Underwater SCR Lifting Frame for Subsea Flex Joint Replacement
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Solution Overview
Problem
Current methods for replacing or inspecting flex joints in deepwater steel catenary pipeline risers require large winches, deck reinforcements, and heavy lifting equipment, which are costly and complex due to the depth and size of the risers, and inefficiently manage the movement and replacement process.
Innovation Solution
An underwater steel catenary pipeline riser lifting frame that eliminates the need for large winches and deck reinforcements by allowing direct, vertical lifting and replacement of flex joints using a customized lifting frame and dry welding habitat, reducing the complexity and cost of the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If large winches and heavy lifting equipment are used to lift and steer the flex joint above water for replacement, then the flex joint can be removed and replaced, but the cost and device complexity increase significantly
Solution Approach 1:
The invention extracts the flex joint replacement operation from the traditional above-water process and moves it to an underwater environment. A specialized underwater lifting frame is deployed that can directly lift and position the flex joint underwater, eliminating the need for complex deck reinforcements and large winches. The lifting frame includes vertical lifting beams and horizontal positioning beams that work together to extract and replace the flex joint in its operational environment.
Solution Approach 2:
The invention introduces an intermediary underwater lifting frame structure that mediates between the riser system and the replacement flex joint. This lifting frame acts as a temporary support structure underwater, providing a stable platform for removing the old flex joint and installing the new one without requiring the facility's existing heavy lifting equipment.
2Ease of operation
If deck reinforcements and temporary cranes are installed to support large lift winches, then the flex joint can be lifted and steered, but the ease of operation and time required increase
Solution Approach 1:
The underwater lifting frame is pre-configured and deployed underwater before the flex joint replacement operation begins. The lifting frame's vertical beams are positioned and secured to the riser structure in advance, creating a ready-to-use lifting mechanism that eliminates the need for time-consuming deck reinforcements and crane installations during the replacement operation.
Solution Approach 2:
The invention replaces the traditional above-water mechanical lifting system (winches, cranes, deck reinforcements) with an underwater mechanical system. The lifting frame uses vertical lifting beams and horizontal positioning beams that operate in the underwater environment, substituting the complex topside mechanical system with a simpler underwater structure that directly addresses the replacement need.
3Ease of operation
If large winches and steering winches are used to lift and steer the flex joint, then the joint can be positioned above water, but the weight of equipment and energy consumption increase
Solution Approach 1:
The invention changes the operational dimension from above-water to underwater. Instead of lifting the flex joint vertically above the water surface using large winches, the lifting frame operates in the underwater dimension, using vertical lifting beams to raise the joint only to the extent needed for replacement while remaining submerged. This dimensional change eliminates the need for heavy steering winches and reduces equipment weight.
Data Source
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AI summary
An underwater steel catenary pipeline riser (SCR) lifting frame (1) comprises a lift frame foundation (10) and an SCR lifting frame (20) comprising a lift frame interface (21) adapted to be connected to the lift frame foundation; a foundation interface (50); a lift guide (30) configured to accept the lift frame foundation; and a lift (32) slidably disposed about the lift guide, the lift comprising an SCR pull head interface (31) configured to be connected to an SCR pull head (131). The underwater steel catenary pipeline riser (SCR) lifting frame (1) and systems using it allow for flex joint repair/replacement subsea which do not require large winches, deck re-enforcements, steering winches, and heavy crane lifts required by facility mounted winches above water and also reduces required heavy lifting and overall complexity of flex joint replacement.