Development Of Extremely Low Frequency Tracking And Positioning System For Pipeline Internal Detector

Pipeline is one of the main means of energy transportation of modern petroleum and natural gas,and the world's “energy blood”.With the demand of economic development,the pipelines laid by petrochemical industry and government departments in China have been increasing rapidly.But the pipeline damage caused by material,construction or corrosion is a serious threat to the effective operation of the pipeline,once there is danger,the consequences will be very serious,not only pollute the environment,and even threaten the safety of human life and property.Therefore,it is necessary to detect and maintain the pipeline regularly to ensure the safe and effective operation of the pipelines.In-pipeline detector tracking and positioning technology can monitor the running status and position of the detector in real time,and in-pipeline detector the tracking and positioning technology is the necessary condition for the pipeline nondestructive testing.This paper aiming at the problem of tracking and positioning of the pipeline internal detector in the process of running,the present situation of the technology of tracking and positioning in the domestic and foreign pipeline detector were analyzed,and the propagation characteristics of low frequency magnetic signal and the distribution characteristics of magnetic field generated by the launch coil were analyzed.Based on the magnetic field symmetrical distribution generated by the launch coil,design a extremely low frequency magnetic signal transmitter mounted on the pipeline internal detector and a portable extremely low frequency magnetic signal receiver.The transmitter is mainly composed of a main control circuit,a power amplifying circuit and a launch coil;The launch coil uses high permeability permalloy as magnetic core to reduce eddy current loss.Series resonance is also used to improve the signal emission efficiency.The receiver includes receiving coil,signal conditioning circuit and liquid crystal display and so on.The receiver adopts induction coil and uses parallel resonance to improve signal receiving range and signal noise ratio.In-pipeline detector tracking and positioning system mainly uses the transmitter to produce a voltage signal source of constant amplitude andfrequency stability,through the power amplifier circuit loaded into the launch coil,and establish electromagnetic field in space.Through the pipeline and environmental media,the changing electromagnetic signal is received by the receiving coil located in the surface,through the signal conditioning circuit to extract the required signal information and achieve the purpose of tracking and locating the pipeline detector.In this paper,the performance of each part of the tracking and positioning system for pipeline internal detector were analyzed in detail,and the work effect of the system was proved by different experiments.The results show that the tracking and positioning system has good stability and reliability.And the received signal has symmetrical characteristics.In underground pipeline experiment,the tracking and positioning system's effective positioning distance is 8 meters,the tracking and positioning range of pipeline internal detector is improved.