In collaboration with the Polish company Graw, LAP GmbH has developed a new system for the inspection of wheels, wheel sets and the running gear of track vehicles. This development increases safety in rail traffic. The system has been in operation since early 2007 at PKP Intercity in Warsaw and is now sold in Germany by Lüneburg-based LAP GmbH Laser Applikationen.

The laser-based system measures with very high precision the profile of wheel tyres and wheel flanges, the wheel diameter and the running gear geometry.

The measurement of gradual changes in wheel profiles due to wear used to be a difficult task. Changes in the flank angle of the wheel flange, for example, or in the radius of the tyre groove may result in increased material fatigue. In the worst case they might even lead to the derailment of railway cars.
This is why PKP Intercity in Warsaw regularly inspects its complete fleet of almost 200 cars with the new measurement system. Used as part of the preventive maintenance process, the system triggers a warning as soon it detects non-compliance with preset tolerance values. Thus the affected wheel sets can be replaced safely at an early stage.

Installed at the entrance of the maintenance shop the laser-based system automatically checks every train when it is rolling in. This can take place at speeds of up to 20 km/h and the train does not even have to stop for the measurement. The system starts the measurement as soon as a train enters the maintenance shop. It automatically checks every axle and whenever out-of-spec values are measured, an alarm is triggered.

PKP Intercity has equipped all cars with RFID tags. This enables the system to assign all measured values to the individual wheels and store the data accordingly in a database. In this way it is possible to track the evolution of the measured values over time and optimize the scheduling of repairs. Graphical evaluations facilitate the analysis of the measured data.

A projection system, which LAP has developed specifically for this application, project laser lines onto the wheel surface. The projected lines are captured by several line and matrix cameras. The sensors, mounted on a measurement frame, are completely encased and purged by air. This ensures that they operate with utmost accuracy at temperatures ranging between -30 and +60 °C and even at air humidity of up 98 percent.

The accuracy of wheel diameter measurements is better than 0.5 mm. The wheel parameters are measured with an accuracy of about 0.2 mm and the diagonal line of the bogie is measured with an accuracy of less than 0.5 mm.