Bolted Riser Tensioner Frame Assembly for Offshore Platforms
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Solution Overview
Problem
Existing riser tensioner systems for offshore drilling face challenges in maintaining precise tension on risers due to difficulties in fabrication and potential weld failures, especially when installed on un-level decks and subjected to lateral loading.
Innovation Solution
A riser tensioner frame assembly that can be quickly bolted together, featuring a support ring with cylinder mounting assemblies and tensioner legs with bores for secure mounting to the deck, allowing for level support and accommodating un-level deck conditions through the use of alignment jigs and slip rings for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tensioner frame is constructed with multiple straight elements welded together at angled joints, then the frame can provide structural strength to react to lateral loading, but the fabrication becomes difficult and weld strength is compromised due to difficult welding positions and angles
Solution Approach 1:
The frame is divided into multiple straight elements (legs, crossbars, bracing members) that can be manufactured separately with standard welding positions and angles, then assembled together using bolted connections. This segmentation allows each component to be fabricated easily while maintaining overall frame strength through the modular assembly approach.
2Strength
If the tensioner frame uses welded joints at angled and coped connections, then the structural elements can transfer loading, but the welds are placed in difficult positions and angles that reduce weld strength and increase failure risk
Solution Approach 1:
The patent replaces the welded mechanical connection system with a bolted mechanical connection system. Instead of relying on welds to transfer loads at angled and coped joints, the frame uses bolts and connection plates that can be assembled at convenient positions, eliminating the reliability issues associated with difficult welding positions while maintaining structural integrity.
3Manufacturing precision
If the guidance device is placed on an upper portion of the riser tensioner frame, then lateral motion of the riser upper termination is decreased, but the frame must be sufficiently strong to react to increased lateral loading
Solution Approach 1:
The frame is segmented into multiple structural elements (legs, crossbars, bracing members) that work together to distribute and react to lateral loads. This modular structure allows the frame to achieve the necessary strength to support upper-mounted guidance devices while maintaining ease of fabrication through standardized components and bolted connections.
4Productivity
If the tensioner frame components are bolted together instead of welded, then assembly and disassembly can be performed quickly in the field, but the structural integrity must be maintained without relying on weld strength
Solution Approach 1:
The patent substitutes welded joints with bolted connections throughout the frame assembly. This mechanical substitution enables rapid assembly and disassembly in the field while maintaining structural integrity through properly designed bolted joints, connection plates, and structural geometry that distributes loads effectively across the modular components.
Data Source
AI summary
A riser tensioner for maintaining a tensile force on a riser extending through an opening in a deck of a floating platform includes a frame assembly that may be quickly bolted together in the field. The frame assembly includes a plurality of tensioner legs that may be installed on an un-level deck yet still provide a level support of the riser. Lower leg mounting assemblies include a slip ring for mounting directly to the deck and a deck mounting member received in the slip ring at a variable angle and having an upwardly extending shaft passing into a bore in a lower end of a tensioner leg.