Patent Publication Number: US-6990718-B2

Title: Tee connection to a pipeline

Description:
BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention relates to tee or branch connections to a pipeline and, more particularly, to a method of connecting tee or branch assemblies to pipelines such as hydrocarbons, for example crude oil or natural gas, or water mains. 
   (2) Description of Related Art 
   An existing technique for repairing damaged steel pipelines uses basically two half-shells which are secured together to form a shell assembly which encircles the pipeline leaving an annulus between the pipeline and the shell assembly which may be filled with grout that bonds the shell assembly to the pipeline wall. The grout thus fills and surrounds the damaged region and supports the damaged pipeline wall. Alternatively, the shell assembly may be secured by welding to the pipeline. 
   An object of the present invention is to provide a method of securing tee or branch connections to pipelines. 
   BRIEF SUMMARY OF THE INVENTION 
   According to the invention, a method is provided for securing a branch assembly to a pipeline, wherein the branch assembly comprises a first part for locating on the side of the pipeline remote from the side from which the branch is to extend, and a second part incorporating the branch, the method comprising positioning a first containment ring on the pipeline at the required position on the pipeline and surrounding the area from which the branch is to extend, positioning a first annular seal on the pipeline so that the seal is wholly radially within the containment ring to provide a first ring/seal arrangement, positioning a second containment ring on the pipeline spaced from the first containment ring and first annular seal, positioning a second annular seal on the pipeline so that the second seal is wholly radially within the second containment ring to provide a second ring/seal arrangement, positioning the second part of the branch assembly onto the seals, positioning the first part of the assembly on the pipeline and securing the first and second parts together so as to compress the seals and leave an annular space between the first and second parts and the external surface of the pipeline, and to leave an annular gap between the first and second ring/seal arrangements, providing an access point or vent in the second part communicating with the annular gap. The access point or vent allows monitoring of the pressure in the annular gap to check for seal integrity. The vent may include a valve via which build up of pressure of fluid in the annular gap can be released through the vent. Once pressure is detected in the annular gap, the vent can be closed or sealed so that the second seal becomes effective, thereby maintaining the integrity of the branch connection. 
   Sealing means may be provided for substantially preventing grout from escaping from the annular space, and grout may be introduced into the annular space that cures to bond the branch assembly in position on the pipeline. 
   It will be appreciated that subsequent to the branch assembly becoming bonded to the pipeline, a known procedure can be executed for cutting a coupon out of the pipeline via access through the branch under “live” conditions of the pipeline. 
   It will also be appreciated that the annular seals must be sufficiently compressible, and also sufficiently robust to withstand and contain with the containment rings line pressure during operation of the pipeline over the working pressures. 
   The grout may, for example, be selected from the following range: 
   urethanes, polyesters, acrylics, epoxies and cementatious compounds. It will be appreciated that each should be selected to satisfy the operating temperature, humidity and curing rate which then leads to the different adhesion strengths for different applications. Different grout material provides a different exothermic reaction which will determine the volume change after installation. It will also be understood that the volume change of epoxy grout should be optimized to minimize the internal stress system within the grout. 
   In order to ensure there is a good key for the grout, the external surface of pipeline and the inner surface of the first and second parts of the branch assembly may be dressed up or grit blasted prior to the assembly being mounted on the pipeline. 
   Conveniently, jacking means are employed to space the first part from the pipeline when the first and second parts have been secured together on the pipeline. 
   The jacking means may be hydraulically operated. For example, the jacking means may comprise a plurality of jacking members slidably mounted in apertures in the first part and pressure-applying means mounted with respect to the first part and behind the jacking members and being urgeable under hydraulic pressure against the jacking members to cause the jacking members to be urged towards the pipeline to positions to space the first part from the pipeline. 
   Conveniently, the jacking members are slidably mounted in bosses or the like secured or fixed to the first part, in which case the pressure-applying members are also slidably mounted in the bosses or the like. 
   When the jacking members are in position spacing the first part from the pipeline, stop means are fixed in position with respect to the first part to prevent the jacking members moving away from the pipeline. 
   Advantageously, the pressure-applying means are removably mounted with respect to the first part, and the stop means are adapted to occupy the positions occupied by the pressure-applying means when the latter are removed. 
   The stop means may be screwed into position in threaded supporting members fixed to the first part. 
   Conveniently, one or more load bearing members are positioned between the pipeline and the jacking members to spread the applied load when the jacking members are in position spacing the first part from the pipeline. 
   The load bearing members may be in the form of enlarged feet on the jacking members, the surfaces of which feet may generally correspond to the profile of the pipeline. Alternatively, the load bearing members may be secured to the pipeline, in positions so that they will be engaged or contacted by the jacking members. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  shows schematically the top and bottom parts of a branch assembly to be used in a method according to the invention; 
       FIG. 2  is a schematic plan view of a pipeline on which are positioned first and second containment rings and associated first and second annular seals in preparation of the pipeline receiving the top part of the branch assembly; 
       FIG. 3  is a schematic side view of the pipeline on which the top and bottom parts of the branch asssembly have been secured together in position; 
       FIG. 4  is a schematic view in the direction of arrow A in  FIG. 3 ; 
       FIG. 5  is a similar view to that shown in  FIG. 4  but of a modified arrangement in which the jacking means is hydraulically operated; and 
       FIG. 6  is a view similar to  FIG. 5  but showing stop means occupying the positions previously occupied by the pressure-applying means, as in  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIG. 1 , there is shown a branch assembly  1  comprising a first part  2  forming the upper part of the assembly and a second part  3  forming the lower part. 
   The upper part and lower parts of the assembly  1  are made of carbon steel and have generally part cylindrical portions  4  and  5 , respectively, which are securable together about a pipeline  6  via flanges  7  and  8  which extend longitudinally along each side of the upper and lower parts, as can be clearly seen in  FIG. 3 . 
   The flanges  7  of the upper part  2  have apertures  9  which are intended to align with apertures  10  in the flanges  8  of the lower part  3  so that securing bolts  11  (see  FIGS. 3 and 4 ) can be passed therethrough to secure the two parts  2  and  32  together on the pipeline. 
   The upper cylindrical portion  4  includes an apertured section  12  from which extends a short branch pipe  13  terminating in an annular flange  14  to which a branch pipeline having an end flange can be connected in a known fashion (not shown) after the assembly  1  is securely bonded to the pipeline  6 . 
   By way of illustration of the invention, a method of securing the tee assembly  1  to a steel pipeline is described below. 
   Initially, the area of the external surface of the pipeline to which the branch assembly is to be secured is grit blasted (not shown), as are the inner surfaces of the part-cylindrical portions  4  and  5  of the upper and lower parts of the branch assembly. 
   First and second containment rings  16  and  116 , respectively, of different diameters and made of steel and shaped so as to conform to the shape of the pipeline are positioned in spaced relationship to each other on the pipeline around the area  6   a  from which the branch pipe  13  of the branch is to extend. 
   First and second annular seals  17  and  117  made for example of rubber or polymer and metal and of greater thickness than the containment rings  16  and  116  are then placed within the first and second containment rings, respectively, so as substantially to conform to the shape of the pipeline  6  (see  FIG. 2 ). 
   The upper part  2  of the branch assembly is lowered onto the seals  17  and  117 , with the bore  13   a  of the branch pipe  13  being centralised with the area  6   a  surrounded by the inner first seal  17  and associated containment ring  16 , the lower part  3  is moved into position on the pipeline, and the upper and lower parts  2  and  3  of the assembly are secured together by means of bolts  11  used in association with the aligned apertures  9  and  10  in the flanges  7  and  8  (see  FIGS. 3 and 4 ). 
   It will be appreciated from  FIGS. 1 to 4  that the first containment ring  16  and associated first annular seal  17  form a first ring/seal arrangement  16 / 17  that is spaced by an annular gap  118  from a second ring/seal arrangement  116 / 117  formed by the second containment ring  116  and the associated second annular seal  117 . The upper part  2  is provided with a closable vent  119  that allows communication to the annular gap  118 . 
   Jacking bolts  18  are mounted in the wall of the lower part  3  of the branch assembly. These jacking bolts extend through the wall of the lower part to engage or bear on the surface of the pipeline  6 , and can be turned from the outside of the assembly to be loosened or tightened against the wall of the pipeline. The jacking bolts  18  are adjusted so that the annular seal  17  is sufficiently compressed to provide a suitable seal prior to the introduction of epoxy grout. 
   Once the tee assembly  1  is in position on the pipeline, a generally cylindrical or annular space  19  is left or defined between the upper and lower parts  2  and  3  and the external surface of the pipeline  6 . 
   The annular space  19  is bounded by sealing means  20 , such as suitable putty which is located between the branch assembly and the pipeline at the opposite ends of the assembly, and by the second annular ring seal arrangement  116 / 117 . 
   The grout is then injected into the annular space  19  via injection opening  21 , located towards the bottom of the lower part of the assembly, to fill the annular space. An outlet opening  22  for expressed air and excess injected grout is provided in the upper part of the assembly. After the annular space  19  is filled with grout, the grout is allowed to cure and thereby bond the upper and lower parts  2  and  3 , and thus the branch assembly  1 , to the pipeline. 
   When the assembly is securely bonded by the grout to the pipeline, the jacking bolts  18  can be, optionally, loosened off to ensure load is fairly or more evenly distributed on the pipeline by the grout. 
   In  FIGS. 5 and 6  an alternative method of jacking is illustrated. The lower part  3  is provided with apertures  23  in which are slidably mounted jacking members  24  each carrying enlarged feet  25  which match the profile of the pipeline and are for engaging or contacting the surface of the pipeline. Bosses  26  having through bores  27  are secured to the lower part  3 . The through bores  27  are for slidably receiving the free, outer ends of the jacking members  24 . Hydraulically operated means  28  comprising cylinder means  29  are mounted on the bosses  26 . Each cylinder means  29  comprises a cylinder  30  and a pressure-applying means  31  in the form of a piston is slidably mounted in the cylinder  30 . The cylinders  30  are aligned with respective ones of the bores  27  of the bosses  26 . The pistons are also slidably mounted in the bores  27  of the bosses  26 . Hydraulic pressure is applied through lines  32 ,  33 ,  34  to the respective cylinders  30  from a common main line  35  to a source  36  of hydraulic pressure. On applying appropriate hydraulic pressure to the cylinders  30  the pistons  3  are urged against the jacking members  24  to cause the jacking members to be urged towards and against the pipeline  6  such that the annular seal  17  is compressed and a generally annular space or gap  19  is formed as described earlier. 
   The enlarged feet  25  serve as load bearing members that spread the load applied to the pipeline via the jacking members. 
   After the grout has been injected into the annular space  19  and allowed to cure, as described above, the cylinder means  29 , including the pistons, are removed from the bosses  26  and stops  37  (see  FIG. 6 ) are inserted into the bosses and fixed in position therein butting up against the back ends of the jacking members, thereby occuping the positions previously occupied by the pistons, to prevent the jacking members moving away from the pipeline. The stops  37  may be externally threaded as at  37   a  and screwed into bosses  26  which are correspondingly internally threaded as at  26   a . The provision of the fixed stops  37  removes reliance on the continued integrity of the cured grout behind the enlarged feet to prevent unwanted movement of the jacking members  24  away from the pipeline. Thus, if the cured grout behind the enlarged feet  25  should deteriorate and disintegrate or “fail”, the stops  37  hold the pipeline in position relative to the shell assembly. 
   The closable vent  119 , which may include a valve (not shown), provides an access or monitoring point via which the pressure in the annular gap  118  can be checked or monitored by connecting the vent to a pressure monitor (not shown) and, for example continually or periodically, to check for seal integrity. Thus, if for example seal  17  should fail the pressure in the annular gap will build up or increase and be detected as a result of the checking via vent  119 . Escape of pressurised fluid carried by the pipeline as a result of leakage past a failed first seal  117  can thus be detected. If such leakage and detection occurs then the vent  119  can be closed or sealed and the second seal  117  the becomes effective, thus maintaining the integrity of the branch connection. 
   In a modification (not shown) the enlarged feet on the jacking members may be replaced by load bearing members secured to the pipeline in positions so that they will be engaged or contacted by the jacking members. 
   With the branch assembly securely bonded to the pipeline, known “live” procedures can be performed for cutting out a coupon from area  6   a  of the pipeline (not shown) and joining a branch pipeline (not shown) to the branch utilising the branch pipe  13 . Such known procedures will not be described here. 
   A method according to the invention, examples of which are described above, enables a branch assembly to be bonded to a pipeline without having to employ welding techniques. This is a particular advantage where “live” pipelines are involved, especially where there are high product flow rates through the pipeline. Other advantages of using such a method include minimising unnecessary pressure reduction in the pipeline and enabling cost savings for installations. 
   Whilst particular embodiments of the invention have been described above, it should be appreciated that various modifications may be made without departing from the scope of the invention. For example, the order in which the first and second containment rings and associated seals are placed in position on the pipeline may be varied. In addition, one of more further containment rings and seals could be employed in the invention beyond the first and second ones specifically described. Further, particularly where the branch assembly needs only temporarily to be connected to the pipeline, grout need not be introduced into the annular space  19  and the annular space  19  need not be bounded by sealing means  20 , in which case the injection opening  21  could be omitted also.