Patent Publication Number: US-8109071-B2

Title: Line structure for marine use in contaminated environments

Description:
RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Patent Application Ser. No. 61/127,881 filed May 16, 2008, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to lines for use in marine environments and, more particularly, to lines designed for use in applications where at least a portion of the line is in a contaminated environment such as on or below the surface of the sea floor. 
     BACKGROUND 
     The term “mud line” is conventionally used in the petroleum industry to refer to the boundary between earth and water. An anchor assembly used as part of an offshore anchoring system is typically submerged in the silt and mud defining the mud line at the bottom of the body of water. Conventional anchor assemblies typically employ chains, wires, or cables made of metal. The need exists for improved anchor assemblies and line structures for use as part of anchor assemblies. 
     SUMMARY 
     The present invention may be embodied as a line assembly comprising a line structure comprising a plurality of strands, where each of the strands comprises a core portion, a jacket portion, and a barrier portion. The barrier portion is arranged between the core portion and the jacket portion to inhibit movement of contaminate material into the core portion. 
     The present invention may also be embodied as a line structure for use as a mud line assembly. In this case, the line structure comprises a plurality of strands, and each of the strands comprises a core portion, a jacket portion, and a barrier portion. The barrier portion is arranged between the core portion and the jacket portion to inhibit movement of contaminate material into the core portion. 
     The present invention may also be embodied as a line assembly comprising a line structure comprising a plurality of strands, where each of the strands comprises a core portion, a jacket portion, and a barrier portion comprising filter material. The filter material is arranged around the core portion to inhibit movement of contaminate material into the core portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first example line assembly constructed in accordance with, and embodying, the principles of the present invention; 
         FIG. 2  is a perspective view of a second example line assembly constructed in accordance with, and embodying, the principles of the present invention; 
         FIG. 3  is a view of a section of the first and second example line assemblies depicted in  FIGS. 1 and 2 ; and 
         FIG. 4  is a view of a section of an example strand that may be used as part of the first and second example line assemblies depicted in  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIG. 1  of the drawing, depicted therein is a first example line assembly  20  of the present invention comprising a line member  22  and optional first and second thimbles  24  and  26 . The line member  22  defines an intermediate portion  30  and first and second end portions  32  and  34 . The first and second end portions  32  and  34  define first and second end openings  40  and  42 , respectively. The end portions  32  and  34  are or may be formed by conventional techniques for terminating line structures. 
     If used, the thimbles  24  and  26  are arranged within the end openings  40  and  42 , respectively, in a conventional manner. The thimbles  24  and  26  are or may be conventional and define generally circular thimble openings  44  and  46 , respectively. The thimbles  24  and  26  are designed to protect the line member  22  while transferring to the line member  22  loads from other components (not shown) of the anchoring system in which the line assembly  20  is used. 
     The first example line assembly  20  defines a length L between the centers of the thimble openings  44  and  46 . The length L of the example line assembly  20  is approximately 335 feet; however the length of any line assembly constructed in accordance with the principles of the present invention will be determined based on the particular operating conditions under which the line assembly is to be used. 
     Turning now to  FIG. 2  of the drawing, depicted therein is a second example line assembly  50  comprises a line member  52 , an optional thimble  54 , and optional first and second protection assemblies  56  and  58 . The line member  52  defines an intermediate portion  60 , a deployment portion  62 , and first, second and third end portions  64 ,  66 , and  68 . The first, second, and third end portions  64 ,  66 , and  68  define first, second, and third end openings  70 ,  72 , and  74 , respectively. The end portions  64 ,  66 , and  68  are or may be formed by conventional techniques for terminating line structures. 
     The thimble  54  is arranged within the first end opening  70  in a conventional manner. The thimble  54  is or may be conventional and defines a generally circular thimble opening  76 . The thimble opening  76  is designed to transfer to the line member  52  loads from other components (not shown) of the anchoring system in which the line assembly  50  is used. 
     The protection structures  56  and  58  are arranged to cover portions of the second and third end portions  66  and  68  of the line member  52  defining the second and third end openings  72  and  74 , respectively. The example protection structures  56  and  58  each comprise a whipping structure  80  and a chafe structure  82 . The whipping structure  80  is first wrapped around portions of the second and third end portions  66  and  68  of the line member  52 . The chafe structure  82  is then wrapped around at least a portion of the whipping structure  80 . The protection structures  56  and  58  are or may be formed in a conventional manner and are designed to protect the line member  52  when the line assembly  50  is connected to other components (not shown) of the anchoring system in which the line assembly  50  is used. 
     The second example line assembly  50  defines a primary length L 1  between the center of the thimble opening  76  and the inside surface of the second end portion  66  defining the second end opening  72 . The second example line assembly  50  further defines a secondary length L 2  between the center of the thimble opening  76  and the point at which the deployment portion  62  extends from the intermediate portion  60 . The example deployment portion  62  is spliced into the intermediate portion  60  over a splice area  90  having a splice length L 3 . The deployment portion  62  defines a deployment length L 4 . The second and third end portions  66  and  68  define first and second end lengths L 5  and L 6 , respectively. 
     In the example line assembly  50 , the primary length L 1  is approximately 105 feet, the secondary length L 2  is approximately 37 feet, the splice length L 3  is approximately 12 feet, the deployment length L 4  is approximately 10 feet, and the first and second end lengths L 5  and L 6 , are approximately 8 feet. Again, the lengths of any line assembly constructed in accordance with the principles of the present invention will be determined based on the particular operating conditions under which the line assembly is to be used. 
     The line members  22  and  52  may differ in construction, composition, geometry, and dimensions, but share certain characteristics that render these members  22  and  52  appropriate for use as part of the line assemblies  20  and  50  described above. In addition, the characteristics shared by the line members  22  and  52  may be configured for use as part of any line system or assembly that will be subjected to operating conditions similar to those encountered by the example line assemblies  20  and  50  described herein. In the following discussion, an example line structure that may be used to form the line members  22  and  52  will be described in further detail. 
     Referring now to  FIGS. 3 and 4  of the drawing, depicted therein is an example line structure  120  that may be used to form the example line members  22  and  52  or any other line member designed for use under similar operating conditions. The example line structure  120  comprises a plurality of strands  122  as shown in  FIG. 3 . The strands  122  are combined in any conventional manner to obtain a line structure  120  that meets the load conditions of the intended use environment. 
     The strands  122  in turn comprise a core portion  130 , a jacket portion  132 , and a barrier portion  134 . The core portion  130  comprises a plurality of core yarns  140  comprising core fibers  142 , while the jacket portion  132  comprises a plurality of jacket yarns  144  comprising a plurality of jacket fibers  146 . The core yarns  140  and jacket yarns  144  in turn may comprise a plurality of components such as smaller yarns or bundles of fibers. The barrier portion  134  comprises at least one strip of barrier material  148  that is arranged between the core portion  130  and the jacket portion  132 . 
     The example strands  122  thus define an interior region  150  that is substantially but not completely occupied by the core fibers  142  forming the core portion  130 . In cross-section, the interior region  150  is substantially in the shape of a circle having a core diameter D 1 . The example strands  122  further define a barrier region  152  that is substantially occupied by the barrier material  148 . In cross-section, the barrier region is substantially annular, with an inner diameter of equal to the core diameter D 1  and an outer diameter equal to a barrier diameter D 2 . The example strands  122  further define a jacket region  154  that is substantially occupied by the jacket fibers  146  defining the jacket portion  132 . In cross-section, the jacket region  154  is substantially annular, with an inner diameter of equal to the barrier diameter D 2  and an outer diameter equal to a jacket diameter D 3 . The jacket diameter D 3  defines the nominal diameter of the example strands  122 . An exterior region  156  is defined as anything outside of the outer boundaries of the barrier region  152 . 
     The barrier material  148  is arranged to inhibit movement of contaminate material from the exterior region  156  to the interior region  150 . Contaminate material is any foreign matter not present in the line structure  120  when originally manufactured. In general, contaminate material enters line structures over time. When mixed in with the fibers forming a line structure, contaminate material can be detrimental to the operation and/or wear life of the line structure. 
     In the context of a line structure intended for use as an anchor assembly or under similar conditions, the line structure is often submerged under pressure in a liquid bath of fine particles suspended within water. The applicant has determined that, under pressure and movement of the line structure, the suspended particles easily flow within the rope structure. The Applicant has further determined that problems associated with the intrusion of contaminate material are exacerbated in the context of a line structure designed for use as part of an anchor assembly or the like because contaminate material between and around the fibers forming the line structure degrades the line structure and can cause failure thereof. 
     In the context of the example line structure  120 , the core portion  130  forms the prime load bearing element of the line structure  120 . The barrier material  148  is arranged to inhibit contamination of the core portion  130  by contaminate material, even though the entire line structure  120  may be submerged within a fluid bath comprising particulates. The barrier material  148  thus improves abrasion resistance of the overall line structure  120 . The operation and/or wear life of the core fibers  142  is thus less likely to be adversely affected by contaminate material. 
     The example barrier material  148  is designed to prevent egression of particulate material down to 2 microns in size (i.e., greater than approximately 2 microns). The exact specifications of the barrier material  148  can be selected based on the particular environment in which the line structure  120  is to be used. 
     The example barrier material  148  is a strip of filter tape that is wrapped in a helical configuration around the core portion  130  with edges of the filter tape overlapping as perhaps best shown at  160  in  FIG. 4 . Accordingly, when wrapped around the entire core portion  130 , the filter tape forming the barrier material  148  forms a continuous barrier in the barrier region  152  that inhibits the egression of particulate from the exterior region  156  to the interior region  150 . 
     The filter tape forming the barrier material  148  may comprise adhesive material on one side such that the barrier material  148  adheres to itself and to the core portion  130 . If used, the adhesive material helps the barrier material to stay in place around the core portion  130 . 
     In the example line structure  120 , the jacket portion  132  is formed by a tight cover braid of urethane coated jacket fibers  146 . The jacket portion  132  surrounds the barrier material  148 , protecting the barrier material  148  and holding the barrier material  148  in place around the core portion  130 . The jacket portion  132  further provides stiffness to the line structure  120 . Providing stiffness to the line structure  120  aids with ROV connections commonly used when installing, servicing, and removing offshore anchoring systems. 
     The example strands  122  employ an 8×3 construction. Although other constructions may be possible, the 8×3 construction provides the advantages of both laid and braided ropes. 
     The core fibers  142  and the jacket fibers  146  of the example line structure  120  employs are formed by high molecular polyethylene (HMPE). HMPE fibers provide good strength and abrasion resistance. HMPE also provides a low specific gravity, meaning that the line structure  120  will float in water. Using a line structure  120  capable of floating in water yields a line member that simplifies the connection of mooring lines and anchor retrieval. Other fibers such as LCPs are also candidates for use in line structures configured for use as anchor line assemblies and the like. 
     The present invention is of particular significance when used as part of the Delmar Systems Inc. Omni-Max anchoring system, and the two example line assemblies  22  and  52  disclosed herein are configured for use as part of the Omni-Max anchoring system. However, the concepts of the present invention may be applied to any line member intended for use under similar operating conditions.