Isolated Shear Coupling for Downhole Tools
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing shear couplings in downhole applications are prone to premature activation due to combined axial, bending, and torsional loading, leading to fatigue and early failure, especially in deviated wells, as they are not effectively isolated from these stresses, resulting in costly disruptions to production.
Innovation Solution
The shear coupling design incorporates a male and female component with cooperating grooves and a breakable wire or strip within an annular recess, isolating the shear mechanism from torsion and bending loads, allowing it to operate only under axial loading, with a reduced diameter portion for stress relief and a key/keyway system for torque transmission without loading the shear mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional shear couplings with shear pins and keyways are used, then the shear coupling can transmit torque and axial loads, but the shear mechanism is subjected to combined axial, bending and torsion loading which causes premature activation and fatigue failure
Solution Approach 1:
The shear coupling is divided into separate functional zones: the shear mechanism (shear pin and shear key) handles axial loads, while the reduced diameter portion and enlarged diameter portion separately handle torsional and bending loads. This segmentation allows each component to be optimized for its specific function, preventing the shear mechanism from being overloaded by combined stresses.
Solution Approach 2:
The reduced diameter portion acts as an intermediary element that isolates the shear mechanism from torsional and bending loads. By creating a stress relief zone with reduced cross-sectional area, this intermediary component absorbs and redirects harmful stresses away from the shear pin and shear key, allowing them to function solely under axial loading conditions.
2Ease of manufacture
If shear pins are aligned in a single plane through the axis of the shear coupling, then the shear coupling can be manufactured simply, but when the shear coupling is bent downhole, this one plane is significantly stiffer than the rest of the shear coupling exposing the shear coupling to undesirable loading conditions which lead to fatigue damage
Solution Approach 1:
The shear pin is positioned at a specific location within the shear coupling where the local structural properties are optimized. By placing the shear pin in a plane that is not the primary bending plane, the design creates local quality differences that distribute stresses more evenly and prevent concentrated fatigue damage at the shear mechanism.
3Ease of operation
If the key and keyway have a looser fit than the pins, then the pins are subject to shear loads before the keyway experiences torsional loading, but the small bearing area of the keyway causes additional torsion to be applied to the pins leading to fatigue
Solution Approach 1:
The harmful torsional and bending loads are extracted from the shear mechanism through the reduced diameter portion. This extraction ensures that the shear pin and shear key only experience axial loads, eliminating the fatigue-causing combined stresses that resulted from the interaction between the keyway bearing area and pin shear loads.
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 design minimizes bending and torsional loading on the shear mechanism, ensuring it activates only at the predetermined axial load, reducing fatigue and maintaining production integrity by isolating the shear mechanism from undesirable loading conditions.
Implementation Method 1
the breakable part contacting against each of the male component and the female component to convey axial forces between the male component and the female component below a first axial load
Implementation Method 2
the breakable part being breakable under axial loads within an operating range of axial loads below the axial load break points of the male component and female component and above the first axial load
Data Source
AI summary
A shearing mechanism in which a male component mates into a female component, the male component having a first groove extending around the male component and the female component having a second groove extending around the female component, the first groove and the second groove cooperating when the male component is inserted into the female component to define an annular recess. A shearing component is provided within the annular recess, the shearing component having a shear load that is controlled by the material and size of the shearing component. An opening is provided within one or both of the male component and female component, the opening being aligned with the annular recess. Stress relief is provided.