Research On Influencing Factors For Stress Measurement Of Pipeline In Service By Ultrasonic

As a non-destructive detection technology,longitudinal critical refractive wave(LCR wave)stress measurement technology has been proven to be used to measure the stress level in the operating state of the oil and gas pipeline.The key to ultrasonic stress testing technology is that ultrasonic propagation time measurements are susceptible to interference from a variety of factors.Firstly,this paper bases on the sound elastic theory,simplifies the elastic equation in the two-way stress state,gives the quantitative relationship between the stress and ultrasonic flight time both in one-way and two-way stress state.Then this paper also uses the built one-way and two-way tensile experiment platform,to study the effect of temperature,coupling state,and steel rolling direction on stress testing,and the one send and two receive ultrasound probes are developed.Finally,based on the results of pipe axial stress measurement,this paper also summarizes the method of pipeline stress safety evaluation,and the engineering application is carried out in combination with mountain pipe stress measurement and its safety evaluation.(1)The LCR wave elastic equation and stress and ultrasonic flight time relationship are derived in two-way stress state.Based on the sound elastic theory,the author finds that the longitudinal wave in stress direction is most sensitive,and determines to measure the axial stress of the pipeline by LCR wave.In combination with the normal operating state of the pipeline,the relationship equation of between stress and velocity of the LCR wave is derived.With the fixed-circulation method and the flat stress physical equation,this paper summarizes the quantitative relationship between the stress and the ultrasonic flight time in one-way and two-way stress state.(2)This paper constructs the one-way and two-way stretched experiment platform,and researches the effects of temperature effect on the measurement accuracy of stress measurement by ultrasonic by theory and experiment.Ultrasonic flight time is measured using a fixed-circulation method,and the effects of temperature on ultrasonic wave elasticity coefficient and propagation time is studied.The temperature compensation formula for ultrasonic test stress is given,and the accuracy of the compensation formula is verified by the temperature experiment;the one send and two receive ultrasound probes is designed,and the effect of the temperature on the measurement results of ultrasonic flight time is designed by path compensation.(3)This paper summarizes the influence of the changes of various factors on the measurement of ultrasonic flight time,including factors the coupling agent type,coupling agent viscosity,steel plate surface roughness,coupling agent viscosity,steel sheet surface roughness,coupling pressure,and steel sheet rolling direction.Through the orthogonal experiment,the primary sequence of the degree of factors has been analyzed,and the precautions when using ultrasonic wavelength measurement of pipeline stress.Two-way ultrasound probe is designed,and the pipeline stress measurement method suitable for two-way ultrasound probe is proposed.(4)Based on the pipe axial stress measurement,the pipeline stress safety evaluation method is summarized,and the calculation formula of the piping bending positive stress is derived.The dangerous point stress measurement has been carried out on a mountain axial landslide and the horizontal pipe,and the safety margin in the current operation state of the pipe has been evaluated,and the surface shift of the lateral slope segment pipe cut has been predicted and verified.