Abstract:
A system and method for securely cradling a subsea pipeline is claimed that lands on one side of the pipeline, is embedded into the sea floor, reaches under the pipeline, positions the cradling structure, and then lifts the pipeline. The system typically comprises a gravity driven pile based device, comprising a pile tower, a roller carriage assembly, and a jacking assembly that engages the roller carriage assembly and pile tower rails.

Description:
RELATION TO OTHER APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/632,981 filed Oct. 1, 2012, currently allowed. 
    
    
     FIELD OF THE INVENTION 
     The disclosed inventions relate to a tool for securely cradling a subsea pipeline. More specifically, the disclosed inventions relate to a tool for securely cradling a subsea pipeline which land on one side of the pipeline and embed into the sea floor near the pipeline. 
     BACKGROUND 
     Subsea pipelines need to be elevated with respect to the sea floor proximate the pipeline on occasion for numerous reasons. It is often advantageous for such a tool to be capable of securely cradling the pipeline. 
    
    
     
       DRAWINGS 
       The various drawings supplied herein describe and are representative of exemplary embodiments of the invention and are described as follows: 
         FIG. 1  is a view in partial perspective of an exemplary embodiment of the device, and  FIG. 1A  is a view in partial perspective of a detail of the device; 
         FIG. 2  is a view in partial perspective of an exemplary embodiment of the roller arm assembly, and  FIGS. 2A-2B  are views in partial perspective of details of the exemplary embodiment of the roller arm assembly; 
         FIG. 3  is a top-down view in partial perspective of an exemplary embodiment of the roller assembly; 
         FIG. 4.1  and  FIG. 4.2 , collectively referred to herein as  FIG. 4 , are top-down views in partial perspective of an exemplary embodiment of the roller assembly, and  FIGS. 4A-4F  are view in partial perspective of details of the exemplary embodiment of the roller assembly; 
         FIG. 5  is a view in partial perspective of an exemplary embodiment of the jacking assembly, and  FIGS. 5A-5G  are views in partial perspective of details of the exemplary embodiment of the device; 
         FIG. 6  is a view in partial perspective of an installed deployment of an exemplary embodiment of the device; 
         FIG. 7  is a view in partial perspective of a device embedded in the sea floor with the roller arm assembly extended underneath a pipeline in an exemplary embodiment of the device; 
         FIG. 8  is a view in partial perspective of a device embedded in the sea floor with the roller arm assembly extended underneath a pipeline and the cylinder extended in an exemplary embodiment of the device; 
         FIG. 9  is a view in partial perspective of a device embedded in the sea floor with the roller arm assembly engaged with and supporting the pipeline in an exemplary embodiment of the device; and 
         FIG. 10  is a view in partial perspective of a device embedded in the sea floor with the cylinder and lead screw assemblies removed in an exemplary embodiment of the device. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring generally to  FIGS. 1 and 6 , in general, in various embodiments device  1  is a tool that lands on one side of a pipeline, e.g. pipeline  100  ( FIG. 6 ), and embeds into the sea floor, usually using gravity. Device  1  comprises components that reach under pipeline  100  in order to position a cradling component of device  1 . Device  1  provides a length of vertical adjustability for pipeline  100  and supports a load applied by the weight of pipeline  100 . The cradle must provide sufficient surface area to avoid excessive stress concentration on pipeline  100 . In preferred embodiments, the main structure of device  1  is fabricated out of 16″ OD, 1″ wall thickness riser pipe. In various embodiments, device  1  is capable of being sent overboard from a vessel in a horizontal position and deployed subsea in a vertical position. 
     In general, device  1  comprises three major subassemblies: pile tower  10 , roller carriage assembly  30 , and jacking assembly  70 . 
     Pile tower  10  is the main structural component of device  1 . In typical configurations it comprises three equally spaced legs  15 . In an embodiment, legs  15  are 16″ OD riser pipes around 57 feet in length. Preferably, legs  15  comprise API X70 steel with the ends, other than I-beams  111  ( FIG. 2A ) and cylinder mounting slots  112  ( FIG. 5A ), made of ASTM A36 steel. I-beams  111 , rails  3  ( FIG. 5E ), and cylinder mounting slots  112  are typically made from grade 70 steel. 
     The top of pile tower  10  is typically tied together with three gussets which are themselves tied to a short section of middle pipe which is raised above the level of legs  15 . A three inch thick pad-eye may protrude from the middle pipe and allow for a vertical deployment of pile tower  10 . 
     Skirt  20  comprises one or more skirts  22  connected to the bottom of legs  15 . Skirt  20  also provides a bearing surface for embedment into seabed  110  ( FIG. 6 ). In a preferred embodiment, skirt  20  comprises three skirts  22 , each of which measures around 1″ thick by around 55″ wide by around 300″ tall. Skirts  22  each have one or more holes to vent seawater during embedment, typically two holes having around a 12″ diameter. Scale  11  may be present to measure a level of embedment, e.g. starting at 5 feet above a mud line. In typical embodiments, skirts  22  are stitch welded to legs  15 . 
     In some embodiments, a small mud mat  21  provides surface area for resistance during embedment. Mud mat  21  typically sits above skirt  20  and extends out past legs  15 . Mud mat  21  has vent holes and, in certain embodiments, provides around at least  4250  square inches of surface area. In certain embodiments, one or more anodes are welded to the top of mud mat  21  to provide cathodic protection, e.g. ten twenty-nine pound anodes  27 . 
     One or more rails  14 , which in a preferred embodiment comprise gear tooth rails, are disposed along the outside of at least two legs  15  of pile tower  10  to provide one part of a ratcheting mechanism. Rails  14  are typically around two-inches wide and extend from mud mat  21  up to the top of pile tower  10 . One of legs  15  may comprise scale  11  which may be painted on an outer surface of leg  15 . Scale  11  may vary according to the desired height of pile tower  10  and usually measures an elevation above mud mat  21 . 
     The top of pile tower  10 , e.g. landing funnel  80 , may be angled toward the center to provide a landing “funnel” for a weighted follower. 
     Lifting bail  2  ( FIG. 1A ) may also be present, attached to the bottom of pile tower  10 , to facilitate horizontal lifting and overboarding operations. 
     In some embodiments, pile tower  10  is coated in three coat epoxy, except for a portion of pile tower  10  below a certain foot mark on  21 , which is left uncoated. 
     Roller carriage assembly  30  is the component that physically contacts pipeline  100  ( FIG. 6 ). Roller carriage assembly  30  comprises three major subassemblies: carriage weldment  40 , lead screw drive assembly  60 , and roller arm assembly  50 . 
     Carriage weldment  40  is a load-bearing part and typically comprises three or more plates  31 , which are preferably 18″ ID rolled plates, which are tied together with top plate  34  and bottom plate  35 . Two rolled plates  31  comprise slots and channels  36  on their respective sides to allow rails  14  to pass through rolled plates  31 . Rails  3  ( FIG. 5E ) mounted to bottom plate  35  secure a sliding roller frame  54  to carriage weldment  40 . 
     Latch mount plates  4  ( FIG. 5A ) on top of each channel  36  act as mounting points for latches  33 . A smaller hole  113  ( FIG. 5 b   ) on each of latch mount plates  4  allows for a lockout pin (not shown in the figures) to be installed which overrides the ratcheting mechanism. 
     Two slotted cylinder plates  112  ( FIG. 5A ) are mounted on top of carriage weldment  40 . Cylinder  114  ( FIG. 5 ) slides into slots  115  ( FIG. 5D ) in slotted cylinder plates  112 . 
     Lead screw drive assembly  60  typically comprises a hydraulically powered unit, e.g. motor  63 , that drives roller arm assembly  50  back and forth along an axis defined by roller frame  54 . In preferred embodiments, lead screw drive assembly  60  is able to be removed subsea to extend its life. Motor  63  is preferably a 240 cc hydraulic motor which is coupled to lead screw  61  which can vary in length as needed, e.g. from around 1.5 inches to around 5 inches, with a typical travel of around 59 inches. 
     Motor mounting frame  6  ( FIG. 4B ) houses a docking probe receptacle,  17 H dual port manifold  7  ( FIG. 5G ), and motor  63 . The docking probe receptacle interfaces with the docking probe on the carriage. Lead screw  61  nut is flanged and is attached to a drive plate. The drive plate interfaces with slots on the roller frame in order to drive it back and forth. Two stainless rods running the length of the screw prevent the drive plate from rotating while the screw is rotating. The  17 H manifold provides an ROV interface for driving roller arm assembly  50 . 
     Roller arm assembly  50  slides in and out of carriage weldment  40  on roller frame  54 . Lead screw drive assembly  60  is removable and interfaces with carriage weldment  40  and roller arm assembly  50  in order to drive roller arm assembly  50  forward and backward with respect an axis defined by carriage weldment  40 . Latches on the sides of carriage weldment  40  interface with the gear rack in order to perform a one-way ratcheting function. Two ROV operable pins on top of carriage weldment  40  allow for the cylinder to be removed subsea. One  725  pound anode is welded to the top of carriage weldment  40  and provides cathodic protection for the carriage, as well as pile tower  10 . UHMW strips line the inside of each of the three rolled plates of the carriage. This reduces friction and eliminates the possibility of carriage weldment  40  binding up while being lifted under load. 
     A set of rollers  52  is mounted to roller frame  54 , which typically comprises a set of cantilevered I-beams, and roller frame  54  is typically mounted to carriage weldment  40  to support pipeline  100 . A hydraulic motor and lead screw are used to drive the I-Beams back and forth. Latch pawls interface with the gear teeth on pile tower  10  to perform a one-way ratcheting action. 
     Roller box assembly  50  defines a pipeline interface and allows for free axial movement of pipeline  100  ( FIG. 6 ) due to expansion via three rollers  52 ,  53 . Roller arm assembly  50  comprises roller frame  54 , typically a set of matching I-beams, slotted drive mount  9  ( FIG. 4C ), and roller box assembly  59 . 
     In embodiments, roller frame uses a set of I-beams that ride along rails  3  ( FIG. 5E ) in carriage assembly  40 . 
     Drive mount  9  is typically bolted to the back of roller frame  54  and accepts drive plate  116  ( FIG. 4A ) on lead screw drive assembly  60 . Machined plate  117  ( FIG. 4D ) rides on top of roller frame  54  and houses the bearing and hub for roller box assembly  59 . 
     Roller box assembly  59  contains typically contains two or more rollers  52 ,  53 , preferably three rollers  52 ,  53  as well as mounting plates  118  ( FIG. 4D ), hub  119  ( FIG. 4E ) (which can be a pivoting base), and bearings  120  ( FIG. 4F ). Two outside rollers  52  match the radius of pipeline  100  ( FIG. 6 ) and extend up to three inches below the centerline of pipeline  100 . Middle roller  53  matches the radius of pipeline  100  but does not extend up the side of pipeline  100 . Rollers  52 ,  53  are typically disposed about stainless steel axles (not specifically shown in the figures). Rollers  52 ,  53  are held together with two mount plates  118  ( FIG. 4D ), which preferably comprise bronze bushings for bearings. 
     A pivoting base  119  ( FIG. 4E ) of roller box assembly  50  allows rollers  52  to dynamically conform (pitch) to the actual pipeline  100  position, thus ensuring an equal distribution of weight on all three rollers  52 ,  53  at all times. 
     The hub weldment supports the rollers  52  and has a bronze bearing cup around it to reduce friction. Roller box assembly can usually pivot up and down, as well as yaw side-to-side, but cannot roll side-to-side. 
     The roller shafts and hub typically comprise  316  stainless steel. The surfaces of rollers  52 ,  53  typically comprise 90 durometer polyurethane. 
     Jacking assembly  70  comprises jacking frame  77 , latches  72 , two ROV operable pins  74 , and two anodes  121  ( FIG. 5F ) and is used to raise roller carriage assembly  30 . Its “inchworm” hydraulic lifting mechanism is typically completely removable and comprises a hydraulic lifting mechanism and lateral adjustment hydraulic motor-driven screw-drive mechanism which allows for removal for ease of repairs and preservation/storage for future deployment/adjustments as required. 
     Jacking frame  77  comprises two rolled plates  71 , which act as interfaces for rails  14 , connected by I-beam  78 . Rolled plates  71  slide up and down along rails  14 . Channels  79  in the sides of rolled plates  71  allow clearance for rails  14  on pile tower  10 . Holes  79   a  in each channel  79  allow for lockout pins (not shown in the figures) to be installed in order to set the location of jacking frame  77  relative to legs  15 . 
     Mounting plates (not shown in the figures) may be used for mounting one-way latches  72 . The mounting plates may also comprise a smaller secondary hole (not shown in the figures) which can be used to unlock and override the one-way ratcheting feature. 
     Two slotted plates  112  ( FIG. 5A ) on the bottom side of I-beam  79  provide a mounting location for cylinder  114  ( FIG. 5 ). 
     Jacking frame  77  also comprises two threaded bosses on the front in order for a continuity pin (not shown in the figures) to be installed. 
     Two  725  pound anodes  121  ( FIG. 5F ) are attached to the back of jacking frame  77  to provide cathodic protection for jacking frame  77  and pile tower  10 . 
     Jacking frame  77  typically uses the same one-way latch pawls  72  as does roller carriage assembly  30 . 
     Cylinder assembly  121  ( FIG. 5F ) is used to alternately raise jacking frame  77  and roller carriage assembly  30 . ROV operable pins allow for removal of cylinder  114  ( FIG. 5 ). Cylinder assembly  122  ( FIG. 5G ) consists of cylinder  114  and hydraulic control panel  123  ( FIG. 5G ). Cylinder  114  typically has a bore of around 5 inches and with 2 feet of total stroke. In preferred embodiments, cylinder  114  is rated for up to 55,000 pounds of force when extending and 45,000 pounds when retracting. 
     Cylinder  114  ( FIG. 5 ) is typically fitted with trunion nuts  124  ( FIG. 5G ) to allow it to be installed and removed from slotted plates  112  ( FIG. 5A ) on carriage weldment  40  and jacking frames  77 . Hydraulic control panel houses a  17 H dual port manifold, as well as a 5000 psi pressure gauge. The gauge can be used to roughly estimate the weight of the load being lifted. The  17 H manifold allows for ROV control of the cylinder. 
     In preferred embodiments, rotating components comprise 45 ksi nickel aluminum bronze; pins, rotating shafts, or areas where corrosion resistance is important comprise  316  stainless steel; and rolled plates which ride up and down legs  15  comprise ultra high molecular weight polyethylene (“UHMW”). 
     In the operation of various embodiments, referring additionally to  FIGS. 6-9 , after device  1  is embedded into sea floor  110 , an ROV will actuate motor  63  which will turn lead screw  61 , thus extending roller box assembly  59  until rollers  52 , 53  are directly under pipeline  100 . The ROV will then swivel roller box assembly  59  until roller box assembly  59  is axially aligned with pipeline  100 . The ROV will then actuate cylinder  114  ( FIG. 5 ) in order to extend it and thereby extend cylinder  114 . One-way latches  33  on carriage weldment  40  will keep carriage weldment  40  from moving down, while one-way latches  72  on jacking frame  77  allow jacking frame  77  to move upward. Once the cylinder is fully extended, the ROV will then retract the cylinder. The cylinder will retract. The one-way latches will keep jacking frame  77  from moving down, while the one-way latches on carriage weldment  40  will allow carriage weldment  40  to be pulled up by the cylinder. This process is repeated until pipeline  100  is at the desired height. The ROV will then install pins in carriage weldment  40  and jacking frame  77  to fix its position. The ROV will install continuity pins in the  5  threaded bosses on carriage weldment  40  and jacking frame  77 . The ROV will then remove cylinder assembly  122  ( FIG. 5G ) as well as lead screw drive assembly  60 . 
     During lifting operations, pile tower  10  will be lifted by a two-part sling via a padeye at the top of pile tower  10 , and a lifting bail at the bottom of pile tower  10 . A 60° sling angle will be used when lifting. This will result in roughly 35,000 pounds of force on each lifting eye. During transport, pile tower  10  will be laid on deck horizontally. Device  1  will lay with its pipeline-facing side facing down on the deck. Timbers or other blocks will be laid under pile tower  10  to raise the structure slightly off of the deck. The 60,000 pound weight of device  1  will rest on these timbers. 
     It will be understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as recited in the appended claims.