Design Of Geophone With Asterisk Shaped Beam And Its Application In The Pipeline Inspection Gauge Above Ground Mark

With the advantages of closeness, safety, continuity and low cost, pipage has become the primary way of transporting the oil gas worldwide. During the process of pipage, the main reason for the accidents is the leaking of oil gas resulted from the pipeline wall being eroded. Nowadays, the most widely used method to inspect the erosion of pipeline wall is the online monitoring technology of pipeline inspection gauge(PIG). When the PIG is conducted to make the inspection, through a measurement on its own travel distance, a corresponding relationship between the distance and the defect information is built in the PIG, so as to provide a data support for the maintenance of pipeline. Moreover, the error measured by the PIG on its travel distance is constantly accumulated with the increase of the pipeline length, which eventually will make the orientation of the defect of pipeline wall lose practical significance. Therefore, when the internal inspection is conducted on the pipeline, the above ground mark technology is usually adopted to make a re-marking on the information about the position of PIG every a certain distance, and amend the distance measured by PIG, so as to ensure the accuracy of the orientation of the defect information about the pipeline wall.In this paper, aiming at the engineering needs for the PIG above ground mark, a kind of multi-axis geophone with asterisk shaped beam is designed by adopting the phonics principle to conduct the above ground mark, and the technology of MEMS is also used to make the design on the detector by combining with the bionic principle and piezoresistive effect. Moreover, based on the sonic source in the running process of PIG and the propagation law for the acoustic wave in the soil medium, centering on the design of the geophone with asterisk shaped beam, the bionic mechanism and pick-up principle of geophone with asterisk shaped beam are mainly introduced. After a finite emulation on the model for the micro structure of the building asterisk shaped beam, the geometric size and the micro processing technology of the micro structure are confirmed, a signal conditioning circuit including power supple module, preamplifier and filter circuit is designed, and the whole structure is packaged to make a model machine for the geophone with asterisk shaped beam. A test is made in the lab on the sensitivity and the directivity of the acoustic detector with asterisk shaped beam, and the result shows that the sensitivity of the detector is 60mV/g with a directivity of 8 shape cosine.After the test on the performance, a practical test on the influence of the concrete application environment of the above ground mark on the acquisition ability of phonic signal and the orientation ability of the acoustic detector with asterisk shaped beam in the soil medium is made. During the process of the test, a kind of coupling frame device with three coccygeal vertebras is proposed to increase the coupling degree between the acoustic detector and the soil medium. The result shows that the sensitivity and signal-to-noise ratio of the geophone in the soil medium can be effectively improved by this kind of coupling device, and because of this, the error of the sonic source orientation of the geophone can be reduced by 2°. In addition, aiming at the characteristics of one structure and multi output of the acoustic detector with asterisk shaped beam, a kind of new thought is put forward for the confirmation of the time for the PIG passing by the mark through the output signal ratio between the orthogonal outputs, and the azimuth estimation on the sonic source passing by the two-coordinate half plane.Finally, in this paper, a simulation experimental instrument for the PIG above ground mark is constructed to make an integral verification on the structure of the designed acoustic detector and the mark thought. The result of the verification shows that the error of the time for the PIG passing by the mark can be controlled within the range of 1s, and the error of the orientation of the sonic source after the PIG being blocked is no more than 4°, which can meet the engineering needs for the ground mark.In a word, the designed scheme of using multi-Axis acoustic detector with asterisk shaped beam to make the PIG above ground mark is simple and feasible, and shares an extensive application prospect. What’ more, it should be the accents in the future that a further study is made on the adaptability of the acoustic detector to the soil mediums with different structures, and the engineering application as well as the popularization in the fields of military unattended and civil security early warning system.