This paper describes a novel technique for the simultaneous measurement of the temperature of solid structures at multiple locations using a single transducer attached to a single bent waveguide with axisymmetric notches. This technique improves upon earlier reported studies using straight waveguides and bent waveguides without notches, where the lack of consideration for the effect of temperature gradients was found to be a significant limitation. This work also describes the L(0, 1) and T(0, 1) mode transmission and reception in the bent waveguide for selecting an appropriate gauge length for the waveguide sensor. The range of temperature measurement is from room temperature to the maximum utility temperature of the pipe structure in a process industry. The change in time-of-fight of the reflected ultrasonic signal from the waveguide features (bend and notch) is used to measure the local temperature of the surrounding media. This work is of interest in several industrial applications, including the petrochemical and nuclear industries.

Krishnan Balasubramaniam

Department of Mechanical Engineering

Suresh Periyannan

Nuclear industry

pipe

Temperature

temperature measurement

transducers

Ultrasonic applications

Ultrasonic transducers

Effect of temperature

Local temperature

Process industries

Simultaneous measurement

SOLID STRUCTURES

STRAIGHT WAVEGUIDES

Ultrasonic signals

WAVEGUIDE SENSORS

Waveguides

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Insight: Non-Destructive Testing and Condition Monitoring

This paper reports on an ultrasonic waveguide sensor for liquid level measurements using three guided wave modes simultaneously. The fundamental wave modes longitudinal L(0,1), torsional T(0,1), and flexural F(1,1) were simultaneously transmitted/received in a thin stainless steel wire-like waveguide using a standard shear wave transducer when oriented at an angle of 45° to the axis of the waveguide. Experiments were conducted in non-viscous fluid (water) and viscous fluid (castor oil). It was observed that the flexural F(1,1) wave mode showed a change in both time of flight (due to the change in velocity and dispersion effects) and amplitude (due to leakage) for different levels (0-9 cm) of immersion of the waveguide in a fluid medium. For the same level of immersion in the fluid, the L(0,1) and the T(0,1) modes show only a relatively smaller change in amplitude and no change in time of flight. The experimental results were validated using finite element model studies. The measured change in time of flight and/or the shift in central frequency of F(1,1) was related to the liquid level measurements. Multiple trials show repeatability with a maximum error of 2.5% in level measurement. Also, by monitoring all three wave modes simultaneously, a more versatile and redundancy in measurements of the fluid level inside critical enclosures of processing industries can be achieved by compensating for changes in the fluid temperature using one mode, while the level is measured using another. This ultrasonic waveguide technique will be helpful for remote measurements in physically inaccessible areas in hostile environments. © 2019 Author(s).

Fulltext

Review of Scientific Instruments

Ultrasonic waveguide based level measurement using flexural mode F(1,1) in addition to the fundamental modes

This paper reports the feasibility of using an ultrasonic waveguide sensor for distributed temperature measurement in two different case studies, that is: 1) skin temperature of a solid structure (pipe) and 2) fluid (water). This technique improves upon the conventional multiple thermocouples approach for multi-level temperature measurements. The range of temperatures is from room temperature to maximum utility temperature for the two case studies (85 °C for water and 200 °C for pipe). Using the interaction of the propagating ultrasonic waves in a thin rodlike waveguide with intentionally designed geometric discontinuities (bends, axisymmetric, non-axisymmetric notches, and so on), the localized information on the temperature is extracted. An ultrasonic technique for accurate temperature measurement by tracking the time-of-flight of reflected guided wave modes from appropriately spaced notch reflectors is therefore proposed here, while using the reflection from a bend is used as a reference. Using a finite element model approach, the notch size and/or the bend radius were selected in order to reduce mode conversion effects as well as to obtain uniform amplitudes of the reflected signals from these designed discontinuities. The numerical results were experimentally validated for the L(0,1) wave mode using a stainless steel waveguide sensor. This paper is of interest to industrial applications including mould cooling jacket temperature monitoring during the steel manufacturing process as well as for furnace wall temperature measurements in petrochemical industries. © 2001-2012 IEEE.

IEEE Sensors Journal

Ultrasonic waveguide-based multi-level temperature sensor for confined space measurements

Ultrasonic waveguide-based distributed temperature measurement on a solid surface

Journal	Insight: Non-Destructive Testing and Condition Monitoring
Publisher	British Institute of Non-Destructive Testing
ISSN	13542575
Open Access	No