Tubular Threaded Joint Lubricating Coating for High Torque
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Solution Overview
Problem
Tubular threaded joints for oil country tubular goods face challenges in maintaining galling resistance and gas tightness without using compound grease, especially when subjected to high torque during makeup and breakout operations, and existing lubricating coatings with viscous or semisolid lubricants fail to provide sufficient torque-on-shoulder resistance (ΔT) to prevent yielding of shoulder portions.
Innovation Solution
A lubricating coating comprising low friction copolymer particles dispersed in a highly viscous matrix, where the copolymer particles protrude at low pressure to reduce friction and embed at high pressure to increase friction, creating a large ΔT, is applied to the contact surfaces of the pin and box, eliminating the need for compound grease and ensuring galling resistance and gas tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound grease containing heavy metal powders is applied to the contact surface, then galling resistance is improved, but environmental harm and human toxicity increase
Solution Approach 1:
The invention extracts and removes the harmful heavy metal powder components from the lubricating coating while retaining the essential lubricating function. The coating now uses only organic lubricants without lead, zinc, or other heavy metals, eliminating environmental and health hazards while maintaining galling resistance through the lubricating film formed by organic compounds.
Solution Approach 2:
The invention changes the chemical composition parameters of the lubricating coating by specifying organic lubricants with particular properties (viscosity range, flash point, chemical structure) instead of heavy metal-based lubricants. This parameter change maintains lubricating performance while eliminating harmful effects.
2Object-affected harmful factors
If viscous liquid or semisolid lubricating coating is applied without heavy metals, then environmental harm is reduced, but torque-on-shoulder resistance (ΔT) becomes insufficient causing yielding
Solution Approach 1:
The invention creates a composite lubricating coating structure combining multiple organic lubricant components with specific viscosity ranges and chemical properties. This composite approach achieves the necessary torque-on-shoulder resistance through synergistic effects of different lubricating compounds while maintaining environmental compatibility.
Solution Approach 2:
The invention optimizes physical parameters of the organic lubricating coating, particularly viscosity (300-5000 cSt at 25°C) and film thickness, to achieve sufficient torque-on-shoulder resistance. By carefully controlling these parameters, the coating provides adequate friction control during makeup operations without requiring heavy metals.
3Reliability
If the coefficient of friction is increased to prevent galling, then galling resistance is improved, but torque-on-shoulder resistance (ΔT) decreases causing shoulder yielding
Solution Approach 1:
The invention creates a dynamic friction characteristic where the coefficient of friction changes during the makeup process. The organic lubricating coating provides higher friction initially to prevent galling, then transitions to appropriate friction levels to maintain torque-on-shoulder resistance, preventing shoulder yielding while ensuring galling protection.
Solution Approach 2:
The invention controls the friction parameters of the lubricating coating by selecting organic lubricants with specific viscosity and chemical properties. This parameter optimization achieves a balanced friction characteristic that simultaneously provides galling resistance and sufficient torque-on-shoulder resistance, unlike conventional heavy metal-based coatings.
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 coating achieves excellent galling resistance and gas tightness without using harmful heavy metals, allowing for high-torque makeup and breakout operations without yielding of shoulder portions, while also preventing rust and maintaining lubricating performance over multiple cycles.
Implementation Method 1
the copolymer particles protrude at low pressure to reduce friction
Implementation Method 2
the copolymer particles protrude at low pressure to reduce friction and embed at high pressure to increase friction
Data Source
AI summary
A lubricating coating which can prevent the occurrence of galling even when makeup is carried out with a high torque and which has excellent rust preventing properties is formed on the contact surfaces of a pin and/or a box of a tubular threaded joint. The lubricating coating contains copolymer particles made from particles of an acrylic-silicone copolymer with an average particle diameter of 10-50 μm dispersed in a highly viscous matrix made from a mixture of a rosin-based substance selected from rosin and its derivatives, wax, a metal soap, and a basic metal salt of an aromatic organic acid (such as highly basic Ca sulfonate).