Abstract:
A pipeline buoyancy control assembly is operable to simultaneously retain a plurality of pipelines against buoyancy forces. Respective ends of two retaining straps corresponding to two respective pipelines engage a tie-down member of a single control assembly. The retaining straps are placed over the respective pipelines and other ends of the retaining straps are attached to additional control assemblies. Further, stresses exerted on the retaining straps when the pipelines are subjected buoyancy forces are minimized by the unique structure of the tie-down member and the manner by which the retaining straps attached thereto.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a tie-down assembly for a pipeline and, more particularly, the invention relates to a tie-down assembly and a tie-down attachment member therefor for retaining a pipeline against buoyancy forces, such as those forces experienced continuously by a submerged oil or gas pipeline or experienced by a pipeline buried in soil with the water table located at or above the pipeline. 
     BACKGROUND OF THE INVENTION 
     Pipelines, such as oil and gas pipelines, often need to be anchored or otherwise stabilized. For example, underwater pipelines and pipelines buried near or in saturated soils are buoyant and, thus, have a tendency to float. To prevent damage to the pipes and, thus, prevent a potential catastrophic leak of the material within the pipe, this buoyancy must be controlled. A variety of assemblies and methods are known for anchoring such pipelines. More particularly, passive gravity systems, such as weights, are common. Other known systems employ helical screw anchors with steel or polyester pipebands. 
     A representative example of a conventional pipeline anchor apparatus is disclosed in U.S. Pat. No. 5,730,552 (“the &#39;552 patent”) to Johannesson et al. The &#39;552 patent discloses a pipeline anchor apparatus with left and right anchor units connected by a tie-down strap made of heavy-duty polyester or nylon webbing. Two respective tie-down brackets located on opposite sides of the pipe hold a respective end of the strap, which is placed over the top of the pipe. The brackets are attached to extension rods which are coupled to anchor rods that are driven into the ground. The tie-down brackets pivot about the extension rods to reduce stress placed on the pipe as the pipe shifts, for example, due to buoyancy forces. 
     The polyester tie-down strap of the &#39;552 patent has a loop formed and sewn at each of its opposite ends. Each loop is secured to a tie-down bracket along a side thereof facing the pipeline. The tie-down brackets are mounted to extension rods which, in turn, are attached to anchor rods of the respective anchor units. Each anchor rod has a helical anchor attached thereabout. Further, each tie-down bracket has a side sleeve-like connector defining a channel or slot running alongside the bracket through which passes one of the tie-down strap loops. Each loop of the tie-down strap wraps around an outer wall of the side connector of one of the tie-down brackets. 
     Another representative example of previously known pipeline anchor apparatuses is disclosed in U.S. Pat. No. 6,132,141 (the &#39;141 patent), to Kirk. The &#39;141 patent discloses a pipeline retainer device having a pair of tie-down attachment members mounted to helical screw anchor rods. The attachment members are connected to opposite portions of a strap that holds the pipeline down. A retainer body comprising an annular shoulder portion attached to each hollow tubular mounting body distributes stress caused by shifting of the pipe at the ends of the strap. 
     An even further representative example of previously known pipeline anchor apparatuses is disclosed in U.S. Pat. No. 4,338,045 (the &#39;045 patent), to Cour. Specifically, the &#39;045 patent discloses a method and apparatus for anchoring a pipeline to a support and a sea-bed. An inflatable body is placed on the upper portion of the pipeline and a rigid saddle clamp is placed over the inflatable body and the pipe, which is coated with concrete. The ends of the saddle clamp are attached to anchors driven into the ground and the inflatable body is then filled with a settable material, such as concrete. Once the settable material has settled, any play between the pipe and the saddle clamp, particularly in the vertical direction, is removed. 
     None of the previously known devices and methods for retaining a buoyant pipeline, including the U.S. patents mentioned above, sufficiently account for vertical stresses exerted on the various respective tie-down straps or retainers. As a result, broken or otherwise damaged retainers and straps could result when previously known pipeline anchoring systems, such as those mentioned above, are used. Furthermore, previously known pipeline anchoring systems such as those identified above are configured to retain a single pipeline. None of the aforementioned pipeline retention systems is designed to accommodate more than one respective pipeline simultaneously. 
     There remains a need, therefore, for a pipeline anchoring device that addresses the aforesaid problems, and others, attendant with conventional and other previously known pipeline anchor devices and which is also easily manufactured and installed. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a tie-down assembly for a pipeline and, more particularly, to a tie-down assembly to retain a submerged buoyant pipeline, such as an oil or gas pipeline, and a tie-down attachment member therefor. 
     The present invention provides a pipeline buoyancy control assembly and a tie-down attachment member therefor designed to satisfy, among other things, the aforementioned needs. 
     A pipeline buoyancy control assembly in accordance with one embodiment of the present invention includes a tie-down device with a body portion having a center plate with two substantially flat portions disposed at each of two ends and a curved center portion disposed between the flat portions and, two opposing side plates fixedly attached to respective sides of the center plate, and an elongated hollow stem portion disposed in an aperture formed in the body portion, wherein the stem portion is fixedly attached to the body portion. 
     According to another embodiment of the invention, a pipeline buoyancy control assembly for retaining a buoyant pipeline is provided which includes an anchor device having at least two ends, wherein at least one of the ends is for attaching to a fixed object, a tie-down attachment member in operational engagement with an end of the anchor device, wherein the tie-down attachment member move along a length of the anchor device, rotate about an axis of the anchor device, or both. The pipeline buoyancy control assembly according to this embodiment further includes at least one tie-down strap each strap being attached to the tie-down attachment member and being operable to retain the pipeline, and a retainer device attached to the anchor device and operable to restrict the movement of the tie-down attachment member beyond a specified location on the length of the anchor device. 
     According to yet a further embodiment of the invention, a pipeline buoyancy control system is provided having a buoyant pipeline, first and second pipeline buoyancy control assemblies provided adjacent to and on respective sides of the buoyant pipeline, wherein each of the first and second pipeline buoyancy control assemblies is operable to retain a plurality of pipelines simultaneously, and a retainer strap engaged at respective ends thereof to the first and second pipeline buoyancy control assemblies, wherein the retainer strap retains the buoyant pipeline against buoyancy forces. 
     According to a yet further embodiment, a pipeline buoyancy control system is provided having at least two pipelines, a first pipeline buoyancy control assembly disposed between a first pipeline and a second pipeline, a second pipeline buoyancy control assembly disposed at an outer side of the first pipeline, a third pipeline buoyancy control assembly disposed at an outer side of the second pipeline, a first strap attached between the first and second pipeline buoyancy control assemblies and operable to retain the first pipeline, and a second strap attached between the second and third pipeline buoyancy control assemblies and operable to retain the second pipeline. 
     These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described illustrative exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The object and features of the present invention will become more readily apparent from the following detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of one exemplary embodiment according to the present invention where a plurality of pipeline buoyancy control assemblies is used to retain two different pipes. 
         FIG. 2  is a perspective view of a single pipeline control assembly in accordance with the present invention. 
         FIG. 3  is a perspective view illustrating the manner by which tie-down straps attach to a tie-down member of a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
         FIG. 4  is a perspective view of a lower end portion of an anchor rod used in connection with a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
         FIG. 5  is a perspective view of an upper end portion of an anchor rod used in connection with a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
         FIGS. 6A AND 6B  are respective front and side perspective views of a retainer device used to retain a tie-down attachment member to an anchor rod of a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
         FIG. 7  is a cutaway view showing the engagement of an upper end portion of an anchor rod and a tie-down attachment member used in connection with a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
         FIG. 8  is a perspective view of an endless strap used in connection with a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
         FIGS. 9-11  are respective isometric, top and side perspective views of a tie-down attachment member used in connection with a pipeline buoyancy control assembly in accordance with one exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Non-limiting exemplary embodiments of the present invention are discussed in detail below. While specific structural configurations are disclosed, it should be understood that the exemplary structural embodiments disclosed are for illustration purposes only and are not intended to limit the scope of coverage afforded by the attendant claims provided herewith. A person skilled in the relevant art will recognize that other configurations may be used without departing from the spirit and scope of the invention. 
     The present invention is directed to a tie-down assembly for a pipeline and, more particularly, to a tie-down assembly for retaining one or more buoyant pipelines, such as oil or gas pipelines, and a tie-down attachment member therefor. 
     Referring to the drawings and particularly to  FIGS. 1 and 2 , there is illustrated a plurality of pipeline buoyancy control assemblies in accordance with a non-limiting exemplary embodiment of the invention. More particularly, in  FIG. 1  a plurality of exemplary pipeline buoyancy control assemblies,  20   a ,  20   b  and  20   c , in accordance with the present invention are illustrated for retaining two adjacent pipelines, P 1  and P 2 .  FIG. 2  illustrates the details of a single exemplary pipeline buoyancy control assembly  20  in accordance with the invention. Further, according to the embodiment shown in  FIG. 1 , pipelines P 1  and P 2  have different diameters. Specifically, pipeline P 2  has a larger diameter than pipeline P 1 . For example, as shown, pipeline P 2  is covered with a coating  10  which renders the effective diameter of pipe P 2  larger than the diameter of pipeline P 1 , which does not have a coating provided on its outer surface. A skilled artisan will understand that two or more pipeline buoyancy control assemblies in accordance with the present invention can be used to retain one or more pipelines, each pipe having the same or a different diameter. 
     Referring to  FIG. 1 , a plurality of pipeline buoyancy control assemblies  20   a ,  20   b  and  20   c , along with retaining straps  50   a  and  50   b , in accordance with the present embodiment are generally designated  100 . Tie-down straps  50   a  and  50   b  in  FIG. 1  have different lengths to accommodate the different respective diameters of pipelines P 1  and P 2 . That is, each strap, generally designated  50  in  FIG. 2 , has a respective length specifically determined based on the diameter of the pipeline which it retains. However, other than having a different length, each strap in accordance with this exemplary embodiment is constructed substantially the same, as described in more detail below. 
     As illustrated in  FIG. 1 , the three anchoring devices  20   a ,  20   b  and  20   c  are disposed at opposite lateral sides S 1  and S 2 , respectively, of pipelines P 1  and P 2  and are securable to portions of the ground, or load-bearing strata, G, beneath the pipelines P 1  and P 2 . Each anchoring device ( 20   a ,  20   b ,  20   c ) is similar in construction, as illustrated for example in  FIG. 2 , and includes an extendible anchor rod ( 21   a ,  21   b ,  21   c ), the components of which are illustrated in more detail in  FIGS. 6 and 7 , a tie-down attachment member ( 40   a ,  40   b ,  40   c ) which itself comprises a feature of the present invention and is illustrated in detail in  FIGS. 9-11  and a retainer section ( 45   a ,  45   b ,  45   c ), shown in detail in  FIGS. 6A and 6B . 
     As shown in  FIG. 8 , strap  50  ( 50   a  and  50   b  in  FIG. 1 ), preferably have an endless loop configuration and include a pair of opposite end portions  51   a  adapted to be coupled to the anchoring devices ( 20   a ,  20   b ,  20   c ) and a pair of main portions  51   b  extending between and interconnecting the opposite portions  51   a . Each endless strap  50  is adapted to be laid over the top of a pipeline and to extend substantially transversely to and downwardly past the opposite lateral sides of the pipeline to the opposite portions  51   a  of the endless strap  50 . Further, an optional covering, or coating,  52 , shown in  FIG. 8 , can be provided over the entire length, or substantially the entire length, of strap  50 . Covering, or coating,  50 , is preferably polyester, which protects the straps  50  from deterioration due to ultraviolet radiation and other environmental conditions, but other materials exhibiting similar properties can also be used. 
     As shown in the exemplary embodiment of  FIG. 1 , two straps  50   a  and  50   b  are respectively provided over the tops, T 1  and T 2 , of pipelines P 1  and P 2 . The tie-down attachment members ( 40   a ,  40   b ,  40   c ) of each of the anchoring devices ( 20   a ,  20   b ,  20   c ) are adapted to receive and retain the endless straps  50   a  and  50   b  at the opposite portions  51   a  thereof.  FIG. 3  illustrates how two respective straps  50  engage a tie-down attachment member in accordance with the present invention, such as the tie-down attachment members ( 40   a ,  40   b ,  40   c ) shown in  FIG. 1  and tie-down attachment member ( 40 ) shown in  FIG. 2 . Specifically, in  FIG. 3 , one respective end of each strap  50  loops around pipe portion  110  of the tie-down attachment member. One end of the strap  50  loops around the pipe portion  110  from the right side thereof and is used to retain a respective pipeline (not shown), and an end of a second strap  50  crosses the first strap  50  and loops around pipe portion  110  from the left side. The second strap  50  is used to retain a second pipeline (also not shown). Referring again to  FIG. 1 , each anchor rod is adapted to be screw-driven into the ground G and to mount to a respective tie-down attachment member ( 40   a ,  40   b ,  40   c ). 
     In the embodiment of  FIG. 1 , anchor rods ( 21  in  FIG. 2 ) of each respective anchoring device ( 20   a ,  20   b ,  20   c ) includes respective opposite upper and lower end portions ( 22   a ,  22   b ,  22   c ) and ( 23   a ,  23   b ,  23   c ). Each of these components is shown separately in  FIGS. 4 and 5 . In particular, the upper end portion ( 22 ) of each anchor rod, as shown in  FIG. 5 , has opposite upper and lower ends  220   a  and  220   b , respectively. The upper end portion  220   a  may have a substantially solid metal, such as steel, body and a generally rectangular shape in transverse cross-section, although other suitable cross-sectional shapes are also contemplated within the scope of the invention, such as polygonal and circular. Each upper end portion  22  has a transverse opening  24  formed adjacent to its upper end  220   a  and a tubular section  25  formed at its lower end  220   b . The tubular section  25  has a substantially rectangular configuration in transverse cross-section and is open at its lower end  25   a  and defines a pair of opposite holes  26  for receiving a suitable fastener, such as bolt  27  shown in  FIG. 5 . 
     The lower end portion ( 23 ) of each anchor rod  21 , as shown in  FIG. 4 , also has respective opposite upper and lower ends  230   a  and  230   b . In one exemplary embodiment, the lower end portion  23  of each anchor rod  21  may have a substantially solid metal, such as steel, body and a generally rectangular shape in transverse cross-section, although other suitable cross-sectional shapes are also contemplated within the scope of the invention, such as polygonal and circular. According to this embodiment, the lower end portion  23  of each anchor rod  21  has a transverse opening  28  formed adjacent to its respective upper end  230   a  and a wedge-shaped point  29  formed at its respective lower end  230   b.    
     The upper end  230   a  of the lower end portion  23  engages with the tubular section  25  of the upper end portion  22 . Upon this engagement, hole  26  in upper end portion  22  and hole  28  in lower end portion  23  align with each other such that the suitable fastener  27 , such as a bolt, can pass therethrough to secure the upper and lower end portions  22  and  23  to one another. According to a further embodiment of the invention, a plurality of upper end portions  22  are attached to one another by securing fastener  27  of one section through hole  24  of another section to provide a variable length anchor device. For example, upper end portions  22  are provided in varying length sections, such as 3, 5, 7 and 10 feet, and one or more section is used to provide the needed length to accommodate the respective pipeline diameter and terrain to which the pipeline is to be retained. Lower end portion  23  is then attached to the upper section  22 . 
     The lower end portion  23  of each anchor rod  21  can be driven into the ground G ( FIG. 1 ) or other load-bearing strata. The wedge-shaped point  29  reduces the amount of force required to insert the lower end portion  23  of each anchor rod  21  into the ground G. The lower end portion  23  of the anchor rod  21  also has a helical screw  30  formed thereon for assisting in driving the anchor rod  21  into the ground and retaining the lower end portion  23  within the ground G as the anchor rod  21  is rotatably inserted, or screwed, into the ground G. As shown in  FIG. 4 , for example, a helical screw  30  in accordance with one exemplary embodiment of the invention has one or more substantially circular helical bearing plate that have individual diameters that generally decrease from a location X in the proximity of hole  28  to a location Y in the proximity of point  29 . 
     According to a further exemplary embodiment, the tie-down attachment member is slidably and rotatably engaged with the upper-most section of anchor rod. Further, as mentioned previously, straps such as strap  50  in  FIG. 3  are attached to the tie-down attachment member to retain the respective pipeline against buoyancy forces. 
     As shown in  FIGS. 9-11 , each tie-down attachment member  40  includes a body portion attached to a pipe portion  110 . The body portion includes two opposing sidewall structures  101  attached on respective sides of a curved center plate  102 . According to this embodiment, sidewalls  101  and center plate  102  are made of ⅜-inch thick steel and are rectangular. However, a skilled artisan would understand that other materials, such as aluminum, as well as other shapes, such as circular or polygonal, and material thickness, could also be used without departing from the scope of the invention. 
     As shown more clearly in  FIGS. 10 and 11 , center plate  102  comprises a single, substantially flat, piece of metal material bent upward in an inverted “C”, or saddle-shape, configuration. Center plate  102  has two substantially flat and preferably smooth outer sections  105  respectively flanking a bend section  106  located midway between the two outer sections  105 . Outer sections  105  form an angle, Z, with respect to the bottom edge of sidewalls  101 , as shown in  FIG. 9 , which is greater than or equal to 60 degrees and, which is preferably between 60 and 90 degrees. More particularly, the greater the value of angle Z, the more potential stress on straps  50  ( FIG. 2 ) is avoided. 
     For example, referring to in  FIG. 1 , if straps  50   a  and  50   b  stretch under the strain of pipes P 1  and P 2  rising due to buoyancy forces on the pipes, the greater the force between the strap and the top edge, for example  105 A in  FIG. 9 , of center plate  102 . Accordingly, to reduce the strain between the strap and the tie-down attachment member  40 , the smooth outer sections  105  of the center plate  102  are bent upwards, i.e., in the same direction as the buoyancy forces, to an angle sufficient to minimize the stress between the straps and the upper-most portion  105 A of the center plate  102 . 
     Further, according to this embodiment, a hole  107  is formed within center plate  102  to accommodate pipe portion  110  which is made of a 9-inch long section of steel pipe having an outside diameter of 2⅞ inches; however, other lengths and diameter pipes can also be used. According to this embodiment, all of the components of tie-down attachment member  40  are permanently secured to each other using an attachment method such as welding. 
     Tie-down attachment member  40  is attached to the upper-most section of the anchor rod  21 , as shown in  FIG. 1 , by sliding the pipe portion  110  over the outside surface of anchor rod  21  and attaching a retainer section  45  to the top of anchor rod  21 . Retainer section  45  can be any device that retains tie-down attachment member  40  from sliding off the top of anchor rod  21 . According to the exemplary embodiment illustrated, however, retainer section  45  is similar in construction to the lower portion of upper end portion  22  of anchor rod  21 . That is, as shown for example in  FIGS. 6A and 6B , retainer  45  according to this embodiment includes a tubular section  325  with a substantially rectangular configuration in transverse cross-section and which is open at its lower end  325 A and which defines a pair of opposing holes  326  for receiving a suitable fastener, such as bolt  327 . In the embodiment of  FIG. 1 , after tie-down attachment  40  is placed over the top of anchor rod  21 , retainer  45  is placed on top of the upper end portion  22   a  of the anchor rod and holes  326  in the retainer and hole  24  ( FIG. 5 ) are aligned and fastener  327  is placed through the holes to attach retainer  45  to the anchor rod  21 . 
     Further, as shown for example in  FIG. 7 , the inside diameter  103  (as opposed to outside diameter  104 ) of pipe portion  110  is larger than the outer-most surface  105  of the upper section of anchor rod  21 . Accordingly, once installed, tie-down attachment member  40  is free to rotate as much as  360  degrees about anchor rod  21  because the friction between pipe portion  110  and anchor rod  21  is minimal. Additionally, this minimal friction also permits tie-down attachment member  40  to freely slide vertically up and/or down on anchor rod  21  between the ground G and retainer  45 . For example, referring again to  FIG. 1 , upon experiencing upward buoyancy forces one or both of pipes P 1  and P 2  rise, forcing straps  50   a  and/or  50   b  to pull their respective tie-down attachment members  40  upwards along respective anchor rods  21  until the tie-down attachment members reach the retainers  45 , at which time no further upward movement of the pipes occurs. 
     Further, if it is desired to reduce or remove the vertical distance by which the respective pipes are permitted to traverse, shown respectively as Y 1  and Y 2  for pipes P 1  and P 2  in  FIG. 1 , a driving device (not shown) can be attached to a retainer  45  and the respective anchor rod  21  can be further driven into the ground G. Because the tie-down attachment member  40  is free to rotate about its respective anchor rod  21 , the additional rotational driving force is not translated to the tie-down attachment member  40  and, thus, no detrimental forces are exerted on the pipes, other than the desired downward force applied as the tie-attachment member and the strap attached thereto are driven downward. 
     While various aspects of the present invention have been particularly shown and described with reference to the exemplary, non-limiting, embodiments above, it will be understood by those skilled in the art that various additional aspects and embodiments may be contemplated without departing from the spirit and scope of the present invention. For example, a skilled artisan would understand that various different types of materials can be used to manufacture the tie-down attachment members and different sizes and dimensions are also contemplated depending on the sizes of the pipes retained. Furthermore, it is also contemplated that the angle Z, shown for example in  FIG. 9 , can be smaller than 60 degrees if necessary to accommodate placing the anchor devices farther from the pipe which it is retaining. 
     It would be understood that a device or method incorporating any of the additional or alternative details mentioned above would fall within the scope of the present invention as determined based upon the claims below and any equivalents thereof. 
     Other aspects, objects and advantages of the present invention can be obtained from a study of the drawings, the disclosure and the appended claims.