Research On Weak Stress Wave Signal Detection In Oil Pipelines

Long pipeline transportation is a convenient and economical way for oil transportation, and is widely adopted by industries. But the leakage accidents of oils not only bring great economic losses but also seriously pollute our environment. Thus researches on pipelines leakage detection will result in remarkable economic and social benefit.The stealth monitoring system based on stress wave detection technique for oil pipeline on-line monitoring is composed of two parts: the detection net nodes for signal acquisition and the host station for oil stealing alarming and location. In this paper, the hardware design, debugging and expanded function of the nodes is investigated. The principle of stress wave detection is analyzed from physical aspect, and the hardware test system is discussed. For the expanded function part, the ultrasonic testing circuits for anti-stealing and the smart detection circuits for failure diagnosis are discussed.The nonlinear threshold de-noising method of wavelet analysis is adopted for background noise cancellation and SNR (Signal to Noise Ratio) increasing. Thus the signal detection performance at long distance can be improved and the detection distance can be extended. Field experiments employing the above methods indicate that the distance of stress wave detection is more than 1 kilometer.The modeling of the stress wave going through the pipelines is discussed finally. By considering some restriction conditions and the earth damping, a simplified mathematical model of underground pipelines is setup.