Magnetic method of rail track joint gaps automated measurement

Abstract

Introduction. Methods of automatic measurement of rail track joint gaps are not accurate enough or require costly equipment and sensors. This is why joint gaps are still monitored manually in many cases. The work is intended to experiment and examine a new method of automatic measurement of gaps in bolted rail joints using magnetic flaw detection (MFL).Materials and methods. The paper uses actual track inspection results obtained by a flaw detection car on one of the railroads of Russian Railways. A specially developed programme used magnetic channel signals to highlight bolted rail joint locations and determine the magnitude of the joint gaps. The joint gaps were also measured manually using video images of bolted joints obtained by the on-board rail video recording system.Results. The authors obtained expressions for calculating the joint gap value using magnetic sensor signals. Small gaps (up to 8 mm) are estimated by amplitude, medium and large gaps (above 9 mm) — by the spatial parameter of the signals from joint gaps. The authors compared the gap measurements from the two specified methods: visual and magnetic.Discussion and conclusion. The research confirmed that automatic identification of bolted joints and determination of the value of joint gaps by magnetic rail flaw detection are sufficiently reliable for practical application. A comparative analysis of the values of the video inspection and the magnetic method showed high accuracy of joint gap measurement when using the latter. The magnetic method signals show high stability and repeatability.

Keywords

• railway track
• continuous welded rail track (cwr)
• bolted joint
• joint gap
• rail flaw detection
• magnetic method
• magnetising system
• magnetic sensors