Threaded Tubular Joint Axial Gap for Pitch Error Sealing
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Solution Overview
Problem
The accumulation of small pitch errors in threaded steel components used in oil and gas, energy, and storage applications can lead to axial interference and docking problems, resulting in excessive stress, embrittlement, plasticization, and potential leaks.
Innovation Solution
A tubular threaded joint design that incorporates a threaded axial gap (TAG) greater than or equal to a minimum threshold, calculated using the equation TAGmin=IT(min)*(1/2(LFpinmin)(DPinmin)+1/2(LFboxmin)(Dboxmin))+(4*Epcoat), which compensates for threading offsets due to pitch errors and ensures proper alignment and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a threaded joint is assembled with small pitch errors that are individually acceptable, then the components can be manufactured within tolerance margins, but the accumulation of pitch errors creates axial interference and docking problems leading to excessive stress and potential leaks
Solution Approach 1:
The patent introduces a threaded axial gap (TAG) as a pre-calculated clearance space between the male and female threading teeth. This gap acts as a cushion that absorbs the accumulated pitch errors before they can cause axial interference. The TAG is dimensioned using a specific equation that considers pitch tolerance, threading length, and coating thickness, ensuring it is large enough to accommodate error accumulation while maintaining proper sealing function.
Solution Approach 2:
The threaded axial gap serves as an intermediary element between the male and female threading components. Rather than allowing the threading teeth to directly contact and transmit the full force, the TAG acts as a mediator that decouples the direct mechanical interaction, thereby preventing the transmission of excessive stresses caused by pitch mismatches while still allowing the joint to function properly.
2Reliability
If the threaded axial gap is increased to compensate for pitch errors, then axial interference is eliminated, but the gap must be precisely controlled to avoid compromising sealing performance
Solution Approach 1:
The patent transforms the design approach by changing the critical parameter from zero-gap contact to a controlled non-zero gap. The TAG is calculated using an equation that incorporates multiple parameters (pitch tolerance ITmin, threading lengths LFpinmin and LFboxmin, pitch distances Dpinmin and Dboxmin, and coating thickness Epcoat), allowing the design to account for accumulated errors while maintaining sealing integrity through precise mathematical relationships.
3Reliability
If anticorrosive and lubricating coatings are applied to the threading, then protection and lubrication are improved, but the risk of axial interference and embrittlement increases
Solution Approach 1:
The threaded axial gap is designed to accommodate not only pitch errors but also the thickness of protective coatings. By including the coating thickness (Epcoat) in the TAG calculation equation, the design预先 provides sufficient clearance to prevent the coatings from causing axial interference, thereby maintaining both corrosion protection and structural integrity.
Data Source
AI summary
A tubular threaded joint for the drilling, operation of hydrocarbon wells, transport of oil and gas, carbon capture or geothermal energy, comprising a male tubular element and a female tubular element, each of said male or female tubular elements comprising respectively a male threaded portion and a female threaded portion, one or the other of the male or female threaded portions optionally comprising an anticorrosive and/or lubricating solid coating, said male threaded portion and female threaded portion comprise respectively at least one male threading tooth or one female threading tooth and a threaded axial gap TAG ensuring a space, in the mounted state, between an stab flank of said male threading tooth and a load flank of said female threading tooth, wherein said threaded axial gap TAG is greater than or equal to a minimum gap TAGmin.