Subsea Cap Locking Dogs with Inclined Faces
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Solution Overview
Problem
Existing subsea well closure technologies face challenges in efficiently and reliably sealing bore elements, particularly in subsea Xmas trees, due to the need for complex locking mechanisms and tools that require secure attachment before operation, which can be cumbersome and prone to failure.
Innovation Solution
A cap with radially movable locking dogs and an actuation sleeve featuring large and small inclination faces, allowing for three-phase movement to facilitate easy initial positioning and subsequent forceful locking, along with an emergency release mechanism and seal holder design for enhanced sealing and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a locking sleeve with inclined face is used to move locking dogs radially, then the locking dogs can be actuated, but a tool must be secured to the well arrangement before moving the sleeve, which increases operational complexity and time
Solution Approach 1:
The locking mechanism is segmented into multiple independent locking dogs (at least three) that can be actuated simultaneously or sequentially. Each locking dog has its own inclination face geometry, allowing distributed locking action across multiple engagement points with the internal profile, eliminating the need for complex sequential tool operations
Solution Approach 2:
The locking dogs are pre-configured with specific inclination face angles (larger and smaller inclination faces) that enable them to be actuated in a predetermined sequence or simultaneously by a single actuation motion. This preliminary design of the inclination faces allows the locking action to be prepared in advance, reducing operational steps
2Productivity
If a locking sleeve with single inclination face is used, then the structure is simpler, but it cannot provide both large movement and forceful locking in different phases
Solution Approach 1:
Different portions of the locking dog have different inclination face geometries - a larger inclination face for the initial movement phase and a smaller inclination face for the final forceful locking phase. This local variation in geometric properties allows each phase of the locking operation to have optimized characteristics for its specific function
Solution Approach 2:
The locking mechanism transitions dynamically between two distinct phases: a first phase with larger radial movement along the larger inclination face for rapid positioning, and a second phase with smaller movement but larger force along the smaller inclination face for secure locking. This dynamic phase transition enables both speed and reliability
3Reliability
If multiple locking dogs are used with different inclination faces, then reliable locking is achieved, but the manufacturing complexity increases
Solution Approach 1:
The locking dogs are designed as standardized components with consistent basic geometry and material properties, differing only in the inclination face angles. This universality allows for simplified manufacturing processes, inventory management, and assembly, while still providing the required different functions through geometric variation rather than complete design customization
Solution Approach 2:
The primary manufacturing variable is the inclination face angle parameter, which can be controlled through standard machining or forming processes. By varying this single geometric parameter while maintaining consistent material composition and overall dimensions, the locking dogs can be manufactured with high reliability using conventional fabrication methods
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
Enables efficient and reliable sealing of subsea well bores with reduced operational resistance and provides an emergency release option, ensuring secure locking and sealing even under pressure, thereby improving the reliability of subsea well closure operations.
Implementation Method 1
the small inclination face is divided by a cam arranged on the locking dog, on which the large inclination face is arranged, which cam is adapted to extend into a slot in the actuation sleeve
Implementation Method 2
a seal arrangement is directly or indirectly connected to the actuation sleeve, in a position adapted to extend further into said bore than the said locking means
Data Source
AI summary
A cap having a stinger adapted to be inserted into a bore of a subsea well element. The stinger includes locking means for locking to a profile in said bore, which locking means include a plurality of locking dogs. The locking dogs exhibit a large inclination face and a small inclination face, and are adapted to be actuated in a radial direction by an actuation sleeve. The small inclination face is divided by a slot, in which slot the large inclination face is arranged. A cam is arranged on the actuation sleeve and is adapted to extend into said slot. Alternatively, the small inclination face is divided by a cam arranged on the locking dog, on which the large inclination face is arranged, which cam is adapted to extend into a slot in the actuation sleeve.