CA1162752A - Rope guiding device - Google Patents

Abstract

Abstract of the disclosure An adjustable two-piece rope guiding device 21, 26, parti-cularly adaptable for use on offshore guyed bower drilling and pro-duction structures 11. On such structures it is necessary to de-flect a taut guy rope 14 into a direction that may not be precisely known, or that may vary with time. Such deflection must not damage the rope by excessive static or cyclic straining or by wearing.
To minimize problems of clearance within the structure the guiding is performed in two parts: 1) a permanent deflection into a direct-ion that satisfies the foregoing clearance reqirements and 2) a va-riable deflection occuring beyond clearance problems that completes the required total deflection. When guiding the guy ropes 14 of an offshore oil production tower 11 from their vertical orienta-tion at the clamping and jacking (tensioning) devices 20 on the tower to a seafloor anchoring system 15, 16 a first bending member 21 changes the vertical direction of the guy ropes 14 to a selected direction (plane) extending toward such anchoring system 15, 16.
A second bending member 26 rotates the rope in a new direction at the periphery of the offshore structure 11 to accommodate positions of the anchoring system 15, 16 with respect to the plane of the selected direction. The first member is a fixed shoe 21 having a grooved rope contacting surface 23 and a sleeve 24. The second member 26 includes an cuter fixed housing 45 and an inner rotat-able housing 46 having a grooved surface 48 for contacting the rope.
me inner surface of the inner housing 46 may have various configu-rations depending upon its application. In its use with guyed tower anchoring the inner surface is preferably a three-sided pyramidal configuration 52, 53, 54 one corner of which comprises the grooved rope-contacting surface 48.

Description

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RDpe Guiding Device Technical Field The present invention ooncerns rope guiding devices and, in particular, rope guiding devices which are applicable for guiding ropes used to anchor m~rine drilling and production structures.

Background Art There are several ofshore platform concepts that have b~en proposed for use as drilling and producing platforms in deep water.
Some of those platform concepts are designed to penmit the plat-form to mDve in response to wave forcesO One such design is theguyed bower. In the guling 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 ~he platform deck by-cable grips in a rope tensioning device and pass around deflecting devices or fairleads located belcw the water surface. The guy ropes then tra~el outwardly at an angle from the vertical to the anchoring system.
In the past both sheave and shoe ~ype rope-deflecting devices have been prcposed for use at the tower-~uy rope juncture. Each type, however, must ~ ate for misalignments of the tower and ~he ~nchor piles in order to minimize wear and fatigue of the guyed ropes. Swivel type deflecting devices have been suggested ~or this pu~pose. In the c~se where tensioning devices are located within the interior of the bower structure a deflecting device should be positioned wi~hin the interior of the tower directly belcw the tensioning device. The use of a swivel type deflecting devioe would .

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result in interferences between the rope and internal structural elements. The problem then is to deflect a taut rope from th~
interior of the tower into the direction of the anchoring systems without interfexenoe frcm structural elements of the tower. The s direction of the anchoring systems to the deflecting device may not be kncwn exactly and, further, may vary with time as the tower may rotate. Such deflecti~g 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 rcpe deflection in tw~ parts- 1) a fixed deflection into a direction that satisfies clearan~e requirements within the tower, and 2) a variable deflection occuring at the periphery of the tc~er to com-plete the required total deflection~ Such problems are enoounteredin ~uiding the rcpes of a guyed offshore oil drilling and prcduc-ticn tower from their vertical orientation at the clamping and jacking (tensioning) devices atop the bower to seafloor anchor fixtures which encircle the tower at a great distance. The direct-ion of the guylines is not known exactly because of unavoidabletower musalignment at installation and mispl cement of the sea-floor fixturesO Further, tower m~vement which may cccur during storms may vary the direction of the guy ropes by several degrees.
Finally, congestion within the tower of structure, wells, and ap-pertenances necessitates guiding the guy rcpes through these struc-tural elements from a first interior deflection to a second deflec-tion at the perimeter of the tower structure.
The devices of the present invention solve this problem in the followLng manner. A first member fixed in po~ition within the bower 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. m e fixed relative positions of the first and seoond memkers maintains a position of the rope which avoids any obstacles within the tcwer and the second mRmker oompletes deflection of the rope beyond the tcwer.

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The first member is a shoe having a grooved~ curved rope-cGntact surface and a sleeve. The second member includes an outer fixed housir~g and an inner rotatable housing. The inner hcusir~ contains the rope and is provided with a grooved rope-cDntact surface ar~
other cortact surfaces to acccmmcdate 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 havir~ rounded corners in which one of the oorners of the pyramid forms the groove contact surface for the rcpe~

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 ~ew of the marine structure shcwn in Fig. l;
Fig. 3 is a schematic, lon~itudinal view illustrating the device vf 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 rcpe 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 d the invention in operational position within the guyed tcwer;
Fig. 8 is a diagramatic top view illustrating the use of se-veral radially extending rope guiding devices on the guyed tcwer;
Fig. 9 is a cross-sectional view of another part of the rcpe guiding device showing a rope extending therethrough;
Fig. 10 is a view taken along lines 10-10 of Fig. 9;
Figs. lOA and lOB are similar to the view illustrated in Fig.
10 but showing, respectively, opposing angular deflections of the rope;
Fig. 11 is ano~her cross-sectional view of the other part of the rope guiding device illustrating, along with Figs. 12 - 17, mDre the design features of that part;
Fig. 12 is a view taken along lines 12-12 of Fig. 11;
Fig. 13 is a vie~ taken along lines 13-13 of Fig. 11;

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Fig. 14 is a view taken along lines 14-14 of Fig. 11;
Fig. 15 is a view taken along lines 15-lS 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 m2nner 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 20-2D of Fig. 19; and Fig. 21 is a view similar to that shown in Fig. 20 illustrat-ing an alternative means for pinning the fixed and rotatable hDus-ings of the other part together.

Best Mbde for Carrying Out the Invention Figs. 1 and 2 illustrate an offshore drilling and producing platform 10 supported on a guyed tcwer 11 founded in the ocean floor 12 by piles (or a spud can or other type of foundation) mdicated at 13. A series of guylines or ropes 14 radiate outwardly from tower 11. Each rope 14 is secured to the upper part of bower 11 at one end and to a suitable clump weight lS and pile anchor or heavy drag anchor 16 on the ocean floor at the other end. A m~re detailed description of the operation and functioning of marine structures of this type may be found in U. S. Patent No. 3,903,70S
entitled "Appara~us for Anchoring Marine S~ructures" by R. W. Beck et al.
Tbwer 11 is constructed of a network of tubular structural members, as indicated. Also, production pipes exter.d upwardly through the interior of th~ tower and, in addition, many other appertenances for support of those pipes and other required drilling and production equipment are located within the confLnes of the tower.
Referring ncw to Fig. 3, there is illustrated a rope clamping and jacking (tensioning) device 20 supported on an interior por-tion of platfonm 10. A deflPcting or bending member or shoe 21 issuitably secured to tower 11, as indicated at 18, vertically below tensioning device 20, as shcwn. As seen in Fig. 4, shoe 21 in-cludes a retainer member 22 containing a grooved, curved rope-contact ~urface 23 and a surrounding U-shaped sleeve ~*~ Sleeve 24 holds rope 14 in place preparatory to tensioning, m2y contain anti-corrosion and/or lubricating material, as indicated at 25, and, as noted above, provides for attachmRnt 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 tLwer 11 which is indicated by line 27. It is secured, as indicated at 28 in Fig. 6, to periph-eral support m~mbers 29 of tcwer 11. As seen also in Fig. 5, rope 14 extends in a straight line between the aligned lcwer end 10 of fixed shoe 21 and the upper end of fixed member 26. R~pe 14 is bent by member 26, as indicated at 30 and 31. It is also de-flectable out of the plane of the bend of member 21u The distance Ll between platform 10 and the upper end of shce 21, the horizontal distance L2 between shoe 21 and memker 26, the 15 vertical distance L3 between sh oe 21 and member 26, the radius of curvature Rs of the shoe and the radius of curvature Rd Of deflect-ing member 26 will vary in accDrdance with any particular applicat-ion. Line 32 designates the center line of nember 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 pro-duction well (oonductor) pipes 33 extending vertically within tower 11. Rope 14 must pass between ~hose pipes, and avoid o~her appertenances within the tcwer. The relationship of rope 14 with 25 respect to the interior clamping and jacking device 20, shoe 21 and mmber 26 are shcwn in this Figure.
Fig. 8 illustrates a complete arrangement of the several radi-ally extending ropes 14, clamping and jacking device~ 20, shoe s 21 and members 26.
Deflecting member 26 is illustrated in more detail in Figs. 9, 10, 10A and 10B. It includes an outer tcone) housing 45, an inner (cone) housing 46, and bearings 47 between tho æ housings. Outer housing 45 attaches to the supporting structure as illustrated in Fig. 6. Inner housing 46 contains rope 14, which is shcwn posi-35 tioned in a grocve 48, and furnishes contact surfaces suitable forall 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 rcpe 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 grocve 48 will produce a correcting rotation, indicated by angle gamma t2~)~ about the axis of housing 46, as illustrated in Figs.
lOA and lOB.
m e mcment arm is indicated by the arrcwed line 55 in Fig. 10.
Arrowed line 56 indicates a force which causes rotation of housing 46 to the right as shown in Fig. lOA. 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 shcws the smallest end of the opening through housing 46 as being circular in shape it may be shaped as the opening is shcwn in Fig. 16 or Fig. 15. That end, in any event, is preferably larger than the size of rope 14 as shown in Figs. 9 and 10.
Lines 60 and 61 illustrate lines of departure of a taut rope 14 from groove surface 48 resulting from two different ~ensions 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. m e exterior surface o 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. Axrcwed line 40 indicates the original rope direction, arrcwed line 41 illustrates the orthogonal direction, and numeral 42 designates the vertical plane of the shoe 21. me angles alpha (~), beta (@) and gamma ( ~) refer to the be~d of sboe 21, the bend of housing 46 in the plane of the shoe and rotation of housing 46 about its axis, respectively.
Referring ncw to Figs. 19 and 20, it may be desirable to re-leasably pin outer housing 45 to inner hDusing 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 oould release bDlt 71 when the device is to be put into operation. Alternatively, a re-mDtely operated pinning device, such as the piston-cylinder arrange~
ment 72 controllable by a hydraulic line 73, may be used instead.

7 ~ 2 Alternatively, a shear pin could be used.
One manner of ins~alling the device is to install shoes 21 and housing members 26 on the ~ower structure~ ~he ends of roEes 14 are attached to the anchoring system 15, 16. Each rope 28 is ~hen threaded through the housing memher 26 and shoe 21 assDciated with it and connected at its upper end to cable grips oonnected into the tensioning device 20 on platfonm 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 ten-sion by tensioning devices 20. As the tension forces are appliedwhen pulling in the ropes the mcment arm will cause each inner housing 46 to rotate to ccmpensate for any directional misalign-ment of the guyed members 21 and 26 with the anchor position. The iMer housing may be rotated manually to any desired position be-lS fore, during or after initially tensioning the r~pe.
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 towers follcws:
R~pe 14 - 5 inches Length of Member 26 - 5 feet Length of Shoe 21 - 15 feet Angle ~- 48 degrees Platform size - 100 feet square Platform height - 1000 feet Angle ~ - 15 degrees Distance from tower to clump weight - 2000 feet Distance Ll - 35 feet Distance from clump weight to pile anchor - 1000 feet Distance L2 - 85 feet Rs - 12 feet Distance L3 - 50 feet R2diussl - 6 feet Angle sides 52 and 54 frcm vertical - 15 degrees m e geometry o the surface opposite groove 48 will depend upon the particular application of the device. The confi~urati~n is chosen to support slack rope 14 p~epara~ory to tensioning without damaging the rcpe. Cbnsequently, while the preferred embodiment is illustrated with respect to guyed offshore drilling and prc-duction ~owers the principal of the invention is useful in other applications, marine or landO Although members 45 and 46 are -8- ~ ~ ~ 2 7~ 2 shown conically shaped they may be formed cylindrically, rectan-gularly 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 applica-tions only one piece, the bending or deflecting member 26, may be used to campensate for any misalignment between two nembers oon-nected together by a rope.
Other changes and modifications may be made in the specific illustrative embodiments of the invention shcwn and/or describ~d herein without departing frcm the sccpe of the invention as defined in the appended claims.
Having fully described the device, objects, advantages and operation of our invention, we claim:

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Rope guiding apparatus for use in anchoring an offshore structure in which a rope extends from such structure to an anchoring system on the ocean floor comprising:
a rope guide member affixed to said structure and having inner and outer housings;
the inner surface of said inner housing forming a three-sided pyramidal configuration, one of the corners of the pyramid forming a curved rope-contacting groove extending in a first plane; and said inner housing being rotatable within said outer groove to rotate and change said first plane of said groove to a second plane of said groove to bend said rope from said first plane to said second plane to accommodate the position of the anchor system relative to said structure, said second plane being the plane of the portion of said rope extending between said rope guide member and said anchor system.

2. Rope guide apparatus as recited in claim 1 including rope tensioning means arranged on the upper end of said structure and connected to said rope; and another rope guide member affixed to said structure vertically below said rope tensioning means and capable of bending said rope to extend rope in said first plane between said rope guiding members.

3. Rope guiding apparatus as recited in claim 2 in which said other rope guiding member comprises a shoe having a grooved, curved rope-contacting surface and a curbed sleeve surrounding said rope-contacting surface.

4. Rope guiding apparatus as recited in claim 3 in which said one rope guiding member is fixed to the periphery of said offshore structure below said other rope guiding member and said curved groove being formed in the upper corner of said pyramid and capable of bending said rope upwardly from said first plane to second plane of said groove, said groove and said rope having substantially the same circumferential radius.

5. Rope guiding apparatus as recited in claim 4 in which said rope guiding members are conically shaped and including bearings arranged between said inner and outer housings of said one rope guide member to permit said inner housing to rotate within said outer housing.

6. Rope guiding apparatus as recited in claim 5 including means for releasably securing said inner and outing housing together to prevent rotation of said inner housing.