressible seals for sealing two pairs of mating arcuate ends of the segments and sealing on the outer periphery of the pipe, at least one threaded hole in each arcuate wall end, a common bolt threaded into each of the threaded holes of each pair of mating arcuate ends and serving to sustain hoop forces in the fitting imposed by fluid leaking out of the pipe and contained by said seals.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to pipeline repair fittings, particularly of the diametrally split sleeve or ring type. 
       PRIOR ART 
       [0002]    Repair of a large pipeline, required because corrosion, collision, other impact, thermal and/or mechanical stress results in a leak, can be made by assembling a split sleeve or ring around the leaking area and then sealing the encircled zone. Conventional split repair fittings, particularly for large diameter pipelines, have often been fabricated from steel plate bent into an arcuate shape configured to fit concentrically over the pipe. Flanges or sidebars, typically cut from heavy steel plate stock, are welded along the axially extending edges of the arcuately bent plates so that the sidebars lie in generally radial directions and complete the arc of a segment comprising one-half of a split fitting. Ultimately, the sidebars of two opposed sleeve or ring segments are bolted together to encircle the pipe being repaired. 
         [0003]    The traditional segment fabricating process is expensive for a variety of reasons. Because of its thickness, particularly for large pipe fittings, the stock used for making the sidebars is costly and is cut with oxygen acetylene rather than a laser. This cutting technique requires the heat affected area to be ground off and is imprecise so that some amount of “fitting” by grinding the parts to a complementary shape is involved when the parts are initially mated up with the arcuate plate for subsequent welding. At this stage, there can be at least three separate individuals involved in bending the plate into an arc, shaping the sidebars, and fitting the sidebars to the arcuate plate. Any one or more of these labor steps can introduce substantial variation in the initial fabrication of a half sleeve or segment. Because of the expected variations, enough extra stock must usually be provided, and then be machined away to provide a serviceable clearance fit on the outside diameter of the pipeline. 
         [0004]    Once the sidebars are fitted to the edges of the arcuate plate, these parts are carefully welded together. Extra pieces of steel can be temporarily welded to these parts to get a full weld at the run off at their ends, and to hold them to their desired shapes until they eventually cool. The parts are then welded together, starting with a manual or service automatic root pass followed, ordinarily, by automatic machines making numerous passes as the parts are oriented and reoriented in multiple steps. Typically, the initial root pass is most prone to show imperfections upon inspection. Thereafter, the fabricated segment part is x-rayed, typically offsite of the fabrication site, to assure the integrity of the welds. Subsequently, the segment is heat treated to relieve the internal stresses developed in the welding process. The extra pieces used to enhance the run off ends of the welds and to hold the shape of the segment are cut off and ground flat. Regulations can impose the burden on the manufacturer of the repair fitting to record the source of the various steel parts, the welding procedure, the welder, and the date when the fitting component was produced. The foregoing is a brief outline of typical material, labor and time considerations involved in the fabrication of sleeve or ring segment weldments commonly used in the past. 
         [0005]    The sidebars, when drawn tight with the associated bolts, apply a bending stress to the wall of the semi-circular shell. Consequently, the shell wall must be made thicker to withstand this stress. A thicker shell wall requires thicker sidebars. The sidebars add weight and girth to a fitting. Weight is reflected by added material costs, shipping and handling costs, as well as installation costs. The overall physical size of the fitting requires correspondingly large equipment for finish machining and can make it difficult or impossible to install at a particular site. Where, after installation, the fitting is coated with a protective material, the sidebars and bolts extending through the sidebars complicate the coating process. Further, bolts extending through the sidebars are difficult to seal weld, particularly when inverted and under water. 
         [0006]    U.S. Pat. Nos. 3,017,204, 3,078,108, 3,152,816, and 3,467,141 illustrate examples of prior art split sleeves and flange repair fittings. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention provides an improved pipe repair fitting of the split sleeve or ring type. With the invention, conventional sidebars or flanges at the split plane are eliminated. The disclosed fitting of the invention is easier and less expensive to manufacture, weighs less, can be installed in confined spaces, and can be more easily seal welded than traditional types of split fittings. 
         [0008]    As disclosed, segment halves of the fitting are each formed with cylindrical walls of generally uniform thickness. This simple structure permits their rough fabrication in a press brake without the need for attaching sidebars and all of the complications and expense attendant to a weldment. At each of their arcuate ends, the segment halves are machined with at least one precision formed internally threaded hole. The threaded holes of opposed arcuate ends of a pair of segment halves are precisely aligned. The threads are formed so that when the segments are properly registered with one another, the threads of one hole and the threads of an opposed hole lie on a common helix. The disclosed relationship of the threads allows a threaded bolt or stud holding the segments together to employ the walls of the segments on both sides of the split plane to function as the equivalent of a nut but without the need for such nuts and the additional space they would require. 
         [0009]    Preferably one of the pair of aligned threaded holes is blind, while the opposing hole in the opposite segment is similarly closed, but for a reduced diameter hole that receives a tool for turning the bolt. Further, preferably one of the holes is deep enough to fully or substantially fully receive an associated bolt before the segments are mated together. Once the segments are in proper registration, the bolts can be extended from one threaded hole into the opposing threaded hole to thereby mechanically join the segments together. With the bolts initially received in the deep holes, they are protected in transit and are not susceptible to being dropped during installation, which is particularly important in underwater applications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a pipe fitting constructed in accordance with the invention; 
           [0011]      FIG. 2  is a fragmentary cross-sectional view of a portion of a wall of a fitting segment taken in the plane  2 - 2  in  FIG. 4 ; 
           [0012]      FIG. 3  is a fragmentary cross-sectional view of the fitting taken in a plane transverse to the pipeline indicated by the lines  3 - 3  in  FIG. 1 ; and 
           [0013]      FIG. 4  is a fragmentary perspective view of the interior of an end portion of a segment of the fitting. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring now to the drawings, there is shown a repair fitting  10  assembled on a pipeline  11  in order to contain leakage from the pipeline due to damage caused by corrosion, accident or other reason. The fitting  10  comprises a hollow cylinder made in two mating half sections or segments  12 ,  13 . The segments  12 ,  13  in their simplest form are generally uniform in their wall thickness. 
         [0015]    While the segments or half rings  12 ,  13  can be fabricated from steel tubing, cast of steel, or otherwise made, they commonly will be fabricated from heavy steel plate, typically in a press brake, particularly when large pipe sizes are involved. For example, the segments  12 ,  13  can be rough formed in a press brake, or with heavy rolls, and then finish machined as required. Typically, the circumferential exterior of the segments  12 ,  13  can be left as fabricated without machining. The inside cylindrical surfaces  16  of the segments  12 ,  13  can be machined to assure a clearance fit around the pipeline  11 . The interior of the segments  12 ,  13  is also machined with axial grooves  17  at their arcuate ends, designated  18  and with arcuate grooves  19  adjacent their axial ends, designated  20 . The grooves  17 ,  19  receive elastomeric compressible seals  23 ,  24 , respectively. Axially oriented seals  23  are retained by metal strips  25 ,  26  welded to the inside surface  16  and an arcuate end surface  27  that lies parallel to the diametral plane at which the segments  12 ,  13  abut. When the segments  12 ,  13  are finally assembled around the pipeline  11  to encircle it, the seals  23  stop fluid from the pipeline from leaking radially through the diametral plane at which they mate. 
         [0016]    The arcuate groove  19  also receives a semi-circular thrust ring section  28  of steel or other suitable rigid material. The seal  24  and thrust ring segment  28  are retained, and in service restrained, by a sheet metal retainer  29  which can be an assembly of two strips  31 ,  32 . One of the strips  31 , is slotted or notched to assist it in conforming radially to the outside surface of the pipeline  11 . A series of axially oriented thrust screws  33  operate in threaded holes spaced about the arcs of both end faces  27  at each end of each segment  12 ,  13 . The thrust screws  33  at each axial end of each segment  12 ,  13 , bear against end faces of respective thrust ring segments  28  ( FIG. 4 ). 
         [0017]    As previously indicated, the segments  12 ,  13  can be rough formed from steel plate in a press brake or roll set. The inside cylindrical surfaces  16  and arcuate end surfaces  27  are preferably machined to finish size and configuration. Arcuate end surfaces  27  can be machined with major surface areas  36  spaced slightly from and parallel to a true diametral plane. Precise locating pads  37  in the form of rectangular islands, can be machined on these arcuate ends at the true diametral plane of their respective segment  12 ,  13 . Alternatively, the full surface of the segment arcuate ends  18  can be made at the diametral plane with provisions to recess the restraining strips  26  or their equivalent. 
         [0018]    Threaded holes  41 ,  42  are machined in each segment arcuate end  18  into the wall of the segment  12 ,  13 . The locations of the holes  41 ,  42  match up between the segments  12 ,  13  when the segments are assembled and aligned on the pipeline  11 . Preferably, the threaded holes  42  in one segment  13  are blind while the threaded holes  41  in the other segment  12  are in the nature of counter bores having concentric reduced diameter holes  43  opening to the exterior of the segment wall. The threads of the holes  41 ,  42  are of the same diameter and pitch and are cut so that when the segments  12 ,  13  are properly aligned with each other, such that the locating pads  37  of the opposed segments are in abutting relation, the thread form (crest and root) of the opposed segments are in phase so that the helix of the thread of one hole  41  is coincident with the helix of the thread of the other opposed hole  42 . 
         [0019]    In their final assembly, the segments  12 ,  13  are joined together and bridged by headless bolts  44  received in the aligned holes  41 ,  42  of the opposed segments. Ideally, the threaded holes  41  are arranged with sufficient length to initially carry the bolts  44  fully or nearly fully retracted within the wall of the respective segment  12 . For sake of simplicity, the holes  41  originally receiving the full length of the bolts  44  can all be located in one segment and these holes can be the ones associated with the reduced diameter holes  43 . It will be understood that rearrangements of parts and geometries of the holes  41 ,  42  and  43  and bolts  44  is possible. 
         [0020]    The fitting  10  is installed by assembling both segments  12 ,  13  around a damaged area of a pipeline  11 . Various expedients including fixtures and/or mechanisms can be devised to align the respective segments to one another. One expedient are alignment pins on one or both arcuate end faces  27  of the segments and suitably placed receiving holes on opposing faces. The segments  12 ,  13  are provisionally held together with a suitable clamping arrangement so that the precision located reference surfaces on the locating pads  37  are in contact when the bolts  44  are extended from the holes  41  in which they are originally received into opposing holes of the other segment. Typical clamping arrangements may include straps, cables, chain, or the like wrapped around the segments  12  and  13 . Another expedient is to provide at least two of the bolts  44 , one on each side of the pipeline  11  with central bores to receive threaded draw bolts assembled through the reduced diameter holes  43  and threaded into minor tapped holes in the segment  13  at the base of respective blind holes  42 . The draw bolts can be used to temporarily hold the segments  12 ,  13  together until a number of the main bolts  44  are extended into the segment  13 . 
         [0021]    The temporary clamping force holding the segments  12 ,  13  together should be enough to bring opposing longitudinal seals  23  into mutual contact. The interior of the fitting  10  can be temporarily vented through a port (not shown) in the wall of one of the segments  12 ,  13 . 
         [0022]    With the segments  12 ,  13  provisionally clamped together, the bolts  44  are turned to extend them into the opposed segment  13 . This is accomplished by positioning a tool through the reduced diameter hole  43  associated with the bolt  44 . The bolt  44  can have an accircular socket  46  such as a hex-shaped blind hole in the end facing the hole  43 , and the tool can have a complementary shape to fit into the socket to drive the same. 
         [0023]    When all of the bolts  44  have been extended, the circumferential seals  24  can be compressed with the thrust ring segments  28  by turning the thrust screws  33  into their respective holes so that they drive the thrust ring segments axially. Axial compression of the circumferential seals  24  causes them to seal tightly on the outside surface of the pipeline  11 . Any vent can be closed at this time and, if needed or desired, a viscous settable sealant can be pumped into the fitting through a vent hole to augment the function of the seals  23 ,  24 . It will be understood that a clearance space or annulus exists typically between the pipe outside surface and the inside surface of the fitting and this space can receive and distribute the settable sealant. The bolts  44  sustain the hoop forces in the fitting  10  created by the pressure of any fluid leaking from the pipe  11 . The provisions for temporarily clamping the segments  12 ,  13  together may be removed once the bolts  44  are deployed. 
         [0024]    After the circumferential seals  24  have been deployed (existing at each end) and any sealant has been injected into the annulus between the interior of the fitting  10  and exterior of the pipeline, the fitting can be seal welded. This will include welding the axial ends  20  to the circumference of the pipeline  11  and the outer edges of the opposed arcuate end surfaces  34  together. The reduced diameter holes  43  are also seal welded. The seal welding steps are substantially less involved and less difficult than what has been necessary to seal weld a traditional split sleeve fitting at longitudinally extending sidebars or flanges including the nuts and bolt heads projecting from them. The sidebar-free construction afforded by the invention can be applied to other pipe repair fittings such as split flange repair rings and split hot tapping saddles, for example. 
         [0025]    It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited. For example, the threaded holes  41  or their equivalents can extend through the wall of the segment  12  thereby eliminating the reduced diameter holes  43 .