Design And Analysis Of Double-tube Drilling Rig’s Clamping And Unclamping Device For Soft Coal Bed

Our country is a consuming nation who based on the coal energy, but thecoalfield geological structure is more complicated and changeful because ofnumerous collisions and seductions between many continental blocks during thegeological movement. Now, except Fushun area，most of the mine coal bed belongto the soft coal bed. In recent years, the drilling technology with casing has beendeveloped in order to solve the problem of low porosity, low depth and constructiondifficulties in soft coal bed. The technology has the following advantages: lessdisturbance and erosion to the wall of the borehole, strong carrying cuttings capacityand any other characteristics. Matching this technology, a new machine double-tubedrilling rig (also called casing drilling rig) has been developing by Xi’an ResearchInstitute, China Coal Technology&Engineering Group Corp. This drilling rig cannot only drill by single pipe, but also drill by casing drilling according to theworking condition, which fundamentally solves the problem of transporting thecasing to the bottom of the drilling hole and adapted to the development trend oflarge diameter long hole.Clamping and unclamping device is one of the most important compositionparts on the drilling rig, its function is to prevent the drill string from sliding byclamping drill pipe at the normal drilling and unclamping drill pipe meshed with therotary mechanism and feed mechanism at the replacing time. As the tripping workspeed of the drilling rig and connection work strength of single drill pipe increased,the proportion of unloading drill pipe is also improved accordingly. So it issignificant for the performance, drilling efficiency and drilling quality of the wholemachine to study the new clamping and unclamping device. So starting with thetraditional clamping and unclamping device, double-tube drilling rig’s clamping andunclamping device have been deeply designed and analyzed based on the casingdrilling project in this paper. The main research items are as follows:(1) Several characteristics, principles and scopes of traditional c lamping and unclamping device have been systematically studied. And then choose the top-openhydraulic clamping and loosening structure for the clamping device and twosymmetric hydraulic cylinders structure for the unclamping device, which is suitablefor the construction requirements of dual tube drilling in soft coal bed.(2) The main parts of the clamping and unclamping device have been designedsystematically, and the key parts have been theoretical calculated and strengthchecked. The strength safety coefficient of the final chosen clamping cylinder isgreater than1.5, which can completely meet the needs of the drilling work; Thechosen unclamping cylinder produce greater torque than the maximum rated torqueof the drill rig, which can ensure to unscrewed the shackle thread.(3) ABAQUS software has been used to analyze the intensity of the designedstructure, and then optimized the structure based on results of FEM simulation. Thestrength safety coefficient of the optimization result is greater t han1.2, which showsthat the mechanical structure is reasonable, the security and accuracy of the designare enhanced significantly.(4) Three-dimensional modeling of the unclamping device by the UGNXsoftware and carried out the simplified model for simulation. In the modelingprocess through virtual prototyping of assembly, check the structural design isreasonable, there is no interference problem.(5)ADAMS software has been used to simulate the system clamping force,unclamping force and torque, and obtained a chuck key components of displacement,velocity curve. The maximum radial displacement of the slip is0.0204meter, themaximum clamping velocity is up to0.102meter per second and the unclampingone is0.153meter per second, which can meet the requirement of rapidly opening-closing speed; The maximum angular velocity is4.2972radians per second whileworking and4.2972while returning, which can meet the requirement of the rapidlyworking angular speed.In this paper, through a series of design and analysis above, a fairly completesystem of double-tube drilling rig’s clamping and unclamping device has beendeveloped, which not only demonstrates the feasibility of the design in theapplication, but also lays a technology foundation for the further development ofthe clamping and unclamping device to meet the different conditions.