“RefraSense”: An Embedded Sensor for Continuous Monitoring of the Thickness of the Refractory Lining of Industrial Boilers, Kilns and Furnaces


RefraSense is a patented sensor from Greece for monitoring the thickness of refractory linings in boilers, furnaces and kilns in real time, evolved from a sensor developed to monitor the thickness of the heat shield in space capsules. RefraSense continuously monitors the refractory lining and leads to cost saving by allowing optimum maintenance planning and reduction of risk and energy use, without any need to stop the production process. The sensor is inexpensive and is available for custom fitting in industrial boilers, furnaces etc. (TRL=6-7).


All industrial boilers, kilns and furnaces used for heating water, calcination, smelting and metal refinement are internally lined with a layer of high-temperature ceramic refractory which protects the container and reduce thermal energy losses. Such refractory linings wear down over a period of use due to mechanical and chemical wear and therefore information of the rate and extent of wear at any given time (i.e. the thickness of refractory lining remaining) is critical to ensure optimum safety and energy utilisation. Currently, the only way to measure the thickness of the remaining refractory is to stop the process, empty the boiler or furnace and use various thickness-measuring instruments internally or externally. This is a very expensive process, since it means a stop to production and very significance production losses, but, because of the criticality of the refractory lining, most industries carry out such maintenance operations conservatively - they replace the lining as often as possible even when it is not necessary.

To address this, the technology provider has developed the RefraSense sensor, which is embedded into the refractory lining to continuously monitor the remaining thickness of the refractory lining during furnace operation without the need to interrupt production. It has been successfully tested, demonstrated in industry and patented and is now ready for custom fitting. The new technology allows continuous monitoring of the refractory lining of boilers, kilns and furnaces and its use will enable major cost-savings by allowing optimum maintenance planning and elimination of risk and energy wastage. The sensor has excellent prospects for monitoring the thickness of the protective heat shield of high speed space craft as they enter the atmosphere, which was the original motivation for developing it.

A worn refractory in a boiler (left) and a RefraSense sensor body without electronics (right) designed for use in a fireclay mass and with a maximum monitoring depth of 7cm.

RefraSense is inexpensive and is now available for custom retrofitting in existing boilers, furnaces and kilns or to incorporate in an integrated system for condition monitoring of new equipment.

Innovations and advantages of the offer

RefraSense is a highly innovative and unique sensor for continuous thickness monitoring of materials where other measuring methods cannot be used, i.e. extreme conditions of temperature, corrosive atmospheres, inaccessibility etc. It is the only sensor available, which can be embedded in a material and gives continuous measurement of the material’s thickness as it wears down without the need for any human intervention or interruption of production. The available resolution depends on the application and it can reach 0.5mm for small amount of surface erosion. Maximum depth of monitoring of industrial refractories (amount of surface recession) can be as much as 10cm with a resolution of about 2mm.

Once installed, the sensor requires no maintenance. The material thickness (or surface recession) can be recorded by a computer for later retrospective analysis etc. It is a very valuable tool for determining the erosion behaviour of new refractories and for planning and evaluating refractory maintenance operations.

Description of Space Heritage

ITI/ESA (Type A: proof of concept), project ReWiG “A resistive wire grid TPS recession sensor”,  2014-2015

Sensors & Measuring Techniques
Reference No.
Could this technology benefit your business? Please contact Paris Rallis Kinno Consultants Ltd (Greece)
Printable Version
TDO0190 - RefraSense
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