Drives and Controls Magazine
Fibre optic sensors check condition of rotating machines
Published:  25 February, 2014

The Danish sound and vibration measurement specialist Brüel & Kjær has developed a fibre-optic acceleration sensor that can be used for high-frequency measurement of small vibrations, making it suitable for condition monitoring of rotating machines such as motors, pumps, turbines and vehicles.

B&K has licenced the technology to UK-based Smart Fibres which will use it to produce fibre optic acceleration sensors that it will sell worldwide. 

The single-axis Fibre Bragg Grating (FBG) acceleration sensors – called SmartAccel-HF – can tolerate extreme environments, while the use of fibre optics allows signals to be transmitted over distances of several kilometres. The intrinsically safe sensors need no power to operate and are immune from the effects of electromagnetic interference. They can measure vibrations from DC up to 900Hz and have a 200g dynamic range.

“One of the key advantages of FBG technology is the ability to multiplex numerous sensors of different measureand types on a few optical fibres,” explains Smart Fibres’ CEO, Chris Staveley. “Acceleration is one of the most interesting measures for machine health monitoring, so we are delighted that Brüel and Kjær has applied its expertise to develop this product.”

Smart Fibres believes the sensor to be the best technology available for high-speed vibration measurements for condition monitoring of rotating machines, when combined with its own SmartScan interrogator. For example, the sensor can be used as part of an integrated fibre-optic system to monitor subsea pumps for the oil and gas industry.

Brüel & Kjær's fibre optic sensor can monitor the condition of rotating machines without needing power

“We have already proven the product in oil and gas applications and we are now looking to apply it to our other industry sectors,” says Staveley.

“Developing this transducer has been a valuable research project that has produced transferable knowledge and expertise in Brüel & Kjær,” says B&K’s transducer r&d manager, Finn Kryger Nielsen. “Now, working together with Smart Fibres, we are excited to see it come into the world.”