Development Of The Above Ground Mark System For Pipelines Inspection Using A Magnetic Flux Leakage Detector

Pipeline transportation has become one of the five chief transporting industries while the other four are highway carriage, railage, air-ferry and water carriage, and is playing a more and more important part in national economy and national defence. However, accidents on pipelines take place quite frequently because of such reasons as the increasing age of pipelines, the construction defaults, the artificial destruction and the corrosion of metal, which have caused great economic loss, polluted the environment seriously and even threatened workers'lives.As the most widely used equipment in detecting pipe corrosion, the inspecting system based on the magnetic flux leakage (MFL) theory comprises of three parts: the MFL-PIG, the above ground mark (AGM) system and the data analyzing software. The AGM system, which is designed to locate the corrosion precisely by eliminating the cumulate error of distance the PIG passing through, plays a pivotal role among the whole system, and its key parameter is the exact time the magnetic sensors on PIG passing beneath those markers. Contraposing the MFL inspecting system developed by China Petroleum Pipeline Bureau (CPP) itself, the AGM system introduced in this paper obtains that exact time using an effective method of analyzing the wave of the faradism stimulated in marker coils by the magnet on PIG to ensure the accuracy and to lower the power dissipation and cost of the markers.The AGM system is made up of the hardware which includes markers and master clocks for collecting, storing and transmitting data, and the software for analyzing data and making the final report. In this dissertation, the principle of the AGM system is firstly brought forward with its possible errors and causations analyzed, and the block diagrams of the whole system and its subsystems are designed. Secondly, the magnetic dipole model is set up to compute magnetic field around PIG and to analyze the faradism caused by the PIG's movement, getting the corresponding position of magnetic sensors in the wave, with the effect of several different status of markers on the wave discussed. Then the schemes, functions and user guides are emphasized in detail, followed by all kinds of experiments for liability and the introduction of a successful application on the natural gas pipeline from Shanxi to Beijing.