Threaded Pipe Connection Coating for Misalignment and Galling
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Solution Overview
Problem
Threaded connections for oil country tubular goods face challenges with misalignment resistance, torque on shoulder resistance, and corrosion resistance, particularly when subjected to repeated use and outdoor storage, leading to decreased galling resistance and gas tightness.
Innovation Solution
A threaded connection system featuring a pin and box with surface roughness of 1-8 μm Ra and 10-40 μm Rz, coated with a Zn-Ni alloy plating layer, a Cu-Sn-Zn alloy plating layer, and a solid lubricant coating layer containing fluororesin particles and epoxy or polyamide-imide resin, deposited in a specific order to enhance adhesion and corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy metal-containing compound greases are used to improve galling resistance, then galling resistance is improved, but environmental harm increases due to heavy metal contamination
Solution Approach 1:
The invention extracts and removes heavy metal components from the lubricant composition, replacing them with non-heavy metal alternatives. The lubricant is formulated without Pb, Zn, Cu, or other heavy metals while maintaining effective galling resistance through alternative lubricating mechanisms.
Solution Approach 2:
The invention changes the chemical composition parameters of the lubricant by eliminating heavy metal compounds and adopting a non-heavy metal-based formulation. This parameter change maintains the functional performance (galling resistance) while eliminating the harmful environmental effects.
2Duration of action of moving object
If threaded connections are subjected to repeated fastening and loosening, then inspection and reuse are enabled, but galling occurs due to strong friction
Solution Approach 1:
The invention applies a lubricant composition to the threaded connection surfaces before fastening operations begin. This preliminary lubrication creates a protective film that reduces friction and prevents galling during subsequent repeated fastening and loosening cycles.
Solution Approach 2:
The lubricant composition acts as an intermediary substance between the mating threaded surfaces. It mediates the interaction by reducing direct metal-to-metal contact and friction, thereby preventing galling while enabling repeated operational cycles.
3Adaptability or versatility
If misalignment occurs during fastening, then connection flexibility is maintained, but shearing stress increases leading to decreased misalignment resistance
Solution Approach 1:
The invention modifies the surface roughness parameters of the threaded connection surfaces to specific ranges (Ra: 0.3-3.0 μm, Rz: 1.2-6.0 μm). These parameter changes optimize the contact characteristics, allowing the connection to accommodate misalignment while maintaining sufficient strength and resistance to shearing stress.
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
The system exhibits improved misalignment resistance, high torque on shoulder resistance, and excellent corrosion resistance, maintaining lubricity and preventing galling even under misalignment and corrosion conditions.
Implementation Method 1
a Zn-Ni alloy plating layer, a Cu-Sn-Zn alloy plating layer, and a solid lubricant coating layer
Implementation Method 2
a solid lubricant coating layer containing fluororesin particles and epoxy or polyamide-imide resin
Data Source
AI summary
This invention provides a threaded connection for pipes or tubes having excellent misalignment resistance and high torque on shoulder resistance, and also having excellent corrosion resistance properties, as well as a method for producing the threaded connection for pipes or tubes. The threaded connection for pipes or tubes includes a pin and a box. The pin and the box include contact surfaces having threaded portions and unthreaded metal contact portions. The threaded connection for pipes or tubes includes, on at least one of the contact surfaces of the pin and the box, surface roughness, a Zn—Ni alloy plating layer, a Cu—Sn—Zn alloy plating layer and a solid lubricant coating layer. These are deposited from the contact surface side in the order of: surface roughness, the Zn—Ni alloy plating layer, the Cu—Sn—Zn alloy plating layer and the solid lubricant coating layer.