EP0058159A1

EP0058159A1 - DEVICE FOR GUIDING A ROPE.

Info

Publication number: EP0058159A1
Application number: EP81901390A
Authority: EP
Inventors: Donald Andrew Hayes; Lyle David Finn; Carl Rhys Brinkmann
Original assignee: Exxon Production Research Co
Current assignee: ExxonMobil Upstream Research Co
Priority date: 1980-08-21
Filing date: 1980-08-21
Publication date: 1982-08-25
Also published as: IT8149132A0; JPS57501292A; NO821203L; NO155059B; BR8009101A; ES8307961A1; EP0058159A4; MY8600687A; WO1982000675A1; ES504851A0; EP0058159B1; IT8149132A1; CA1162752A; IT1171474B

Abstract

Un dispositif de guidage ajustable en deux pieces d'un cordage (21, 26) est particulierement adapte pour etre utilise sur des structures de production et de forage d'une tour "off-shore" amarree (11). Sur de telles structures, il est necessaire de deflechir un cordage de retenue tendu (14) dans une direction qui peut ne pas etre connue de maniere precise ou qui peut varier avec le temps. Une telle deflexion ne doit pas endommager le cordage par des contraintes ou usures excessives statiques ou cycliques. Pour reduire au minimum les problemes de degagement de la structure le guidage s'effectue en deux parties: 1) une deflexion permanente dans une direction satisfaisant les besoins de degagement precites et 2) une deflexion variable depassant la deflexion se rapportant au degagement et completant la deflexion totale requise. Lorsque l'on guide les cordages de retenue (14) d'une tour de production de petrole "off-shore" (11) depuis leur orientation verticale au niveau des dispositifs de serrage et de verin (tension) sur la tour vers un systeme d'ancrage au fond de la mer (15, 16), un premier organe de flexion (21) change la direction verticale des cordages de retenue (14) vers une direction selectionnee (plane) s'etendant vers ce systeme d'ancrage (15, 16). Un second organe de flexion (26) fait tourner le cordage dans une nouvelle direction a la peripherie de la structure "off-shore" (11) pour accommoder les positions du systeme d'ancrage (15, 16) par rapport au plan de la direction choisie. Le premier organe est un patin fin (21) ayant une surface a rainure en contact avec le cordage (23) et un manchon (24). Le second organe (26) comprend une enceinte externe fixe (45) et une enceinte interne rotative (46) ayant une surface a rainure (48) en contact avec le cordage. La surface interne de l'enceinte interne (46) peut avoir differentes configurations en fonction de son application. Lorsqu'elle est utilisee avec un ancrage d'une tour haubanee, la surface interne possede de preference une configuration en pyramide aA two-piece adjustable guide device of a rope (21, 26) is particularly suitable for use on production and drilling structures of an anchored "off-shore" tower (11). On such structures, it is necessary to deflect a tensioned retaining cord (14) in a direction which may not be known in a precise manner or which may vary over time. Such deflection must not damage the rope by excessive static or cyclic stresses or wear. To minimize the clearance problems of the structure, the guidance is carried out in two parts: 1) a permanent deflection in a direction satisfying the aforementioned clearance needs and 2) a variable deflection exceeding the deflection relating to the clearance and completing the total deflection required. When guiding the retaining ropes (14) of an "off-shore" petroleum production tower (11) from their vertical orientation at the level of the tightening and jack (tension) devices on the tower towards a system anchoring at the bottom of the sea (15, 16), a first flexing member (21) changes the vertical direction of the retaining ropes (14) to a selected direction (plane) extending towards this anchoring system ( 15, 16). A second flexing member (26) rotates the rope in a new direction at the periphery of the "off-shore" structure (11) to accommodate the positions of the anchoring system (15, 16) relative to the plane of the chosen direction. The first member is a thin shoe (21) having a grooved surface in contact with the rope (23) and a sleeve (24). The second member (26) includes a fixed outer enclosure (45) and a rotatable inner enclosure (46) having a grooved surface (48) in contact with the rope. The internal surface of the internal enclosure (46) can have different configurations depending on its application. When used with a guyed tower anchor, the inner surface preferably has a pyramid configuration with

Description

ROPE GUIDING DEVICE

Technical Field

The present invention concerns rope guiding devices and, in particular, rope guiding devices which are appli cable for guiding ropes used to anchor marine drilling and production structures.

Background Art

There are several offshore platform concepts that have been proposed for use as drilling and producing platforms in deep water. Some of those platform concepts are designed to permit that platform to move in response to wave forces. One such design is the guyed tower. In the guying system for a guyed tower, guylines or ropes are run from the platform to anchor systems on the ocean floor. The guy ropes are secured at the platform deck by cable grips in a rope tensioning device and pass around deflecting devices or fairleads located below the water surface. The guy ropes then travel outwardly at an angle from the vertical to the anchoring system. In the past both sheave and shoe type rope-deflecting devices have been proposed for use at the tower-guy rope juncture. Each type, however, must accommodate for misalignments of the tower and the anchor piles in order to minimize wear and fatigue of the guyed ropes. Swivel type deflecting devices have been suggested for this purpose. In the case where tensioning devices are located within the interior of the tower structure a deflecting device should be positioned within the interior of the tower directly below the tensioning device. The use of a swivel type deflecting device would result in interferences between the rope and internal structural elements. The problem then is to deflect a taut rope from the interior of the tower into the direction of the anchoring systems without interference from structural elements of the tower. The direction of the anchoring systems to the deflecting device may not be known exactly and, further, may vary with time as the tower may rotate. Such deflecting must not damage the rope by excessive static or cyclic straining or by wearing and clearance requirements within the tower itself must be met .

Disclosure of Invention

The foregoing problems are overcome by performing the rope deflection in two parts: 1) a fixed deflection into a direct ion that satisfies clearance requirements within the tower, and 2) a variable deflection occuring at the periphery of the tower to complete the required total deflection. Such problems are encountered in guiding the ropes of a guyed offshore oil drilling and production tower from their vertical orientation at the clamping and jacking (tensioning) devices atop the tower to seafloor anchor fixtures which encircle the tower at a great distance. The direction of the guylines is not known exactly because of unavoidable tower misalignment at installation and misplacement of the seafloor fixtures. Further tower movement which may occur during storms may vary the direction of the guy ropes by several degrees. Finally, congestion within the tower of structure, wells, and appertenances necessitates guiding the guy ropes through these structural elements from a first interior deflection to a second deflection at the perimeter of the tower structure. The devices of the present invention solve this problem in the following manner. A first member fixed in position within the tower bends the rope in a first plane to a predetermined degree. A second member, also fixed in position on the periphery of the tower, bends the rope in the first plane, if necessary, and, also, deflects the rope in a direction out of the first plane. The fixed relative positions of the first and second members maintains a position of the rope which avoids any ob stacles within the tower and the second member completes deflection of the rope beyond the tower.

The first member is a shoe having a grooved, curved rope-contact surface and a sleeve. The second member includes an outer fixed housing and an inner rotatable housing. The inner housing contains the rope and is provided with a grooved rope-contact surface and other contact surfaces to accommodate for all rope directions and forces expected. Bearing means between the housings permit the inner housing to rotate, thus, increasing the size and variety of potential rope deflections. The inner surface of the inner housing may have a triangular pyramidal configuration having rounded corners in which one of the corners of the pyramid forms the groove contact surface for the rope.

Brief Description of Drawings

Fig. 1 is a schematic, longitudinal view of a guyed tower marine drilling and production structure;

Fig. 2 is a top view of the marine structure shown in Fig . 1 ; Fig. 3 is a schematic, longitudinal view illustrating the device of the invention in operational position on a guyed tower;

Fig. 4 is a view taken along lines 4-4 of Fig. 3; Fig. 5 is a view taken along lines 5-5 of Fig. 3; Fig. 6 is a schematic, longitudinal view illustrating one part of the rope guiding device of the invention secured to a peripheral structural member of the guyed tower; Fig. 7 is a diagramatic top view of the rope guiding device of the invention in operational position within the guyed tower;

Fig. 8 is a diagramatic top view illustrating the use of several radially extending rope guiding devices on the guyed tower;

Fig. 9 is a cross-sectional view of another part of the rope guiding device showing a rope extending therethrough;

Fig. 10 is a view taken along lines 10-10 of Fig. 9; Figs. 10A and 10B are similar to the view illustrated in Fig. 10 but showing, respectively, opposing angular deflections of the rope;

Fig. 11 is another cross-sectional view of the other part of the rope guiding device illustrating, along with Figs. 12 - 17, more the design features of that part;

Fig. 12 is a view taken along lines 12-12 of Fig. 11

Fig. 13 is a view taken along lines 13-13 of Fig. 11

Fig. 14 is a view taken along lines 14-14 of Fig. 11

Fig. 15 is a view taken along lines 15-15 of Fig. 11 Fig. 16 is a view taken along lines 16-16 of Fig. 11

Fig. 17 is a view taken along lines 17-17 of Fig. 11

Fig. 18 is a diagramatic illustration of the manner in which the rope guiding device operates;

Fig. 19 is a partial cross-sectional view of the other part of the rope guiding device illustrating one manner of initially pinning the fixed housing to the rotatable housing of that part;

Fig. 20 is a view taken along lines 20-20 of Fig. 19; and Fig. 21 is a view similar to that shown in Fig. 20 illustrating an alternative means for pinning the fixed and rotatable housings of the other part together

Best Mode for Carrying Out the Invention

Figs. 1 and 2 illustrate an offshore drilling and producing platform 10 supported on a guyed tower 11 founded in the ocean floor 12 by piles (or a spud can or other type of foundation) indicated at 13. A series of guylines or ropes 14 radiate outwardly from tower 11. Each rope 14 is secured to the upper part of tower 11 at one end and to a suitable clump weight 15 and pile anchor or heavy drag anchor 16 on the ocean floor at the other end. A more detailed description of the operation and functioning of marine structures of this type may be found in U. S. Patent No. 3,903,705 entitled "Apparatus for Anchoring Marine Structures" by R. W. Beck et al. Tower 11 is constructed of a network of tubular structural members, as indicated. Also, production pipes extend upwardly through the interior of the tower and, in addition, many other apper tenances for support of those pipes and other required drilling and production equipment are located within the confines of the tower.

Referring now to Fig. 3, there is illustrated a rope clamping and jacking (tensioning) device 20 supported on an interior portion of platform 10. A deflecting or bending member or shoe 21 is suitably secured to tower 11, as indicated at 18, vertically below tensioning device 20, as shown. As seen in Fig. 4, shoe 21 includes a retainer member 22 containing a grooved, curved rope- contact surface 23 and a surrounding U-shaped sleeve 34. Sleeve 24 holds rope 14 in place preparatory to tensioning, may contain anti-corrosion and/or lubricating material, as indicated at 25, and, as noted above, provides for attachment of shoe 21 to the tower.

A deflecting or bending member 26 is fixed in a position located below shoe 21 on the periphery of tower 11 which is indicated by line 27. It is secured, as indicated at 28 in Fig. 6, to peripheral support members 29 of tower 11. As seen also in Fig. 5, rope 14 extends in a straight line between the aligned lower end of fixed shoe 21 and the upper end of fixed member 26. Rope 14 is bent by member 26, as indicated at 30 and 31. It is also deflectable out of the plane of the bend of member 21.

The distance L₁ between platform 10 and the upper end of shoe 21, the horizontal distance L₂ between shoe 21 and member 26, the vertical distance L₃ between shoe 21 and member 26, the radius of curvature R_s of the shoe and the radius of curvature R_d of deflecting member 26 will vary in accordance with any particular application. Line 32 designates the center line of member 26 which is also the center line of shoe 21.

The significance of the straight line design is apparent in the diagram of Fig. 7 where there are shown a plurality of production well (conductor) pipes 33 extending vertically within tower 11. Rope 14 must pass between those pipes, and avoid other appertenances within the tower. The relationship of rope 14 with respect to the interior clamping and jacking device 20, shoe 21 and member 26 are shown in this Figure.

Fig. 8 illustrates a complete arrangement of the several radially extending ropes 14, clamping and jacking devices 20, shoes 21 and members 26.

Deflecting member 26 is illustrated in more detail in Figs. 9, 10, 10A and 10B . It includes an outer (cone) housing 45, an inner (cone) housing 46, and bearings 47 between those housings. Outer housing 45 attaches to the supporting structure as illustrated in Fig. 6. Inner housing 46 contains rope 14, which is shown positioned in a groove 48, and furnishes contact surfaces suitable for all rope directions and forces expected. Bearings 47 transfer forces between housings 45 and 46 while permitting inner housing 46 to rotate, thereby increasing the size and variety of potential rope deflections. As long as inner housing 46 is free to rotate within outer housing 45, any attempt by rope 14 to leave the plane of groove 48 will produce a correcting rotation, indica ted by angle gamma , about the axis of housing 46, as illustrated in Figs. 10A and 10B.

The moment arm is indicated by the arrowed line 55 in Fig. 10. Arrowed line 56 indicates a force which causes rotation of housing 46 to the right as shown in Fig. 10A. The configuration of the interior surfaces of housing 46 is also illustrated in Figs. 11 through 17. The straight side surfaces 52 and 54 and curved surface 53 and rounded corners 48, 56 and 57 form a three- sided pyramidal configuration. While Fig. 17 shows the smallest end of the opening through housing 46 as being circular in shape it may be shaped as the opening is shown in Fig. 16 or Fig. 15. That end, in any event, is preferably larger than the size of rope 14 as shown in Fig. 9 and 10. Lines 60 and 61 illustrate lines of departure of a taut rope 14 from groove surface 48 resulting from two different tensions applied to rope 14. Line 63 indicates rope 14 in slack position.

Seal rings 70 may be provided between the housings at each end thereof to seal in the bearings. The exterior surface of housing 46 and the interior surface of housing 45 may themselves comprise bearing surfaces which would make separate bearings unnecessary.

The ability of the two-part rope guiding device to deflect the rope 14 is illustrated in Fig. 18. Arrowed line 40 indicates the original rope direction, arrowed line 41 illustrates the orthogonal direction, and numeral 42 designates the vertical plane of the shoe 21. The angles alpha (α ) , beta ( β ) and gamma refer to the bend of shoe 21, the bend of housing 46 in the plane of the shoe and rotation of housing 46 about its axis, respectively .

Referring now to Figs. 19 and 20, it may be desirable to releasably pin outer housing 45 to inner housing 46 so that groove 48 of the inner housing will be in proper alignment with the axis of shoe 21. For that purpose, a bolt 71 threadable into housing 46 may be used to pin the two together. A diver could release bolt 71 when the device is to be put into operation. Alternatively, a remotely operated pinning device, such as the piston-cylinder arrangement 72 controllable by a hydraulic line 73, may be used instead. Alternatively, a shear pin could be used.

One manner of installing the device is to install shoes 21 and housing members 26 on the tower structure. The ends of ropes 14 are attached to the anchoring system 15, 16. Each rope 28 is then threaded through the housing member 26 and shoe 21 associated with it and connected at its upper end to cable grips connected into the tensioning device 20 on platform 10. If pinning means to pin outer housings 45 to inner housings 46 are used, the two housings are unpinned and ropes 14 made taut under catenary tension by tensioning devices 20. As the tension forces are applied when pulling in the ropes, the moment arm will cause each inner housing 46 to rotate to compensate for any directional misalignment of the guyed members 21 and 26 with the anchor position. The inner housing may be rotated manually to any desired position before, during or after initially tensioning the rope . Examples of some equipment sizes, angles and other dimensions which may be involved in an application of the rope guiding device described herein to guyed tower follows:

Rope 14 - 5 inches Length of Member 26 - 5 feet Length of Shoe 21 - 15 feet

Anglenα- 48 degrees Platform size - 100 feet square Platform height - 1000 feet

Angle β- 15 degrees Distance from tower to clump weight - 2000 feet

Distance L₁ - 35 feet Distance from clump weight to pile anchor - 1000 feet

Distance L₂ - 85 feet R_s - 12 feet Distance L₃ - 50 feet Radiussι - 6 feet

Angle sides 52 and 54 from vertical - 15 degrees

The geometry of the surface opposite groove 48 will depend upon the particular application of the device. The configuration is chosen to support slack rope 14 preparatory to tensioning without damaging the rope. Con sequently, while the preferred embodiment is illustrated with respect to guyed offshore drilling and production towers the principal of the invention is useful in other applications, marine or land. Although members 45 and 46 are shown conically shaped they may be formed cylin- drically, rectangularly or in other shapes. The axis of rotation of housing 46 need not necessarily be through the center of the line of rope 14 extended between members 21 and 26. While the device is shown and described as a two-piece rope guiding device, in some applications only one piece, the bending or deflecting member 26, may be used to compensate for any misalignment between two members connected together by a rope.

Other changes and modifications may be made in the specific illustrative embodiments of the invention shown and/or described herein without departing from the scope of the invention as defined in the appended claims.

Having fully described the device, objects, advantages and operation of our invention, we claim:

Claims

C la ims

1. A device for use in guiding rope comprising: a member fixed in position for bending said rope in a selected plane and, in addition, for deflecting said rope in a direction out of said selected plane.

2. A device as recited in claim 1 in which said member comprises an outer housing and an inner housing rotatable with respect to said outer housing, said inner housing having a grooved rope-contacting surface.

3. A device as recited in claim 2 in which the inner surface of said inner housing forms a three-sided pyramidal configuration, one of the corners of said pyramid forming said grooved surface, said side opposite said groove being curved for engaging slack rope.

4. A device for use in guiding rope comprising: a first member fixed in position for bending said rope in a first selected plane; a second member fixed in position for bending said rope in said first plane and, also, for deflecting said rope in a direction out of said first selected plane into a second, plane.

5. A device as recited in claim 4 in which said first member comprises a shoe having a grooved, curved rope-contact surface and a curved sleeve and said second member comprises an outer housing fixed in position and an inner housing rotatable with respect to said outer housing, said inner housing having a rope-contacting groove on its inner surface.

6. A device as recited in claim 5 in which the inner surface of said inner housing forms a three-sided pyramidal configuration, one of the corners of said pyramid forming said groove, said side opposite said groove being curved for engaging slack rope.

7. A device as recited in claim 6 in which said first member is affixed to an offshore structure below the surface of water and within the interior of said structure vertically below a tensioning device on said offshore structure and said second member is located below said first member and on the periphery of said offshore structure.

8. A device for use in guiding tensionable anchoring ropes from an anchor system on the ocean floor to tensioning means on an offshore structure comprising: a first member fixed in position on said offshore structure below the surface of water for bending said rope from one direction to another direction in a selected plane; and a second member fixed in position on the periphery of said offshore structure for bending said rope in said selected plane and also for deflecting said rope in a direction out of said selected plane into another plane in the direction of said anchor means.

9. A device as recited in claim 8 in which said first member is positioned vertically below said tensioning means and comprises a grooved, curved rope-contact surface and a curved sleeve; and said second member is positioned on the periphery of said structure and comprises an outer housing fixed in position below and spaced from said first member and an inner housing rotatable with respect to and within said outer housing, said inner housing having a rope contacting groove formed on its inner surface.

10. A device as recited in claim 9 in which the inner surface of said inner housing containing said groove forms a three-sided pyramidal configuration, one of the corners of said pyramid forming said groove, and said side opposite said groove being curved inwardly for engaging said rope.

11. A device as recited in claim 10 in which said inner and outer housings are initially secured together to prevent rotation of said inner housing.