Key technology of automatic loading and unloading system for dual-pipe directional drilling rig and its application in soft–fragmentized coal seam

To improve the automatic level and efficiency of loading and unloading of drilling rigs during the construction of dual-pipe directional drilling, an automatic loading and unloading device of dual pipe was developed to realize the fully automatic loading and unloading of drilling rigs under different working conditions and to solve the technical problems of loading and unloading the drill pipes and casing simultaneously during the dual-pipe directional drilling. Meanwhile, the device structure and control system was designed to restrict the load applied to the device during construction with the end-compliant technique. Besides, the key boundary conditions of the control program were clarified, and the process of automatic loading and unloading of drilling rigs under different working conditions was developed. The industrial test was carried out in Qinan Coal Mine of Huaibei Mining Holdings Co., Ltd. in Anhui, with 4 boreholes in a total footage of 1 170 m drilled. During the test, the automatic loading and unloading device of dual-pipe operated smoothly and was able to meet the loading and unloading requirements of drilling rigs under different working conditions. By applying this device, the automatic loading and unloading of drilling rigs, which originally requires the close cooperation of 2‒3 people, could be done automatically by program control, and the average efficiency of simultaneous and separate loading and unloading of drill pipe and casing increased by 350% and 110% respectively. In addition, the comprehensive construction efficiency of dual-pipe directional drilling was assured, with the number of workers reduced, the labor intensity of workers lowered and the construction safety ensured. The test results show that the automatic loading and unloading device of dual-pipe operates stably and reliably with reasonable construction process and the performances of the device meets the needs of dual-pipe directional drilling. The research results provide technical and equipment support for the automatic loading and unloading of dual-pipe directional drilling rigs and lay the foundation for the popularization and application of dual-pipe directional drilling technology in the relevant fields of CBM mining.