A combined detection method of electromagnetic ultrasonic longitudinal guided wave and magnetic flux leakage detection

Abstract

The invention discloses an electromagnetic ultrasonic longitudinal guided wave and magnetic leakage detection compounded nondestructive detection method. On the original basis of magnetic leakage, an electromagnetic ultrasonic (EMAT) exciting coil and an electromagnetic ultrasonic (EMAT) receiving coil are added. When the detection process is normal, only magnetic leakage detection is performed. When a defect is found by the magnetic leakage method, the electromagnetic ultrasonic (EMAT) exciting coil sends an ultrasonic longitudinal guided wave on the inner surface of a steel plate to be detected. Through analyzing the ultrasonic longitudinal guided signal received by the electromagnetic ultrasonic (EMAT) receiving coil, it can be determined whether a defect exists in the inner surface of the steel plate to be detected, thus determination of defects in the inner / outer surfaces of the steel plate to be detected is realized. The electromagnetic ultrasonic longitudinal guided wave and magnetic leakage detection compounded detection method effectively overcomes the shortages of low accurate rate of determination on defects and low detection speed in the prior art, and has the advantages of simple structure, little information processing amount and non-contact measurement.

Description

technical field [0001] The invention relates to the field of non-destructive testing, in particular to a combined testing method of electromagnetic ultrasonic longitudinal guided wave and magnetic flux leakage testing. Background technique [0002] Since long-distance oil and gas pipelines have been widely used as a means of energy transportation in recent years, the scale of laying oil and gas pipelines and storage tanks has become extremely large. With the gradual aging of existing equipment and the continuous deterioration of crude oil quality, it has become very important to detect its safety and reliability. Steel plate defects used in long-distance pipelines and storage tanks can be mainly divided into two categories, namely "external corrosion" and "internal corrosion". "External corrosion" is generally caused by groundwater or rainwater erosion around the steel plate; "internal corrosion" is generally caused by corrosive impurities contained in crude oil and steel p...

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Problems solved by technology

The corrosion mechanism of the two is different, so there are obvious differences in the corresponding treatment methods

However, at present, most of the existing non-destructive testing equipment at home and abroad are based on magnetic flux leakage detection, and the magnetic flux leakage detection technology can excite similar magnetic flux leakage signals on the inner and outer surfaces of the steel plate, which makes the traditional magnetic flux leakage detection methods unable to effectively distinguish the magnetic flux leakage on the steel plate. Internal and external surface defects

[0003] Chinese Patent No. CN101354380A discloses a non-destructive testing method combining eddy current and electromagnetic ultrasound. This method uses the skin effect of eddy current testing to detect defects on the inner surface of the steel plate to be tested. The results of ultrasonic wave detection are combined to distinguish the defects on the inner surface and near surface of the tested steel plate. However, the electromagnetic ultrasonic part of this method uses the plate surface wave for detection, so the detection sensitivity to the outer surface of the tested steel plate is low.

However, this method needs to be combined with the time difference information and amplitude information of the ultrasonic echo for comprehensive judgment when performing electromagnetic ultrasonic thickness measurement. The logic is relatively complicated and time-consuming, which is not conducive to the application of online detection

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