Abstract:
An isolation tool for closing a pipeline including a packer module having a cylindrical body member and at least one ring of elastomeric material slidably received on the cylindrical body, the ring being radially outwardly compressible in response to axial force, and including a grip module having a central body with a plurality of at least three rails radially extending in spaced apart relationship from the central body, each rail having an edge inclined at an angle to a longitudinal axis, a grip shoe contoured to bite into the pipe interior wall surface slidably supported on each inclined edge and a hydraulic cylinder/piston member secured to translate the grip shoes on the rail edges, the grip module being linked to and serving to selectable anchor the packer module in the pipeline.

Description:
REFERENCE TO PENDING APPLICATIONS  
       [0001]     This application is not based upon any pending domestic or international patent applications.  
       REFERENCE TO MICROFICHE APPENDIX  
       [0002]     This application is not referenced in any microfiche appendix.  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     This invention relates to an isolation tool for selectably closing the interior of a pipeline and in particular to a pipeline isolation tool that is self-energized by pipeline differential pressure across the plugging apparatus in which the radial sealing and locking pressures exerted against the pipeline are utilized to achieve isolation of portions of the length of the pipeline.  
         [0005]     2. Description of the Prior Art  
         [0006]     The invention herein is a device for use in pipelines to selectably close the interior of pipelines against fluid flow, either liquids or gases. The isolation tool of this invention may be used, as an example, in a system for pipeline repairs in which a portion of the length of the pipeline is closed against fluid pressure that permits that portion to be repaired. Other applications of the invention includes the use of the isolation tool to close fluid flow through the pipeline such as to control leakage of the fluid from the pipeline due to an accident to the pipeline or due to leakage that can be developed as a consequence of normal degradation of the pipeline due to corrosion. Irrespective of the cause that results in the necessity to close off fluid flow through a pipeline, the isolation tool of this invention may be utilized in the system that provides the possibility of introducing the isolation tool into the pipeline and remotely actuating the device as it travels through the pipeline to stop at a pre-determined location of the pipeline and to close against the internal wall of the pipeline to thereby prevent further fluid flow past the isolation tool. By using a pair of isolation tools that are stopped at different locations in the pipeline, sections of the length of the pipeline may be isolated for repair. The isolation tool of this invention typically is in the form of a train that includes a control module, a grip module and a packer module. However, the particular utility of the modules can be combined in such a way so that the entire isolation tool may consist of separate modules or as few as one module wherein different portions of the module have different functions.  
         [0007]     For background information relating to isolation tools and for plugging modules, reference may be had to the following previously issued patents and publications:  
                                       Patent               Number   Inventor   Title                   3,011,555   Clark Jr.   Well Packers       3,107,696   Ver Nooy   Plugging Pig       3,381,714   Johnson   Pipeline Blocking Device and               Process For Its Use       3,483,895   Barto   Pipeline Shutoff Device       3,886,977   Dorgebray   Plug For Pipes Under Pressure       4,332,277   Adkins et al.   Pipeline Pigging Plug       4,390,043   Ward   Internal Pipeline Plug For Deep               Subsea Operations       4,422,477   Wittman et al.   Pressure Energized Pipeline Plug       4,854,384   Campbell   Pipeline Packer       4,991,651   Campbell   Pipeline Packer For Plugging A Pipeline               At A Desired Location       5,209,266   Hiemsoth   High Pressure Inflatable Plug Device       5,293,905   Friedrich   Pipeline Pig       5,826,652   Tapp   Hydraulic Setting Tool       5,924,454   Dyck et al.   Isolation Tool       6,129,118   Friedrich et al.   Downstream Plug       6,467,336   Gotowik   Apparatus For Testing Or Isolating               A Segment Of Pipe       6,601,437   Gotowik   Apparatus For Testing or Isolating               A Segment Of Pipe       6,712,153   Turley et al.   Resin Impregnated Continuous Fiber               Plug With Non-Metallic Element               System       6,752,175   Willschuetz et   Auxiliary Device For Repairing A           al.   Pipeline       PCT NO2003/   Syse   Arrangement At A Hydraulic Cylinder       000203       On A Manoeuvrable Plug For Plugging               of Pipes       PCT NO2003/   Syse   Device For Fastening A Manoeuvrable       000204       Plug For Plugging Of Pipes                  
 
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The isolation tool of this invention basically consists of a command and control module, a grip module and a packer module.  
         [0009]     Traditionally an isolation tool packer module is activated by a wedging effect from two components each with a geometric shape resembling a cone. The cone is usually defined by a cone angle of about 17.5°. In the case of isolation tools, the internal cone shaped device is often called the “bowl”.  
         [0010]     Grips or slips are segments of a ring which have internal conical surfaces and move axially, with respect to the bowl, in a manner that allows them to expand their collective diameter outward by sliding on the exterior cone of the bowl. The grips have an interior conical face that is in contact with the exterior conical face of the bowl and have an exterior surface that is covered with thread-like teeth. These teeth are the features that come in contact with the pipe wall internal diameter as the grip moves outward along the conical surface of the bowl. The purpose of the teeth is to bite into the pipe and form a non-slip contact as the bowl&#39;s movement wedges them tighter against the pipe internal diameter. The real locking action occurs when pipeline pressure is exerted against the large radial face and attempts to push or wedge the conical surface of each bowl under the conical internal diameter of each grip and wedge the grips against the pipeline internal diameter and the bowl.  
         [0011]     This system is an effective wedging technique for getting the grips out against the pipe wall. However, it does not provide for a clean transfer of axial force generated by pipeline pressure to achieve a radial force that is sufficient to ensure the grips are adequately held against the pipe wall. The main defect in this well known wedging system is that it relies on conical surfaces. If two conical surfaces of a bowl and grip segments are equal to each other in exactly one axial location, at any other axial location the conical internal diameter will not match the outer diameter of the mating component. The two components will rub against each other in a way that will push low pressure lubrications out of the way. This results in coefficients of friction characterized by bare metal against bare metal.  
         [0012]     The grips in the new design of this invention are activated individually via individual hydraulic rams. This feature allows the tool to grip a pipe wall evenly when the pipe internal diameter is not perfectly circular. This feature is superior in axial pressure load distribution than spring compensated systems on current plug technology. The grips are moved towards the pipe wall with a double ended piston. This maintains equal swept volumes during manipulation of the grip positions. The grips of this invention ride along rails from their retracted positions to their extended positions. The use of rails for positioning the grips ensures an equal transfer of axial force from the pipeline pressure to radial force that ensures the grips are adequately held against the pipe wall regardless of pipe wall thickness. Further, the use of rails ensure that there are no design and performance compromises for a wide range of pipe wall thicknesses and tolerances.  
         [0013]     Further the support frame in this invention is utilized as the hydraulic distribution manifold for the individual hydraulic cylinders that activate the grips against the pipe wall.  
         [0014]     Another unique feature of the new plug design is that the packer module has the ability to adjust the activation factor and thereby adjust to high and low pressure applications without compromising the total induced radial hoop stress that is applied to the pipe wall. The radial hoop stress generated by the plug is a product of the axial force from the pipeline pressure (which is the product of the cross-sectional area of the pipe internal diameter and the pipeline pressure) converted to a rubber pressure in the packer elements. The packers are able to seal because they are situated in a manner that produces a greater pressure against the pipe wall than is generated by the pipeline pressure. This pressure amplification is the mechanism of self-activation and is the product of surface area advantage the pipeline pressure has over the surface area of the packers that is resisting that pressure. If two pistons of different diameters are connected mechanically end to end in correspondingly sized cylinders the same scenario would exist as the relationship between pipeline pressure and packer rubber pressure.  
         [0015]     In traditional plugs the pressure head is made of solid construction and presents a unified structure to the pipeline pressure. The entire force from the pipeline pressure is focused through a reduced cross-sectional area of the packer. If a pressure head flange is acted upon by the pipeline pressure, the pressure head flange reacts to the force induced by the pipeline pressure by compressing the packers. Because the cross-sectional area of the packers is smaller than the cross-sectional area of the pipeline internal diameter the pressure built up in the packers to resist the force from the pressure head flange will be larger than the pipeline pressure. The ratio of cross-sectional area of the pipeline internal diameter and the cross-sectional area of the packers is referred to as the “activation factor”.  
         [0016]     In the isolation tool of this invention, the pressure head flange cross-sectional area is broken down into two areas and thus divides the load path from the force induced by pipeline pressure into two major components. One load path is through the packers and its source is the reduced cross-sectional area of the pressure head flange that is allowed to compress the packers without moving the hydraulic cylinder assembly; and a second load path which is the load induced by pipeline pressure on the cross-sectional area of the hydraulic cylinder assembly through the piston rod.  
         [0017]     This breakup of presented area to the pipeline pressure that creates the force to be routed through the packer elements results in a lower activation factor for the same packer geometry. A unique feature of this invention is that the cylinder can be configured such that its surface induced force will float the cylinder&#39;s position towards the pressure head flange and find a load path through the packer as well and not the piston rod. This has the effect of providing a tool with two distinct activation factors. The advantage of this feature is that it gives the tool the ability to have high pressure and low pressure operating ranges. Further it allows the tool to be configured in the pipe and on the fly to operate in both ranges without having to be removed from the pipeline and reconfigured.  
         [0018]     Every tool undergoes two modes of the operation called “setting”. The first mode is the “hydraulic set” whereby the internal hydraulic cylinder or other comparable means of constricting the length of the tool causes the packers to be compressed axially and expand the packers outward until they contact the pipe wall internal diameter. This mode initiates the first sealing mechanism of the isolation tool. The second mode uses the force induced from pipeline differential pressure across the plug to further compress the tool axially and drive the packers harder against the pipe wall internal diameter. This mode of operation is pressure set. The force from the pressure set can be and is typically much larger than the hydraulic set. It is desirable to employ the differential pressure to keep the tool set even if it is accidentally instructed to unset via the hydraulics. This constitutes an additional level of safety for the operator that the tool cannot be unset in a situation that may be dangerous to personnel and equipment. If during an isolation project with the tradition style tools the operator&#39;s pipeline pressure drops below that required for a safe level the condition could exist that an untrained person could inadvertently command the plug to unset. With the tool of this invention the activation factor can be changed to decrease the required pressure of that safe level so that safe operation can continue.  
         [0019]     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  
       [0020]      FIG. 1  is an elevational view of a modular tool train that includes concepts of the invention. The isolation tool train is made up of flexibly linked modules, including a control module, a grip module and a packer module. The invention herein is concerned essentially with the grip module and the packer module.  
         [0021]      FIG. 2  is a cross-sectional view of the control module taken along the line  2 - 2  of  FIG. 1 . This figure shows representative means whereby the control module is centrally supported within a pipeline and is representative of the system for controlling the application of hydraulic pressures to the gripper and packer modules.  
         [0022]      FIG. 3  is a view taken along the line  3 - 3  of  FIG. 1  showing the construction of the gripper module.  FIG. 3  is a partial cross-sectional view along the upper half of the gripper module with the lower half shown in elevational view.  
         [0023]      FIG. 4  is a cross-sectional view taken along the line  4 - 4  of  FIG. 1  showing details of a first, although not a preferred embodiment of the packer module.  
         [0024]      FIG. 5  is a cross-sectional view of the gripper module as taken along the line  5 - 5  of  FIG. 3 .  
         [0025]      FIG. 6  is a cross-sectional view of an alternate embodiment of the grip module.  
         [0026]      FIG. 7  is a cross-sectional view of a preferred embodiment of a packer module that is similar in many respects to  FIG. 4 . In this figure, a system is shown providing a two stage type of packer module.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     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.  
         [0028]     Elements illustrated in the drawings are identified by the following numbers:  
                                       10   Isolation tool       12   Control module       14   Grip module       16   Packer module       18   Ball joint       20   Ball joint       24   Tubular housing       26 A-D   Elastomeric discs       28   Electronic instrumentation       30   Hydraulic control compartment       32   Pipeline       34   Interior wall       36   Frame member       38   Rails       40   Longitudinal axis       42   Rail edge       44   Grip saddle       46   Inclined edge       48   Grip shoe       50   Grip shoe surface       52   Actuator body       54   Piston       56 A-B   Opposed cylinder       58   Intermediate portion       60   Wheels       62   Leaf springs       64   Legs       66   Small wheels       68   Forward female half of ball joint 18       70   Female half of ball joint 20       72   Coiled springs       73 A-B   Packer module       74   Tubular body       76   External cylindrical surface       78   Forward flange       80   Internal cylindrical surface       82   Piston rod       84   Rearward flange       86   Backup flange       88   First elastomeric packer       90   Second elastomeric packer       92   Internal cylindrical surface       94   Contacting surface       96   Sidewall surfaces       98   Backup ring       100    Internal opening       102    Backup ring sidewalls       104    Outer circumferential surface       106    Cylinder wall       108    Piston       112    Cylinder head       114    Opening       116    Cylindrical area       118    Rearward wheels       120    Springs       122    Forward wheels       124    Ball joint       126    Cylindrical sidewall       128    Forward flange       130    Forward cylinder head       132    Central opening       134    Piston rod extension       138    Coiled springs                  
 
         [0029]     The invention herein provides a system for closing fluid flow through the interior of a pipeline. More specifically, the invention herein relates to improvements in isolation tools in the form of pipeline pig elements that can be transported through a pipeline by the force of fluid flow and remotely actuated so as to stop travel through the pipeline and to form a seal that terminates fluid flow. The type of tools of this invention are known in the industry as “isolation tools” since they can be used to isolate portions of a pipeline. One application of the isolation tools of this invention is to terminate flow from a leaking pipeline. Isolation tools can be used in pairs, spaced apart by a few feet or by many feet, to permit a portion of the pipeline to be repaired or replaced.  
         [0030]     The invention herein is not concerned with the specific instrumentation that is utilized to react to a remote signal to cause an isolation tool to set itself in a selected position within a pipeline but instead the invention herein relates to improved mechanisms for removably anchoring the isolation tool at a selected spot within the interior of a pipeline and for closing fluid flow through the pipeline. Stated another way, the invention herein is not concerned primarily or essentially with the electronics by which a pipeline pig is remotely controlled by means from exterior of the pipeline but is concerned with mechanisms that are acted upon by control systems that function in response to remote signals. Stating it even more specifically, the invention herein is in an improved internal pipeline gripper and an improved internal packer and in the combination of an improved gripper and improved packer.  
         [0031]     In  FIG. 1 , an isolation tool is indicated generally by the numeral  10  and is in the form of a train of components flexibly coupled together and configured to travel within a pipeline as a unit and for isolating a portion of the pipeline by closing off fluid flow through it. The isolation tool  10  includes, as major components thereof, a control module  12 , a grip module  14  and a packer module  16 . The rearward end of grip module  14  is secured to the forward end of control module  12  by means of a ball joint  18 . In like manner, the rearward end of packer module  16  is secured to the forward end of grip module  14  by a ball joint  20 . Ball joints  18  and  20  are representative of mechanical means of flexibly connecting the basic elements of the isolation tool train to each other so that the train can move around bends in a pipeline without putting stress on the individual connected components.  
         [0032]      FIG. 2  is a cross-sectional view showing basic components employed in control module  12 . This module includes a housing  24  which is typically tubular as indicated with closed ends and in which the forward closed end includes a portion of ball joint  18 . Positioned on the exterior of tubular housing  24  are radially extending elastomeric discs  26 A,  26 B,  26 C and  26 D that have exterior diameters that are less than that of the pipeline (not shown) in which the isolation tool train is to be employed. Discs  26 A,  26 B,  26 C and  26 D function essentially to support tubular housing  24  centrally within the interior of a pipeline. Elastomeric discs  26  are not intended to necessarily form a tight seal but are primarily designed and constructed as a way of centrally supporting tubular housing  24  within the pipeline in a way that the pipeline will not be damaged.  
         [0033]     Within tubular housing  24  of control module  12  there is electronic instrumentation, diagrammatically illustrated and identified by the numeral  28 . Instrumentation  28  functions in accordance to known techniques familiar to those in the pipeline pigging and isolation tool industry by which signals can be received from the exterior of a pipeline. A hydraulic control compartment generally indicated by the numeral  30  includes an onboard power source, usually battery powered, hydraulic control valves, actuators and other components as necessary to control the application of hydraulic fluid pressure to the gripper module  14  and the packer module  26 . Hydraulic control compartment  30  includes a battery powered hydraulic pump or pumps to supply hydraulic energy as may be needed in the actuation of the grip module  14  and packer module  26 .  
         [0034]     The invention herein is specifically concerned with the systems, methods and construction techniques employed in controlling grip module  14  and packer module  16 . The grip module of this invention is illustrated in  FIGS. 3, 5  and  6 .  FIG. 6  shows a pipeline  32  in which grip module  14  is positioned. Referring now to  FIGS. 3, 5  and  6 , the grip module  14  includes an elongated central body frame member  36  that is shown to be of hexagonal cross-section in  FIG. 5 . Radially extending from frame member  36  are six radially extending rails  38  each being elongated with flat sides and opposed ends. Rails  38  each extend in a plane of the longitudinal axis  40  of frame member  36 . Each of rails  38  is in the form of a flat metal plate with a rail edge  42  that is inclined relative to longitudinal axis  40 . Slidably received on each rail edge  42  is a grip saddle  44 . Each saddle  44  has an inclined edge  46  that slides on a rail edge  42 . Affixed to each of the grip saddle  44  is a grip shoe  48  that has an outer gripping surface  50  configured to engage the interior wall  34  of pipeline  32 . Each of the grip shoes  48  is preferably removable and replaceable and has on the grip shoe surface serrated edges as seen in  FIGS. 3 and 6  to non-slidably engage pipeline interior wall  34 . Further, the angular relationship between rail edge  42  and grip saddle inclined edge  46  is such that the grip shoe surface  50  engage the pipeline interior surface  34  in a parallel relationship.  
         [0035]     Secured to a side wall of each of rails  38  is an actuator body  52 , best seen in  FIG. 5 , each of which slidably supports a double ended piston  54  that is best seen in  FIG. 3 . As seen in  FIG. 3 , opposed cylinders  56 A and  56 B are formed in each of the actuator body  52  and slidably receives opposed ends of a piston  54 . An intermediate portion  58  of each piston  54  is secured to a grip saddle  44  so that the displacement of each grip saddle  44  and in turn each grip shoe  48  that slides on an edge  42  of each rail  38  is controlled by a piston  54 . Each cylinder  56 A in each of the actuator bodies  52  is an actuating cylinder. When pressure is applied to the actuating cylinders, pistons  54  function to move the grip saddles  44  and thereby grip shoes  48  in the direction to engage the pipeline interior wall  34 . Conversely, when hydraulic pressure is applied to the opposite end, that is, to piston cylinders  56 B, grip shoes  58  are moved away from engagement with the pipeline interior wall. In a preferred method of operating the grip module  14 , hydraulic pressure is not applied at the same pressure level simultaneously to the actuating cylinders  56 A but is preferably supplied in an alternate or sequence method to move the grip shoes individually or at least in pairs rather than all at the same time, to sequentially engage the interior wall of the pipe. This method of actuation is important in order to achieve maximum effective gripping of the interior wall of the pipeline since very few pipelines have interior surfaces that are perfectly cylindrical. Putting it another way, pipelines universally have a slight degree of out of roundness or ovality or differentiations in internal diameters so in actuating hydraulic pistons  54  more effective results can be obtained if pressure applied to cylinders  56 A is not simultaneously equal.  
         [0036]     It is important that the grip shoes  48  are not in engagement with the interior surface of pipeline, such as surface  34  as seen in  FIG. 6 , as the isolation tool moves through the pipeline prior to reaching a point where closure of the pipeline is required. For this reason the grip module  14 , as seen best in  FIGS. 3 and 6 , include wheels  60  that roll along the interior surface of the pipeline. Each wheel  60  is rotatably supported at the outer end of a leaf spring  62  as seen in  FIG. 3 . Each leaf spring  62  is attached at its rearward end to a rail  38 . Thus in the embodiment illustrated there are six rails and correspondingly six leaf springs  62  and six wheels  60 . Leaf springs  62  force wheels  60  into resilient engagement with the pipeline interior wall and centers the grip module within the pipe as the isolation tool moves through the pipe, the leaf springs serving to flex in response to changes in ovality of the pipeline. To further ensure that grip shoes  48  do not drag on the interior of the pipe, especially if grip module  14  passes irregularities in the pipe wall surface, each rail  38  is provided with an integral radially extending leg  64 , each of which has at its outer end a rotatable small wheel  66 . These elements are best seen in  FIG. 6 . When grip saddles  44  are each in their retracted position, wheels  66  extend radially beyond grip shoes  48  and hold them out of contact with the pipeline. Wheels  66  are relatively small and are not intended to normally contact the interior surface of the pipe as the grip module moves through the pipe in contrast with the wheels  60  at the outer end of the leaf springs  62 . In other words, the leaf springs  62  and wheels  60  are designed for continuous service as the tool moves through a pipeline however the legs  64  and small wheels  66  are designed to serve as security for protection of the grip shoes in unusual situations.  
         [0037]     Leaf springs  62  are illustrated and described as one means of maintaining grip module  14  centered within a pipeline but the invention herein is not limited to the use of leaf springs for this purpose. Other systems exist, well known in the industry, for centering a tool, such as grip-module  14  within a pipeline and such previously known systems may, in some applications be preferable to the use of leaf springs.  
         [0038]     As seen in  FIG. 1  grip module  14  is connected at its rearward end to ball joint  18  that is positioned between the grip module and control module  12 .  FIGS. 3 and 6  each show a female half  68  of ball joint  18  and, at the forward end thereof, the female half  70  of ball joint  20 . As a part of ball joint  18  is seen in  FIGS. 3 and 6  a coil spring  72  is employed for the purposes of preventing relative rotation between the components making up the isolation tool train.  
         [0039]     In the embodiment of gripper module  14  shown in  FIGS. 3 and 5  separate opposed cylinders  56 A and  56 B are illustrated to separately actuate each grip saddle  44 . This arrangement is optional. In the design of a grip module for a smaller diameter pipeline, instead of separate actuating cylinders a single cylinder can be employed to simultaneously actuate all the grip saddles.  
         [0040]     A first embodiment of the packer module, indicated by the numeral  16  in  FIG. 1 , is illustrated in the cross-sectional view of  FIG. 4  and generally identified by  73 A while a second and preferred embodiment of the packer module is shown in the cross-sectional view of  FIG. 7  and identified by  73 B. Reference will first be had to the embodiment  73 A of  FIG. 4 .  
         [0041]     In the embodiment of  FIG. 4  the packer module  73 A includes a tubular body  74  having an external cylindrical surface  76  and, at one end thereof, a radially extending fixed forward flange  78 . The tubular body  74  includes a portion defining a cylinder wall  106  with an internal cylinder surface  80 . Centrally received within cylindrical wall  106  is a double ended piston rod  82 . Secured to a rearward end of piston rod  82  is a radially extending rearward flange  84 . In the illustrated embodiment, rearward flange  84  has a central opening that receives a reduced external diameter portion of piston rod  82 . Piston rod  82  has a threaded opening in the rearward end thereof that receives a threaded end of a ball joint. Rearward flange  84  is captured between the rearward end of piston rod  82  and the ball joint. Secured to a forward surface of rearward flange  84  is a moveable backup flange  86  that is slidably received on external cylindrical surface  76 . Thus backup flange  86  is opposed to fixed forward flange  78 .  
         [0042]     Received on external cylindrical surface  76  is a first elastomeric packer  88  and an identical second elastomeric packer  90 . Each of the elastomeric packers  88  and  90  is, in radial cross-section, frusto-conical, that is, each has sloped wall surfaces. Each of the elastomeric packers have an internal cylindrical surface  92  that is slidably positioned on external cylindrical surface  76 . Each of the elastomeric packers has an outer pipe wall contacting surface  94  and connecting the inner and outer surfaces are opposed side wall surfaces  96 . The width of the outer contacting surfaces  94  is greater than that of the internal cylindrical surface  92  of each of the elastomeric packers  88  and  90 .  
         [0043]     Slidably received on the tubular body external cylindrical surface  76  is a backup ring  98  that has a radially extending internal opening  100  therethrough that communicates with external cylindrical surface  76 . Backup ring  98  has opposed sidewalls  102  that taper towards the outer circumferential surface  104 . Thus the side walls surfaces  102  of backup ring  98  mirror the side wall surfaces  96  of elastomeric packers  88  and  90 . Radial internal opening  100  in backup ring  98  can be used to measure pressure between packers  88  and  90 .  
         [0044]     Formed as a part of tubular body  74  is a cylinder wall  106  that provides internal cylindrical surface  80 . Extending radially from piston rod  82  is a piston  108  having an outer cylindrical surface that sealably engages internal cylindrical surface  80 .  
         [0045]     Affixed at the rearward end of cylinder wall  106  is a cylinder head  112  having an opening  114  therein that receives piston rod  82 . Thus there is created within cylindrical wall  106  a cylindrical area  116  that, when pressure is applied thereto tends to move piston  108  forwardly towards the right, and consequently rearward flange  84  and backup flange  86  towards the right, to compress elastomeric packers  88  and  90  against forward flange  78 . This action causes the outward displacement of the elastomeric packers so that the outer circumferential surfaces  94  thereof engage the interior wall of a pipeline to thereby close fluid flow through the pipeline. That is, when fluid pressure is applied to cylindrical area  116 , as dictated by control module  12 , elastomeric packers  88  and  90  are squeezed and radially outwardly expanded to close fluid flow through the pipeline.  
         [0046]     In the embodiment of packer module  73 A as shown in  FIG. 4 , forward flange  78  has a sloping cylindrical wall and, in like manner, backup flange  86  has a sloping sidewall  96 . Received between these sloping surfaces are first and second elastomeric packers  88  and  90  each with sloping sidewall surfaces  96 . The use of sloping surfaces for these components is optional. These surfaces can be radial and the elastomeric packers will then have radial surfaces, that is, the packers will each be in the form of a flat toroid. Whether the elastomeric packers are flat or have frusto-conical sidewalls as shown, the plugging apparatus functions by squeezing the packers to cause radial expansion to close against the internal cylindrical surface of a pipeline.  
         [0047]     To support the plugging apparatus of  FIG. 4 , a number of rearward wheels  118  are radially extended at the outer end of springs  120 . While only a single wheel and spring are seen in  FIG. 4 , it is understood that a minimum of six springs and wheels are radially spaced around the plugging apparatus. In the same way, forward wheels  122  support the forward end of the plugging apparatus away from a pipeline internal wall as the isolation tool train moves through a pipeline.  
         [0048]      FIG. 4  shows a ball joint  124  which is a part of the ball joint unit  20  as is identified in  FIG. 1  by which the plugging apparatus of  FIG. 4  is secured as a part of the isolation tool train.  
         [0049]      FIG. 7  is an alternate embodiment of the invention of  FIG. 4  wherein the same essential components are assigned the same numbers. A basic difference in these embodiments is that the element  74  identified as a tubular body in  FIG. 4  is in  FIG. 7  formed of three separate components. These components are a separate cylindrical side wall  126 , a separate forward flange  128  that serves the same function as flange  78  in  FIG. 4 , and a separate forward cylinder head  130  that closes the cylindrical area formed by cylindrical sidewall  126 . Forward cylinder head  130  has a central opening  132  that slidably and sealably receives a forward extension  134  of piston rod  82 .  
         [0050]     An important difference between the embodiment of  FIG. 7  compared to that of  FIG. 4  is that the forward flange  128  is slidably and sealably secured on the external surface of cylindrical side wall  126 . In the embodiment of  FIG. 7  fluid pressure can be employed to force flanges  86  and  128  towards each other, squeezing elastomeric packers  88  and  90  to force their outer surfaces into contact with a pipeline interior wall. In addition, fluid pressure within cylindrical sidewall  126  forces piston  108  and thereby piston rod  134  to the right, drawing with it rearward flange  84  and backup flange  86  to further compress elastomeric packers  88  and  90 . Thus in the embodiment of  FIG. 7  essentially two cylinders provide compressive force to achieve expansion of the elastomeric packers for more effective closure of a pipeline interior.  
         [0051]     Each of elastomeric packers  88  and  90  have a pair of circumferentially positioned coiled springs  138  that tend to keep the packers circumferentially collapsed except when they are being squeezed to close fluid flow through a pipeline.  
         [0052]     Fluid flow passageways that communicate with pressurized areas within the internal cylindrical surface  80  of  FIGS. 4 and 7  and within cylindrical sidewall  126  of  FIG. 7  are not seen. They exist in different cross-sectional views of piston rod  82  and the placement of such passageways is a matter of choice to an engineer skilled in the design of hydraulic mechanisms.  
         [0053]     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 claim or claims, including the full range of equivalency to which each element thereof is entitled.