Research On The Deflection Detected System For Large-Diameter Longitudinal Seam Weld Steel Pipe

As a major shape error of large-diameter longitudinal seam weld steel pipe, deflection error affects the quality of pipeline's installation. Before straightening to large-diameter longitudinal seam weld steel pipes, deflection along the axis must be known firstly. How to measure straightness error of weld pipe's deflection with a high accuracy and a high speed has been a metrology problem which has not been fixed properly by now. Deflection can be measured and surveyed by traditional mechanical methods and optical means. Optical deflection measuring system has the advantages of nor-contact, high resolution, fast response, and so on.To begin with, the measuring principle of deflection for the large-diameter longitudinal seam weld steel pipe is discussed in this paper, which is based on the research of the status in domestic and the trends of overseas in this area. Many measuring methods are analyzed and compared here. According to this, the overall structure of the measuring apparatus has been contrived. With the shape and size characteristic, OptoNCDT 1302 Reflective Laser Displacement Sensor is chosen. The mathematical model has been created accordingly. The structure and scheme designs for the measuring system have been realized.And then taking the Virtual Instrument software as a starting point, the concept, typical structure and development process of Virtual Instrument are illuminated. Also the function characteristics and operation methods of virtual instrument software environment LabVIEW are introduced here. According to the Virtual Instrument 's principle of design, the system has used the modular design. Then, the realization of the main acquisition and processing functions of deflection detection system program procedures of large-diameter longitudinal seam weld steel pipes are specified detailedly. At last, deflection examinations are carried on with the longitudinal seam welded pipeφ75×800mm with different amount of deflection. Through the experiments of stability, repeatability, measurement data comparison with the Three coordinates measuring machine's, the feasibility and reliability of the measurement system is testified.