Subsea Laydown Head Retrieval Arrangement
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Solution Overview
Problem
The retrieval of a laydown head from a pipeline end section secured to a pipeline termination skid at the seabed is currently a complex and time-consuming process, requiring subsea mounting and operation of a lifting frame.
Innovation Solution
A detachable arrangement with a base frame, rigid supporting units, and a locking device that allows for controlled vertical movement and secure positioning of the laydown head, enabling its rapid and safe retrieval to a surface vessel without interfering with pipeline connection operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lifting frame with chains and ROV operated chain hoists is used to retrieve the laydown head, then the laydown head can be disconnected and suspended, but the retrieval operation becomes complicated and time-consuming
Solution Approach 1:
The invention extracts the essential function of laydown head retrieval by removing the complex lifting frame, chains, and ROV operated chain hoists system. Instead, it uses a simple retrieval device that integrates the suspension and lifting functions into a single compact unit that can be directly positioned under and lift the laydown head without the intermediary chains and hoists system.
Solution Approach 2:
The invention merges multiple functions (positioning, suspending, and lifting) into a single integrated retrieval device. The retrieval device combines the support structure, lifting mechanism, and suspension elements into one unified unit, eliminating the need for separate lifting frame, chains, and chain hoists that were previously required.
2Reliability
If a lifting frame with multiple chains and ROV operated chain hoists is used, then the laydown head can be securely suspended, but the operation becomes time-consuming
Solution Approach 1:
The invention extracts and eliminates the time-consuming elements of the previous system (multiple chains and ROV operated chain hoists) while retaining the essential function of secure suspension through a simplified retrieval device that achieves the same result more efficiently.
Solution Approach 2:
The invention skips the lengthy process of deploying and operating multiple chains and chain hoists by using a retrieval device that can be quickly positioned and operated, significantly reducing the time required for the retrieval operation while maintaining secure suspension of the laydown head.
3Reliability
If subsea mounting operations are performed to secure the pipeline end section, then the pipeline can be connected, but additional time and operational complexity are required
Solution Approach 1:
The retrieval device is mounted on the pipeline termination skid before the pipeline end section is lowered to the seabed. This preliminary mounting action allows the device to be in position and ready for immediate use once the pipeline is connected and the laydown head needs retrieval, eliminating the need for separate subsea mounting operations after pipeline connection.
Solution Approach 2:
The invention merges the mounting of the retrieval device with the pipeline installation process itself. By securing the retrieval device to the pipeline termination skid during the initial setup phase, the pipeline connection operations and retrieval device installation are combined into a single operational sequence, reducing total time and complexity.
Data Source
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AI summary
The invention relates to an arrangement (1 ) to be used for retrieving a laydown head (2) to a surface vessel from a pipeline end section (3) that is secured to a pipeline termination skid (4) at the seabed. The arrangement is detachably mountable to the pipeline termination skid and comprises: - a base frame (10) configured to bear against the pipeline termination skid when the arrangement is mounted to the pipeline termination skid; and - one or more rigid supporting units (12a, 12b) provided on the base frame for supporting the laydown head from below, each supporting unit comprising an upwardly directed seat (13) for receiving the laydown head and an actuating device (14) for moving said seat in the vertical direction. The invention also relates to a system comprising such an arrangement and a pipeline termination skid, and a method for retrieving a laydown head by means of such an arrangement.