Abstract:
A method for separating two flanges joined by bolts extending through boltholes provided therein comprises the use of a clamshell cutting apparatus having a rotating annulus with at least one cutting tool. The cutting tools are rotated and advanced against the bolts until they are sheared. The flanges are then separated from each other.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application claims priority from U.S. application Ser. No. 60/778,415, filed on Mar. 3, 2006, the entire contents of which are incorporated herein by reference. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an improved method of separating flanges connected together with bolts to form a joint in pipes and the like. More particularly, the invention relates to a method of flanges by the cutting of shearing of the bolts joining such flanges together. 
       DESCRIPTION OF THE PRIOR ART 
       [0003]    The use of flanges on pipes is well known. Flanges serve to connect the ends of pipes to other pipes, vessels or other such equipment. Generally, a flange includes a stem portion that is permanently secured (normally with welds) to the end of a pipe or similar structure. The flange includes a face portion opposite to the stem. The flange face includes a rim or disc with a plurality of circumferentially spaced boltholes. In connecting, for example, two pipe segments together, the stems of two flanges are first each secured to one end of the respective pipe segments. The segments are then axially advanced towards each other so that the flange faces are brought into opposition, with the respective boltholes aligned. The flanges are then secured to each other by inserting bolts through the boltholes. One or both ends of the bolts may be provided with threaded portions to receive nuts as is commonly known in the art. The nuts are tightened to join the flanges together. In some cases, the boltholes of the flanges may be provided with threading to engage the bolts. 
         [0004]    It is sometimes necessary to separate flanges from each other. To do so, the above mentioned nuts are first removed followed by removal of the bolts and, subsequently, separation of the flanges. However, it is commonly known that the nuts and/or bolts are subject to corrosion of other such damage and, in the result, removal of the nuts and/or bolts is rendered difficult or impossible. In such cases, the bolts are removed with a cutting torch. As will be appreciated, this process is time consuming and expensive. Moreover, the use of a torch may pose a significant hazard such as in cases where the pipes had contained flammable chemicals. 
         [0005]    Various devices have been provided in the art for cutting sections of pipe. One such cutting apparatus that has been found to be relatively efficient is known in the art as a “clamshell” pipe cutter or pipe lathe. Examples of clamshell cutters are provided in U.S. Pat. Nos. 5,189,933, 5,549,024 and 7,000,510, the entire contents of which are incorporated herein by reference. In general, a clamshell apparatus includes two concentric annular rings that are adapted to circumferentially surround the pipe to be cut. In such apparatus, one of the rings is stationary and is secured to the outer wall of the pipe. The other of the rings is capable of being rotated circumferentially about the pipe. The rotating ring is provided with a cutting tool that is adapted to be gradually advanced against the pipe outer wall in a radially inward direction. In operation, the second ring is rotated (by means of a motor for example) and the cutting tool is advanced against the pipe wall. The advancement of the cutting tool progresses until the cutting tool cuts through the pipe wall. Although clamshell devices are well designed for cutting pipes, they are not used for separation of flanges from each other. 
       SUMMARY OF THE INVENTION  
       [0006]    In one aspect, the present invention provides a method of separating a joint formed by two flanges, the flanges being connected together by means of bolts extending through boltholes provided on each of the flanges, the method comprising:
       providing a cutting apparatus proximal to the joint, the cutting apparatus having a rotating annulus, the annulus having an inner diameter greater than the outer diameter of the flanges, wherein the annulus includes at least one cutting tool on the inner diameter, the cutting tool being directed radially inwardly and wherein the cutting tools are moveable radially inwardly;   positioning the cutting apparatus circumferentially over the joint and over the flanges;   positioning the cutting apparatus whereby the cutting tool is positioned adjacent the bolts;   rotating the annulus circumferentially about the joint;   advancing the cutting tool radially inwardly until the bolts are sheared; and   separating the flanges.       
 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    These and other features of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein: 
           [0014]      FIG. 1  is a side elevation illustrating the junction of two flanges. 
           [0015]      FIG. 2  is a side elevation of the junction of  FIG. 1  provided with a cutting apparatus. 
           [0016]      FIG. 3  is a side elevation of the junction of  FIG. 1  provided with a cutting apparatus. 
           [0017]      FIG. 4  is a partial cross sectional view of a joint created with two raised face flanges. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1  illustrates a typical junction of two flanges. As shown, the flanges  12  and  14  include, respectively, stem portions  16  and  18  and face portions  20  and  22 . The stem portions are secured, such as with welds  23  and  25 , respectively to the ends of pipes  24  and  26 . Each of the face portions of the flanges include a plurality of circumferentially spaced bolt holes  28 . In joining the flanges together, the bolt holes of each flange are aligned together and bolts  30  are passed there-through. The bolts are secured in position with nuts  32  that can be provided on one or both ends of the bolts  30 . In some situations, the boltholes on the flanges may be provided with threads to engage the bolts. As will be apparent to persons skilled in the art, it is common to provide a gasket or other such sealing means between the opposed flange faces. However, for clarity, such gasket is not illustrated in the drawings. 
         [0019]    As discussed above, when separation of a flange joint is desired, the nuts  32  are removed so as to allow the bolts  30  to be removed. The flanges can then be separated. However, as also discussed above, it is often found that either the nuts  32  or bolts  30  are either corroded or otherwise damaged in such a manner that removal of the nuts is not possible. In such cases, the bolts  30  are cut with torches and the like. 
         [0020]    As mentioned above, examples of clamshell pipe cutters are provided in U.S. Pat. Nos. 5,189,933, 5,549,024 and 7,000,510. The tools described in these references generally comprise first and second semi-circular segments that are designed to be joined together to form an annular assembly for encircling a shaft or pipe to be machined (i.e. cut or lathed). The assembly also generally includes a stationary ring, and a rotatable ring supported by bearings affixed to the stationary ring. The rotatable ring includes a spur gear on its outer peripheral surface and is journaled to the stationary ring for rotation about a concentrically disposed pipe or work piece. A motor is attached to the stationary assembly and includes a drive gear designed to mesh with the spur gear on the rotatable segment of the pipe lathe. A tool block for supporting a cutting tool is mounted to the rotatable segment and is designed such that a cutting tool is advanced in small incremental steps in a radial direction against the pipe to be machined upon each orbit of the ring gear about the work piece. Various other examples of clamshell cutting apparatus are known in the art. 
         [0021]    As discussed above, clamshell type cutting apparatus are known for the purpose of completely or partially effecting a circumferential cut in a pipe. However, with the present invention, a method is provided wherein known clamshell cutting apparatus are used for the purpose of cutting the bolts and/or nuts used in a flange joint. 
         [0022]    More specifically,  FIG. 2  illustrates the flange joint of  FIG. 1  wherein nuts  32  on one side of the joint have been slightly loosened in order to expose a portion of the underlying bolts  30 . A clamshell apparatus, generally indicated at  34  is positioned over the joint between the two flanges. The apparatus includes a stationary ring  36  and a rotating ring  38 . The rotating ring  38  is provided with one or more cutting tools  40  comprising a blade. As known in the art and as described in the aforementioned U.S. patents, the rotating ring  38  is driven by a motor (not shown) and is caused to rotate about the circumference of the flanges  20  and  22 . In accordance with the standard operation of the apparatus  34 , as the ring  38  is rotated, the cutting tools  40  are gradually advanced radially inwardly until they begin contacting the bolts  30 . Such advancement of the cutting tools  40  is continued gradually until the bolts  3  are sheared. Following this, the flanges are separated. 
         [0023]    In some situations the loosening of the nuts  32  as described above is not possible. In such case, the clamshell apparatus discussed above may be used to shear both the nut and the bolt. Such a situation is illustrated in  FIG. 3 , where like elements are identified with like reference numerals. As illustrated, the nuts  32  are not separated from the respective flange face. The clamshell apparatus is positioned similarly to that shown in  FIG. 2  but, in this case, the cutting tools  40  are positioned so as to first contact the nuts  32 . The apparatus is operated in the same manner as described above and advancement of the cutting tools  40  first results in shearing of the nuts  32  followed by shearing of the bolts  30  as the tools  40  are continually advanced. 
         [0024]    In the description provided above, it has been assumed that the bolts are provided with nuts on both ends thereof. It will be appreciated that it is common for one set of nuts to be integral with the bolts or welded (or otherwise attached) thereto. In such case, only one set of nuts would be rotatable or removable. 
         [0025]    In a further embodiment, one of the flanges may be provided with a threaded bolthole to receive and engage a bolt. In such case, it will be understood that no nuts may be required and that the bolts are screwed into the threaded boltholes instead. 
         [0026]    A further embodiment of the invention is illustrated in  FIG. 4 , which depicts a “raised face flange”. As will be known to persons skilled in the art, a raised face flange generally comprises the same shape as the flanges discussed above. However, a raised face flange includes a step portion forming the raised face. A shown in  FIG. 4 , flanges  42  and  44  are generally as described above. However, the faces of the flanges,  46  and  48 , respectively, include raised portions  50  and  52 , respectively. When arranged to form a joint, as shown in  FIG. 4 , the raised portions  50  and  52  are brought into contact and bolts  54  are inserted through aligned boltholes  56   a  and  56   b  in each of the flanges  46  and  48 . As shown, the bolts  54  may include integral nut portions  58  and opposite threaded portions  60 . Nuts  62  are then provided on the threaded portions  60  and tightened to force the flanges against each other. As shown in  FIG. 4 , once joined together, the flange faces  46  and  48  are separated by a gap  64  due to the presence of the raised faces discussed above. The gap  64  exposes a section of the bolts  54 . The gap may be wider if a gasket, such as that shown at  66  is provided. According to the method of the present invention, a clam shell cutting apparatus may be provided on the joint shown in  FIG. 4  with the cutting tool positioned over the gap  64 . As will be understood, the cutting tool in this example is advanced and serves to cut the exposed section of the bolts  54 . It will also be understood that although  FIG. 4  illustrates a joint involving two oppositely oriented raised face flanges, other joints may be possible with only one raised face flange, with the opposite flange including a flat face as shown in  FIGS. 1 to 3 . The size of the cutting tool used in the embodiments described in  FIG. 4  will be understood to be dependent upon the width of the gap  64 . Such sizing will be apparent to persons skilled in the art. 
         [0027]    The method of the invention can be used or adapted for any of the embodiments described above and other embodiments that would be known to persons skilled in the art. 
         [0028]    It will be understood that the material chosen for manufacturing the cutting tools will be of sufficient strength as to withstand the cutting of the bolts and/or nut. In addition, it will be understood that the clamshell cutting apparatus will be provided in a variety of sizes depending upon the diameter of the flanges. Normally, a certain amount of clearance will be provided between the outer diameter of the flanges and the inner diameter of the annuli of the cutting apparatus so as to facilitate positioning of the device. Such sizing criteria will be apparent to persons skilled in the art. 
         [0029]    Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto. The disclosure of all prior art recited herein are incorporated herein by reference in their entirety.