Tapered Drill Pipe End Joint for Crack-Resistant Shrink Fit
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Solution Overview
Problem
Existing drill pipe joints in rotary and DTH drilling rigs suffer from crack formation and reduced durability due to inadequate stress distribution and interference, leading to compromised load-carrying capacity.
Innovation Solution
The drill pipe assembly incorporates end pieces with tapered coupling means, utilizing a shrink fit between male and female configurations to enhance stress distribution and alignment, allowing for greater wall thickness and reduced interference, thereby improving durability and load-carrying capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional shrink fit joints are used between end pieces and drill pipe, then the assembly can be formed, but crack formation occurs and durability is reduced due to poor stress distribution
Solution Approach 1:
The patent applies parameter changes by modifying the geometry of the coupling surfaces from traditional cylindrical or flat interfaces to tapered surfaces with specific angle ranges (5-15 degrees). This geometric parameter change transforms the stress distribution pattern in the joint, distributing loads more evenly across the interface and reducing stress concentration points that lead to crack initiation and propagation, thereby improving joint durability while preventing crack formation.
Solution Approach 2:
The patent implements local quality by creating a tapered surface configuration specifically at the coupling interface between the end piece and drill pipe, while maintaining the original cylindrical geometry of the main pipe body. This localized geometric modification concentrates the stress distribution improvement exactly where the joint occurs, enhancing durability at the critical interface without altering the overall pipe structure or requiring changes to other components.
2Strength
If traditional coupling designs are used, then manufacturing is simpler, but load carrying capacity is compromised due to inadequate stress distribution
Solution Approach 1:
The patent employs parameter changes by specifying tapered surface angles within the range of 5-15 degrees, which optimizes the balance between load carrying capacity and manufacturability. This angular parameter enables the tapered surfaces to effectively distribute axial and radial loads across the joint interface, significantly improving load carrying capacity. Simultaneously, this moderate angle range remains within the capabilities of standard machining operations, avoiding excessive manufacturing complexity while achieving superior structural performance.
Solution Approach 2:
The patent applies the principle of curvature by replacing traditional flat or cylindrical coupling surfaces with tapered surfaces that have a gradual angular transition. This curved geometric form allows for smooth stress flow across the joint interface, preventing stress concentration and enhancing load carrying capacity. The tapered curvature can be efficiently produced using conventional tapering machining operations, maintaining ease of manufacture while achieving improved strength characteristics.
3Reliability
If greater wall thickness is used at drill pipe ends to improve durability, then load carrying capacity increases, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by modifying the wall thickness distribution along the drill pipe length, specifically increasing wall thickness at the end piece coupling regions while maintaining standard thickness in the main pipe body. This localized thickness parameter change reinforces the areas subjected to highest stresses during operation, improving overall durability and load carrying capacity. The selective thickening is achieved through controlled machining or forming operations during manufacturing, adding minimal complexity compared to uniform thickening of the entire pipe.
Solution Approach 2:
The patent implements local quality by providing enhanced wall thickness specifically at the drill pipe ends where coupling with end pieces occurs, rather than uniformly increasing thickness throughout the entire pipe. This localized reinforcement concentrates material and strength exactly where needed to improve durability under operational loads. The local quality approach minimizes manufacturing complexity by limiting the modified regions to specific zones, avoiding the need to manufacture entirely thicker-walled pipes.
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 tapered design provides improved stress distribution, reduces crack formation, and enhances the assembly's durability and load-carrying capacity while being simple and cost-effective to manufacture.
Implementation Method 1
The end piece is an elongated tubular piece having a first end provided with first coupling means including thread surfaces for thread mounting with other drill components. An opposite second end is provided with second coupling means for coupling the end piece to the drill pipe by means of a shrink fit.
Data Source
AI summary
An end piece, a drill pipe assembly and method is provided. The drill pipe assembly is for rotary drilling and DTH drilling and includes a drill pipe provided with end pieces at its opposite ends. For the mounting of the end pieces a shrink fit and welding is implemented. For improving the shrink fit, the contact surfaces between the components are tapered.