Cu-Ni-Sn Well Pump Couplings for Galling and Wear Reduction
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Solution Overview
Problem
Conventional couplings used in hydrocarbon extraction systems, particularly those made from steel or nickel alloys, lack sufficient galling resistance and compatibility with conduit materials, leading to mechanical integrity issues, wear, and increased maintenance costs due to the need for frequent surface treatments and coatings that may not be compatible with other system components.
Innovation Solution
The development of couplings made from spinodally-hardened copper-nickel-tin alloys with specific compositions (8-20 wt% nickel and 5-11 wt% tin) that provide high tensile strength, fatigue strength, fracture toughness, galling resistance, and corrosion resistance, featuring a unique geometry with linear tapers and rounded edges to reduce friction and wear, and are compatible with both sucker rods and valve rod bushings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional steel or nickel alloy couplings are used, then high tensile strength is achieved, but galling resistance is insufficient leading to wear and mechanical integrity issues
Solution Approach 1:
The patent employs a composite material system consisting of a copper-nickel-tin alloy coupling combined with a PTFE-based lubricating coating. The copper-nickel-tin alloy provides the structural tensile strength while the PTFE coating contributes exceptional galling resistance and low friction properties. This composite approach allows the system to achieve both high strength and high reliability simultaneously, resolving the technical contradiction between these two properties.
2Reliability
If expensive surface treatments are applied to steel or nickel alloy couplings, then wear resistance is improved, but compatibility with conduit materials deteriorates due to coating incompatibility
Solution Approach 1:
The patent fundamentally changes the material parameter of the coupling from conventional steel or nickel alloy to copper-nickel-tin alloy. This material parameter change inherently provides both the desired wear resistance and the chemical compatibility with carbon steel conduit materials. The copper-based alloy creates a compatible friction pair with steel conduit, eliminating the coating incompatibility issue while maintaining enhanced wear resistance through the material's inherent properties combined with PTFE coating.
3Reliability
If coatings are applied to reduce wear, then wear resistance is improved, but frictional losses increase due to coating incompatibility
Solution Approach 1:
The patent introduces PTFE (polytetrafluoroethylene) as an intermediary lubricating coating between the copper-nickel-tin coupling and the carbon steel conduit. PTFE acts as a mediator that provides exceptional lubrication properties with a very low coefficient of friction (typically 0.04-0.08). This intermediary layer reduces both wear and frictional energy losses simultaneously, as the PTFE coating's inherent low-friction properties minimize energy dissipation while protecting the mating surfaces from wear.
4Ease of operation
If conventional couplings are used, then mechanical functionality is maintained, but service life is reduced due to repetitive contact wear with conduit
Solution Approach 1:
The patent applies a PTFE-based lubricating coating beforehand to the surface of the copper-nickel-tin coupling. This protective layer is applied in advance to cushion and protect the coupling surface from repetitive contact wear with the carbon steel conduit during operation. The PTFE coating acts as a sacrificial protective layer that prevents direct metal-to-metal contact, thereby significantly extending the service life of the coupling while maintaining its mechanical functionality throughout the extended period.
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
These couplings significantly extend the service life of components, reduce frictional losses, and minimize wear, thereby lowering maintenance costs and preventing costly failures by providing enhanced mechanical functionality and compatibility within hydrocarbon recovery operations.
Implementation Method 1
the alloy has a sliding coefficient of friction of less than 0.4 when measured against carbon steel
Implementation Method 2
galling resistance, and corrosion resistance. Conventional couplings are typically comprised of steel or nickel alloys which lack the full complement of preferred intrinsic characteristics, particularly galling resistance
Data Source
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AI summary
A coupling for joining a downhole pump to a sucker rod string is disclosed. The coupling includes a core having a first end, a central portion, and a second end. The first end and the second end each have an end surface. The first end tapers linearly inwards from the central portion to the first end surface. The second end has a rounded edge along the second end surface. The coupling is made from a spinodally-hardened copper-nickel-tin alloy and has a sliding coefficient of friction of less than 0.4 when measured against carbon steel.