Guaranteeing the safety and stability of railway track when transporting passengers or goods is critical these days. The increased loading of the rail network and the higher speeds of modern trains lead to higher stressing of the rails. The track itself is therefore the most important safety aspect and so needs to be inspected regularly to prevent any accidents.
The latest non-contact, laser-based profile measurement sensors from Micro-Epsilon are being used by several leading rail inspection companies around the world. Infotrans, for example, a leading supplier of inspection systems and services to Russia’s sole railway network company ‘Russichen Eisen Bahn’ (REB) is using Micro-Epsilon sensors on a newly-developed wagon inspection system to measure and monitor for wear on the track. This ensures improved safety and reliability, but is helping the customer significantly reduce maintenance and downtime costs. Nine Micro-Epsilon ScanCONTROL ‘LLT 2800-100 (205)’ sensors are being used in the application.
The wear of the rail head itself is clearly an important safety parameter in assessing overall reliability of the track and condition of the rails. If the wear is too high, this can potentially lead to train derailment. Conventional inspection methods are based on manual inspection or, more recently, light-section sensors. However, the manual method is fraught with difficulties: it is slow, inaccurate and therefore inefficient for track inspection teams. Before purchasing Micro-Epsilon sensors 12 months ago, wear on the rail head was monitored manually by teams of engineers.
Scanning the track with laser sensors (or light-section sensors) has been available for some time now, but extensive tests have shown that the sensors are too slow and also have problems coping with the different reflective properties of the tracks, which are often made from shiny, metallic materials that have become corroded in places. In addition, the resolution of the laser sensor needs to be very high so that the required number of measurements can be taken as the inspection train moves along the track.
The LLT 2800-100 (205) sensors are unaffected by shiny, metallic rails. It has an integrated, highly-sensitive CMOS array, which enables measurements of almost any shiny, reflective or transparent surface, independent of the reflection from the target. This means excellent accuracy, resolution and reliability are achieved, even at high measurement speeds. A line optical system projects a laser line onto the surface of the rail. The back scattered light from the laser line is registered on the CMOS matrix by a high quality optical system. Along with distance information (z-axis), the controller also calculates the true position along the laser line (x-axis) from the camera image and outputs both values in the sensor’s 2D coordinate system. A moving target or a traversing sensor generates a 3D representation of the object being measured.