Abstract:
A system and method of plugging a pipe including sealably securing onto the exterior of a pipe first and second spaced apart collars, each collar having a sealing face in a plane perpendicular the pipe axis, cutting and removing a length of pipe from between the collars leaving two open pipe ends, positioning first and second seal cups between the collars, each seal cup having a forwardly extending circumferential lip of internal diameter greater than the external diameter of the pipe, each seal cup having top and bottom cam followers, moving cam surfaces against the cam followers to guide the seal cups into sealing engagement with the sealing faces of the collars, and forcing a wedge between rearward surfaces of the seal cups.

Description:
REFERENCE TO PENDING APPLICATIONS 
     This application is not based upon any pending domestic or international patent applications. 
     REFERENCE TO MICROFICHE APPENDIX 
     This application is not referenced in any microfiche appendix. 
     FIELD OF THE INVENTION 
     This invention relates to apparatus systems and methods for plugging a pipe or pipeline having high temperature liquids or gases flowing therethrough. 
     BACKGROUND OF THE INVENTION 
     This invention relates to cam guided systems and methods for plugging a pipe under pressure, and is particularly applicable for plugging a pipe, or pipeline having therein high temperature liquids or gases. “Pipe” as used hereinafter is inclusive of any tubular member made of metal for carrying fluid (liquids or gases). 
     The invention described herein is a cam-assisted, wedge actuated, double block and bleed, metal-to-metal high temperature valve. 
     Machines for tapping an opening in a pipe are well-known. Prior issued U.S. patents for tapping machines include U.S. Pat. No. 3,614,252 entitled TAPPING APPARATUS; U.S. Pat. No. 4,579,484 entitled UNDER WATER TAPPING MACHINE; U.S. Pat. No. 4,880,028 entitled COMPLETION MACHINES; U.S. Pat. No. 5,439,331 entitled HIGH PRESSURE TAPPING APPARATUS; U.S. Pat. No. 5,612,499 entitled METHOD OF INSERTING A SENSOR INTO A PIPELINE and U.S. Pat. No. 6,012,878 entitled PRESSURE BALANCED SUBSEA TAPPING MACHINE. 
     Tapping machines, such as the kind described in the above-mentioned U.S. patents, are for tapping a hole in a pipe while liquids or gases are flowing through them, that is, while the pipe is under pressure. Tapping procedures of this type are customarily carried out primarily for one of two purposes, that is, to provide a branch fitting on the pipe or to enable fluid flow through the pipe to be blocked. Other examples of prior art that describe and illustrate plugging the interior of a pipe usually associated with first tapping the pipe, include the following United States patents: 
     
       
         
               
               
               
             
           
               
                   
               
               
                 PATENT NO. 
                 INVENTOR 
                 TITLE 
               
               
                   
               
             
             
               
                 U.S. Pat. No. 3,170,226 
                 Allan 
                 Line Stopping and Valve Inserting 
               
               
                   
                   
                 Apparatus and Method 
               
               
                 U.S. Pat. No. 3,599,663 
                 Ver Nooy 
                 Hot Tapping Apparatus 
               
               
                 U.S. Pat. No. 3,626,475 
                 Hicks 
                 High Temperature Pipe-Plugging 
               
               
                   
                   
                 Apparatus 
               
               
                 U.S. Pat. No. 3,665,966 
                 Ver Nooy 
                 Pipe Plugger 
               
               
                 U.S. Pat. No. 3,785,041 
                 Smith 
                 Method For Plugging Pipe 
               
               
                 U.S. Pat. No. 3,872,880 
                 Ver Nooy et al. 
                 Plugging Apparatus 
               
               
                 U.S. Pat. No. 4,411,459 
                 Ver Nooy 
                 Branch Fitting for Providing Access to 
               
               
                   
                   
                 the Interior of a Pipe 
               
               
                 U.S. Pat. No. 5,443,095 
                 Glossop, Jr. 
                 Fluid Blocking Device 
               
               
                 U.S. Pat. No. 5,531,250 
                 Freeman et al. 
                 Device for Plugging the Interior of a 
               
               
                   
                   
                 Pipe 
               
               
                 GB1,064,398 
                 Pass and Co. Ltd. 
                 Pipe Line Plugger 
               
               
                 WO2004/099661 
                 TDW Delaware, Inc. 
                 Apparatus, Systems and Methods For 
               
               
                   
                   
                 Plugging A High Temperature Pipe 
               
               
                   
               
             
          
         
       
     
     BRIEF SUMMARY OF THE INVENTION 
     The invention described herein is a cam-assisted, wedge actuated, double block and bleed, metal-to-metal, high temperature plugging tool. 
     The invention herein makes use of the known technology of welding onto a pipe having fluid flow therethrough a pair of collars. Each of the collars is a toroidal that is severed to provide a set of two toroidal halves that are fitted together around the pipe. Each collar set consisting of two spaced apart parallel collars are first secured to the exterior of the pipe. Each collar has a machined face which can be achieved by machining and grinding before the collars have been welded to the pipe. Thus a set of collars affixed to the exterior surface of a pipe provide forward planar faces that face each other. The collar faces are parallel to each other and spaced apart an accurately establish distance. After each collar is affixed to the pipe, the collar halves are then welded to each other. Further, the two halves of each collar are welded where the back face meets the pipe around the 360° circumference of the pipe. After the collars are installed, they provide uninterrupted circumferentially planar sealing surfaces that face each other. The sealing surfaces are parallel to each other and in radial planes perpendicular to longitudinal axis of the pipe. 
     After the collars are welded to the exterior surface of a pipe containment fittings are welded to the collars to provide a housing of internal dimensions greater than the external surface of the pipe. The containment housing has a bottom usually in the form of a cup-shaped member and a flange fitting at the upper end. After the containment housing, including the bottom member and the upper flange have been welded to the collars, the containment housing is typically pressure tested to ensure there are no leaks and that the collars and the containment housing have the structural integrity to contain the maximum pressure to which they will be subjected. 
     After the collars and the containment housing components have been installed and tested, a valve is secured to the containment housing flange. A tapping machine system, well known in the industry, is secured to the upper surface of the valve and then pressure is applied to test for leaks. Thereafter, by use of the tapping machine, a complete section of the pipeline is removed from between the collars. The concept of removing a complete section rather than tapping only a hole in the pipe is illustrated in U.S. Pat. No. 5,612,499 entitled “Method of Inserting A Sensor Into A Pipeline”. When a section of the pipeline has been cut, it is removed exposing the opposed ends of the cutout section of the pipeline, the exposed ends being surrounded by the collars that have previously been attached to the pipe. 
     After the collars and the containment housing have been affixed to the exterior of the pipe, and a tapping machine attached and a section of the pipe cut and removed, the next step is to seal the opposed ends of the pipe employing a plugging tool that is the subject of the present disclosure. The plugging tool is inserted as an assembly into the interior of the containment housing. The tool contains opposed sealing cups, each having a circumferential sealing surface of internal diameter greater than the external diameter of the pipe. The plugging tool assembly is lowered into the containment housing and actuated such that the opposed sealing cups are advanced in directions towards the open ends of a severed pipe and towards the opposed planar circumferential sealing surfaces provided by the collars. 
     The plugging tool assembly includes upper and lower cam followers affixed to each of the seal cups rearwardly of the forward faces thereof. Top and bottom supports each having a pair of cam slots for receiving the cam followers and are configured to urge the seal cups towards the toroidal sealing surfaces on the collars. The plugging tool assembly includes translation apparatus for moving the top and bottom supports toward and away from each other to thereby urge the seal cups towards and away from the toroidal collar sealing surfaces. 
     A pair of wedge members are forced against rearward surfaces of the seal cups to simultaneously force them into metal-to-metal sealing contact with the sealing surfaces formed on the toroidal collars. In this manner a double block and bleed, metal-to-metal seal, high temperature plugging tool is achieved. After the seal cups are forced into sealing condition the interior of the containment housing can be tested to verify that both seal cups are in leak-proof contact with the toroidal collars. 
     The sealing assembly is moved into or out of the containment housing by means of a hydraulic cylinder with a piston therein and a piston rod extending sealably from the hydraulic cylinder. The plugging tool assembly is supported by the piston rod. It is important that the plugging assembly be accurately positioned within the housing and therefore the piston rod that holds the assembly must be non-rotatably secured with respect to the housing. For this purpose, a type of hydraulic cylinder/piston assembly is provided in an arrangement that rotationally fixes the piston and piston rod with respect to the cylinder, that is, it allows the piston rod to be axially displaced relative to the cylinder but prevents the piston rod from rotating about its axis relative to the cylinder axis. 
     A better understanding of the invention will be obtained from the following detailed description of the preferred embodiments and claims taken in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational cross-sectional view of portions of the length of a pipeline having affixed to it a set of collars and a containment housing in which a portion of the pipeline between the collars has been removed. Shown positioned partially within the containment housing, in external view, is a cam-actuated plugging assembly that is the basic subject of this invention. 
         FIG. 2  is an enlarged cross-sectional view of the plugging assembly as shown in  FIG. 1 . 
         FIG. 3  is an isometric external view of the plugging assembly in its non-operated state, that is, in the state as it would appear prior to being inserted into a housing for closing the opposed ends of a pipe. 
         FIG. 4A  is an exploded external view of the plugging assembly body with guide portions that are attached to it. 
         FIG. 4B  is a further exploded view of components that, together with the body portion as shown in  FIG. 4A , complete the plugging assembly. 
         FIG. 5  is a partial cross-sectional view of the plugging assembly shown in its non-actuated condition with the sealing cups withdrawn towards each other. 
         FIG. 6  is a view as in  FIG. 5  of the plugging assembly shown in its actuated condition with the sealing cups moved outwardly away from each other so as to perform a sealing function within a containment housing. 
         FIG. 7  is a cross-sectional view of a containment housing with collars affixed to the exterior length of a pipe and a portion of the pipe having been removed as shown in  FIG. 1  and showing the plugging assembly having been inserted into the containment housing and the sealing cups forced outwardly into seal relationship with the collars. 
         FIG. 8A  is an upper portion of the apparatus used for installing the plugging assembly into a containment housing and showing, in cross-section, the arrangement of a piston within a cylinder wherein the piston is supported in a manner that allows axial displacement but that prevents rotational displacement relative to the cylinder. 
         FIG. 8B  is a cross-sectional view of a lower portion of the apparatus of  FIG. 8A  showing the plugging assembly secured to the lower end of a piston actuated mechanism by which the assembly can be positioned into or removed from the interior of a confinement housing. 
         FIG. 9  is a cross-sectional view taken along the line  9 - 9  of  FIG. 8A  showing a cylinder and a piston rod and showing guide rods by which the piston, as seen in  FIG. 8A , and therefore the piston rod are guided in a way to prevent axial rotation. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It is to be understood that the invention that is now to be described is not limited in its application to the details of the construction and arrangement of the parts illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. The phraseology and terminology employed herein are for purposes of description and not limitation. 
     Elements illustrated in the drawings are identified by the following numbers: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 10 
                 Pipeline 
               
               
                 12 
                 First collar 
               
               
                 14 
                 Second collar 
               
               
                 16 
                 Welds 
               
               
                 18 
                 First collar inner face 
               
               
                 20 
                 Second collar inner face 
               
               
                 22 
                 External circumferential surface of 
               
               
                   
                 collar 12 
               
               
                 24 
                 External circumferential surface of 
               
               
                   
                 collar 14 
               
               
                 26 
                 Lower containment housing portion 
               
               
                 28 
                 Upper containment housing portion 
               
               
                 30 
                 Welds 
               
               
                 32 
                 End cap 
               
               
                 34 
                 Weld 
               
               
                 36 
                 Flange member 
               
               
                 38 
                 Weld 
               
               
                 40 
                 Passageway 
               
               
                 42 
                 Pipe end 
               
               
                 44 
                 Pipe end 
               
               
                 45 
                 Upper surface 
               
               
                 46 
                 Pipe sealing assembly 
               
               
                 48 
                 First wedge member 
               
               
                 50 
                 Second wedge member 
               
               
                 52 
                 Top plate 
               
               
                 54 
                 Lower support 
               
               
                 56 
                 Shaft 
               
               
                 58 
                 Threaded opening 
               
               
                 60 
                 Shaft guide 
               
               
                 62 
                 Top support 
               
               
                 64 
                 Passageway 
               
               
                 66 
                 First seal cup 
               
               
                 68 
                 Second seal cup 
               
               
                 70 
                 Upper arms 
               
               
                 72 
                 First roller 
               
               
                 74 
                 Second roller 
               
               
                 76 
                 Downward arms 
               
               
                 78 
                 Lower roller 
               
               
                 80 
                 Lower roller 
               
               
                 82 
                 Cam slot 
               
               
                 84 
                 Cam slot 
               
               
                 86 
                 Cam slot 
               
               
                 88 
                 Cam slot 
               
               
                 90 
                 Springs 
               
               
                 92 
                 Stop post 
               
               
                 94 
                 Front surface of the first seal cup 
               
               
                 96 
                 Circumferential recess 
               
               
                 98 
                 Front surface 
               
               
                 100 
                 Circumferential recess 
               
               
                 102 
                 Circumferential sealing surface 
               
               
                 104 
                 Circumferential sealing surface 
               
               
                 106 
                 Brackets 
               
               
                 108 
                 Rollers 
               
               
                 110 
                 Back surfaces of the wedge members 
               
               
                 112 
                 Forward surfaces of the wedge members 
               
               
                 114 
                 Divider guide 
               
               
                 116 
                 Runners 
               
               
                 118 
                 Guide disc 
               
               
                 120 
                 Guide ring 
               
               
                 122 
                 Recess 
               
               
                 124 
                 Valve 
               
               
                 126 
                 Lower flange 
               
               
                 128 
                 Upper flange 
               
               
                 130 
                 Passageway 
               
               
                 132 
                 Adapter casing 
               
               
                 134 
                 Lower flange 
               
               
                 136 
                 Upper flange 
               
               
                 138 
                 Adapter 
               
               
                 140 
                 Hydraulic cylinder 
               
               
                 142 
                 Piston 
               
               
                 144 
                 Closure member 
               
               
                 146 
                 Piston rod 
               
               
                 148 
                 Sealable opening 
               
               
                 150 
                 Tubular piston rod extender 
               
               
                 152 
                 Guide rod 
               
               
                 154 
                 Guide rod 
               
               
                 156 
                 First passageway in the piston 
               
               
                 158 
                 Second passageway in the piston 
               
               
                   
               
             
          
         
       
     
     Referring to the drawings and first to  FIG. 1 , the first step in practicing the systems and methods of this invention is to affix a first collar, generally indicated by the number  12  to the exterior of pipe  10 . Then a second, spaced apart, collar  14  is affixed to the pipe. Each of collars  12  and  14  are made up of two semi-circular pieces. Each of the collars is geometrically shaped as a toroidal. While not seen in the drawings, collars  12  and  14  are each formed of an upper half and a lower half that are positioned on pipe  10 . The collar halves are then welded to each other and to the pipe  10 , the welds to pipe  10  being indicated by reference numeral  16 . In  FIGS. 1 and 7 , welds  16  are shown only on exterior faces of collars  12  and  14  although interior welds can in like manner be applied. Welds  16  extend around the full interior of the toroidal collars  12  and  14  and around the complete external circumference of pipe  10 . In addition, though not seen in the drawings, the upper and lower halves of each of the collars  12  and  14  are welded to each other so that the collars  12  and  14  become unitary. The collars are spaced apart from each other at an accurately determined distance and are each in a radial plane perpendicular of the longitudinal axis of pipe  10 . 
     Collar  12  has an inner face  18  that is circumferential and uninterrupted around pipe  10  and second collar  14  has a matching circumferential inner face  20 . In the practice of this invention it is important that the inner faces  18  and  20  be parallel to each other and spaced apart an accurate pre-determined distance. For this reason, a cradle-like structure (not shown) can be used to support the upper and lower halves of each of the collars as they are being positioned on and secured to the pipe. 
     After collars  12  and  14  have been accurately positioned and welded to pipe  10 , a containment housing is affixed to the external circumferential surface  22  of collar  12  and the matching external circumferential surface  24  of collar  14 . This housing typically consists of a lower containment housing portion  26  and a mating upper containment housing portion  28 . These upper and lower containment housing portions are secured to collars  12  and  14  by welds  30  and the collar portions are welded to each other. To close the open bottom of lower containment housing portion  26  an end cap  32  is employed, the end cap being welded to the lower containment housing portion  26  by a circumferential weld  34 . In a similar manner, the open upper containment housing portion  28  receives a flange member  36 , the flange being secured to the upper containment housing portion  28  by a circumferential weld  38 . The flange member  36  has a passageway  40  therethrough. 
     With collars  12  and  14  in place, with the upper and lower containment housing portions  26  and  28  welded to them and with end cap  32  and flange member  36  welded to the housing portions, a short section of the length of pipe  10  is fully enclosed. 
     After the components that have been described are in place as illustrated in  FIGS. 1 and 7 , the next step in preparing the pipe to be closed is to remove a section of the pipe. This is accomplished by attaching a tapping machine (not shown) to the upper surface  45  of flange  36  using a procedure that is known in the industry. A tapping machine has provision for guiding a circular saw down through the passageway  40  to engage pipe  10 . The circular saw cuts out a section of pipe  10  leaving the pipe ends  42  and  44  exposed. The removed section of the pipe  10  is extracted from within the housing. The pipe is then ready to be closed off by employing a pipe sealing assembly of this invention that will now be described. 
     Looking first at  FIG. 3 , the pipe sealing assembly  46  includes first and second wedge members  48  and  50  that are held together at the top by a plate  52  and, at the bottom, by a lower support  54  that has a portion extending between the lower ends of the wedge members and as best seen in  FIGS. 4B ,  5  and  6 . 
     As seen in  FIGS. 4 ,  5 ,  6  and  7  an elongated shaft  56  extends between wedge members  48  and  50 . Shaft  56  is threaded at its lower end and engages a threaded opening  58  in the top of lower support  54 . A shaft guide  60  has a central opening therethrough slidably receiving shaft  56 , the shaft guide being secured by bolts to an upper surface of top plate  52 . Slidably positioned between wedge members  48  and  50  is a top support  62  that, as seen in  FIG. 7 , has a passageway  64  therethrough that slidably receives shaft  56 . 
     Positioned with respect to wedge members  48  and  50  is a first seal cup  66  and an opposed second seal cup  68 . As seen in  FIG. 4B , seal cup  66  has upwardly extending arms  70  that support a first roller  72 . Seal cup  68  has upwardly extending arms  70  that supports a second roller  74 . 
     First seal cup  66  has downwardly extending arms  76  that support a lower roller  78  and second seal cup  68  has similar downwardly extending arms that support a lower roller  80 . 
     Lower support  54  has a pair of cam slots  82  and  84  that receives lower rollers  78  and  80  respectfully. In like manner, top support  62  has a pair of cam slots  86  and  88  that receives upper rollers  72  and  74  respectfully. It can be seen that when top support  62  is moved in a direction towards lower support  54  that rollers  72 ,  74 ,  78  and  80  acting in cam slots  82 ,  84 ,  86  and  88  serves to deflect seal cups  66  and  68  away from each other and contrarily when top support  62  moves away from lower support  54  the action between the rollers and cam slots retract the seal cup towards each other. Seal cups  66  and  68  are resiliently restrained towards each other by springs  90  as illustrated in  FIG. 4B . Springs  90  are not shown in  FIG. 3 . 
     Received on shaft  56  and compressibly positioned between lower support  54  and top support  62  is a compression spring  90 . The downward translation of shaft guide  60  and thereby top plate  52  and with it, first and second wedge members  48  and  50 , forces the top support  62  towards lower support  54 , compressing spring  90  and moving the top rollers  72  and  74  within the cams formed in top support  62  and the bottom rollers  78  and  80  within the cams formed in lower support  54 . This cam action causes first and second seal cups  66  to displace outwardly with respect to each other. The downward movement of lower support  54  is limited by a stop post  92  affixed to the interior of end cap  32  as shown in  FIGS. 7 and 8B . 
     First seal cup  66  has a front surface  94  having therein a circumferential recess  96 . In like manner, second seal cup  68  has a front surface  98  with a circumferential recess  100 . The function of recesses  96  and  100  is to receive the outer pipe ends  42  and  44  as the seal cups  66  and  68  are expanded outwardly. This allows a circumferential sealing surface  102  on cup  66  and a corresponding circumferential sealing surface  104  on the front face of seal cup  68  to engage first collar inner face  18  and second collar inner face  20  respectfully to form metal-to-metal seals. The circumferential metal-to-metal seal of first seal cup  66  against first collar inner face  18  closes the end  42  of pipe  10  and correspondingly, the circumferential metal-to-metal seal of second seal cup  68  against second collar inner face  20  closes the end  44  of pipe  10 . Thus when the seals  66  and  68  are expanded away from each other, they close both exposed ends of pipe  10  in a metal-to-metal sealing arrangement effectively blocking fluid flow through the pipe. This achieves a double block and bleed plugging arrangement. With both seal cups  66  and  68  in simultaneous sealed conditions as shown in  FIG. 7  the interior of the containment housing can be tapped to verify that both seal cups are in leak-proof closure. 
     Affixed to opposite sides of top support  62  are opposed brackets  106 , each having an axle with a pair of rollers  108 . Rollers  108  roll against the back surfaces  110  (see  FIG. 2 ) of each of wedge members  48  and  50 . Brackets  106  and rollers  108  are seen in  FIGS. 2 ,  3  and  4 B. Only one bracket and one roller are seen in  FIG. 3 . 
     Affixed to the forward surface  112  of each of the wedge members  48  and  50  is a divider guide  114 . Affixed to each of the seal cups  66  and  68  are a pair of runners  116 , thereby being four runners  116 . Each pair of runners  116  is engaged by a divider guide  114  as the wedge members  48  and  50  are moved downwardly during the process of installing pipe sealing assembly  46  within a housing between exposed pipe ends  42  and  44 . Thus, the interaction of the divider guides  114  and runners  116  initiate displacement of seal cups  66  and  68  away from each other. The cam action provided by the cam slots formed in lower support  54  and top support  62  further assist in guiding the seal cups between their tool open and tool closed positions. 
     Lower support  54  that has cam slots  82  and  84  therein, has, shown integrally formed with it, a horizontal guide disc  118 . Secured to the bottom of the guide disc is a guide ring  120 . The guide disc/guide ring combination serves to guide the lower end of the assembly  46  as it is positioned within the housing and between the ends  42  and  44  of pipe  10 . Further, there is recess  122  formed in the bottom of guide disc  118  and guide ring  120 . Recess  122  receives stop post  92  when the assembly is forced downward into the housing. Stop post  92  defines the lower limit of travel of assembly  46  so that continued downward movement of guide  60  and with it wedge members  48  and  50  force upper rollers  72  and  74  to move within cam slots  86  and  88  and lower rollers  78  and  80  to move within cam slots  82  and  84  to guide seal cups  66  and  68  to move radially apart and towards their sealed positions as shown in  FIG. 7 . 
     The translation of seal cups  66  and  68  from their open positions as shown in  FIG. 5  to their closed positions as shown in  FIGS. 6 and 7  is achieved by four separate but cooperative actions. First is the action of divider guides  114  against runners  116 . Second, the bottom ends of wedge members  48  and  50  engage the top edges of the rearward surfaces of the seal cups to urge them apart. Third, the action of cam surfaces formed in lower support  54  and top support  62  guide the displacement of the seal cups away from each other. Fourth, the wedge surfaces of wedge member  48  and  50  slide against the rearward surfaces of seal cups  66  and  68  forcing the seal cup into metal-to-metal sealing relationship with the toroidal collars  12  and  14  as seen in  FIG. 7 . The first, second and third actions listed herein are primarily guiding actions. The actual sealing forces of the seal cups against the toroidal collars are achieved by the action of the wedge members  48  and  50  against the rearward surfaces of the sealing cups. 
     Referring to  FIGS. 8A and 8B , the systems and methods that are employed in the insertion of pipe sealing assembly  46  into and removing it out of the containment housing surrounding pipe  10  is illustrated. As shown in  FIG. 8B , there is affixed to the upper surface  45  of flange member  36  a valve  124  that has a lower flange  126  and an upper flange  128 . Lower flange  126  is secured to the upper surface  45  of flange member  36 . Valve  124  functions to open and close passageway  130  therethrough to enable different operating systems to be inserted into or removed from the interior of the containment housing surrounding pipe  10 . The internal working portions of valve  124  are not shown but the use of valves in systems for tapping pipelines under pressure are well known. 
     An adaptor casing  132  has a lower flange  134  that is secured to plugging tool upper flange  128 . Further, adaptor casing  132  has an upper flange  136  seen in  FIG. 8A . Secured to upper flange  136  is a hydraulic cylinder adaptor  138  and secured to a hydraulic cylinder  140  that receives therein a slidable piston  142 . The upper end of hydraulic cylinder  140  receives closure member  144 . 
     Affixed to piston  142  is a piston rod  146  that extends to a sealable opening  148  in adaptor  138 . The lower end of piston rod  146  is attached to the upper end of a tubular piston rod extender  150 , the lower end of which is secured to the pipe sealing assembly top plate  52 . In this manner, insertion or removal of pipe sealing assembly  46  is controlled by the actuation of piston  142  and thereby piston rod  146 . 
     It is important that pipe sealing assembly  46  be accurately rotationally positioned with respect to the pipe ends  42  and  44  when it is inserted within the containment housing so that the seal cups  66  and  68  will properly align to form a sealing relationship with collars  12  and  14 . Normally a piston and piston rod operating within a cylinder have no means for maintaining rotational relationship with the cylinder. To alleviate this problem and to provide for accurate alignment of the pipe sealing assembly when it is inserted into a containment housing to seal the opposed ends of a pipe, the cylinder  140  and piston  142  of this invention operate in a system that ensure their rotational relationship. For this purpose there is provided within the interior of hydraulic cylinder  140  first and second guide rods  152  and  154 . The upper ends of guide rods  152  and  154  are secured to closure member  144  while the lower ends are received within recesses formed in adapter  138 . Piston  142  has passageways  156  and  158  therein that sealably receive guide rods  152  and  154 . In this way, piston  142  can be displaced by fluid pressure to move axially within cylinder  140  while guide rods  152  and  154  prevent the piston from rotating relative to the cylinder.  FIG. 9  shows the relationship between guide rods  152  and  154  and piston  142 . 
     By reference to  FIGS. 8A and 8B  the method of operation of the system of this invention to provide high temperature closure of pipe  10  can be seen. By application of hydraulic pressure to cylinder  140 , piston  142  can be forced downwardly, moving piston rod  146  and thereby tubular piston rod extender  150  downwardly so that the attached pipe sealing assembly  46  is moved into the interior of the assembly surrounding pipe  10 . When the assembly reaches its lowest level as defined by stop post  92  further downward force on the assembly initiates the movement of seal cups  66  and  68  away from each other and towards the plugging tool closed condition as shown in  FIGS. 6 and 7 . This action is achieved by four separate but cooperative actions as previously mentioned. First, divider guides  114  act against runners  116  to spread the cups apart. Then, the bottom ends of wedge members  48  and  50  engage the top edges of the rearward surfaces of the seal cups to urge them apart. In addition, the action of cam surfaces formed in lower support  54  and top support  62  guide the displacement of the seal cups away from each other. Finally the wedge surfaces of wedge member  48  and  50  slide against the rearward surfaces of seal cups  66  and  68  forcing them into metal-to-metal sealing relationship with toroidal collars  12  and  14  as seen in  FIG. 7 . 
     The pipe sealing assembly  46  is left in the double block and bleed position as shown in  FIG. 7  as long as it is necessary to block fluid flow through pipe  10 . When the need for blockage of flow through the pipe has ended the pipe sealing assembly  46  can be withdrawn and valve  124  closed. After removing the pipe sealing member  46 , a completion plug (not shown) can be inserted through the valve and into passageway  40  within flange member  36 . By mechanisms controlled through valve  124  the completion plug can be actuated to permanently close opening  40  through flange  36 . Thereafter pressure is contained within the containment assembly that surrounds pipe  10  and valve  124  can be removed. A flange plate can be then secured to flange member  36  top surface  45  and thereafter flow through pipe  10  can continue indefinitely. 
     While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.