Patent Publication Number: US-2005121091-A1

Title: Removable closure system and plug for conduit

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application is a regular application claiming priority of U.S. Provisional Patent Application Ser. No. 60/566,098 filed Apr. 29, 2004 and entitled, “NOVEL HOT TAPPING METHOD, SYSTEM AND APPARATUS”, the entirety of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to a system for removably placing a device inside a conduit, and more particular to a system for removably placing a plug in a branch pipeline or other tubular member which was hot tapped onto a main pipeline.  
     BACKGROUND OF THE INVENTION  
      In pipeline hot tapping operations it is frequently necessary to close, or to block access to, the interior of a tubular member either permanently or semi-permanently. Pipeline hot taps are used when repairing a defective area of a line without taking it out of service, by setting up a bypass line to provide a path for fluid flow while the defect is repaired. Hot taps may also be used to install a new branch line; again without taking the main pipeline out of service.  
      After the hot tap operations are completed, tubular members, such as flanges or nipples which are welded onto the main line during the hot tap, may need to be closed or partially blocked. For example, after repairs are complete the openings that provide communication between the main line and bypass line will need to be closed. Preferably the closure is made in such a way that at some future date access can again be obtained through the same opening. Alternatively, in the case of the addition of a branch line, it is often desirable to place a device in the opening which causes pipeline pigs to traverse it, but which still allows for adequate flow of fluid to continue to pass. Without such a blocking device pipeline pigs could lodge themselves in the opening between the main pipeline and branch line.  
      One conventional means for locking a device in place inside a flange is the Lock-O-Ring™ system from T. D. Williamson, Inc. of Tulsa, Okla. and as disclosed in T. D. Williamson, Inc.&#39;s Bulletin No. 1120.001.01. The Lock-O-Ring™ system utilizes a flange, a retainer ring mounted on an inner cylindrical bore therein, a plug having an annular groove for insertion into the flange and for receiving a portion of the retainer ring, and retainer screws carried in radial passages in the flange for advancing the retainer ring partially into the plug&#39;s annular groove thereby locking the plug in place. The T. D. Williamson Bulletin also discloses a plug with guide bars to permit pigs to traverse the opening while allowing for an adequate flow of fluid to continue to pass.  
      However, the Lock-O-Ring™ system suffers from a number of disadvantages. One primary disadvantage is that it requires the precise coaxial alignment of the plug&#39;s annular groove with the retainer ring in the flange, all while rotating the retainer screws to advance the ring. A related problem is that if a worker rotates the screws before the plug is in place, it is possible for the retainer ring&#39;s segments to fall into the main pipeline. Furthermore, the Lock-O-Ring™ system provides little, if anything, in the way of feedback to the operator to indicate that it is securely locked in place.  
      Another system for locking a device in place, inside a flange, is disclosed in U.S. Pat. No. 6,286,553 to Morgan. Morgan teaches a plug which utilizes a radially outward movable snap ring, which engages an annular groove inside a flange, to retain the plug in position. Morgan also discloses an internal circumferential ledge, inside the flange, to assist with the coaxial alignment of the snap ring with the annular groove. Although this solves some of the problems of the prior art, the system is complex, provides little, if any, feedback to indicate that it is securely locked in place, and is generally not suitable to withstand great pressures.  
      What is needed is a system to removably place a closure plug inside a conduit which is simple, able to withstand great pressures and provides feedback to the operator that it is locked in place.  
     SUMMARY OF THE INVENTION  
      The invention provides a removable closure system comprising a tubular member having an internal surface with an internal profile therein, an entrance end and a plug end, the internal profile providing a dog shoulder and a plug stopping shoulder. In a typical application of the invention the tubular member may be in the form of a flange member, that is, a tubular member that has an integral radially extending flange portion that is readily adaptable for the attachment of other structural or piping devices. In another application of the invention the tubular member may be in the form of a nipple.  
      A plug assembly is positioned within the tubular member. The plug assembly has a plug, suitable for insertion through the tubular member at the entrance end and past the dog shoulder, and a plurality of dogs. The dogs are moveable between a collapsed and an expanded condition, the collapsed condition suitable for insertion of the plug assembly through the tubular member past the dog shoulder and the expanded condition suitable for engaging the dog shoulder.  
      When the plug assembly is placed in the tubular member against the plug stopping shoulder, and the dogs are in the expanded condition engaging the dog shoulder, the plug assembly is removably secured in the tubular member.  
      In certain embodiments of the invention springs are provided to move the dogs to their expanded condition. In other embodiments of the invention a lock ring is provided to move the dogs to their expanded condition. In yet other embodiments, both a lock ring and springs are provided to move the dogs to their expanded condition.  
      In certain embodiments of the invention a lock ring is provided to keep the dogs in their expanded condition once the plug assembly is removably secured inside the tubular member.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a sectioned side view of one embodiment of a tubular member having an inner profile suitable for use with the plug assembly of the present invention;  
       FIGS. 2   a - 2   c  are various views of one embodiment of a plug assembly suitable for use with the tubular member of the present invention;  
       FIGS. 2   d - 2   g  are various views of the plug assembly of the embodiment of  FIGS. 2   a - 2   c , further showing cap screws, shear posts and shear pins ( FIG. 2   f  is a partial sectional view taken along line X-X in  FIG. 2   e ;  FIG. 2   g  is a sectional view taken along line XX-XX in  FIG. 2   e );  
       FIGS. 3   a - 3   c  are various views of one embodiment of a setting tool attached to the plug assembly of the embodiment of  FIGS. 2   a - 2   g;    
       FIGS. 4   a - 4   c  are various views of one embodiment of a retrieval tool near the plug assembly of the embodiment of  FIGS. 2   a - 2   g;    
       FIG. 5  is a perspective view of the retrieval tool of the embodiment of  FIGS. 4   a - 4   c  near the plug assembly of the embodiment of  FIGS. 2   a - 2   g  (the plug shown in an exploded perspective view);  
       FIGS. 6   a - 8   c  are various views of the components of the plug assembly of the embodiment of  FIGS. 2   a - 2   g;    
       FIGS. 9   a - 10   d  are various views of the components of the setting tool of  FIGS. 3   a - 3   c;    
       FIGS. 11   a - 11   c  are various views of the retrieval tool of the embodiment of  FIGS. 4   a - 4   c;    
       FIGS. 12   a - 12   b  are perspective exploded views of a second embodiment of a plug assembly, each figure also showing a lock ring, a shear post assembly, a shear pin and another embodiment of a setting tool (threaded section on the shear post not shown);  
       FIG. 13  is a sectioned perspective view of the plug assembly of the embodiment of  FIGS. 12   a - 12   b;    
       FIG. 14  is a sectioned perspective view of a third embodiment of a plug assembly, having a pig deflector (or coupon) attached below the plug, shown removably placed inside a second embodiment of a tubular member apparatus, and also showing a lock ring and setting tool;  
       FIG. 15  is a sectioned perspective view of the plug assembly of  FIG. 14 , the plug assembly is shown removably placed inside the second embodiment of a tubular member apparatus, the setting tool and shear post having been removed;  
       FIG. 16  is a perspective view of the plug assembly of  FIG. 14 , also showing a lock ring and setting tool;  
       FIGS. 17   a - 19  are various views of a fourth embodiment of a plug assembly, wherein an alignment ring and a pig deflector are provided, and also showing the second embodiment of the tubular member apparatus;  
       FIGS. 20-28  are various views of a fifth embodiment of a plug assembly, with a pig deflector but without an alignment ring; and  
       FIG. 29  is a sectioned perspective view of a sixth embodiment of a plug assembly, which is similar to the fourth embodiment shown in  FIGS. 17   a - 19  but with a longer connecting flange between the plug and the pig deflector so as to operate inside a third embodiment of a tubular member apparatus (also shown). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Reference is to be had to the Figures in which identical reference numbers identify similar components.  
      Referring to the Figures, the removable closure system  10  of the present invention comprises a tubular member  12  having a opening  20  for the passage of tools or for flow of liquids or gases and a plug assembly  14 . The tubular member  12  may be a nipple  12   a  (see  FIG. 1 ) which is attachable to a pipeline  13 . The invention herein is not limited in use only to a nipple  12   a , but is a system for removably placing a plug assembly  14  inside any tubular member  12  or opening  20 ; the nipple  12   a  being example of a tubular member and illustrated herein only because it is a typical environment for the application of the removable plug system  10  of this invention. For example, the tubular member  12  may also be a low-profile flange  12   b  (see  FIGS. 14-15 ), a flanged section of pipe  12   c  (see  FIG. 29 ) or a section of pipeline (not shown).  
      The tubular member  12  has an entrance end  16  and a plug end  18 . The plug end  18  is shown of the type that is particularly configured for welding to a pipe  13  or to other conduit. The opening  20  defines an internal surface  22  with a profile  24  therein. The profile  24  provides a dog shoulder  26  and a plug stopping shoulder  28 . Preferably the dog shoulder  26  is provided by a circumferential groove  26   a  in the profile  24  and the plug stopping shoulder  28  is provided by a circumferential ledge  28   a  on the profile  24 . Preferably, the dog shoulder  26  is closer to the entrance end  16 , compared to the plug stopping shoulder  28  and the shoulders  24 ,  26  face towards each other.  
      The plug assembly  14  comprises a plug or plug body  30  having an external surface and being removably and sealably receivable within the tubular member  12  and a plurality of dogs  32 . Preferably the dogs  32  are held in place by a top plate or top ring  33  (as shown in the Figures). The dogs  32  are able to radially deflect between an expanded state or condition and a contracted or retracted state or condition. Preferably, when in the collapsed condition the outer edge of each dog  32  is substantially even with or within said external surface of the plug  30  and when in the expanded condition the outer edge of each dog  32  is beyond said external surface and receivable within the circumferential groove  26   a.    
      Preferably, the dogs  32  are biased outward, to the expanded state, by a pair of springs  34  placed in spring cavities  36  inside each of the dogs  32  and wherein one end of the spring engages one end  36   a  of the spring cavity  36  and the other end of the spring engages a projection  30   a  on the plug assembly  30 , said projection  30   a  being receivable in the cavity  36 . More preferably, the contracting of the dogs  32 , to enable passage of the plug assembly  14  past the dog shoulder  26 , is facilitated by the shape of the profile  24  and the shape of the dogs  32  (as shown in the Figures), the dogs  32  pushing against the profile  24  as the assembly  14  is inserted into the tubular member  12 , overcoming the force of the springs  34  and moving the dogs to the contracted state.  
      In another embodiment, the dogs  32  are biased outward, to the expanded state, by a lock ring  50  (see  FIGS. 12   a - 18 ,  23 - 24  and  26 - 27 ). Preferably the lock ring  50  has an external dog-engaging circumferential ledge  50   a , said ledge  50   a  causing the dogs  32  to bias outward when the lock ring  50  is positioned between the dogs  32  and against the plug  30 . More preferably the dog-engaging circumferential ledge  50   a  has a wedge or a frusto-conical aspect to its surface to fascilitate engagement with the dogs  32  (see  FIG. 13 ).  
      In one embodiment, the lock ring  50  further comprises an internal threaded opening  50   o  to match the external threads  40   t  of a partially treaded shear post  40   a  of a setting tool  40  or arbour  52  (see  FIG. 13 ). In this embodiment the lock ring  50  is mounted on the setting tool  40  or arbour  52  and on the treaded shearing post  40   a . Rotational forces or torque are transferred from the setting tool  40  or arbour  52  to the lock ring  50 , so that rotation of the setting tool  40  or arbour  52  causes the lock ring  50  to be treaded down the shearing post  40   a  and positioned between the dogs  32  (see  FIGS. 12   a - 14 ). Preferably the rotational force or torque from the arbour  52  is transferred to the lock ring  50  by means of arbour posts  52   p  fastened to the arbour  52  and extending through openings  50   m  in the lock ring  50  (see  FIGS. 12   a - 13 ). Thus, in this embodiment, the dogs  32  are moved outward, to the expanded state, by the lock ring  50  being rotated down the threaded section  40   t  of the shearing post  40   a , engaging the dogs  32  and biasing them outward. Once the plug assembly  14  is removably secured in the tubular member  12 , the shear pin  40   b , connecting the arbour  52  to the shearing post  40   a , is sheared (preferably by additional application of torque to the arbour  52  after the lock ring  50  is positioned between the dogs  32  and engages the plug  30 ). Once the shear pin  40   b  is sheared, the arbour  52  is free to be lifted from the plug assembly  14  leaving the lock ring  50  positioned between the dogs  32 .  
      Preferably, the dogs  32  each have an outer edge or surface  38  which is suitable for engaging the dog shoulder  26  when the dogs  32  are in the expanded state, the surface  38  assisting in securing the plug assembly  30 .  
      The diameter of the plug assembly  14 , regardless of the state of radial deflection of the dogs  32 , is such that it cannot pass through the tubular member  12  past the plug stopping shoulder  28 . The plug stopping shoulder  28  thus functions as a stop to retain the plug assembly  14  and prevent further axial movement of the assembly  14  through the tubular member  12 , reducing or eliminating the chance of the plug falling in the pipe  13 . Furthermore, the diameter of the plug assembly  14 , when the dogs  32  are in the contracted state, is such that it can pass through the tubular member  12  past the dog shoulder  26 .  
      Preferably, the plug assembly  14  is removably secured, inside the tubular member  12 , as follows: 
          inserting the assembly  14 , plug  30  first, into the entrance end  16  of the tubular member  12 ;     advancing the assembly  14 , with the plug  30  first, past the dog shoulder  26  and towards the plug stopping shoulder  28 ;     contracting the dogs  32  as they passes the dog shoulder  26 ;     resting the plug  30  against the plug stopping shoulder  28 ; and     expanding the dogs  32  so that surfaces  38  engage the dog shoulder  26  (see  FIGS. 14, 15 ,  17   b  and  29 ).        

      Preferably, a lock ring  50 , having an external dog-engaging circumferential surface  50   s  and being of such dimensions so as to be positionable between the dogs  32  in their expanded state and against the plug  30 , is employed to keep the dogs  32  in their expanded condition once the plug assembly  14  is removably secured inside the tubular member  12 . The lock ring  50 , by ensuring that the dogs  32  will continue to engage the dog shoulder  26  while the assembly  14  is in the tubular member  12 , advantageously provides an additional safety feature and allows the system  10  to withstand great pressures.  
      Once the plug assembly  14  is set inside the tubular member  12  it may be removed by reversing the above steps: contracting the dog  32  and disengaging the surfaces  38  from the dog shoulder  26 , retracting the assembly  14  past the dog shoulder  26  and removing it from the tubular member  12 .  
      Preferably a setting tool  40  is used to insert and advance a plug assembly  14  through the tubular member  12  (see  FIGS. 3   a - 3   c ,  9   a - 10   d ,  12   a - 14 ,  16 - 24 ). More preferably, the setting tool  40  further comprises a shear post  40   a  and shear pin  40   b  to assist with disconnecting the setting tool  40  from the plug assembly  14  after insertion of the plug assembly  14 . Setting tools having shear posts and shear pins are well known to those skilled in the art. Even more preferably, a retrieval tool  42  is used to contract the dogs  32  and remove the plug assembly  14  from the tubular member  12  (see  FIGS. 4   a - 5  and  11   a - 11   c ).  
      The plug assembly  14  may comprise either a flow-through type of plug (not shown), to partially close the tubular member  12 , or a solid plug  30  to completely close the tubular member  12 .  
      Preferably, one or more circumferential grooves  30   g  are provided on the external circumferential surface of the plug  30 , each groove receiving an O-ring or other form of sealing gasket  30   o . Advantageously, the o-ring or sealing gasket  30   o  further improves the sealing capability of the plug assembly  14 , so as to ensure against leakage of fluids or gases past the plug assembly  14 .  
      Various Embodiments of the Plug Assembly  
       FIGS. 2   a  to  8   c  illustrate one embodiment of a plug assembly  14  and  FIGS. 12   a - 13  illustrate a second embodiment of a plug assembly  14 .  
       FIGS. 14-16  illustrate a third embodiment of a plug assembly  14 , having a pig deflector or coupon  44  attached below the plug  30  by means of a connecting flange or pig deflector flange  46 . The pig deflector  44  is preferably made from the coupon cut from the main pipe  13  during hot tap operations. Advantageously the pig deflector  44  prevents pipeline pigs from entering, or getting caught, on the opening into the branch line  12  into which the plug is placed.  
       FIGS. 17   a - 19  illustrate a fourth embodiment of a plug assembly  14 , wherein an alignment ring  48  is provided around the pig deflector flange  46  near the plug  30 . Preferably the alignment ring  48  is heat-shrunk around the pig deflector flange  46 . The alignment ring  48  is tapered to prevent the plug assembly  14  from getting stuck as the hot tap machine lowers the plug assembly  14  into position.  
       FIGS. 20-28  illustrate a fifth embodiment of a plug assembly  14 , with a pig deflector  44  but without an alignment ring.  
       FIG. 29  is a partially sectioned perspective view of a sixth embodiment of a plug assembly, which is similar to the fourth embodiment shown in  FIGS. 17   a - 19  but with a longer pig deflector flange  46  between the plug  30  and the pig deflector  44  and a third embodiment of the tubular member  12   c.    
      Method of Plug Assembly Installation in a Hot Tapping Application  
       FIGS. 17   a - 18  and  20 - 28  illustrate one method of installing, or removably securing, a plug assembly  14  of the present invention into a tubular member  12  during hot tapping operations, the method comprising the following steps: 
          1) Threading a two-piece shear post  40   a  onto the plug  30  (see  FIG. 20 ). Preferably, Moly-lube™ lubricant is applied between the two pieces of the post  40   a  (see  FIG. 21 ).     3) Inserting nylon shear pin  40   b  into place, through the two pieces of the shear post  40   a  (see  FIG. 22 ).     4) Turning a temporary lock ring  50   t  onto the shear post  40   a  until ring  50   t  is sitting just below the top of the shear post (see  FIG. 23 ).     5) Preferably checking that the dogs  32  can still slide in and out (i.e. that the temporary lock ring  50   t  has not actually locked the dogs  32  yet).     6) Sliding an arbour  52  onto the two piece shear post  40   a  (the arbour  52  functioning as a setting tool  40 );     7) Inserting a steel pin  54  through the arbour  52  and post  40   a  (see  FIG. 24 ). Preferably, covering pin  54  in grease first to help prevent it from falling out.     8) Attaching the plug assembly  14  to a hot tap machine  56  via the arbour  52 .     9) Preferably installing a retaining security pin (not shown) to keep the arbour  52  on the hot tap machine  56 .     10) Retracting the hot tap machine  56  until the bottom of the plug  30  is distance M 1  away from the open end of a spool adaptor flange  58  (see  FIG. 18 ).     11) Preferably marking a measuring rod (not shown), preferably with electrical tape.     12) Preferably marking the distance M 3  (see  FIG. 18 ) on the measuring rod, also preferably with electrical tape.     13) Rotating the plug assembly  14  so that a marked dog  32   m  is lined up with a two-hole mark  58   m  on the spool adaptor flange  58  (see  FIG. 25 ).     14) Bolting the spool adaptor flange  58  onto a valve  60 , with the two-hole mark  58   m  lined up with the main line  13 .  15 ) Installing the applicable hoses, manifolds and valves; ensuring that all valves are closed (see  FIGS. 17   a  and  18 ).     16) Opening valve  62  and allow the system to equalize.     17 Lowering the plug assembly  14  onto the plug stopping shoulder  28  (i.e. move distance M 3 , preferably measured with the measuring rod) using the hot tap machine  56  (See  FIG. 17   b ).     18) Backing out the hot tap machine  56  to shear the shear pin  40   b , preferably out no more than 1″.     19) Lowering the hot tap machine  58 , so it pushes the plug assembly  14  down to shoulder  28 .     20) Raising the hot tap machine  56  a ¼ turn so that the arbour  52  is no longer pushing against the plug  30 .     21) Turn the hot tap machine  56  counter-clockwise direction until the measuring rod has made at least 6 full rotations.     22) Backing out the hot tap machine  56 , retracting the drill rod fully.     23) Closing valves  61  and  62 .     24). Slowly bleeding off pressure in the hose  63  using manifold  64 .     25) Reducing the pressure in the spool adaptor flange  58  to 400 psi using manifold  66 . Preferably, holding the pressure for 10 minutes while watching for any pressure increase.     26) Slowly bleeding off the spool adaptor flange  58 , using manifold  66 .     27) Removing the hose  63 .     28) Unbolting the spool adaptor flange  58  from valve  60 .     29) Preferably inspecting the temporary lock ring  50   t . Preferably, the temporary lock ring  50   t  should be against the plug  30 , and none of the dogs  32  should be touching it; because otherwise it means that the temporary lock ring  50   t  forced the dogs  32  out during installation and that the springs on the underside of the dogs  32  were not sufficient to push them out; e.g. due to obstruction within the branch line, or spring failure (see  FIG. 26 , valve  60  not shown). If the temporary lock ring  50   t  is forced against some or all of the dogs  32 , then this ring  50   t  should not be removed, to ensure that the dogs  32  will continue to engage the dog shoulder  26  in the tubular member  12 .     30) Removing the valve  60 .     31) Removing the shear post  40   a  (see  FIG. 27 ).     32) If the temporary ring  50   t  is not engaging one or more of the dogs  32 , preferably replace the temporary lock ring with a permanent lock ring  50   p  (see  FIG. 28 ). Advantageously, the temporary lock ring  50   t  can then be re-used on subsequent installations and the dogs  32  of the installed plug assembly  14  are secured by a less expensive ring  50   p . Either of the lock rings  50   t ,  50   p  will ensure that the dogs  32  remain in place, even if subjected to vibration or other loading, thereby providing an additional safety feature in installations where there are high pressures in the pipe  13 .        
      Other methods of plug installation are known to those skilled in the art.