Patent Publication Number: US-2022228690-A1

Title: Pipeline isolation tool with large-gap sealing element having mini pressure heads and iris-like structural sealing elements

Description:
CROSS-REFERENCE To RELATED APPLICATIONS 
     This application claims the priority of U.S. Provisional Patent Application No. 63/139,598 titled “PIPELINE ISOLATION TOOL WITH LARGE-GAP SEALING ELEMENT HAVING MINI PRESSURE HEADS AND IRIS-LIKE STRUCTURAL SEALING ELEMENTS,” filed Jan. 20, 2021, the contents of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     This disclosure relates to pipeline tools designed to block product flow during pipeline maintenance and repair operations. In particular, this disclosure relates to seals that are used on the plugging heads or modules of these types of tools when having to span a large gap between the seal in its unset and set positions. For purposes of this application, a large gap means a seal gap extrusion where the ratio of pipeline inner diameter to tool outer diameter is greater than approximately 1.10. 
     Prior art large-gap seals can exhibit high strain or strain gradients when activated to the set position and then forced inward radially to seal against its unset inner diameter. The absolute strain levels in the seal may or may not be of major significance to damage of the elastomer. Where structural segments are used to reinforce the seal, there is a potential danger of segments flipping or experiencing permanent deformation at high isolation pressures that would cause jamming of the segments and prevent the seal from retracting. Point loads of the structural segments to the inner pipe wall can introduce high stress peaks that may cause damage to the pipe as well as difficulties when trying to achieve compliance with the pipeline standards. 
     Creep crack growth can be a primary cause of failure when the seal is under load for extended periods of time. The complexity of the seal side profile may be directly related to the risk of crack initiation. The selection of a more “exotic” material that is not susceptible to creep crack growth is expensive due to low volume and potential requirement for unconventional manufacturing methods. The complexity of the seal side profile directly affects manufacturing cost. Additionally, in large-gap seal designs, the required piston stroke is large, making the tool long and therefore less piggable. The length of the tool reduces the benefits of the high expansion sealing capability. 
     SUMMARY 
     Embodiments of an isolation tool of this disclosure are intended for intrusive (hot tap) applications and can span a large gap by way of “T-bone” or T-shaped” seal, with pressure heads on each side of the lower profile of the seal that act as support and prevent extrusion of the seal ID. Structural support elements that overlap one another provide support to the upper profile of the seal. Embodiments may also be arranged for non-intrusive applications in which the tool is pigged into a predetermined location within the pipeline. 
     Because the pressure heads located on each side of the lower profile of the seal have a diameter (radial height) less than that of the sealing element when the sealing element is in its unset position, this disclosure sometimes refers to the heads as “mini” pressure heads. The heads are also smaller in size than the angle plates that apply pressure to the seal through the structural elements and the mini-pressure heads. 
     The structural elements are overlapping structural elements that act like an iris. The structural elements eliminate the use of gap segments like those used in the prior art. See e.g. U.S. Pat. No. 10,436,372 B2 to Bjorsvik et al, the contents of which are incorporated by reference herein. This arrangement provides more options to seal around a primary seal such as, for example, a seal on a pressure head or bowl side. 
     For purposes of this disclosure, a large gap means a seal gap extrusion where the ratio of pipeline inner diameter to tool outer diameter is greater than approximately 1.10 (e.g. 10% radial expansion). 
     Advantages of the embodiments of this disclosure include:
         a) Elimination or reduction of the risk of elastomer tearing;   b) Allowing for control of the amount of seal squeeze and thus the seal contact pressure;   c) Elimination of tilting of supporting segments;   d) Simplifying the side profile of the seal compared to prior art large gap seal designs;   e) Elimination of the need for “exotic” materials for the seal and reduce the cost of manufacturing;   f) Allowing for size scaling;   g) Allowing for low- and high-pressure isolations;   h) Reduction in the amount of required piston stroke (compared to prior art designs) and therefore shorter overall length of the tool;   i) Elimination of the need for a secondary sealing head, a primary (high pressure side) sealing head being sufficient;   j) Allowing sealing of large gaps, including gaps above 20% radial expansion.       

     Embodiments of this disclosure may be used in a pipeline isolation tool like that disclosed in U.S. Pat. No. 10,989,347 to McKone et al. (“McKone”), the content of which is incorporated by reference herein. The tool, for example, may include a pair of plugging heads, one being on the higher pressure side of the tool and serving as the primary seal, the other being on the lower pressure side of the seal and serving as the secondary seal. The tool, therefore, defines two independent sealing systems and two independent locking systems. In some embodiments of the tool, a single plugging head is used. 
     Regardless of whether a single plugging head or a pair of plugging heads is used, in some embodiments the hydraulically actuated piston is encased in a hydraulic cylinder formed at least in part by each of the two pressure heads. The cylinder head may be formed by an opposing pressure head of that forming the cylinder body. 
     A pipeline isolation tool of this disclosure includes a sealing element having an expanding, reusable seal wherein one seal may be used for a wide range of pipe wall thickness of the same nominal size. The seal can be self-energizing, its actuating force being in a same direction as a force from isolation pressure. 
     The structural segments of this disclosure allow for a larger range of extrusion with higher pressure retention capabilities. The plugging head may use a hydraulically activated piston and cylinder arrangement to compress the seal axially which, in turn, expands the seal radially for sealing against the pipe wall. The structural segments slide radially with the seal, maintaining a degree of overlap with one another and supporting the extruded rubber against the differential pressure. 
     The tool may include some machining and assembly methods to deliver hydraulic fluid from a location outside the excavation, to the jackscrew, connect through multiple components and ultimate control double acting pistons in the plugging heads. In some embodiments, the tool includes a control bar that contains a hydraulic transfer sleeve and manifold. The manifold is arranged for connection to external fluid lines, the sleeve providing the fluid to the inside of the tool. Transfer pins may be used to transfer fluid between components. In embodiments, the end of the piston may include trapezoidal shaped threads that accommodate variable spacing between components and require less precision in their placement during assembly. Spacing between the components may be off by up to one full turn and still accommodated. 
     Some embodiments of the tool include an tool of this disclosure include an arcuate-shaped bumper that makes contact with the ID of the pipe to distribute forces experienced by the tool back into the pipe when sealing against the pipe. The bumper may be cam-actuated, for example, connected to an arm that moves into contact with the ID of the pipe as the tool enters the pipe and moves into a position ready for sealing against the ID. In other embodiments, the cam-actuated arm arrangement may be replaced by a bumper connected to an arm or body that is hydraulically actuated. 
     An additional feature in some embodiments is a urethane disc mounted on the front of the tool that pushes chips away from sealing surfaces. This “chip sweep” makes it easier to form a seal. The sweep may be replaced or supplemented by a nozzle that injects fluid ahead of the tool. 
     The tool may be arranged as an intrusive tool. It may also be arranged as a non-intrusive tool, including gripping means and an hydraulic actuation cylinder in communication with the sealing and gripping means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-section of a large-gap seal of this disclosure. 
         FIG. 2  is a schematic cross-section of the seal illustrating key dimensions. 
         FIG. 3A  shows equivalent strain at activation. This linear FEA is sufficient for a qualitative assessment of embodiments of this disclosure. The strain field is uniform across the cross-section and reaches up to 50% (hoop component of the strain is dominant). The maximum reported strains are located at the boundary between the structural (interlocking) segments, however, because of non-optimized geometry these values can be disregarded for other embodiments. A plurality of O-rings provide sealing between an axially oriented surface of the pressure head and the guide. 
         FIG. 3B  is a cut-away perspective view of the seal of  FIG. 3A . 
         FIG. 4A  shows an embodiment of this disclosure that makes use of a mini pressure head to completely prevent extrusion of the seal ID. The seal is shown in its unset position. A pair of O-rings provide sealing between an axially oriented surface of the pressure head and the guide. 
         FIG. 4B  is the embodiment of  FIG. 4A  as it transitions to the set position. 
         FIG. 5  is a screenshot from an FEA animation showing the structural elements when the seal is in its unset position. 
         FIG. 6  is a screenshot from an FEA animation showing the structural elements when the seal is in its set position. 
         FIG. 7  is an isometric view of a large-gap seal of this disclosure when in a test fixture. 
         FIG. 8  is a cross-section view of the seal of  FIG. 7 . 
         FIG. 9  is a front elevation view of an embodiment of a structural element of this disclosure. 
         FIG. 10  is a top plan view of the element of  FIG. 9 . 
         FIG. 11  is a bottom plan view of the element of  FIG. 9 . 
         FIG. 12  is a rear elevation view of the element of  FIG. 9 . 
         FIG. 13  is a left side elevation view of the element of  FIG. 9 . 
         FIG. 14  is a right side elevation view of the element of  FIG. 9 . 
         FIG. 15  is an isometric view of an embodiment of a T-bone-shaped seal of this disclosure. 
         FIG. 16  is a cross-section view of the seal of  FIG. 15 . 
         FIG. 17  is a front elevation view of an embodiment of an angle plate of this disclosure. In some embodiments, the plate includes angled surfaces in a range of 10° to 20°, there being subranges and discrete values within this broader range. 
         FIG. 18  is a right side elevation view of the plate of  FIG. 17 . 
         FIG. 19  is an isometric view of an embodiment of a mini pressure head of this disclosure. 
         FIG. 20  is a cross-section view of the mini-pressure head of  FIG. 19 . 
         FIG. 21  is an isometric view of an embodiment of a mini pressure head of this disclosure and more suitable for higher pressures than the head of  FIG. 19 . 
         FIG. 22  is a cross-section view of the mini-pressure head of  FIG. 21 . 
         FIG. 23  is an isometric, exploded view of an isolation tool of this disclosure. The tool may include a pair of bumpers on the primary plugging head, the bumpers making contact with a pipe wall (lateral access) cutout when the tool is inserted and retracted into the main pipeline. 
         FIG. 24A  is an embodiment of an isolation tool of this disclosure including an arm with an arcuate-shaped bumper that makes contact with the ID of the pipe to distribute forces experienced by the tool back into the pipe when sealing against the pipe. Only one plugging head is shown for purpose of illustration. The arm is shown in its set or fully deployed position with the sealing element in its unset position. The arm may be connected to the control bar and moved into position as the tool enters the pipeline or it may be hydraulically actuated. Once in its set position, the sealing element may be deployed. 
         FIG. 24B  is a top view of the isolation tool of  FIG. 24A . 
         FIG. 25A  is side view of the arm of  FIG. 24A  when in an unset position. 
         FIG. 25B  is a side view of the arm of  FIG. 24A  when in a set or fully deployed position. 
         FIG. 25C  is a top view of the arm of  FIG. 24A  (unset position). 
         FIG. 25D  is a top view of the arm of  FIG. 24A  (set position). 
         FIG. 26A  is an isometric view of an embodiment of a transfer pin of this disclosure. The transfer pin helps continue the fluid circuit between adjacent components like the control bar and yoke or the yoke and plugging head. 
         FIG. 26B  is a cross-section view of the transfer pin of  FIG. 26A . The transfer pin is threaded along the length opposite that of the o-ring grooves. 
         FIG. 27A  is a cross-section view illustrating the transfer pin located along a hydraulic fluid passageway between two adjacent components of the isolation tool. 
         FIG. 27B  is a view of the transfer pin and an anti-rotation pin on a lower pressure side of the tool between the secondary hinge and secondary piston. 
         FIG. 28A  is cross-section view of an embodiment of a spring-loaded anti-rotation pin of this disclosure located on the higher pressure side, with the stem in a retracted (minimum stroke) position. The spring may be a wave spring. 
         FIG. 28B  is cross-section view of the spring-loaded anti-rotation pin of  FIG. 28A  with the stem in an extended (maximum stroke) position. 
         FIG. 29  is an embodiment of an actuator bar for use with isolation tools of this disclosure. 
       The actuator includes an hydraulic transfer sleeve ( FIG. 32 ) that contains a manifold ( FIG. 33 ) that passes hydraulic fluid from outside of the pipe into the isolation tool. 
         FIG. 30  is a cross-section view of an upper end of the actuator bar indicated by section 30 of  FIG. 29 . 
         FIG. 31  is a cross-section view of a portion of the upper end of the actuator bar indicated by section 31 of  FIG. 30 . 
         FIG. 32  is an embodiment of a hydraulic transfer sleeve of  FIGS. 30 &amp; 31 . 
         FIG. 33  is an embodiment of the manifold block of  FIGS. 30 &amp; 31 . 
         FIG. 34  is an embodiment of a plugging head of this disclosure with a hydraulic cylinder formed at least in part by each of the two pressure heads. The cylinder head may be formed by an opposing pressure head of that forming the cylinder body. Arranging the hydraulic cylinder in this way provides for a shorter overall tool length. 
         FIG. 35  is an embodiment of the hydraulic cylinder of  FIG. 34  integrated into a high pressure plugging head. Use of the hydraulic cylinder is not limited to the T-shaped seal of this disclosure and may be used with other circumferential seal designs. 
         FIG. 36  is an embodiment of a non-intrusive arrangement of the pipeline isolation tool. The tool includes gripping means. Sealing cups or discs of a kind known in the art may be arranged about the tool body to center the tool in the pipe and help propel it forward under differential pressure. Means known in the art may also be used to arrange the tool as part of a plugging train. 
         FIG. 37  is an embodiment of a piston and pressure head assembly of this disclosure. The piston includes trapezoidal threads at each end. The threads accommodate variable spacing between the piston and components to which it is connected such that the spacing can be off a much as one full thread turn. 
     
    
    
     ELEMENTS AND NUMBERING USED IN THE DRAWINGS AND DESCRIPTION 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 10 
                 Pipeline isolation tool 
               
               
                 20 
                 Pipe 
               
               
                 22 
                 Pipe wall 
               
               
                 30 
                 Seal 
               
               
                 32 
                 First side 
               
               
                 34 
                 Second side 
               
               
                 36 
                 Lower seal profile 
               
               
                 37 
                 Lower end 
               
               
                 38 
                 Upper seal profile 
               
               
                 40 
                 Pressure head 
               
               
                 41 
                 Inner surface 
               
               
                 42 
                 Outer surface 
               
               
                 43 
                 Angled surface 
               
               
                 44 
                 Upper end 
               
               
                 45 
                 Lower end 
               
               
                 47 
                 Recess 
               
               
                 50 
                 Pressure head 
               
               
                 51 
                 Inner surface 
               
               
                 52 
                 Outer surface 
               
               
                 53 
                 Angled surface 
               
               
                 54 
                 Upper end 
               
               
                 55 
                 Lower end 
               
               
                 56 
                 Axially oriented surface 
               
               
                 57 
                 Recess 
               
               
                 58 
                 Lower face surface 
               
               
                 59 
                 O-ring 
               
               
                 60 
                 Structural elements 
               
               
                 62 
                 Upper end 
               
               
                 64 
                 Inner face 
               
               
                 66 
                 Outer face 
               
               
                 68 
                 Overlap 
               
               
                 70 
                 Concave area 
               
               
                 72 
                 Second outer diameter 
               
               
                 74 
                 First outer diameter 
               
               
                 80 
                 Structural elements 
               
               
                 82 
                 Upper end 
               
               
                 84 
                 Inner face 
               
               
                 86 
                 Outer face 
               
               
                 88 
                 Overlap 
               
               
                 90 
                 Concave area 
               
               
                 92 
                 First outer diameter 
               
               
                 94 
                 Second outer diameter 
               
               
                 100 
                 Angle plate 
               
               
                 102 
                 Inner angle surface 
               
               
                 110 
                 Angle plate 
               
               
                 112 
                 Inner angle surface 
               
               
                 114 
                 Face surface 
               
               
                 210 
                 First plugging head 
               
               
                 212 
                 Carrier 
               
               
                 214 
                 Yoke 
               
               
                 216 
                 Yoke pin 
               
               
                 218 
                 Nose 
               
               
                 220 
                 Second plugging head 
               
               
                 222 
                 Upper end 
               
               
                 230 
                 Control bar 
               
               
                 231 
                 Lower end 
               
               
                 232 
                 Transfer sleeve 
               
               
                 234 
                 Ports 
               
               
                 236 
                 Manifold 
               
               
                 238 
                 Yoke 
               
               
                 240 
                 Yoke pin 
               
               
                 242 
                 Bumpers 
               
               
                 250 
                 Sweep 
               
               
                 260 
                 Arm 
               
               
                 262 
                 Bumper 
               
               
                 264 
                 Distal end 
               
               
                 266 
                 Linkage 
               
               
                 268 
                 Proximal end 
               
               
                 270 
                 End 
               
               
                 272 
                 End 
               
               
                 276 
                 Cam surface 
               
               
                 278 
                 Cam 
               
               
                 290 
                 Transfer pin 
               
               
                 292 
                 Passageway 
               
               
                 294 
                 Threaded length 
               
               
                 296 
                 Hex-shaped head 
               
               
                 298 
                 O-ring groove/O-ring 
               
               
                 300 
                 Anti-rotation pin 
               
               
                 302 
                 Spring 
               
               
                 304 
                 Stem 
               
               
                 306 
                 Piston 
               
               
                 308 
                 Hydraulic cylinder 
               
               
                 310 
                 Deactivation volume 
               
               
                 312 
                 Activation volume 
               
               
                 314 
                 Trapezoidal threads 
               
               
                 320 
                 Gripping means 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION 
     Referring now to the drawing figures, embodiments of a pipeline isolation tool  10  are shown and described. Pipeline isolation tool  10  is received in pipe  20 . Pipe  20  defines pipe wall  22 . Pipeline isolation tool  10  includes circumferential seal  30 . Circumferential seal  30  has first side  32  and second side  34 . Seal  30  is expandable between an unset position and a set position. 
     Seal  30  is configured to sealable engage pipe wall  22  in the set position. When in the set and unset positions, seal  30  defines a T-shaped cross section defining a radially v oriented lower seal profile  36  and a horizontally oriented upper seal profile  38 . In some embodiments, radially oriented lower seal profile  36  is smaller in cross section than axially oriented upper seal profile  38 . 
     For purposes of this disclosure, the radial direction and axial direction are relative to the seal  30 . For example, when tool  10  is set in a horizontally oriented pipe, the radial direction is vertical (z-axis) and the axial direction is horizontal (y-axis). When tool  10  is set in a vertically oriented pipe, the radial direction is horizontal (y-axis) and the axial direction is vertical (z-axis). 
     Circumferential pressure heads  40 ,  50  are located on each side  32 ,  34  of the seal  30 . First circumferential pressure head  40  is located adjacent first side  32  of radially oriented lower seal profile  36 . First circumferential pressure head  40  defines outer surface  42 . Second circumferential pressure head  50  is located adjacent second side  34  of radially oriented lower seal profile  36 . Second circumferential pressure head  50  defines outer surface  52 . 
     A plurality of first structural) elements  60  are located adjacent first side  32  of seal  30 . Each of plurality of first structural elements  60  have an upper end  62 , an inner face  64 , and an outer face  66 . Each of plurality of first structural elements  60  define overlap  68  (see e.g.,  FIG. 5 ) with at least a portion of an adjacent first structural element  60 . Each of plurality of first structural elements  60  defines concave area  70  proximate to upper end  62  for receiving a portion of axially oriented upper seal profile  38  of seal  30 . Inner face  64  of plurality of first structural elements  60  contacts outer surface  42  of first circumferential pressure head  40 . 
     An amount of overlap  68  of adjacent ones of plurality of first structural elements  60  decreases as seal  30  moves from the unset position (see e.g.,  FIGS. 1, 2, 4 ) to the set position (see e.g.,  FIG. 3A ). An amount of overlap  68  of adjacent ones of plurality of first structural elements  60  increases as seal  30  moves from the set position (minimum or lesser overlap) to the unset position (maximum or greater overlap). Therefore, the plurality of first structural elements  60  define an first outer diameter  74  in the unset position (see  FIG. 5 ) and define a second outer diameter  72  in the set position (see  FIG. 5 ). The second outer diameter  72  is greater than the first outer diameter  74 . 
     A plurality of second structural (interlocking) elements  80  is located on second side  34  of seal  30 . Each of the plurality of second structural elements  80  have an upper end  82 , an inner face  84 , and an outer face  86 . Each of the plurality of second structural elements  80  define an overlap  88  (see e.g.,  FIGS. 5, 6 &amp; 13 ) with at least a portion of an adjacent second structural element  80 . Each of the plurality of second structural elements  80  define a concave area  90  proximate to upper end  82  for receiving a portion of axially oriented upper seal profile  38  of seal  30 . Inner face  84  of the plurality of second structural elements  80  contact outer surface  52  of second circumferential pressure head  50 . 
     An amount of overlap  88  of adjacent ones of the plurality of second structural elements  80  decrease as seal  30  moves from the unset position to the set position. An amount of overlap  88  of adjacent ones of the plurality of second structural elements  80  increases as seal  30  moves from the set position (minimum or lesser overlap) to the unset position (maximum or greater overlap). Therefore, the plurality of second structural elements  80  define a first outer diameter  92  (see e.g.,  FIGS. 3A, 6 ) in the set position and define a second outer diameter  94  (see e.g.,  FIGS. 1, 2, 4, 5 ) in the unset position. The second outer diameter  94  is greater than the first outer diameter  92 . 
     The first and second structural elements  60 ,  80  engage with respective circumferential angle plates  100 ,  110 . First circumferential angle plate  100  defines an inner angle surface  102 . Inner angle surface  102  is in contact with outer face  66  of each of the plurality of first structural elements  60 . Second circumferential angle plate  110  defines inner angle surface  112 . Inner angle surface  112  is in contact with outer face  86  of each of the plurality of second structural elements  80 . The angle plates  100 ,  110  function as pressure heads, applying pressure to the structural elements as well as the mini-pressure heads  40 ,  50 . 
     The plates  100 ,  110  may span the radial distance from the lower end  45 ,  55  of the pressure heads  40 ,  50  to an upper end  62 ,  82  of the structural elements  60 ,  80  (and therefore are larger size pressure heads than the pressure heads  40 ,  50 ). In embodiments, the plates  100 ,  110  are not mirror images of another, nor are the pressure heads  40 ,  50 . 
     Embodiments of disclosure further include a “T-bone” or T-shaped” seal  30  in cross-section, see  FIGS. 1, 3, 4A , &amp;  15 - 16 . the sealing element  30  having an upper profile  38  and a lower profile  36 , the lower profile  36 . The two profiles  36 ,  38  may be different in shape from one another. In some embodiments, the lower profile  36  is narrower in cross-section than the upper-profile  38 . A circumferential pressure head  40 ,  50  is located on each side of, and in contact with, the lower profile  36  of the sealing element  30 . A plurality of structural elements  60 ,  80  are arranged about the pressure heads  40 ,  50 , each structural element  60 ,  80  overlapping at least a portion of an adjacent structural element  60 ,  80 . 
     In embodiments, the pair of circumferential angle plates  100 ,  110  and pair of circumferential pressure heads  40 ,  50  may be arranged such that, as the circumferential seal  30  moves from the unset position to the set position, the pair of circumferential angle plates  100 ,  110  apply pressure to the plurality of structural elements  60 ,  80  prior to the pair of circumferential pressure heads  40 ,  50  applying pressure to the radially oriented lower profile  36 . 
     The structural elements  60 ,  80  include a concavity  70 ,  90  at an upper end  62 ,  82 , into which a portion of the upper profile  38  of the sealing element  30  resides, and an inner face surface  64 ,  84  in contact with an outer surface  42 ,  52  of the pressure head  40 ,  50 . The amount of overlap  68 ,  88  between the adjacent structural elements  60 ,  80  decrease as the sealing element  30  moves from an unset to a set position, the amount of overlap  68 ,  88  increasing as the sealing element  30  moves from the set to the unset position. Because the amount of overlap  68 ,  88  increases and decreases, the structural elements  60 ,  80  expand between a first size and a second size. A circumferential angle plate  100 ,  110  includes an inner angled surface  102 ,  112  that contacts an outer face surface  66 ,  86  of the structural element  60 ,  80 . 
     The radially oriented lower seal profile  36  may be smaller in cross-section than the axially oriented upper profile  38  of the seal  30 . However, the smaller cross-section is not important for the seal  30  to work as intended. The mini pressure heads  40 ,  50 , see  FIGS. 19-22 , on each side  32 ,  34  of the lower seal profile  36  act as supporting structures and prevent extrusion of the seal ID. 
     In the unset position, the lower profile  36  resides between the mini pressure heads  40 ,  50 , with the upper profile  38  being entirely above upper end  44 ,  54  of the heads  40 ,  50 . The seal  30  expands towards the pipe  20  in near pure “natural” (hoop) stretch in order to achieve a uniform strain distribution along the entire seal cross-section. 
     Note that in some embodiments the lower end  37  of the seal  30  does not contact an opposing axially oriented surface  56  of the pressure head  50 , and the radial distance between the two increases as the seal  30  moves between the unset and set positions (compare  FIG. 4A  (in unset position) to  FIGS. 3A  (set position) and  4 B (moving to set position)). The lower end  37  is spaced a first radial distance from the axially oriented surface  56  when the circumferential seal  30  is in the unset position and a second radial distance greater than that of the first when the seal  30  is in the set position, the first radial distance being greater than zero. Because of this arrangement, and by way of a non-limiting example, the seal  30  may expand to about 60% to 70% of the radial area available. 
     As contact with the pipe ID  22  occurs, the mini pressure heads  40 ,  50  get compressed towards the seal  30  and act across a large cross-section in order to distribute the load from the isolation pressure. See  FIGS. 4A &amp; 4B . Unlike the outer surface  42 ,  52  of the pressure heads  40 ,  50 , which have a constant slope, the inner surface  41 ,  51  of the pressure heads  40 ,  50  does not. In some embodiments, the inner surfaces  41 ,  51  may include a plurality of surfaces  43 A-C,  53  A-C oriented at different angles such that a recessed area  47  is formed (thereby providing greater axial distance between the heads  40 ,  50  at the upper end  44 ,  54 , than at the lower end  45 ,  55 ). For example, surface  43 A,  53 A may be vertical, surface  43 B,  53 B may then angle toward outer surface  42 ,  52 , and surface  43 C,  53 C may be vertical or slightly off vertical, angling toward the outer surface  42 ,  52 . 
     When transitioning to the set position, and when in the set position, a portion of the lower profile  38  may reside within the recess  47 —that is, in contact with surfaces  43 B-C,  53 B-C but not  43 A,  53 A—with another portion of the lower profile residing entirely above the upper ends  44 ,  54  of the pressure heads  40 ,  50 . A pair of O-rings  59  located between a lower face surface  58  of pressure head  50  and an opposing face surface  114  of the angle plate  110  provide sealing between pressure head  50  and angle plate  110 . The o-rings  59  do not expand. 
     Referring to  FIG. 2 , the main dimensions “A” and “B” of T-shaped seal  30 , together with distance “D” between the structural segments  60 ,  80 , dictate when contact between the elastomer and steel components get established. In embodiments, the mini pressure heads  40 ,  50  do not start squeezing the seal  30  immediately but do so later in the activation cycle in order to allow for building a uniform strain field within the seal  30 . Dimensions “A”, “B” and “C” are predetermined to account for the design expansion gap and can be optimized to accommodate one or more pipe IDs. Note that where two or more pipe IDs are designed for, the seal  30  would have multiple set positions, that is, one for each pipe ID. For example, the circumferential seal  30  can have a first set position and a second set position, the first set position being for a first pipe diameter and second set position being for a second pipe diameter greater than that of the first pipe diameter. Thickness “C” should (in general) be sized to bring the segments  60 ,  80  together as much as possible and prevent the rubber seal  30  from extruding inward into the cavity between the mini pressure heads  40 ,  50 . Thickness “C” may be smaller than that of “B”. In some embodiments, the overall height of the seal  30  (in the radial direction when unset) is less than the radial distance “G” (see e.g.  FIGS. 3 to 4B ). Distance “E” also helps with the preventing extrusion; making sure the seal  30  has enough support on the segments  60 ,  80 , which will reduce the risk of extruding the seal  30  radially inwards. The pressure heads  40 ,  50  include a radius “F” at their upper end where the seal  30  transitions between its lower and upper profiles  36 ,  38 . 
     ID extrusion of seal  30  at high pressure can be a risk.  FIG. 3  shows an embodiment in which the ID extrusion of seal  30  is limited, but possible. Such a design is considered for low pressure applications, and can be optimized as stated above by manipulating dimensions “C”, “D” and “E” as well as “G.”.  FIGS. 4A and 4B  shows an embodiment that prevents extrusion of the ID of seal  30  completely. See also  FIGS. 21 &amp; 22 . The lower profile  36  of the seal  30  does not contact an upper axially oriented surface  51  of pressure head  50 . The lower end  37  of the profile  36  may be narrower in cross-section than the middle and upper portions of the profile  36 . In some embodiments, the cross-section of toward the lower end  37  is semi-hexagonal in shape. When the seal  30  gets activated, the mini pressure heads  40 ,  50  squeeze the ID extension of seal  30  and also make contact. This introduces an adjustable reinforcing effect that can be tailored for high-pressure isolations. 
     Furthermore, a high Shore rubber can be molded to the ID of the seal  30  in order to achieve a hard seal that would prevent radial extrusion (with a lower Shore rubber on the OD of the seal). The contact between the mini pressure heads  40 ,  50  and the seal  30  can also be designed as a high-friction contact to help minimize this effect. In some embodiments, a higher Shore rubber is used on the upper corners of the seal  30  than in other areas of the seal  30 . 
     Increased stress and jamming of the movable mini pressure heads  40 ,  50  is another risk that can also be addressed by design features, such as increasing material thickness, ensuring a low friction surface and proper gap tolerance between the mini pressure heads  40 ,  50 , angle features angle plates  100 ,  110 . 
     A large-gap seal  30  of this disclosure expands radially with low force, remains relatively unstrained from the axial direction during setting, and introduces a reinforcing effect to supporting segments that prevents them from tilting at large expansion gaps. Embodiments of this disclosure expand radially by 20% or more to engage the pipe wall  22  due to the reinforcing effect of segments  60 ,  80  and no need to extrude the seal  30  radially inwards. The seal  30  is also independent of the isolation pressure magnitude with no ID of seal  30  extrusion. The seal  30  also is highly customizable in that in can be optimized for a variety of expansion gaps and isolation pressures by manipulating angles, thicknesses and heights of the segments  60 ,  80  and T-bone shaped seal  30 . 
     Referring now to  FIGS. 23 &amp; 35 , embodiments of an isolation tool  10  of this disclosure may include a first and second plugging head  210 ,  220  in pivotal relation to one another. When inserted into pipe  20  in a same direction as pipeline product flow, plugging head  210  serves as the primary plugging head (on the higher pressure side of the tool  10 , there being a pressure differential across the head  210 ) and plugging head  220  serves as the secondary plugging head (on the lower pressure side of the tool, there being a pressure differential across the head  220 ). Each plugging head  210 ,  220  includes seal  30 , pressure heads  40 ,  50 , and segments  60 ,  80  as previously described. Any pipeline product leaking past the first head  210  is prevented from passing the second head  220 . The tool  10 , therefore, defines a double barrier or double block because it has two independent sealing systems and two independent locking systems. Bleed or venting of pipeline product can be provided between the heads  210 ,  220  when in their sealing positions. 
     When arranged as an intrusive tool, plugging head  210  is pivotally connected by a yoke  214  to a carrier  212 . Yoke  214  rotates about a yoke pin  216  contained within a yoke mount  218  connected to carrier  212 . Plugging head  220 , which may be the secondary plugging head (on the low pressure side of tool  10 ), is connected to plugging head  210  by a yoke  238  that rotates about a yoke pin  240 . Yoke  238  may include a pair of bumpers  242  that help prevent yoke  214  and plugging head  210  from becoming entrapped in the access connection to pipe  20  during installation into, and removal from, the pipe  20 . 
     In embodiments, the tool  10  travels downward through a lateral access connection and travels into the pipe  20  in a way similar to that described in U.S. Pat. No. 7,841,364 B2 to Yeazel et al. (“Yeazel”), the content of which is incorporated by reference herein. Venting between the heads  210 ,  220  may occur by way of a bleed port. See e.g. Yeazel. The tool  10  also may be configured as a non-intrusive tool as shown in  FIG. 36  and include gripping means  320 . Sealing cups or discs of a kind known in the art may be arranged about the tool body to center the tool  10  in the pipe  20  and help propel the tool  10  forward under differential pressure. Means known in the art may also be used to arrange the tool  10  as part of a plugging train. Each plugging head  210 ,  220  may be a separate module of the plugging train. 
     Referring to  FIGS. 29 to 33 , when configured or arranged as an intrusive tool, carrier  212  is connected at its upper end  222  to a control bar  230 . The control bar  230  is used, along with control bar head  212  and yokes  214 ,  238 , to radially insert, rotate, and position the tool  10  into a final sealing position within the pipe  20 . The control bar  230  also supplies hydraulic fluid to each plugging head  210 ,  220 . In some embodiments, control bar head  212  may be the same or similar to that disclosed in U.S. Pat. No. 10,989,347 to McKone et al. 
     Some embodiments of the tool  10  may include a control bar  230  that includes an hydraulic transfer sleeve  232  ( FIG. 32 ) that contains a manifold  236  ( FIG. 33 ) that passes hydraulic fluid from outside of the pipe  20  into the isolation tool  10 . The hydraulic transfer sleeve  232  includes a set of ports  234  that communicate with a complementary set of ports  238  of the manifold  236 . The ports  238  then communicate with external fluid lines. 
     In embodiments, the leading plugging head  210  or  220  during insertion into pipe  20 , may include a chip sweep  250 . The chips being swept downstream of the tool  10  by sweep  250  are typically the result of a hot tap operation. The chips may also include other pipeline debris that could interfere with seal  30  when engaging the pipe wall  22 . In some embodiments, the sweep  250  may be a urethane disc. In other embodiments, sweep  250  may be supplemented (or replaced) by a nozzle arranged to inject an inert gas such as nitrogen or a liquid, or a pipeline product, ahead of the sweep  250  or tool  10 . The nozzle may include ports arranged to draw the gas or liquid into the nozzle by way of venturi effect as the tool  10  is being inserted into the pipe  20 . 
     Referring now to  FIGS. 24A to 25D , in some embodiments tool  10  may include an arcuate-shaped bumper  262  that engages with the pipe wall  22  and distribute forces experienced by the tool  10  to the pipe  20 . The bumper  262  may be deployed through mechanical means such as an arm  260  or extended and retracted by way of an hydraulic cylinder The arcuate-shaped bumper  262  is moveable between a first position and a second position. When in the first position, the arcuate-shaped bumper  262  is inward of a sealing diameter of the circumferential seal  30 . When in the second position, the arcuate-shaped bumper  262  extends to a sealing diameter of the circumferential seal  30 . 
     In one embodiment, the arm  260  is fixed at a lower end  231  of the control bar  230 . The arm  260  is arranged to move between a first (non-deployed) position and a second (fully deployed) position as the tool  10  is positioned within the pipe  20 . The arm  260  is curved between its two ends  264 ,  268  and includes an arcuate-shaped bumper  262  at its upper (distal) end  264 . The bumper  262  is shaped complementary to the ID of the pipe  20 . A linkage  266  is connected at one end  270  to the lower (proximal) end  268  of the arm  260  and is fixed at another end  272  to the yoke  214  or control bar  230 . The lower end  268  of the arm  260  includes a cam surface  276  and the end  272  of the-linkage  266  includes a cam  278 . 
     As the yoke  214  travels into the pipeline  20 , the yoke  214  pushes the cam  278  and the arm  260  moves between the first and second positions and, when in the second position, the bumper  262  contacts the inner diameter of the pipeline  20 . The forces experienced by the tool  10  are distributed to the pipe  20 . When in the second position, the arm  260  may overlap a portion of the plugging head  210  but is rearward of the seal  30 . 
     The arm  260  may be sized and arranged so that contact with the ID of the pipe  20  occurs within the length of the pipe  20  that is enclosed by the fitting located on the outside of the pipe  20 . The fitting is typically a saddle branch fitting of a kind known in the art for lateral access connections used in hot tapping operations. 
     Referring now to  FIGS. 26A to 27B , transfer pins  290  including a hydraulic passageway  292  may be used between adjacent components of the tool  10  to avoid external hydraulic lines and deliver hydraulic fluid to each plugging head  210 ,  220 . For example, a transfer pin  290  can be placed between a yoke and a piston. The transfer pin  290  includes O-ring grooves  298  at one end and a threaded length  294  at another end. The threaded length  294  may be a standard metric thread. In embodiments, the transfer pin  290  may include a hex-shaped head  296  to accommodate assembly of the tool  10 . 
     Referring to  FIGS. 27B to 28B , embodiments of tool  10  may include a spring-loaded anti-rotation pin  300 . The anti-rotation pin  300  prevents relative rotation between the nose of the plugging head  210  or  220  and the hydraulically actuated piston  306 . The spring may be a wave spring  302 . 
     During assembly of the tool  10 , use of the spring  302  in connection with a stem  304  allows an assembler to grab the anti-rotation pin  300  and lock it in the unlocked position. Because the end of the stem  304  is threaded, the assembler and can secure a nut on the end of stem  304  to keep spring  302  compressed. 
     In embodiments, the piston  306  has threads  314  at each end, see  FIG. 37 , that are not clocked so the gap between the piston  306  and hinge (yoke)  214  can be as much as one whole thread pitch (e.g. a 6 mm thread allows for a gap from 0-6 mm). The threads, which may be trapezoidal threads, allow for variable gap spacing between whatever component is threading onto the piston. In this way, a gap of zero to one full turn may be accommodated in order to have the component and piston  306  clocked properly relative to one another. 
     In some embodiment of a plugging head  210  or  220  of this disclosure, a piston or hydraulic cylinder  308  formed, at least in part, by each of the two angle plates  100 ,  110 . See  FIGS. 34 &amp; 35 . The cylinder  308  may be arranged such that the deactivation volume  310  is greater than that of the actuation volume  312 . Compared to embodiments that make use of piston  306 , hydraulic cylinder  308  provides for a shorter overall tool length. The cylinder head may be formed by an opposing angle plates  100 ,  110  of that forming the cylinder body  308 . Use of the cylinder  308  is not limited to a T-shaped seal  30  but may be used with other sealing elements. For example, the cylinder  308  may be used with sealing elements the same as or similar to those disclosed by McKone et al. 
     While embodiments have been described, an isolation tool of this disclosure may be modified by persons of ordinary skill in the art without departing from the scope of the following claims, the elements recited in the claims being entitled to their full range of equivalents.