Shear Pin with Localized Neck for Controlled Rod String Failure
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Solution Overview
Problem
Sucker rod string systems in oil wells face unpredictable failure points, leading to costly downtime and potential environmental hazards due to uncontrolled rupture of equipment, as existing shear couplings either fail to rupture when intended or rupture too easily, causing unnecessary downtime or fluid spillage.
Innovation Solution
A shear pin with a cylindrical shape and curved portion, featuring opposite-handed threads and clutches at each end, is designed to threadably connect within a shear coupling, providing a controlled point of failure and enhanced fatigue life by distributing stress evenly and securely engaging sleeves, with a hollow chamber filled with a corrosive-resistant polymer to prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing shear couplings are designed to provide a controlled point of failure, then equipment damage is reduced, but the shear coupling may rupture too easily causing unnecessary downtime
Solution Approach 1:
The shear pin incorporates a narrowed section with reduced cross-sectional area at a specific location, creating a localized weak point that is intentionally designed to fail first. This narrowed section has different geometric properties than the rest of the pin, concentrating stress at this specific location to ensure predictable failure behavior while protecting the stronger sucker rod string components.
2Strength
If the shear coupling is designed to withstand higher stress, then equipment protection is improved, but it fails to rupture when intended causing damage to other elements
Solution Approach 1:
The shear pin features a narrowed section with deliberately reduced dimensions compared to the rest of the pin body. This local geometric modification creates a stress concentration zone that ensures the pin will fail at the narrowed section before other components, providing controlled failure while protecting the stronger sucker rod string elements from damage.
3Reliability
If the shear coupling ruptures easily to provide safety, then equipment damage is reduced, but needless downtime occurs under non-dangerous stress conditions
Solution Approach 1:
The narrowed section of the shear pin is designed with specific dimensional reductions that create a controlled weak point. This localized geometric feature ensures the pin fails at a predictable load threshold, preventing both premature failure under normal conditions and catastrophic failure that would damage other components, thereby optimizing the balance between protection and operational continuity.
4Stability of the object's composition
If threaded connections are made secure to prevent loosening, then connection stability is improved, but assembly and disassembly become more difficult
Solution Approach 1:
The shear pin incorporates clutch mechanisms with asymmetric tooth configurations at its ends. These asymmetric features engage with corresponding elements in the coupling, providing secure anti-rotation and stable connection during operation, while still allowing for controlled disassembly when needed through the designed failure mechanism.
Data Source
AI summary
The present disclosure relates, according to some embodiments, to a shear pin including a cylindrical shape positioned along a vertical axis having a first end having a common diameter with a second end; the first end and containing a first clutch at a point along the vertical axis that is furthest from the second end, the first clutch containing one of a recessing shape and a protruding shape; (c) the second end containing a second clutch at a point along the vertical axis that is furthest from the first end, the second clutch containing one of a recessing shape and a protruding shape; and (d) the curved portion including a diameter that is largest where the curved portion connects to each of the first end and the second end and then narrows along the curved portion, forming a curve that culminates at a neck where the diameter is smallest.