Hydraulic and earth engineering – Marine structure or fabrication thereof – With anchoring of structure to marine floor
Patent
1981-12-17
1984-02-07
Taylor, Dennis L.
Hydraulic and earth engineering
Marine structure or fabrication thereof
With anchoring of structure to marine floor
254389, 405195, 405202, 114293, E02D 2100, B63B 2124
Patent
active
044300239
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention concerns rope guiding devices and, in particular, rope guiding devices which are applicable 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 direction 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 obstacles 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 betwee
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Brinkmann Carl R.
Finn Lyle D.
Hayes Donald A.
Exxon Production Research Co.
Schneider John S.
Taylor Dennis L.
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