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KANDE International has a long history of innovative development of high temperature ultrasonic probes and measurement systems for use in long term monitoring applications on plant such as power stations, where operating temperatures typically fall in the range from 350ºC to 600ºC. Probe sensitivity and long term reliability at high temperature are key concerns of plant operators looking to install monitoring systems and it is difficult to address these concerns other than by experimental trials. So when KANDE began developing a new range of high temperature ultrasonic probes, the work programme included long term tests on the pre-production prototypes to prove the capabilities of the new design. The first of these tests were soak tests in which probes were operated continuously at a constant temperature. In the most arduous example, the probe operated at 500°C for 30 weeks with no significant change in sensitivity. Other tests were performed to show how the probes stand up to thermal cycling and in the longest running test, the probe exceeded 1000 thermal cycles between 40°C and 450°C without sign of any significant  deterioration. This number of cycles is equivalent to at least several years of operation in typical applications. The graph shows sample data from several days of this test, which started in late April 2015.  The red trace shows the temperature cycling with a period of 6 hours and the blue trace shows the measured amplitude of a selected ultrasonic echo, which can be seen to remain stable within ±1dB at all times.
Long term test completed A year long temperature cycling test was carried out on a KANDE probe, in which it was temperature cycled more than 1460 times between 40°C and 450°C.  The KANDE high temperature probe showed no significant change in sensitivity over this time.
Latest Update  One of KANDE's latest range of high temperature probes has undergone a three month soak test at 660°C and further tests at 750°C showed excellent ongoing stability through five thermal cycles over four days, as shown in the plot.
The standard range of KANDE high temperature probes is designed for long term operation, including exposure to thermal cycling, at temperatures of up to 500°C.  The probes are designed to be attached directly onto the surface of the components being monitored, either by welding or by clamping, and because they are able to withstand direct exposure to such high temperatures they can be installed under lagging. KANDE developed USBox monitoring software turns inexpensive hardware such as Lecoeur Electronique’s USBox/USKey or OPTEL’s Opbox into highly capable measurement systems for long-term ultrasonic monitoring applications, with capabilities including: recording and logging of A-scan, B-scan and temperature data at programmable intervals, or at user defined temperature set-points, for periods of anything up to months or even years. Previously KANDE high temperature probes have been used to demonstrate the use of a two probe TOFD type technique to monitor high temperature fatigue crack growth in 70mm thick steel pipe sections (Baltica presentation), and on-site trials at two UK power stations have enabled us to develop and test ultrasonic monitoring techniques on operational plant. Our in-house software development capability and our extensive practical experience in this area enable KANDE to offer bespoke solutions for customers' unique monitoring requirements. Today KANDE continues to be at the forefront of practical developments in high temperature ultrasonic probes and measurement. Prototype single element probes have been tested to 956°C in the laboratory. A 16 element linear array was recently built to demonstrate the feasibility of using permanently installed phased array probes to perform monitoring at high temperatures. A 36 element matrix array and instrumentation for FMC data acquisition and analysis were built as part of a TSB funded collaborative study into long term monitoring. Innovative new designs of single and multiple element probes are undergoing tests in our on-going R&D programme.
KANDE can supply a range of 10mm and 1/4" probes, with various operating frequencies, designed for continuous operation at up to 500°C (932°F).  These are available as straight, or angled stud type probes, for either welding or clamping.  In addition, low profile clamped probles are available in various configurations. Please contact KANDE international for further details or to discuss your requirements. Selected  presentations on KANDE High Temperature Probes and monitoring can be viewed by clicking on the links below
Technical Note 1 - HTP sensitivity Technical Note 2 - Crack Growth Monitoring Technical Note 3 - Maximum Working Temperature Thermal Cycle Test