Research And Analysis Of Ultrasonic Shear Waves Testing And Influential Factors Of Pressure Vessel & Piping In High-temperature Environment

In the field of quality control and in-service testing in pressure vessel and pipeline production, ultrasonic inspection technology has been widely applied as an important testing means for a long time. But unfortunately, due to limitation of conditions, there is not yet a systematic research at home on the online ultrasonic detection of weld defects of pressure vessels and pipelines in high temperature environment. However, the equipment of many sectors operates at high temperatures, people often need to know the safety condition of equipment under high-temperature operating condition, such as whether the equipment has defects, whether the defects propagate, whether the defect size falls within the range of safe allowance, the growth rate of defect, service life prediction of the equipment. So there are a lot of problems left for the safefy of pressure vessels and pipings. Through tests and analysis, the following results have been achieved in this paper: (1)Within the range of room temperature~450, variation law of shear wave sound velocity in carbon steel for pressure vessel and pressure pipeline is measured, and the regression equation for shear wave sound velocity Vs = Vo-aT is established.(2) Variation law of echo position of artificial reflector with temperature is measured. On the base of it, the correction method of measurement error and correction formulaYcorrection = Yactual =Yactual due to temperature variation is given, and measurement error caused bymeasurement error of sound velocity and sound path due to thermal expansion is analyzed and discussed.(3) Attenuation coefficient of ultrasonic shear wave of low carbon steel within the range of room temperature~450 is measured. The attenuation coefficient a increases with temperature, from 0.006dB/mm at room temperature to 0.08dB/mm at 450.(4) The relational expression for interface attenuation loss established, due to temperature effect, within the range of 100~450 , the attenuation caused byinterface is increased to 12~16dB, indicating that the inspection interface is a major factor of sound wave attenuation in ultrasonic defect testing at high temperature.(5) High-temperature couplant which can be used in the range from room temperature to 450 癈 is prepared successfully.The ultrasonic shear wave testing method of weld defects in high-temperature environment established based on laboratory tests, calculation analysis and simulating tests have been successfully applied to more than 20 sets of pressure vessels and tens kilometers of pressure pipelines of more than ten large-scale enterprises. Online inspection is conducted on SCC on internal walls of regenerator, precipitator, third-stage hydrocyclone, online monitoring is conducted on the prehydrogenating reactor and reduced pressure distillation column with cracks and defects in combination with defect assessment method using fracture mechanics; and online crack inspection and safety assessment is conducted on high-temperature pipelines. The high-temperature ultrasonic testing technology has been successfully applied to engineering practice, thus filled the domestic blank and solved the urgent problem of pressure vessels and pipings under high-temperature operating condition for the enterprises.