Researchers are developing an ultrasonic sensor for trains that can detect whether a vital form of lubrication is present between railway wheels and the track. This initiative is part of the EU-funded PIVOT2 project aimed at developing technologies that enhance the operational reliability of trains.
Why is track lubrication so important?
“It is not commonly known outside railway circles, that in curved track, a special type of grease is applied between the wheel and rail,” states Prof. Paul Allen from the University of Huddersfield’s Institute of Railway Research (IRR) in a news item posted on the website of ‘The Engineer’. “This lubrication is applied to reduce wear but also the risk of derailment, whereby in some circumstances the wheel can climb up and over the railhead,” Prof. Allen explains. The leading railway researcher developed the concept of an ultrasonic sensor embedded in a railway wheel a few years before the IRR began working with PIVOT2 project partner Network Rail (NR), the United Kingdom, on this undertaking. Currently, simple mechanical or electromechanical devices are used to apply lubricant to hundreds of track locations throughout the United Kingdom’s rail lines. However, these devices can sometimes stop working or run out of lubricant. Additionally, at the moment, NR is using manual inspection to check for the presence or absence of lubrication across the rail network. “Manual inspection is time-consuming and requires personnel to be on track, so NR is trying to reduce this for safety reasons. As well as this, the result of manual inspections can be subjective – it’s based on a fairly simple ‘rub of a thumb’ on the rail technique,” observes Prof. Allen in an interview posted on ‘AZoSensors’. By obtaining real-time information on lubrication levels with the help of ultrasonic sensors, NR will be able to overcome the disadvantages of manual inspection, thus reducing maintenance costs and improving railway safety.
How the ultrasonic sensor works
Prof. Allen explains in the interview: “The ultrasonic sensor contains a transmitter and receiver. Emitted ultrasound waves are passed through the wheel flange and into the rail gauge corner, where the lubricant is applied.” The sensor uses the time-of-flight principle, where the distance between a sensor and an object is measured based on the time that elapsed between a signal’s emission and its return to the sensor after being reflected by the object. “Very small differences in the time of flight of the reflected signals are detected and analyzed to differentiate between a dry (unlubricated) rail and one that is effectively lubricated; the system can also distinguish between lubricant and water – an essential performance requirement!” Prof. Allen remarks. The researchers will conduct experimental trials under real-world conditions, with axle loads of up to 25 t and a target operating speed of 200 km/h. As noted by NR’s senior engineer James Lineton in ‘The Engineer’, the sensor “has the potential to disrupt how rail infrastructure is managed around the world.” The PIVOT2 (Performance Improvement for Vehicles on Track 2) project ends in March 2023. For more information, please see: PIVOT2 project
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