Fluked Burying Devices

Abstract

A fluked burying device ( 1, 1 A), for augmenting the burying and holding capability of a drag embedment marine anchor and chain cable system while being fixedly located thereon, comprises a fluke member ( 8 ) inclinedly attached to a body member ( 7 ) including pockets ( 12 A, 12 B, 12 C) for accommodating links ( 16, 17 ) of a chain cable ( 4 ) passing there-through in a defined attitude such that axial and transverse loading is impressed in the chain cable ( 4 ) via separate links ( 17 A, 17 C) to maintain bending stresses therein similar to that occurring in a 5-pocket wildcat of a chain windlass and such that emergent links ( 16 A, 16 B) have sufficient articulation in service while embedded to permit the chain cable ( 4 ) to perform the function of and eliminate need for heavy expensive shackles. The fluked burying device ( 1, 1 A) enables soil loading from a plurality thereof to be distributed along a length of chain cable ( 4 ) and is preferably provided with a body member ( 7 ) less wide than the effective footing width of a chain cable ( 4 ) and preferably split about a plane of symmetry ( 5 ) in two halves ( 2, 3 ) for ease of transport within container gauge.

1 . A fluked burying device ( 1 ,  1 A) includes a plane of symmetry ( 5 ) and comprises:
 a body member ( 7 ) and a fluke member ( 8 ) attached thereto at an acute angle of inclination to a longitudinal axis ( 14 ) of said body member ( 7 ), and includes attachment means ( 12 A,  12 B,  12 C,  19 A,  19 B) for holding said body member ( 7 ) in a fixed position on a chain cable ( 4 ) comprising a series of links ( 16 ,  17 ),   whereby said longitudinal axis ( 14 ) is maintained substantially aligned with an axis ( 6 ) of said chain cable ( 4 ),   said body member ( 7 ) being adapted to maintain said chain cable ( 4 ) extending in a defined attitude therein,   said attachment means ( 12 B,  12 C) including first contact points ( 19 A,  19 B,  19 C,  19 D) on said body member ( 7 ) for transferring axial load therefrom to corresponding points on a link ( 17 B,  17 C) of said chain cable ( 4 ) and second contact points (A, B) on said body member ( 7 ) for transferring transverse load therefrom to corresponding points on a link ( 17 A,  17 C) of said chain cable ( 4 ).   
     
     
         2 . A fluked burying device ( 1 ,  1 A), according to  claim 1 , wherein said defined attitude comprises alternate links ( 17 ) of said chain cable ( 4 ) being maintained in a plane at right angles to said plane of symmetry ( 5 ). 
     
     
         3 . A fluked burying device ( 1 ,  1 A), according to  claim 1 , wherein said second contact points (A, B) are positioned such as to constrain induction of bending stresses in said link ( 17 A,  17 C) of said chain cable ( 4 ) during operation of said fluked burying device ( 1 ,  1 A) to be similar to that which occurs in a wildcat of a windlass when tensioning said chain cable ( 4 ). 
     
     
         4 . A fluked burying device ( 1 ), as claimed in  claim 1 , wherein said second contact points (A, B) are positioned on said body member ( 7 ) at two locations to bear on two of said links ( 17 A,  17 C) spaced apart such as to oppose turning moment induced in said fluked burying device ( 1 ) during interaction with a seabed soil ( 38 ) while penetrating therein when said chain cable ( 4 ) is taut. 
     
     
         5 . A fluked burying device ( 1 ), according to  claim 4 , wherein said two locations of said second contact points (A, B) are spaced apart by not less than 12 times a bar diameter (D) of said links ( 16 ,  17 ) and, preferably, not less than 20 times said bar diameter (D). 
     
     
         6 . A fluked burying device ( 1 ,  1 A), according to  claim 1 , wherein said second contact points (A, B) are positioned such that said corresponding load transfer points on said link ( 17 A,  17 C) lying in a plane at right angles to said plane of symmetry ( 5 ) are spaced from said plane of symmetry ( 5 ) by a distance in the range of 0.8 to 1.0 times a nominal of a bar diameter (D) of said link ( 17 A,  17 C). 
     
     
         7 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 1 , wherein said second contact points (A, B) are positioned such that said corresponding load transfer points on said link ( 17 A,  17 C) lying in a plane at right angles to said plane of symmetry ( 5 ) are separated from a central point of a crown section, lying in said plane of symmetry ( 5 ), of said link ( 17 A,  17 C) by a distance in the range of 0.4 to 0.6 times a nominal of a bar diameter (D) of said link ( 17 A,  17 C) measured in a direction parallel to said axis ( 6 ) of said chain cable. 
     
     
         8 . A fluked burying device ( 1 ,  1 A), according  claim 1 , wherein said attachment means ( 12 A,  12 B,  12 C,  19 A,  19 B) comprises a pocket ( 12 A,  12 B,  12 C) in said body member arranged to accommodate a link ( 17 A,  17 B,  17 C) of said chain cable ( 4 ). 
     
     
         9 . A fluked burying device ( 1 ,  1 A), according to  claim 8 , wherein said pocket ( 12 A,  12 B,  12 C) constrains said link ( 17 A,  17 B,  17 C) of said chain cable ( 4 ) to lie in a plane at right angles to said plane of symmetry ( 5 ). 
     
     
         10 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 1 , wherein said fluked burying device ( 1 ,  1 A) is formed substantially in two halves ( 2 ,  3 ) for opposed sideways assembly on said chain cable ( 4 ). 
     
     
         11 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 1 , wherein said first contact points ( 19 A,  19 B,  19 C,  19 D) are located adjacent said fluke member ( 8 ) whereby tensile loading impressed in said chain cable ( 4 ) by said fluked burying device ( 1 ,  1 A) substantially bypasses that portion of said body member ( 7 ) lying forward of said first contact points ( 19 A,  19 B,  19 C,  19 D). 
     
     
         12 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 1 , wherein said body member ( 7 ) comprises two elongate members ( 9 ,  10 ) each disposed substantially parallel to said plane of symmetry ( 5 ) and each extending along one of two opposed sides of said chain cable ( 4 ). 
     
     
         13 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 12 , wherein said elongate members ( 9 ,  10 ) are plate-like. 
     
     
         14 . A fluked burying device ( 1 ,  1 A), according to  claim 12 , wherein a pocket ( 12 A,  12 B,  12 C) in said body member arranged to accommodate a link ( 17 A,  17 B,  17 C) of said chain cable ( 4 ) comprises an elongate slot ( 12 A,  12 B,  12 C) perforating each of said plate-like elongate members ( 9 ,  10 ) to accommodate said link ( 17 A,  17 B,  17 C). 
     
     
         15 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 12 , wherein said plate-like elongate members ( 9 ,  10 ) are spaced apart by a distance between 1.06 and 1.1 times a nominal diameter of said link ( 16 ,  17 ). 
     
     
         16 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 1 , wherein said body member ( 7 ) has a width less than that of a link ( 16 ,  17 ) of said chain cable ( 4 ), measured transverse to said chain cable ( 4 ). 
     
     
         17 . A fluked burying device ( 1 ,  1 A), as claimed in  claim 13 , wherein said plate-like elongate members ( 9 ,  10 ) each have a thickness (t 9 ) less than a bar diameter (D) of a one of said link ( 16 ,  17 ) of said chain cable. 
     
     
         18 . A fluked burying device ( 1 ,  1 A), according to  claim 15 , wherein said elongate members ( 9 ,  10 ) are splayed apart at an extremity ( 28 ,  29 ) such that a link ( 16 A,  16 B) of said chain cable ( 4 ) emergent from said extremity ( 28 ,  29 ) can swing freely sideways from said plane of symmetry ( 5 ) through an angle (⊖) of up to 20°. 
     
     
         19 . A fluked burying device ( 1 ,  1 A), according to  claim 18 , wherein said emergent link ( 16 A,  16 B) can swing in said plane of symmetry ( 5 ) through an angle of up to 90° from said longitudinal axis ( 14 ). 
     
     
         20 . A fluked burying device ( 1 ), according to  claim 1 , wherein said fluked burying device ( 1 ) includes roll stabilizers ( 42 ). 
     
     
         21 . A fluked burying device ( 1 A), according to  claim 1 , wherein said fluked burying device ( 1 A) includes yaw stabilizers ( 46 ). 
     
     
         22 . A fluked burying device ( 1 ,  1 A), according to  claim 1 , wherein said fluked burying device ( 1 ,  1 A) is arranged such that a straight line ( 22 ) containing a centre point of a forward crown section, lying in said plane of symmetry ( 5 ), of a link ( 17 A) in a foremost pocket ( 12 A) in said body member ( 7 ) and a point of projection ( 25 ) onto said plane of symmetry ( 5 ) of a foremost point ( 20 ) of said fluke member ( 8 ) is inclined to said longitudinal axis ( 14 ) at an angle (δ) in the range of 25° to 35°.