Subsea Tieback Connector Radial Locking Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current subsea oil and gas well production systems face challenges in securely connecting tieback conduits from the seafloor wellhead assembly to a surface platform, particularly in maintaining a reliable seal and locking mechanism under varying pressure and temperature conditions.
Innovation Solution
The tieback apparatus features a movable mandrel with external threads and a radially expansible load ring, which engages with an internal profile of the subsea well assembly, combined with a locking mechanism using dogs and threads to ensure secure connection and sealing, allowing for both linear and rotational movement modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tieback connector is used to connect inner and outer tieback conduits, then the connection between subsea well and surface platform is established, but the reliability of sealing and locking under varying pressure and temperature conditions is insufficient
Solution Approach 1:
The mandrel is designed to move between an upper running-in position and a lower landed position, and can rotate relative to the sleeve and load ring. This dynamic capability allows the connector to adapt to pressure and temperature variations by adjusting its position and orientation, maintaining sealing and locking reliability under varying conditions.
Solution Approach 2:
The load ring is designed to be radially expansible, changing its radial dimension to engage with the internal profile of the subsea well assembly. The mandrel's tapered portion with external threads works with the load ring's internal threads to control this expansion. By changing the radial parameter of the load ring, the connector maintains reliable engagement and sealing under varying pressure and temperature conditions.
2Reliability
If the mandrel moves from upper position to lower position to engage the load ring, then secure connection is achieved, but the complexity of the locking mechanism increases
Solution Approach 1:
The locking mechanism is designed to be self-actuating through the movement of the mandrel itself. As the mandrel moves from the upper running-in position to the lower landed position, its exterior tapered portion with external threads automatically engages with the interior threads of the load ring, causing radial expansion and locking. The mandrel's own movement provides the driving force for locking, eliminating the need for separate actuating mechanisms and reducing overall complexity.
Solution Approach 2:
The movement function and locking function are merged into a single integrated mechanism. The mandrel's downward movement simultaneously achieves both the engagement of the load ring and the activation of the locking mechanism through thread engagement. This merging of functions reduces the number of separate components and simplifies the overall locking mechanism while maintaining connection security.
3Reliability
If the load ring is radially expansible to engage the internal profile, then secure locking is achieved, but the device complexity increases due to additional components
Solution Approach 1:
The load ring serves multiple functions: it provides radial expansion for locking engagement with the internal profile, transmits axial loads through its threaded interaction with the mandrel, and maintains the structural connection between the inner and outer tieback conduits. By making the load ring multi-functional, the patent reduces the need for separate locking components, thereby reducing device complexity while maintaining locking integrity.
Solution Approach 2:
The load ring is nested within the sleeve structure, and the mandrel passes through the load ring. This nested arrangement allows compact integration of multiple components in a space-efficient manner. The load ring's radial expansion for locking does not require additional external space, as it expands within the confines of the sleeve and engages with the internal profile already present in the subsea well assembly.
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
This solution provides a robust and reliable connection that maintains sealing and locking integrity even under high pressure and temperature conditions, ensuring stable operation and easy disconnection if needed, while allowing for efficient installation and operation of subsea well production systems.
Implementation Method 1
A radially expansible load ring is carried by the sleeve. The load ring has a set of internal threads that ratchet over the external threads as the mandrel moves from the upper position to the lower position.
Implementation Method 2
The mandrel has an exterior tapered portion with a set of external threads. The threads increase in diameter from a lower end to an upper end. The load ring has a set of internal threads that ratchet over the external threads
Implementation Method 3
The mandrel has an exterior cam surface that slides downward relative to the locking member to expand it outward at the same time as the load ring is being expanded outward.
Data Source
AI summary
A tieback connector connects a tieback conduit from an offshore platform to a subsea wellhead assembly. The tieback connector has a mandrel that is connected to a string of tieback conduit and a sleeve and load ring that are carried by the mandrel. The load ring is radially expansible and has a conical portion with internal threads. The load ring has an external grooved profile that engages an internal grooved profile in the subsea assembly. The mandrel is rotatable relative to the sleeve while in its lower position, causing the load ring to further expand outward into engagement with the internal profile. A locking member is carried below the load ring on an exterior cam surface of the mandrel. The cam surface moves the locking member outward when the mandrel moves downward into engagement with an internal profile in the subsea assembly.