Research On Ultrasonic Detection Probe For Underground Oil Pipeline Leakage

The continuous promotion of natural gas energy has put forward higher requirements for the safety of oil and gas exploitation,storage and transportation.Detecting oil pipe leakage in natural gas wells is an important part in the safe production of oil and gas.According to the leakage of underground natural gas pipeline,the demand for leakage detection technology,the principle of ultrasonic leakage detection and the application of piezoelectric sensors,this paper studies the ultrasonic detection probe of underground oil pipeline leakage from the aspects of piezoelectric effect mechanism,finite element simulation,probe structure design and experimental test.The main content and achievements of this paper are as follows(1)Aiming at the leakage problem of natural gas underground oil pipe,the mechanism of ultrasonic leakage detection and the working conditions of leakage detection of underground natural gas wells were studied,the working principle and characteristics of piezoelectric materials were analyzed,and the radially polarized piezoelectric ceramics made of PZT-5H material was selected as the sensitive element of the ultrasonic probe.The theoretical calculation formula of the resonance frequency of the piezoelectric ceramic tube is introduced.(2)The finite element model of the piezoelectric sensitive element is established,and the static analysis,modal analysis and harmonic response analysis are carried out.The results show that:under the action of 1kPa load,the maximum voltage generated by the piezoelectric sensitive element is 75.45mV;the first-order natural frequency of the piezoelectric sensitive element is 34.465kHz,the second-order natural frequency is 35.810kHz,and the sensitivity is 75.45mV/kPa;The relationship curve between the voltage of the piezoelectric sensitive element in the frequency range of 20kHz-60kHz and the external load frequency is obtained by the analysis of the harmonic response.The excitation load of lkPa can generate a maximum voltage of 6.79V when the second-order natural frequency of the element is 34.465kHz.(3)Through the finite element simulation,the influence curves of the parameters of the piezoelectric ceramic tube and the epoxy resin potting layer on the sensitivity and vibration mode of the piezoelectric sensitive element are obtained.The simulation results show that the thickness and average radius of the piezoelectric ceramic tube have little influence on the working stability of the piezoelectric sensitive element,and the thickness of the epoxy resin potting layer is the most important factor affecting the response speed and stability of the piezoelectric sensitive element.(4)The ultrasonic probe is designed and implemented.The design criteria and technical steps of the probe were analyzed,and three design schemes of the ultrasonic probe were proposed.Through the comparison and evaluation of each scheme,the optimal scheme was selected,and the material selection,processing and assembly of the probe parts were completed.(5)The ultrasonic probe was impedance tested.The impedance frequency plot of piezoelectric ceramic tube and ultrasonic probe was plotted using an impedance analyzer,and the influence of potting materials on the sensitivity of ultrasonic probe was compared.The results show that the sensitivity of the ultrasonic probe after potting is 17%of the sensitivity before potting,and the ultrasonic probe after potting obtains a wider working frequency band than before potting,indicating that the potting material reduces the sensitivity of the probe and broadens the working frequency range of the probe,which verifies the performance of the ultrasonic probe.