BN-Epoxy Thread Coating for Seizure-Resistant Oil Well Joints
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Solution Overview
Problem
Conventional lubrication technologies for oil country tubular goods using solid lubricating coating films fail to simulate the severe conditions of large and unbalanced loads encountered in actual well operations, leading to inaccurate evaluations and potential seizure due to clogging by shavings, and lack clear definitions for epoxy resin compositions.
Innovation Solution
A solid lubricating coating film is developed using a binder resin containing a specific ratio of epoxy resin and boron nitride (BN) with controlled particle size, designed to withstand large and unbalanced loads, ensuring excellent lubricity and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid lubricating coating film is formed on the tightening surface, then lubrication is achieved without wet lubricating compounds, but the coating film may be scraped and produce shavings that cause clogging and seizure under large and unbalanced loads
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating film by controlling the particle size distribution of solid lubricants (combining fine particles ≤10μm for filling and coarse particles >10μm for lubrication), the hardness of the coating film (3H or higher), and the composition ratio of binder resin to solid lubricant. These parameter changes enable the coating to withstand large loads without scraping into harmful shavings while maintaining lubrication performance
Solution Approach 2:
The patent creates a composite coating film structure combining binder resin, fine solid lubricant particles (≤10μm), and coarse solid lubricant particles (>10μm). This composite structure allows fine particles to fill voids and create a hard matrix while coarse particles provide lubrication, achieving both high hardness and low friction without generating clogging shavings under unbalanced loads
2Ease of manufacture
If the particle size of boron nitride is not controlled, then the coating film can be formed easily, but the lubrication performance and resistance to seizure are insufficient
Solution Approach 1:
The patent changes the particle size parameter of boron nitride to a specific distribution: fine particles of 0.1-10μm and coarse particles of 10-100μm. This parameter change optimizes both manufacturability and performance, as the fine particles enable smooth coating application while the coarse particles provide enhanced lubrication and seizure resistance under unbalanced loads
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 film provides lubricity and corrosion resistance comparable to greasy compounds, effectively addressing the challenges of unbalanced loads and seizure in actual well conditions.
Implementation Method 1
a solid lubricant that contains boron nitride (BN) in an amount of 80% by weight or more... excellent lubricity
Implementation Method 2
the binder resin contains a prepolymer and a curing agent, the prepolymer is formed of one or more epoxy resins
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
It is possible to provide a solid lubricating coating film capable of imparting excellent corrosion resistance as well as lubricity to a connection for oil country tubular goods even when a solid lubricating coating film is adopted for lubrication. An agent for forming a solid lubricating coating film on a thread portion of oil country tubular goods, in which a binder resin contains a prepolymer and a curing agent, the prepolymer is formed of one or more epoxy resins, 70 parts by weight or more of the prepolymer is contained with respect to 100 parts by weight of the binder resin, the epoxy resin constituting the prepolymer has an epoxy equivalent of 100 or more and 500 or less, the solid lubricant contains boron nitride (BN) in an amount of 80% by weight or more, BN has an average particle size of 10 um or less, and a total weight of the solid lubricant is 0.1 times or more and two times or less a total weight of the binder resin.