Lubricant Coating for Threaded Pipe Connections Under Repeated Torque
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Solution Overview
Problem
Threaded connections for oil country tubular goods face challenges in maintaining galling resistance and over-torque performance, particularly when metal seal portions and shoulder portions undergo plastic deformation during repeated fastening and loosening, and existing solutions using heavy metal-containing greases pose environmental concerns.
Innovation Solution
A lubricant coating layer composition containing Cr2O3, a metal soap, a wax, and a basic metal salt of an aromatic organic acid is applied to the threaded connections, enhancing galling resistance and over-torque performance without using heavy metal greases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy metal-containing compound greases are used to improve galling resistance, then the galling resistance of threaded connections is improved, but environmental harm increases due to heavy metal contamination
Solution Approach 1:
The patent extracts and removes heavy metal components (Pb, Zn, Cu) from the lubricant composition while retaining the essential lubricating function through alternative organic-based compounds and additives, thereby eliminating environmental harm while maintaining galling resistance
Solution Approach 2:
The patent changes the chemical composition parameters of the lubricant by replacing heavy metal-based compounds with organic additives and alternative lubricating substances, transforming the composition from heavy metal-containing to heavy metal-free while preserving functional performance
2Adaptability or versatility
If threaded connections undergo repeated fastening and loosening to inspect thread faces, then maintenance and re-use are enabled, but galling occurs due to insufficient friction resistance
Solution Approach 1:
The patent applies lubricant coating before threaded connections undergo repeated fastening and loosening operations, preparing the surface in advance to prevent galling during subsequent maintenance operations and ensuring reliable repeated use
Solution Approach 2:
The patent uses a consumable lubricant coating that can be applied fresh before each maintenance operation, providing reliable galling protection for repeated fastening and loosening without requiring permanent modification to the threaded connection structure
3Reliability
If fastening torque is increased to enhance gas tightness after shouldering torque is reached, then sealing performance is improved, but metal plastic deformation occurs leading to yield torque
Solution Approach 1:
The patent introduces lubricant coating as an intermediary substance between the mating threaded surfaces, reducing friction and allowing controlled fastening that achieves gas tightness through proper shouldering torque without exceeding yield torque and causing plastic deformation
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 composition significantly improves galling resistance and over-torque performance, allowing for repeated fastening and loosening without galling, while being environmentally friendly by eliminating heavy metals.
Implementation Method 1
a lubricant coating layer that is formed from the composition on at least one of the contact surfaces of the pin and the box
Data Source
AI summary
The composition according to the present embodiment is a composition for forming a lubricant coating layer on a threaded connection for pipes or tubes, and contains Cr2O3, a metal soap, a wax and a basic metal salt of an aromatic organic acid. The threaded connection for pipes or tubes according to the present embodiment includes a pin and a box. The pin and the box each include a contact surface including a threaded portion. The threaded connection for pipes or tubes includes, as an outermost layer, a lubricant coating layer formed from the aforementioned composition on at least one of the contact surfaces of the pin and the box.