Abstract:
Linear pipe recovery/lay tensioners can include one or more pivot assemblies for rotatably moving an upper track away from a lower track to facilitate placement of a pipe segment between the two tracks. In addition, or alternatively, the tensioners can include one or more hydraulic cylinders that provide flexible suspension to the upper and lower tracks so the tracks can move and rotate as necessary due to differing pipe segment shapes. In addition, or alternatively, the upper and lower tracks include one or more gripping pad having one or more gripping member that is sheathed by a compliant member until such time as the pipe segment compresses the compliant member causing the gripping member(s) to protrude from the compliant member and bite into the pipe segment. Rotation of the tracks is controlled by a hydraulic pump capable of rotating the tracks at the same rate or at different rates.

Description:
BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    The invention is directed to roller assemblies for linearly transporting one or more pipe segments, or joints, such as pipelines, and in particular, to linear pipe recovery/lay tensioners for pulling a portion of pipeline from the ocean to be recovered on an offshore lay-barge and for laying pipeline from an offshore lay-barge and onto the ocean floor. 
         [0003]    2. Description of Art 
         [0004]    Linear pipe tensioners are generally known in the art. These devices are generally installed on a ship or lay barge to facilitate laying or retrieving pipe, such as pipelines and other pipe segments. Linear pipe tensioners are designed to maintain a constant tension on the pipe while the pipes are being lowered into, or retrieved from, the sea during offshore pipe laying operations. 
         [0005]    Broadly, linear pipe tensioners consist of an upper and a lower track, each supported in a frame assembly. Pneumatically actuated squeeze bags within the track loops apply squeeze forces on the tracks holding the pipe. The tracks are driven by hydraulic motors through cage-mounted gear reducers. The upper track can be adjustable vertically for handling of various sizes of pipe. An electronics package comprising a control console and PLC operates the electronic components necessary for system operation. Pressure to track drive motors is controlled to maintain pipe tension within selected limits. 
         [0006]    Two or more linear pipe tensioners can be arranged in series to provide the desired or necessary tension in the pipeline for laying or retrieving the pipeline. 
         [0007]    In operation, generally, when an operator sets a tension value and starts the linear pipe tensioner, stepper motors mounted on the hydraulic pumps are rotated under command from the electronic control system. Greater rotation increases the volume of hydraulic fluid from the pumps to the motors. The motors then increase the amount of tension against the pipe. 
         [0008]    Load cells, mounted between the linear pipe tensioners and their bedplates, transmit a signal proportional to the amount of tension against the pipe to the electronic control system. When the signal from the load cells balances the signal from the tension, a preset circuit the stepper motors stop rotating and hold their positions. This keeps the hydraulic pumps on a stroke which produces sufficient pressure to hold the desired tension. Small movements of the lay-barge do not produce any significant change in the tension. Movements beyond a pre-set dead-band will produce changes in tension transmitted back to the control system. The tension command will become unbalanced and the control system will drive the pumps producing pressure to the hydraulic motors to bring the tension back into line. 
       SUMMARY OF INVENTION 
       [0009]    The linear pipe tensioners disclosed herein facilitate one or both of recovery of pipe segments from their locations of installation, and installation of the pipe segments in their locations of installation. In certain embodiments, the linear pipe tensioner comprise upper and lower frames, the upper frame having an upper track and the lower frame having a lower track. The upper and lower frames are pivotally connected to each other to facilitate movement of the upper frame and, thus, the upper track, between a closed position and a plurality of opened positions. Movement of the upper frame facilitates placement of a pipe segment between the upper and lower tracks. 
         [0010]    In other certain embodiments of the linear pipe tensioners, the upper and lower frames are not required to be pivotally connected, although the upper and lower frames can be pivotally connected. In these embodiments, one or both of the upper or lower tracks are operatively associated with one or more cylinders that permit vertical and/or rotational movement of one or both of upper and lower tracks. 
         [0011]    In still other embodiments of the linear pipe tensioners, the upper and lower frames are not required to be pivotally connected and the one or more cylinders are not required to be present, although one or more of these features can be included. In these embodiments, one or more gripping pads is operatively associated with either the upper or lower tracks. One or more of these gripping pads comprise a compliant member having a slot and a gripping member disposed within the first slot such that compression of the compliant member causes at least a portion of the gripping member to be exposed from the slot. In so doing, the gripping member engages a pipe segment to facilitate linear movement of the pipe segment through the linear pipe tensioners. 
         [0012]    In additional embodiments, which may or may not include one or more of the features discussed above, two drive assemblies move the tracks which, in turn, linearly move a pipe segment through the linear pipe tensioners. The two drive assemblies are operatively associated with a motor or pump and a valve. The valve facilitates placing the drive assemblies in either series or parallel such that the two drive assemblies can rotate at substantially the same rate or at different rates. In these embodiments, the structural components identified above in this Summary can also be part of the linear pipe tensioners, although they are not required. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a side view of one specific embodiment of a linear pipe tensioner disclosed herein. 
           [0014]      FIG. 2A  is a front view of the linear pipe tensioner shown in  FIG. 1 . 
           [0015]      FIG. 2B  is a front view of the linear pipe tensioner shown in  FIG. 2A  showing the top track pivoted to an open position for receiving a segment of pipe. 
           [0016]      FIG. 3  is a partial cross-sectional side view of a roller assembly of the linear pipe tensioner shown in  FIG. 1 . 
           [0017]      FIG. 4  is a perspective view of the roller assembly of  FIG. 3 . 
           [0018]      FIG. 5  is a perspective view of a gripping pad of the linear pipe tensioner shown in  FIG. 1 . 
           [0019]      FIG. 6  is a longitudinal side view of the gripping pad of  FIG. 5 . 
           [0020]      FIG. 7  is a lateral side view of the gripping pad of  FIG. 5 . 
           [0021]      FIG. 8  is a perspective view of the gripping member plate of the gripping pad of  FIG. 5 . 
           [0022]      FIG. 9  is a top view of the gripping member plate of  FIG. 8 . 
           [0023]      FIG. 10  is a partial cross-sectional view of the gripping member plate of  FIG. 8  taken along line  10 - 10  shown in  FIG. 9 . 
           [0024]      FIG. 11  is a schematic of one specific drive motor flow control system for actuating the drive assemblies of the various linear pipe tensioners disclosed herein. 
           [0025]      FIG. 12  is a schematic of another specific drive motor flow control system for actuating the drive assemblies of the various linear pipe tensioners disclosed herein. 
       
    
    
       [0026]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0027]    Referring now to  FIGS. 1-10 , in one specific embodiment linear pipe tensioner  10  includes frame  12 . In this particular embodiment, frame  12  comprises upper frame member  13  and lower frame member  14  rotatably connected to each other by pivot assembly  15 . As shown in  FIGS. 1 ,  2 A, and  2 B, pivot assembly  15  comprises two hinge members comprising pins  16  inserted through brackets  17 , and cylinder  18 . Pivot assembly  15  permits the movement of upper track assembly  20  along the trajectory of the arrow shown in  FIG. 2B  to facilitate insertion of a pipe segment (not shown) within space  30  between upper track assembly  20  and lower track assembly  40 . 
         [0028]    Although frame  12  is shown as having upper and lower frame members  13 ,  14  pivotally connected by pivot assembly  15 , it is to be understood that frame  12  is not required to have these components. To the contrary, frame  12  may be a structure that is not capable of being opened to facilitate insertion of a pipe segment. 
         [0029]    Upper track assembly  20  is operatively associated with upper frame member  13  by front axle  21  and back axle  22  which are rotatable by drive assembly  23  being operatively associated with upper track  24 . As shown in the embodiment of  FIGS. 1-10 , drive assembly  23  is directly connected to front axle  21 . Upper track  24  is disposed on a plurality of suspension assemblies  60 , front axle  21 , and back axle  22 . Discussed in greater detail below, track includes a plurality of gripping pads  75  for engaging a pipe segment to facilitate pulling the pipe segment through linear pipe tensioner  10  in a linear direction. 
         [0030]    Lower track assembly  40  is operatively associated with lower frame member  14  by front axle  41  and back axle  42  which are rotatable by drive assembly  43  being operatively associated with lower track  44 . As shown in the embodiment of  FIGS. 1-10 , drive assembly  43  is directly connected to front axle  41 . Lower track  44  is disposed on a plurality of suspension assemblies  60 , front axle  41 , and back axle  42  and includes a plurality of gripping pads  75 . 
         [0031]    Broadly, in operation of linear pipe tensioner  10 , a segment of pipe (not shown) is disposed within area  30 , such as by pulling the pipe segment linearly through area  30  or by pivoting upper track assembly  20  to the opened position shown in  FIG. 2B , disposing the pipe segment within area  30 , and then closing upper track assembly  20 . As a result, gripping pads  75  engage the pipe segment above and below the pipe segment. Drive assemblies  23 ,  43 , are activated causing tracks  24 ,  44  and move around front and back axles,  21 ,  41 ,  22 ,  42 . In so doing, the pipe segment is pulled linearly through area  30  causing the pipe segment to be removed from its installed position to its recovered position. As mentioned above, the installed position can be on the ocean floor or within an earthen formation and the recovered position can be on a lay-barge or other ocean-going vessel or on a terrestrial location such as a truck or on the ground of a worksite. 
         [0032]    In one particular embodiment, drive assembly  23  and drive assembly  43  are operatively associated with a drive motor flow control system. The drive motor flow control system permits synchronization of rotation of front axles  21 ,  41 . The simultaneous action of drive assemblies  23 ,  43  prevent one track moving faster than the other track which, in turn, prevents slippage of gripping pads  75 . By preventing slippage of gripping pads  75 , wear on gripping pads  75  and other components of linear pipe tensioner  10  are reduced. In one such embodiment, a hydraulic power unit supplies fluid to a set of rotary flow dividers or gear pumps that are coupled together by a common shaft. One rotary flow divider/gear pump feeds fluid to drive assembly  23 , and the other rotary flow divider/gear pump feeds fluid to drive assembly  43 . Coupling both rotary flow divider/gear pumps together causes rotation of both flow divider/gear pumps at the same rate. As a result, the same volume of fluid is delivered to drive assemblies  23 ,  43  providing simultaneous action of drive assemblies  23 ,  43 . Thus, front axles  21 ,  41  are rotated at the same. To reduce the likelihood of cavitation when fluid is pumped in the opposite direction through the rotary flow divider/gear pumps, a hot fluid shuttle circuit is disposed between the two rotary flow divider/gear pumps. 
         [0033]    In another particular embodiment, as illustrated in the schematics of  FIGS. 11-12 , the drive motor flow control system includes a transfer valve disposed between the hydraulic power unit which supplies fluid to the rotary flow divider/gear pumps. The transfer valve permits the flow of fluid to the rotary flow divider/gear pumps to be changed from being in series ( FIG. 11 ) to being in parallel ( FIG. 12 ), and vice versa. When placed in the “series” mode, the fluid flows from the hydraulic power unit through the transfer valve, to one of drive assemblies  23 ,  43 , to the other of drive assemblies  23 ,  43 , back through the transfer valve to the hydraulic power unit, as illustrated by the clockwise and counterclockwise arrows between the transfer valve, the upper drive assembly  23 , and the lower drive assembly  43  shown in  FIG. 11 . For example, the fluid can flow from the hydraulic power unit through the transfer valve, to drive assembly  23 , to drive assembly  43 , back through the transfer valve (counterclockwise in  FIG. 11 ), and to the hydraulic power unit. Alternatively, the fluid can flow from the hydraulic power unit through the transfer valve, to drive assembly  43 , to drive assembly  23 , back through the transfer valve (clockwise in  FIG. 11 ), and to the hydraulic power unit. Thus, the “series” mode functions as discussed above to provide synchronization of rotation of front axles  21 ,  41  such as during pipe recovery operations. 
         [0034]    When placed in the “parallel” mode, as shown in  FIG. 12 , the fluid flows from the hydraulic power unit through the transfer valve and to drive assemblies  23 ,  43  simultaneously before being transported back through the transfer valve to the hydraulic power unit. Thus, the “parallel” mode allows the two drive assemblies  23 ,  43  to operate independently of each other to provide rapid response and speed from both drive assemblies  23 ,  43  when demanded such as during pipe lay operations. 
         [0035]    To facilitate switching between the “parallel” mode and the “series” mode, the transfer valve is operatively associated with an electronics package. 
         [0036]    Referring now to  FIGS. 3-4 , roller assemblies  60  each comprise hydraulic cylinder  61  having hydraulic piston  62  disposed therein. Hydraulic cylinders  61  have hydraulic fluid (not shown) disposed therein. As shown in  FIG. 3 , hydraulic cylinders  61  comprise upper chamber  70  and lower chamber  71  divided by divider  72 . Divider  72  is in sliding engagement with the inner wall surfaces of upper and lower chambers  70 ,  71 . Aperture  73  is in fluid communication with lower chamber  71 . As shown in  FIG. 3 , aperture  73  is disposed in the bottom of hydraulic cylinder  61 . It is to be understood that aperture  73  is not required to be disposed in the bottom of hydraulic cylinder  61 . Connected to aperture  73  is a hose (not shown) that places aperture  73  and, thus, lower chamber  71 , in fluid communication with a reservoir (not shown). Each hose can be connected to a separate reservoir. Alternatively, the hoses can be connected to a manifold on the reservoir. Thus, lower chambers  71  function as accumulators to facilitate movement of hydraulic piston  62  within hydraulic cylinder  61 . 
         [0037]    Roller assemblies  60  also comprise swivel members  63  to facilitate rotational movement of piston  62 , roller carriage  64  pivotally connected to an upper end of piston  62  for pivotal movement of roller carriages  64  and, thus, rollers  66 . Roller carriages  64  are pivotally connected to each other such as by bar  67  having slots  68  for receiving pins  69  that are secured to roller carriages  64 . 
         [0038]    In the arrangement shown in  FIGS. 3-4 , cylinders  61  and pistons  62  provide up and down movement of rollers  66 , swivel members  63  provide rotational movement of rollers  66 , and roller carriages  64  and bar  67  provide longitudinal pivoting of rollers  66  between adjacent roller carriages  64 . Therefore, this arrangement provides tracks  24 ,  44  to be compliant or adjustable as the pipe segment linearly moves through linear pipe tensioner  10  so as to adjust for any changes in shape or outer diameter size of the pipe segment caused by such items as cement, biological growth, anodes, valves, bent portions of the pipe segment, and the like as those portions of the pipe segment pass through linear pipe tensioner  10 . 
         [0039]    Referring now to  FIGS. 5-10 , in one embodiment of gripping pads  75 , gripping pad  75  comprises gripping member plate  80 , top plate  90 , and compliant member  92 . Gripping member plate  80  comprises bottom surface  81 , top surface  82  (best shown in  FIGS. 8-10 ), two longitudinal side surfaces  83 , and two lateral side surfaces  84 . In the embodiment of  FIGS. 5-10 , top plate  90  includes shoulder  91  running the length of one of the two longitudinal side surfaces of top plate  90  to facilitate placement of gripping pad  75  on tracks  24 ,  44  at the desired or necessary orientation to facilitate gripping pad  75  engaging the pipe section so that the pipe section can be pulled through linear pipe tensioner  10 . Top plate  90  also includes one or more slots (not shown) for receiving gripping members, such as gripping members  100  discussed in greater detail below. 
         [0040]    Disposed on an upper surface of top plate  90  is compliant member  92 . Complaint member  92  can be bonded or molded to the upper surface of top plate  90 . Complaint member  92  can be formed out of any material that, when placed under load, can compress and, when the load is removed, return toward its original configuration. In one particular embodiment, complaint member  92  is formed out of a resilient, elastomeric or polymeric material of a commercially available type that will withstand high temperatures that occur in some wells. Preferably, the durometer hardness of material forming the complaint member  92  is in the range from about 60 to 100 Shore A and more particularly from 80 to 90 Shore A. In one embodiment, the durometer hardness is about 85 Shore A. 
         [0041]    Compliant member  92  comprises a bottom surface that is engaged with the upper surface of top plate  90 , top surface  93 , two longitudinal side surfaces  94 , and two lateral side surfaces  95 . Complaint member  92  includes one or more slots  96  for receiving gripping members  100  (discussed in greater detail below with respect to  FIGS. 8-10 ). In the embodiment of  FIGS. 5-10 , compliant member  92  also includes grooves  97 ,  98  to permit access to two of the fastener openings  110  ( FIGS. 8-9 ) disposed through top plate  90  and gripping plate member  80  to facilitate securing gripping pads  75  to tracks  24 ,  44 . In the embodiment shown in  FIGS. 5-10 , top surface  93  of compliant member  92  also includes beveled portion  99  to facilitate gripping the pipe (not shown). 
         [0042]    Referring now to  FIGS. 8-10  gripping member plate  80  comprises three identical gripping members  100 . Gripping members  100  comprise an upper end  101 , a lower end  102 , and length  104 , width  106 , and a height  108 . Upper end  101  includes chamfers  103  to provide a point at upper end  101 . As shown in the specific embodiment of  FIGS. 8-10 , gripping members  100  are rectangular-shaped and disposed at non-right angles relative to both the longitudinal axis and the lateral axis of gripping member plate  80 . 
         [0043]    Length  104 , width  106 , and height  108  may be any measurement desired or necessary to facilitate gripping the pipe segment when gripping pad  75  engages the pipe segment. As shown in  FIG. 5 , in this particular embodiment height  108  is such that gripping members  100  do not protrude out of slots  96  of compliant member  92  when gripping pad  75  is not engaged with the pipe segment. In one particular embodiment, gripping members  100  are rectangular-shaped having length  104  in the range from 1.75 inches to 2.25 inches, width in the range from 0.60 inches to 0.85 inches, and height  108  in the range from 2.5 inches to 2.75 inches. In specific embodiments, upper ends  101  of gripping members  100  do not protrude out of slots  96  to facilitate protecting upper ends  101  from being damaged, prior to gripping pad  75  engaging a pipe segment and compliant member  92  being compressed to expose upper ends  101  of gripping members  100 . In certain of these embodiments, the height of slots  96  can be approximately 10-15% longer in length as compared to height  108 . Thus, in embodiments where height  108  is in the range from 2.5 inches to 2.75 inches, slots  96  have a height in the range from 2.75 inches to 3.1625 inches. 
         [0044]    As mentioned above, gripping member plate  80  and top plate  90  include a number of fastener holes  110  for receiving fasteners (not shown) to secure top plate  90  to gripping member plate  80  and to secure gripping member plate  80  to tracks  24 ,  44 . 
         [0045]    Although gripping member plate  80  is shown as having three identical gripping members  100 , it is to be understood that the number of gripping members  100  and the shapes, and sizes of gripping member  100  is not required to be identical. To the contrary, each gripping member  100  can be different in shape and size as compared to the other gripping members  100 . In addition, the number of gripping members  100  can be any number desired or necessary to provide sufficient gripping engagement with the pipe segment disposed within area  30  of linear pipe tensioner  10 . For example, a single gripping member  100  may be disposed on gripping member plate  80 . Alternatively, one or more of the gripping members  100  can be cylindrically shaped with a pointed tip. In addition, the tip(s) of each gripping member  100  can comprise angled spikes or other configurations and can be formed out of a hardened material, such as carbide, to further facilitate gripping the pipe segment. 
         [0046]    Broadly, in one specific embodiment of an operation using the linear pipe tensioners disclosed herein, a pipe segment is disposed between the upper and lower tracks by pivoting the upper track from a closed position to an opened position. Upon being disposed between the upper and lower tracks, the drive assemblies are actuated either in parallel mode or series mode as discussed above. In so doing, the pipe segment, which can be a series of pipe joints forming a pipeline, is moved linearly through the linear pipe tensioner to either recover pipeline from the ocean or to lay pipeline on the ocean floor. During operation of certain of the linear pipe tensioners, one or more roller assemblies operatively associated within the upper track and/or the lower track, move, pivot, and/or rotate to accommodate fluctuations in the outer diameter of the pipeline being moved through the linear pipe tensioner. In addition, gripping pads having one or more gripping members disposed through a compliant member engage the pipeline, such as due to the compression of the compliant member, to facilitate linear movement of the pipeline through the linear pipe tensioner. 
         [0047]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the gripping members are not required to have sharpened upper ends, nor are they required to be rectangular-shaped as shown in the Figures. Instead, the gripping members can be spikes with or without sharpened upper ends, or any other shape desired or necessary to provide adequate gripping of the pipe segment. In addition, as discussed above, the gripping members  100  are not required to be identical in shape or size and can be as few as one or as many as desired or necessary to facilitate gripping of the pipe segment. Further, the pivot assembly is not required to include a hydraulic cylinder, but instead can comprise a swivel member such as a ball joint, or other hinge assembly. Moreover, the roller carriages can be pivotally connected to one another using devices other than the bar and pin connection shown in the Figures, such as ball joints and the like. Additionally, each roller carriage can include as few as one roller or three or more rollers instead of the two rollers shown in the Figures. Further, the gripping pads are not required to include both a top plate and a gripping member plate. To the contrary, a single plate can provide the gripping members and can receive the complaint member. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.