Subsea BOP Tethering System with Capstan and Hydraulic Gripper
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Solution Overview
Problem
Existing tethering systems for subsea Blow-Out-Preventers face challenges in maintaining tension over time due to rope relaxation and limitations in accommodating variable anchor distances, with reels allowing adjustable tension but prone to relaxation and in-line tensioners requiring pre-cut ropes that are not reusable.
Innovation Solution
A tensioning system comprising a frame, a rotatable reel, a tensioning cylinder with a reciprocally disposed piston, a gripper assembly with an elastically deformable sleeve, and a capstan that can lock and unlock to manage rope tension and length, allowing for adjustable and secure tethering to anchors with variable distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If reels with locking mechanisms are used to allow adjusting tension with good resolution, then tension adjustment capability is improved, but rope tension relaxation occurs during use due to rope loop movement on the reel drum
Solution Approach 1:
A capstan is introduced as an intermediary component between the reel and the rope. The capstan with its locking mechanism prevents rope slip and maintains tension without requiring the rope to be wound in loops on the reel drum, thereby eliminating the relaxation problem while preserving tension adjustability
Solution Approach 2:
The tensioning system is divided into separate functional components: the reel for rope storage and length adjustment, and the capstan for tension maintenance and locking. This segmentation allows each component to perform its specific function optimally without the drawbacks of the integrated reel-drum design
2Device complexity
If in-line tensioners are used to provide structurally simpler design, then device complexity is reduced, but ropes must be pre-cut based on measured distance which prevents reuse on different subsea BOPs
Solution Approach 1:
The reel is designed to accommodate ropes of variable lengths and the capstan can be repositioned along the rope to different anchor points. This universal design allows the same tensioning system to be reused on different subsea BOPs with different anchor distances, eliminating the need for pre-cut ropes
Solution Approach 2:
The system transitions from a static, fixed-length rope configuration to a dynamic configuration where the rope length and capstan position can be adjusted. This allows the system to adapt to different operational requirements and different subsea BOP installations
3Manufacturing precision
If pre-cut ropes are used with in-line tensioners to match measured anchor distances, then tensioning accuracy for specific distance is improved, but rope length adaptability and reusability are lost
Solution Approach 1:
The reel is pre-loaded with a long rope that exceeds the maximum expected anchor distance. This preliminary preparation eliminates the need for pre-cutting ropes to specific lengths, as the required length can be simply unwound from the reel during installation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively maintains tension and allows for flexible rope length adjustments, enhancing the stability and reusability of subsea BOP tethering by using hydraulic mechanisms to control rope tension and prevent relaxation, while accommodating various anchor distances without the need for pre-cut ropes.
Implementation Method 1
a tensioning cylinder (36) attached to the frame (12) and a tensioning piston (38) reciprocally disposed in the tensioning cylinder (36)
Implementation Method 2
The gripper sleeve (60) may be elastically deformable. Engagement of the lock sleeve (64) with the outer diameter of the end of the gripper sleeve (60) may cause the gripper sleeve (60) to elastically deform toward the collapsed position
Implementation Method 3
The capstan may have a locked position wherein rotation of the capstan is prevented. The capstan may have an unlocked position wherein the capstan is capable of rotating freely
Implementation Method 4
The gripper assembly may include a lock sleeve (64) attached to the gripper cylinder (54). The lock sleeve (64) may be configured to selectively engage an outer diameter of an end of the gripper sleeve (60)
Data Source
AI summary
A tensioning system includes a combined rope gripper and tension cylinder. A rope passes through the combined rope gripper and tension cylinder. Once the length and/or tension of the rope has been adjusted, a reel lock handle can be actuated to prevent further rotation of the reel. The combined rope gripper and tension cylinder can be actuated to hold the rope. The combined rope gripper and tension cylinder can also be actuated to reduce or prevent the release of tension in the rope.