Sacrificial ESP Coupling with Torsional Undercut for Shaft Protection
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Solution Overview
Problem
In electric submersible pump (ESP) systems, existing couplings often fail due to torsional or shear stress, leading to costly and time-consuming shaft replacements, as they are designed to withstand stresses similar to or greater than the shafts they connect, resulting in unnecessary damage and downtime.
Innovation Solution
The design of couplings with torsional undercuts and pins that are engineered to fail before the shafts, with specific strength reductions (97%-99% of the shaft's strength) at strategic locations, allowing for controlled failure and reduced operational downtime by automatically or manually suspending operations for replacement, thus minimizing resource expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If couplings are designed to withstand stresses similar to or greater than the shafts, then the shafts are protected from failure, but the couplings themselves fail due to torsional or shear stress, leading to costly and time-consuming replacements
Solution Approach 1:
The coupling is designed with a torsional undercut that creates a predetermined weakness, causing the coupling to fail in a controlled manner before the shaft fails. This preliminary design feature ensures that the coupling sacrifices itself to protect the more valuable shaft, and the replacement process is simplified because the failure mode is predictable and the coupling can be quickly identified and replaced without complex diagnostics.
2Strength
If couplings are designed with higher strength to match shaft strength, then shaft protection is improved, but maintenance costs increase due to coupling failure and replacement
Solution Approach 1:
The coupling is designed as a sacrificial component with a torsional undercut that causes it to fail before the shaft. By making the coupling a lower-cost, replaceable component with a predetermined failure mode, the system protects the more expensive shaft while accepting that the coupling will need periodic replacement. This approach reduces overall maintenance costs compared to designing both components with equal high strength.
3Loss of time
If couplings are designed to fail before shafts, then replacement time is reduced, but the couplings must be designed with specific strength reductions that complicate the design process
Solution Approach 1:
The coupling has uniform strength throughout most of its structure, but a localized torsional undercut is introduced at a specific location to create a predetermined weakness. This local modification allows the coupling to fail in a controlled manner before the shaft fails, while the rest of the coupling maintains its structural integrity and protective function. The localized nature of the undercut simplifies the overall design compared to creating a completely different coupling structure.
Data Source
AI summary
A coupling includes an inner surface configured to receive a shaft of an electric submersible pump system through the inner surface. The coupling also includes an outer surface having a torsional undercut into the coupling, where the torsional undercut is configured to induce a failure of the coupling prior to a failure of the shaft.