The Research And Design Of Metal Magnetic Memory Testing System

Pipes are used in a wide range of areas now, whether in engineering or industrialengineering, pipeline is one of the very significant constituent, especially for oil andgas, it is the most important means of transportation. According to statistics, theworld has8.2×104kmpipeline for oil and gas, and the increment of pipeline willincrease7%everyday. Long-distance transport of the pipeline also has huge millingand tear. With the time advances, in DaQing oil field, the pipeline planted more than10years account for a large part of the total pipelines，which makes the phenomenonof perforation and fracture always happen, inspection and maintenance of thepipeline is an important guarantee for the safe transport of oil. Traditional detectionmethods, such as ultrasonic testing, magnetic flux leakage testing and so on havetheir limitations, however, the long-distance pipeline often setted in harshenvironment areas, which makes these detection device not working.In this paper, the metal magnetic memory method overcomes these limitations,the metal by using the characteristic of ferromagnetic metal which produce its ownleakage magnetic field under the action of external stress in earth’s magnetic field todetect the the stress concentration area of ferromagnetic metal, in order to determinethe location of damage or defects, and to achieve the purpose of detecting conduit.Metal magnetic memory testing is put forward by Russian experts Dubov，also maderelative mature products at the same time, the domestic is still in the stage of researchin this area currently.This article analyzed the principle of metal magnetic memory’s generate.According to the actual situation of the DaQing’s oil refining fifth factory, designedthe testing system of metal magnetic memory, in order to achieve two parts ofcontent which are the inspection of adherent pipeline and buried pipelines. Thisarticle chose Honeywell’s three-axis magnetoresistive sensor as the probe to collectsignal, and achieve the A/D’s conversion and amplified signal etc through the SCM’s control. Due to the strength of magnetic field is extremely weak, the collectedmagnetic signal always accompanied by a lot of noise, this article, according to thehardware filtering and the characteristics of signal after filtering, filter the waveagain by using the method of wavelet transform noise reduction. And finally chosemethod of dbN wavelet threshold de-noising through the comparison and analysis,makes the true signal to the maximum extent.This article explains the relationship between defects and area of stressconcentration and the factors affect signal’s characteristics etc through comparing thesimulation and actual experimental. The function which expected to achieve of metalmagnetic memory testing system is achieved basically.