High Pressure Lock Assembly Strut Load Bypass
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Solution Overview
Problem
In downhole drilling and completions, existing lock assemblies face challenges with dog-type locking systems where the narrow struts between windows are prone to failure under high pressure, requiring a balance between dog width and strut width to prevent system failure.
Innovation Solution
A lock assembly design featuring a mandrel with alternating windows and struts, where radially extendable dogs are operatively coupled with an extender member to bypass loading on the struts during assembly, using a threaded connection and ramps to ensure the dogs are fixed between the mandrel and extender, thereby transferring loads without stressing the struts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the width of dogs is increased to improve locking reliability, then the locking capability is improved, but the strut width must be reduced which increases the risk of strut fracture under high pressure
Solution Approach 1:
The locking force is segmented and distributed across multiple dogs that engage with corresponding features on the tubular, rather than relying on a single large locking element. This allows the locking function to be distributed while maintaining individual dog dimensions that do not compromise strut integrity.
Solution Approach 2:
The dogs act as intermediary elements between the mandrel and the tubular, transferring locking forces through controlled engagement points. This intermediary mechanism allows the struts to remain narrow without directly bearing the full locking load, as the dogs distribute these forces across multiple engagement points.
2Reliability
If the width of struts is reduced to accommodate larger dogs, then the locking capability is improved, but the strut becomes more prone to fracture under heavy loading
Solution Approach 1:
The locking function is segmented into multiple discrete dogs that engage at different locations around the mandrel circumference. This segmentation allows each dog to be optimized for locking engagement while the struts between them can be minimized in width without compromising overall structural integrity, as the locking loads are distributed rather than concentrated.
Solution Approach 2:
The dogs are designed to be radially extendable from a retracted position to an extended locking position. This dynamic capability allows the dogs to engage with the tubular features only when needed for locking, while remaining retracted during normal operations to minimize stress on the struts. The extender member controls the radial movement of all dogs in unison.
Data Source
AI summary
A lock assembly including a mandrel having one or more windows arranged alternatingly with one or more struts. One or more dogs are included corresponding to the one or more windows and are radially extendable therethrough. A member is operatively arranged for radially extending each of the one or more dogs. Each of the one or more dogs is operatively coupled between the member and the mandrel when fully radially extended by the member for bypassing loading in the one or more struts during loading of the assembly.