Curved Thread Flanks for High Torque Drilling Connections
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Solution Overview
Problem
Conventional threaded connections in drilling components for hydrocarbon wells face challenges in transmitting sufficient torque due to the limited contact surface area, leading to stress concentrations and potential breakout or overtorquing, especially in complex drilling conditions.
Innovation Solution
The development of novel threading profiles with circular arc profiles for stabbing and load flanks, connected by fillets, which increase the contact surface area between threads, allowing for higher torque transmission and reduced stress concentrations, featuring radii between 3 to 13 mm for fillets and 25 to 127 mm for arc profiles, with specific angles and lead lengths to optimize torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional threaded connections are used with limited contact surface area, then the structure is simple and easy to manufacture, but the torque transmission capability is insufficient leading to stress concentrations and potential breakout or overtorquing
Solution Approach 1:
The patent applies curved profiles (circular arcs) to the stabbing and load flanks of the threads instead of conventional straight profiles. The stabbing flank has a circular arc profile with radius R1 and the load flank has a circular arc profile with radius R2, creating a curved contact surface that increases the contact area between mating threads. This curvature allows for more distributed stress and higher torque transmission capability while maintaining manufacturability through standard machining processes.
2Strength
If the contact surface area between threads is increased to transmit higher torque, then the torque transmission capability improves, but the manufacturing precision requirements increase due to specific radius and angle specifications
Solution Approach 1:
The patent specifies precise geometric parameters for the curved threading profile, including radius R1 for the stabbing flank arc, radius R2 for the load flank arc, lead angle alpha, and included angle beta. These parameter changes from conventional straight threads to curved threads with specific radii and angles enable increased contact surface area and improved torque transmission. The defined parameters provide a balance between achieving sufficient contact area for high torque applications and maintaining manufacturability through controlled precision requirements.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention concerns a threaded connection comprising a first and a second tubular component, each being provided with a respective male (1) and female (2) end, the male end (1) comprising at least one threaded zone (3) on its external peripheral surface and ending in a terminal surface (7), the female end (2) comprising at least one threaded zone (4) on its internal peripheral surface and ending in a terminal surface (8), the threaded zones (3; 4) comprising, over at least a portion of their length, threads (32, 42) each comprising, viewed in longitudinal section passing through the axis of the tubular component, a thread crest (36, 46), a thread root (35, 45), a load flank (30; 40) and a stabbing flank (31; 41), characterized in that the profiles of the male and female load flanks (30; 40), viewed in longitudinal section passing through the axis of revolution (10) of the connection, are a continuous curve with a convex or concave form, the profile of the male flanks being complementary to that of the female flanks over at least 70%, preferably 90% of said continuous curve.