Synchronous double-thread anti-drop technology for mining drill pipes

DONG Changle; DONG Mengmeng; ZHAO Jianguo

doi:10.11799/ce202512014

Abstract：To address the issue of drill pipe dropping caused by fractures in the male and female joints'threads,the drop mechanism for fractures at different thread positions is analyzed,leading to the proposal of a synchronous double-thread anti-drop technology.This design adopts a structure that combines synchronous double threads with a connecting rod,in which the primary thread bears the operational load.Should the primary thread fracture,the secondary thread and connecting rod maintain axial connectivity to prevent the drill tool dropping.The design principles for the male and female joints utilizing the synchronous double-thread system are introduced,and calculation methods are provided for the load-bearing capacity of the primary thread and the anti-drop capacity of the secondary thread and connecting rod.Performance tests conducted on Φ89 mm double-thread drill pipes demonstrated a torsional capacity of 34904 N·m and a tensile capacity of 1878 kN,representing 2.33 and 6.26 times the rated capacity of the matching drill rig,respectively.Following simulated fractures of the male and female joint threads,the residual tensile capacities measured 517 kN and 433 kN,corresponding to 1.72 and 1.44 times the rated tensile capacity of the drill rig.These values fully meet the safety requirements for drill string hoisting.The results confirm that the synchronous double-thread structure can resolve the problem of drill pipe dropping caused by joint fractures,enhancing the reliability of the drill pipe and the safety of construction operations.