Abstract:
The invention relates to an intervention method for acting on the wall of a fluid pipeline by using a tool comprising a pipe segment and at least first means for creating sealing and second means for creating sealing, the method comprising a step of moving the tool inside the pipeline until the pipe segment is positioned facing a zone of the wall of said pipeline, the method further comprising a step of creating sealing upstream and downstream from said zone respectively by using the first and second means for creating sealing so as to seal off an outer portion of a segment of the pipeline around said zone, followed by a step of acting on said zone of the wall.

Description:
TECHNICAL FIELD 
       [0001]    The invention lies in the field of tools and methods for acting on the walls of pipelines for transporting fluid, such as pipelines for hydrocarbons in liquid or gaseous form, or indeed pipelines for transporting water. Generally, the fluid (liquid or gas) is under pressure while the network of which the pipeline forms a part is in use. More particularly, the purpose of such action is to repair the pipeline, or indeed to weld fittings to the pipeline. 
         [0002]    The pipelines concerned may be in the open air, or they may be buried pipelines, or they may be undersea pipelines. While they are in use, which may continue for numerous years, their walls may present defects due to phenomena of corrosion or of mechanical attack, and thus be in need of repair. 
         [0003]    As a general rule, a repair needs to be performed by removing pressure from a segment of the pipeline on either side of the defect that is to be repaired, while still allowing the fluid to pass through, since any interruption could have severe economic consequences for the operator of the pipeline or of the network. The repair is preferably performed after removing fluid from the segment on either side of the defect (e.g. removing gas or removing water). 
         [0004]    In the same manner, when it is desired to make a weld to the outer wall of the pipeline, it is sometimes necessary to interrupt the flow of fluid in the segment in question, in particular in order to avoid the material cooling excessively, which would be harmful for the quality of the welding and for its durability. 
         [0005]    There exist systems, which are expensive and complex to use that are suitable for removing pressure and discharging the fluid, such as stoppers under load and their associated accessories (stopple, reinforcing saddle, hot tapping, balloons). There also exist systems involving a temporary jumper hose for maintaining transit, which systems are complex in structure and also complex to handle given their implications in terms of operator safety. 
         [0006]    Also known is Document WO 2007/141554, which discloses apparatus serving in particular to patch a defect by introducing an inner pipe into the pipeline, the inner pipe being positioned facing the defect, and by introducing an expandable component that is arranged around the pipe and that is activated so as to be inflated in order to plug the defect from the inside. A variant of the apparatus is also used to put a valve into place in the pipeline. 
         [0007]    That apparatus implies leaving a voluminous tool in place in the pipeline, and it is therefore not very satisfactory since the pipeline remains partially obstructed after the action has been taken. 
         [0008]    Also known is Document WO 03/067134, which discloses apparatus for interrupting (shutting off) fluid flow in a high pressure pipeline. The use of that apparatus requires fluid flow to be interrupted or a branch connection to be made, which is not satisfactory. 
       Definition of the Invention and Associated Advantages 
       [0009]    In this context, the invention proposes an intervention tool for taking action on the wall of a fluid pipeline, the tool comprising a pipe segment for positioning inside the pipeline facing a zone of the wall and one or more first or upstream means for creating sealing between the wall of the pipeline and the pipe segment. 
         [0010]    According to a general characteristic, the tool further comprises one or more second or downstream means for creating sealing between the wall of the pipeline and the pipe segment in order to isolate an outer portion of a segment of the pipeline from the flowing fluid between the two means for creating sealing, and at least the first or the second means for creating sealing are in two portions, defining a sealing lock between the two portions of said first or second means for creating sealing. 
         [0011]    By means of such a tool, it is possible to create a sealed peripheral zone (or volume) in a segment of the pipeline facing and in contact with the zone (or surface) of the wall on which it is desired to take action. 
         [0012]    This sealed zone is isolated from the flowing fluid, which can be advantageous thermally speaking in the context of taking welding type action on the wall. However the sealed zone may also, where necessary, be subjected to decompression or indeed emptying in order to take action on the wall without pressure and indeed without the presence of the fluid, even though the fluid continues to flow through the pipe segment. Thus, the tool enables a pipeline to be repaired (or some other action to be taken thereon) without interrupting the operation of the network, and it also makes it possible to reduce the time needed for taking action. Its ease and reliability of use makes this tool particularly advantageous compared with the above-mentioned prior art systems. It should be observed in particular that there is no external bypass system, since such a system is made pointless by the presence of the pipe segment inside the tool. 
         [0013]    The locks defined by the two portions serve to improve safety, in particular for applications in which pressures are high. This applies in particular for gas transport networks where pressures may be as great as 67 bars. The safety provided by the tool is then reinforced, as is the reliability of the intervention process. 
         [0014]    In a particular embodiment, the first or the second means for creating sealing comprise expandable and retractable sealing gaskets, e.g. inflated with oil using an oil/nitrogen accumulator, or expandable by compression using a system of moving plates. 
         [0015]    In an advantageous embodiment, the tool further comprises adjustable propulsion means for propelling it in the pipeline. These means may be controllable, and they may also be arranged to make use of the movement of the fluid so as to take advantage of an entrainment phenomenon for driving the tool. The propulsion means may comprise at least one adjustable flap installed in the pipe segment. The propulsion means may for example be actuated for adjustment and control purposes by means of a hydraulic system powered by an oil/nitrogen accumulator, by an electromechanical system powered by batteries, or indeed by a combination of such systems. 
         [0016]    In certain embodiments, the tool may also include a system guiding the tool inside the pipeline. The guide system may in particular comprise at least one wheel or deformable disk at each end of the pipe segment. 
         [0017]    In optional and advantageous manner, it is also proposed that the pipe segment includes a length of bellows in order to enable it to travel in curved pipelines. 
         [0018]    Advantageously, the tool may include a braking system and/or a system for holding the tool in position by contact with the inside wall of the pipeline. This braking and/or position-maintaining system may operate by friction against the inside wall of the pipeline, contact with the inside wall, or by braking the guide wheels. 
         [0019]    In an embodiment, the tool may also include a retarder system suitable for slowing down the movement of the tool without being capable of stopping it. By way of example, this system may be of the electromagnetic type. 
         [0020]    Advantageously, the tool may also include a communication system enabling the tool to be located and controlled remotely from outside the pipeline, e.g. by using electromagnetic waves or sound waves. 
         [0021]    In advantageous, but optional, manner, the sealing systems may be configured to brake the movement of the tool by rubbing against the inside wall of the pipeline and/or to hold the tool in position by coming into contact with the inside wall of the pipeline. 
         [0022]    The invention also provides a method for acting on the wall of a fluid pipeline by using a tool of the invention, the method comprising a step of moving the tool inside the pipeline until the pipe segment is positioned inside the pipeline facing a zone of the wall of said pipeline, a step of creating sealing upstream and downstream from said zone respectively by using first and second means for creating sealing in order to seal off an outer portion of a segment of the pipeline around the zone of the wall (or to seal off a volume defined by the tool and the pipeline), and then, if necessary, a step of decompressing said portion (or said volume). Finally, the method comprises a step of taking action on said zone of the wall. 
         [0023]    At least the first or the second means for creating sealing are in two portions, defining a sealing lock between the two portions of said first or second means for creating sealing. 
         [0024]    The action is preferably taken from the outside of the pipe by a human operator or by apparatus. 
         [0025]    In implementations in which the first or the second sealing means are expandable and retractable, they are actuated to expand in order to create sealing and to retract after action has been taken. 
         [0026]    In certain implementations, the tool is propelled by the movement of the fluid. 
         [0027]    In certain implementations, the movement of the tool in the pipeline and the actuation of the sealing means are remotely controlled. 
         [0028]    In an implementation, the positioning is performed by using an abutment placed inside the pipeline, the method including a prior step of hot tapping the pipeline in order to put said abutment into place. 
         [0029]    In a particular implementation, the outer portion facing the zone where action is to be taken is decompressed by using a valve, the method comprising a prior step of hot tapping the pipeline in order to put said valve into place. 
         [0030]    In an implementation, a braking device, which may include or be included in the sealing systems acting by friction, may be used in order to brake the movement of the tool before it reaches the abutment. 
         [0031]    In an implementation, a retarder device may be used to slow down the movements of the tool, without necessarily stopping it. 
         [0032]    In an implementation, a position-maintaining system that may include or be included in the sealing system, may be used to hold the tool in position by making contact with the inside wall of the pipeline. 
         [0033]    Finally, it is specified that the step of taking action may comprise, amongst other possible actions: making a repair by a welded patch, making a repair by build-out welding, or welding a fitting to the pipeline. 
         [0034]    In an implementation, the method includes decompressing each of the locks by using a valve. 
     
    
     
       LIST OF FIGURES 
         [0035]    The present invention is described below with reference to the accompanying figures. 
           [0036]      FIG. 1  is a three-quarter view of the tool in an embodiment of the invention. 
           [0037]      FIG. 2  is a longitudinal section of the  FIG. 1  tool. 
           [0038]      FIG. 3  shows the same section, with the propulsion flap open. 
           [0039]      FIG. 4  shows the tool being moved in a pipeline. 
           [0040]      FIG. 5  shows the tool being positioned by being blocked by an abutment in the pipeline, in order to make a repair. 
           [0041]      FIG. 6  shows the tool in the  FIG. 5  position, after sealing has been put into place. 
           [0042]      FIG. 7  shows the wall of the pipeline repaired, after pressure has been removed. 
           [0043]      FIG. 8  shows the departure of the tool after the repair has been made and the abutment moved out of the way. 
       
    
    
     DETAILED DESCRIPTION 
       [0044]      FIG. 1  shows a tool  1  in an embodiment of the invention, in a three-quarter view. It comprises a pipe segment  100 , which in this example is a rigid circular cylinder with open mouths  101  and  102  that are plane and lie in planes that are perpendicular to the axis of the cylinder, thereby constituting circles. 
         [0045]    Close to the mouth  101 , the outside of the pipe segment  100  carries guide wheels  110  (or guide casters) that are arranged in regular manner around its circumference, e.g. in a common plane. In the example shown, there are four of them. Similar guide means, in this example other guide wheels  110 , are present in the proximity of the mouth  102 . Other guide means could be used, such as for example guide disks. It is possible to combine guide means of different types. 
         [0046]    Still in the proximity of the mouth  101 , on the outside of the pipe segment, there is a first inflatable sealing gasket  120 . When inflated, this inflatable sealing gasket  120  is designed to press against the inside wall of the pipeline in which the tool travels. Conversely, when deflated, the gasket is folded down against the pipe segment  100 . The inflatable gasket  120  constitutes a body of revolution of profile that is circular or non-circular, e.g. a toroidal body having as its axis of revolution the axis of revolution of the pipe segment, and surrounding the pipe segment. The inflatable sealing gasket  120  can be inflated by means of a hydraulic system that is remotely controllable and that includes an oil/nitrogen accumulator. It is followed on the pipe segment at a short distance towards the second mouth  102  by a second inflatable sealing gasket  125 , similar to the first, and likewise surrounding the pipe segment  100 . Continuing towards the second mouth  102 , there is a third inflatable sealing gasket  130  that is once more similar to the first two. Finally, a fourth inflatable sealing gasket  135  is present coming up towards the second mouth  102 . The distance between the third and fourth inflatable gaskets  130  and  135  is similar or identical to the distance between the first and second inflatable gaskets  120  and  125 , whereas the distance between the second and third inflatable gaskets  125  and  130  is greater. 
         [0047]    Other sealing means could be used, such as gaskets that expand by compression or  0 -rings or lip gaskets capable of expanding so as to be pressed against the inside wall of the pipeline. Gaskets that expand under compression may comprise elastomer elements suitable for being expanded by a wormscrew mechanism or a hydraulic system having movable plane or conical plates serving to compress elements made of elastomer. 
         [0048]    Instead of being constituted essentially by a rigid cylinder, the pipe segment may be constituted by two rigid cylinders connected together by a bellows, in order to enable the tool to travel along a pipeline that presents curves such as bends. 
         [0049]      FIG. 2  shows the same elements as can be seen in  FIG. 1 , in a section view on a plane containing the axis of revolution of the tool  1 . It can be seen that the four inflatable gaskets are installed in grooves provided for this purpose in the surface of the pipe segment  100 . It can also be seen that the guide wheels  110 , whether close to the mouth  101  or to the mouth  102 , are all configured in the same direction in order to make it easier for the tool to travel in the pipeline in a particular direction. These wheels may be movable radially in order to provide good guidance in spite of geometrical variations to be encountered in pipelines (manufacturing tolerances of the tubes, welds, curves, local deformations, . . . ). It is also specified that in the embodiment shown, the guide means  110  lie between the corresponding mouth ( 101  or  102 ) and the nearest inflatable gasket ( 120 ,  135 ), but that the guide means could be positioned elsewhere on the tool. 
         [0050]    The tool also has propulsion means that are constituted in this example in particular by an adjustable flap  140  placed inside the pipe segment  100 , halfway between the two mouths  101  and  102 . The flap  140  is shown in its closed position in  FIG. 2 , thereby providing the tool with maximum drive by the fluid, while in  FIG. 3  it is shown in its open position, thereby minimizing drive and making it easier to stop the tool. The flap  140  is motor-driven to pass from one of its positions to the other or to adopt an intermediate position, and to conserve the position it has adopted while the tool is moving with the stream. It thus provides a variable “windage” function depending on its degree of opening. The flap  140  thus enables the tool  1  to move inside the pipeline with the fluid, in the same direction as the fluid, by making use of the movement of the fluid to provide a drive phenomenon. The tool  1  also has a motor system for the flap  140 , or the flaps if a plurality of flaps are used, and optionally, but not necessarily, an on-board source of energy. It is specified that instead of one or more flaps, it is possible to use one or more diaphragms or one or more adjustable grids. Furthermore, the system is designed to be remotely locatable or controllable by means of a communication system between the tool and the outside of the tube. 
         [0051]    The tool  1  may also include an electromagnetic retarder (not shown) acting on the wheels to enable the speed of the tool to be reduced, but that does not enable the movement of the tool to be stopped completely. 
         [0052]    The tool  1  may also include a braking system acting by friction against the inside wall of the pipeline (not shown). 
         [0053]    The tool  1  may also include a system for holding the tool in a static position inside the pipeline by adhering to the inside wall of the pipeline once the tool has stopped in the position where action is to be taken. 
         [0054]    The sealing means may be used in order to brake the movement of the tool by rubbing against the inside wall of the pipeline. 
         [0055]    The sealing means may also be used to hold the tool in position by contact with the inside wall of the pipeline. 
         [0056]    Conversely, it is possible to use a tool braking system that is distinct from the sealing means. By way of example, it could comprise a sacrificial gasket that is changed between two uses of the tool, or skids that come into contact with the wall of the pipeline, or indeed wheels that run along the wall of the pipeline and that have brakes. 
         [0057]    It is also possible to use a system for holding the tool in position that is distinct from the sealing means. By way of example, this system could comprise metal jaws. 
         [0058]      FIG. 4  shows the tool  1  moving in a fluid transport pipeline  200 . The fluid may be a liquid or a gas. The pipeline may be buried, in the open air, or it may pass under the sea or under a lake. 
         [0059]    The tool is previously inserted via a launch station (not shown), i.e. pipeline equipment that conventionally enables cleaning or inspection tools to be inserted into the pipeline. Before the tool is inserted, it is verified that the pipeline  200  is pistonable, i.e. that such an item can travel along the pipeline without becoming jammed therein. The tool  1  has an outside diameter that enables it to travel inside the pipeline  200 , the guide means  110  being in contact with the inside surface of the wall of the pipeline  200  for guidance purposes. The tool is driven by the flow of fluid flowing in the pipeline, at a speed that depends on the extent to which the flap  140  is open and on the flow rate of the fluid. The fluid flows both around the tool  1  and through the inside of the pipe segment  100 . 
         [0060]      FIG. 5  shows the tool  1  stopped at a defect  210  that needs to be repaired in the wall of the pipeline  200 . The tool  1  is stopped by its mouth  101  encountering an abutment  220  that has previously been put into place in the pipeline  200  from outside the pipeline. In an embodiment, the abutment  200  is put into place by hot tapping. The method may comprise welding a socket on the pipeline and then piercing the socket while the pipeline is under fluid pressure. In this example, a metal rod is implanted in the tap and forms an abutment inside the pipeline for an item having the diameter of the tool  1 . 
         [0061]    The abutment is positioned in the pipeline  200  in such a manner that the defect  210  faces the section of the pipe segment  100  that lies between these inflatable gaskets  125  and  130  once the tool is in position against the abutment. Furthermore, three taps  240 ,  242 , and  244 , each having its own decompression valve, are formed beforehand, or after the tool is in position, each facing a respective one of the sections of the pipe segment  100  between a pair of inflatable gaskets. These taps may be made by hot tapping. 
         [0062]    Once the tool is stopped by the abutment  220 , the fluid under pressure continues to flow around the tool, and also through the inside of the pipe segment  100 . The flap  140  is opened so as to reduce the “windage” of the tool  1 . 
         [0063]    In  FIG. 6 , the inflatable gaskets  120 ,  125 ,  130 , and  135  of the tool  1  are shown inflated. Each of these elements comes into contact with the wall of the pipeline to prevent fluid passing around the pipe segment  100 . Thus, three sealed toroidal zones  310 ,  320 , and  330  are created, each facing one of the taps  240 ,  242 , and  244  fitted with its decompression valve. The fluid continues to flow through the inside of the pipe segment  100 . 
         [0064]    Using the valves in the taps  240 ,  242 , and  244 , each of the toroidal sealed zones  310 ,  320 , and  330  is then decompressed, with the zone  320  between the inflatable gaskets  125 ,  130  being the main zone in which the action is to be taken, while the other two zones  310  and  330  serve as sealing locks for ensuring that there is no fluid leak into the main zone from the free zones of the pipeline  200 , upstream and downstream. 
         [0065]    It is specified at this point that although the embodiment shown thus makes use of two sealing locks  310  and  330 , such locks are not essential elements, and the invention can thus be performed with only two inflatable gaskets. Nevertheless, it should be understood that the presence of these locks is highly advantageous. 
         [0066]    It is also specified that although the presently-described embodiment uses three taps, one of the two taps  240  and  244  could be superfluous in the event of the tool having an internal channel enabling fluid to flow between the locks  310  and  330  formed by the gaskets. 
         [0067]      FIG. 7  shows the repair  212  to the defect  210 , which repair may constitute welding a patch to take the place of the defective portion of the pipeline or making a repair by building out by welding, or by some other type of repair. This is done without pressure, and possibly after draining the fluid through the tap  242 . Repair is preferably performed by taking action from the outside of the pipe, by an operator or by an apparatus. 
         [0068]    After the repair process, the inflatable gaskets  120 ,  125 ,  130 , and  135  are deflated, and the entire pipeline  200  is thus put back under pressure, including in the zones  310 ,  320 , and  330 . As can be seen in  FIG. 8 , the abutment  220  is moved so that it no longer retains the tool  1  in the pipeline, and the tool  1  continues to travel in the flow direction of the fluid, at a speed that is determined by the extent to which the flap  140  is open and by the flow rate of the fluid, which flap is opened in order to be able to recover the tool quickly in an arrival station of the pipeline. At this stage, it is desirable to close off the taps  240 ,  242 , and  244 . 
         [0069]    The invention is not limited to the embodiments described, but extends to any variant coming within the ambit of the scope of the claims. 
         [0070]    By enabling the wall to be isolated from the fluid, the tool makes it possible in particular to perform a welding operation on pipelines in which the forced convection generated by the fluid would lead to excessive cooling that would be harmful for the mechanical soundness of the welding bead. This phenomenon can be encountered in certain pipelines as a function of the diameter, of the flow rate, and of the temperature of the fluid. Welding can thus be carried out with or without decompression of the zone that is sealed off by using the tool.