Expandable Centralizer With Sliding Links and Sacrificial Fins
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Solution Overview
Problem
Conventional expandable bow spring centralizers suffer from plastic deformation at collar and bow spring connections during expansion, leading to instability and potential twisting of the bow springs out of alignment, and existing methods for restraining and deploying bow springs are costly, complex, or introduce unwanted materials into the borehole.
Innovation Solution
The design features a close-tolerance expandable centralizer with slidably coupled links that expand primarily through sliding rather than plastic deformation, and a sacrificial restraining band formed by bow spring fins that collapses and deploys without introducing additional materials, allowing for stable and twist-resistant collar and bow spring connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional expandable centralizer collars are expanded, then the pipe string can be expanded to larger diameter, but plastic deformation occurs at collar and bow spring connections causing instability and misalignment
Solution Approach 1:
The collar is divided into multiple individual links that are coupled together, allowing the collar to expand through relative movement between links rather than through plastic deformation of the entire collar structure. This segmentation maintains connection integrity while enabling expansion.
Solution Approach 2:
The collar transitions from a static rigid structure to a dynamic articulated structure with movable links. The links can slide and rotate relative to each other, allowing the collar to adapt its shape and size during expansion while maintaining structural integrity at connection points.
2Length of moving object
If bow springs are restrained in collapsed configuration for installation, then the centralizer can be installed through bore restrictions, but additional deployment systems or materials are required
Solution Approach 1:
The bow springs are equipped with integrated fins that automatically engage with the collar links during expansion. The fins serve dual purposes: they provide structural support when collapsed and automatically deploy the bow springs outward as the collar expands, eliminating the need for separate deployment mechanisms.
Solution Approach 2:
The deployment function is merged with the collar expansion mechanism itself. The collar links and bow spring fins work together as an integrated system where the expansion motion directly drives the deployment action, combining two functions into one coordinated mechanism.
3Volume of moving object
If close-tolerance centralizer is used to minimize diameter, then installation through restrictions is facilitated, but plastic deformation is more likely at connections
Solution Approach 1:
By segmenting the collar into multiple links with standardized connection interfaces, the design achieves compact dimensions while distributing stress across multiple connection points. The modular link structure allows for precise manufacturing of individual components that assemble to form the complete collar.
Solution Approach 2:
The connection design uses sliding and rotating joint mechanisms that change the degrees of freedom available to the links. These parametric changes in movement capability allow the connections to accommodate dimensional variations while maintaining structural integrity during expansion.
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 reduces plastic deformation at collar and bow spring connections, ensuring stable and reliable deployment of the bow springs to center the pipe string effectively within the borehole, while minimizing the overall diameter of the collapsed centralizer and eliminating the need for additional stop collars or complex deployment systems.
Implementation Method 1
The flexible bow springs can be biased toward a deployed configuration to bow radially outwardly and away from the axis of the bore through the centralizer to engage the wall of the borehole and can center a pipe string received through the bores of the collars. Configured in this manner, the bow springs provide stand-off from the wall of the borehole, and flex or collapse radially inwardly to accommodate restrictions and or irregularities in the wall of the borehole.
Implementation Method 2
Each link slidably coupled to two adjacent links. The links may slide relative to one another as the pipe string and centralizer are expanded to a larger diameter without substantial plastic deformation of the collar and bow spring connections.
Data Source
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AI summary
A close-tolerance expandable bow spring centralizer (8) having a first expandable collar (10A) coupled to and spaced apart from a second expandable collar (10B) through a plurality of bow springs (30) wherein expandable collars (1OA, 10B) comprise a plurality of slidably coupled links (16) that separate to expand the diameter of the collars (1OA, 10B), e.g., upon expansion of an expandable pipe string (80) on which the centralizer (8) is received. Expandable bow spring centralizer (8) may grip the expandable pipe string (80) when in the collapsed configuration to eliminate the need for a stop collar. Additionally or alternatively, a fin (32) may be connected to each bow spring (30), and then connected to one or more adjacent fins (32) upon collapse of the bow springs (30) to form a restraining band (39) that may be ruptured, e.g., upon expansion of the expandable pipe string (80).