Acoustic emission detection technology is widely used in petrochemical, power industry, aerospace and aviation industry, metal processing and other fields. Acoustic emission testing is a kind of dynamic non-destructive testing, which can carry out real-time continuous detection of the force process of the object, and find the defect changes in the force process in real time.The boiler of a petrochemical company recently experienced several cracks in the membrane wall tube, causing leakage and shutdown accidents. The cracks mainly appear at the inner pipe hole of the drum, the wall pipe reducing pipe section (including the welded joint of the reducing pipe and the horizontal pipe), the horizontal pipe section, the elbow section and the vertical pipe section. In order to realize the detection and evaluation of boiler membrane wall pipes without dismantling the machine, to avoid sudden shutdown caused by leakage, which may cause serious economic losses. When the boiler was shut down, the acoustic emission test was carried out on the boiler water wall tube.This article introduces the entire process of acoustic emission detection of boiler water wall tubes. Due to the large curvature of the furnace tube surface, the sensor can only be installed in the area of ​​the connecting plate between the furnace tubes, resulting in serious lateral attenuation, and the distance between laterally adjacent sensors should be controlled. Within 40cm, but the longitudinal sensor can accept at least the acoustic emission signal within the range of 80cm.According to the standard of NB/T 47013.9-2012 "Non-destructive Testing of Pressure Equipment Part 9: Acoustic Emission Testing", in accordance with the pressurization procedure of the pressure equipment in use, the water wall tube of the boiler is subjected to hydraulic pressure test. During the entire loading process, a positioning source signal appears. Mainly distributed in the 0-0.9MPa pressure rise, 0.9MPa pressure hold and 1.25MPa pressure hold stages. According to the activity and intensity of the acoustic emission localization source, the level of the acoustic emission localization source can be evaluated. Among them, there are 11 Class I acoustic emission positioning sources, which do not need to be verified. There are two Class II acoustic emission positioning sources. Since the acoustic emission signal amplitude corresponding to the deformation and fracture of 20 steel is above 60DB, it is judged that the positioning source is not active. Defects, there are two Class III acoustic emission positioning sources, it is recommended to verify them.

Acoustic Emission Detection and Signal Source Analysis of Boiler Water Wall Tube

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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