Monitoring of Soft Deposition Layers in Liquid-Filled Tubes with Guided Acoustic Waves Excited by Clamp-on Transducers

Abstract

The monitoring of liquid-filled tubes with respect to the formation of soft deposition layers such as biofilms on the inner walls calls for non-invasive and long-term stable sensors, which can be attached to existing pipe structures. For this task a method is developed, which uses an ultrasonic clamp-on device. This method is based on the impact of such deposition layers on the propagation of circumferential guided waves on the pipe wall. Such waves are partly converted into longitudinal compressional waves in the liquid, which are back-converted to guided waves in a circular cross section of the pipe. Validating this approach, laboratory experiments with gelatin deposition layers on steel tubes exhibited a distinguishable sensitivity of both wave branches with respect to the thickness of such layers. This allows the monitoring of the layer growth.

A novel ultrasonic inspection method of the heat exchangers based on circumferential waves and deep neural networks

“…In recent research works, the guided wave was successfully applied for the detection of circumferential fatigue, 5 , 6 and radial cracks detection, 7 to detect internal load, 8 , 9 and variation of the thickness in the cylindrical specimen. 10 , 11 The advantages of the CW are sensibilities to both small and large defects to stress-induced corrosion. The most common method of generating the CW is through angle beams.…”

Numerical and experimental investigations on mode conversion of guided waves in partially immersed plates

“…Ultrasonic guided waves are elastic waves that travel along the boundary of a structure and have been widely used for identifying damage in structures [1][2][3][4][5], detecting debonding in adhesively bonded structures [6][7][8][9], sensing liquid levels and properties [10][11][12], and assessing coatings on the substrate surface [13,14]. The advantages of ultrasonic guided waves are that they can propagate for a long distance, enabling an efficient large-area inspection.…”

Ultrasonic Guided Waves for Liquid Water Localization in Fuel Cells: An Ex Situ Proof of Principle

“…Apart from defects in the structure itself, guided waves are also sensitive to changes in the adjacent media, e.g., due to deposits on the structure. This effect has been used for the monitoring of soft depositions in liquid-filled tubes [ 24 ], ice detection on windmill wings [ 25 , 26 ], and for monitoring the wetting on simple plate-like structures [ 27 ]. Guided wave tomography has been applied to localize ice deposits on simple plate structures [ 28 ]…”

“…It can be assumed that the guided wave responses of such a structure are much more complex and it is unknown how they change due to deposits such as water drops. Therefore, methods that have been applied successfully to detect deposits on simple plate-like structures, e.g., mode identification and time-of-flight measurements [ 24 ], cannot be easily adapted to this problem. With regard to localization, tomography-based imaging methods might fail as well since the signal paths between the transmitting and receiving transducers depend on the unknown guided wave propagation within the flow field.…”