Straightness measuring and finite element analysis of the drilling pipe straightening based on the LPD

The drilling pipes used in oil industry are special seamless steel pipes, whose ends are upset, with length of 200mm, during the pipe processing due to the field interconnection. With the gravitational effecting, there will be a shadow zone of straightening on the pipe and therefore some defects, such as straightness out-of-tolerance and panting in connection parts, are inevitable. A new method will be applied to solve the problem in Shanghai Bao Steel, where the drilling pipes are used to be straighten by manpower with lower precision and efficiency. Based on the LPD (laser position detector), straightness measuring method for drill pipe is put forward in this paper. We analyze the pipe bending condition by collecting multi-tunnel LPD data and present a novel mechanical model to simulate the elastic-plastic process during the straightening. With the help of commercial nonlinear finite element analysis code, a nonlinear finite element model for pipe straightening is set up. Finally, some experiments are made to demonstrate the validity of the model.