Ultrasonic liquid level measuring technology has been extensively applied in the industrial field, which is characterized by its high accuracy, strong ability of anti-electromagnetic interference and simple structure. However, its measurement results are easily affected by the tilt of liquid level and ripple. In this study, the traditional gas-liquid interface was transformed into a solid-liquid interface based on the acoustic scattering by a rigid sphere and a circular waveguide, and the liquid level was measured with the stable reflecting surface by complying with the liquid level in the duct. Such a method could overcome the effect of the tilt of liquid level and ripple on the measurement results. In this study, a signal processing method to improve the signal to noise ratio of the direct wave was proposed. To improve the sound intensity of the direct wave and reduce the effect of high-order mode waves on the signal, the transceiver was applied with a matching layer, and the appropriate waveguide material should be selected to absorb a portion of high-order mode waves. As revealed from the experimentally achieved results, an optimized lightweight ultrasonic liquid level sensor was proposed to eliminate the effect of ripple, and the tilt of liquid level increased from 20° to 60°.

With the development of the petrochemical industry, pipeline inspection technology plays a vital role in terms of avoiding explosions and protecting people’s life and property. Pipelines working in high temperature environments suffer from dual dangers of internal and external wall defects. It is often difficult to find a single nondestructive testing (NDT) method that can cover internal and external defects detection especially in high temperature environments. In order to discover pipeline defects in time, we propose a hybrid online monitoring method for comprehensive defects inspection in high temperature environments. This hybrid monitoring method combines eddy current testing (ECT) with electromagnetic acoustic transducer (EMAT) techniques. Specifically, we split the coil signal into two channels; one channel gives ECT signal and the other gives EMAT signal. Furthermore, we demonstrate the feasibility of the proposed hybrid monitoring method by numerical simulations and laboratory experiments. The results show that the proposed hybrid online monitoring method can be used successfully to simultaneously monitor surface and internal defects and has high stability even at temperatures above 300 °C. Our approach achieves the genuine integration of ECT/EMAT technologies, effectively addressing the challenge of incomplete monitoring of pipeline defects in high-temperature environments.

A multi-frequency alternating current field signature method (MACFSM) that combines multi-frequency excitation and zero phase is proposed to detect subsurface defects in metal pipes. In a numerical analysis, multi-frequency exciting currents are applied to a metal pipe (wall thickness T = 10mm) which contains different depth defects, and then zero phase is extracted from phase spectrum to assess defect depth. The investigation shows that in comparison with derivative extremum, the monotonic relationship between zero phase and defect depth can enable accurate determinations of defect depths. A general solution for calculating defect depth using zero phase is given in MACFSM. Pulse excitation field signature method is proposed for future research of quantitative nondestructive evaluation (QNDE) in the end of this paper.

Corrosion in the pressure pipelines of nuclear reactors is a major threat to the structural safety of nuclear submarines. Online monitoring techniques are needed, rather than offline inspection techniques, owing to the special nature of nuclear reactors. The traditional ultrasonic thickness measurement technique is usually used for the offline estimation of pipe thickness, but it is difficult to use as an online monitoring technique because it requires periodic calibration. This paper proposes an ultrasonic thickness measuring technique with a self-calibration function through the introduction of a calibration block. However, the introduction of the calibration block generates trailing echoes and therefore a threaded cylindrical calibration block is designed to eliminate such trailing echoes.

Spherical air pressure tanks are used in long-term service under alternating positive and negative pressures, and the dramatic changes in their internal pressures generate both residual stresses and internal defects. A single critically refracted longitudinal (LCR) wave can only detect residual stress on the surface layer of the spherical air pressure tank, and it cannot identify defects on the inner layer at the same time. To address these problems, this article proposes a multimodal ultrasonic methodology for stress and defect detection based on the joint action of LCR and transverse waves. This article analyzes the principles of using multimodal waves to detect stress and defects, studies the variable-frequency high-amplitude ultrasonic excitation source acting on the piezoelectric transducer, and enhances ultrasonic signal identifiability via multiparameter fusion. A detection platform is then established to detect plane stress, gradient stress, internal defects, and interior surface defects; and a method for simultaneous detection of stress and defect under the joint action of LCR waves and transverse waves is obtained. The experimental results demonstrate both the feasibility and the application value of the multimodal ultrasonic methodology for stress and defect detection in spherical pressure tanks.

In the petrochemical industry, plants must be shut down regularly for maintenance to safeguard human lives and property from catastrophic explosions. The introduction of nondestructive monitoring technologies has made this process more efficient and economical. However, nondestructive monitoring in extreme heat environments (⩾ 600 °C) remains a challenge. Electromagnetic ultrasound technology has notable advantages in monitoring high-temperature equipment due to the absence of coupling agents and the allowance of lift-off distances. However, weak signal amplitudes and low operating temperatures of electromagnetic acoustic transducers (EMATs) severely limit their application in harsh high-temperature scenarios. To improve the signal amplitude and solve the problem of monitoring extreme heat equipment, we propose a circumferential radially magnetized electromagnetic acoustic transducer (CRM-EMAT). It consists of eight circumferential radially magnetized sector-shaped permanent magnets, wrapped around a cylindrical core, and a permalloy patch attached to the lower surface of this magnetic combination. Three-dimensional numerical simulations and laboratory experiments were carried out to obtain the optimal dimensions of each part and to demonstrate that the probe improves the signal amplitude by a factor of over 6 and can operate stably up to 600 °C. The CRM-EMAT represents a breakthrough in the operation temperature of EMATs and realizes superior signals with lower power consumption, thus accelerating the industrial application of electromagnetic ultrasound technology.