Leaves on the rails compressed by the wheels of trains as well as grease and thin oxide layers form a thin layer of contamination which reduces the friction between the rail and the wheel and may also increase the electrical resistance. Conventional methods like high pressure water jetting or traction improvement by using sand do not meet the demand on process speed. For removing this contamination, a fiber coupled pulsed Nd:YAG-laser is used. In contrast to conventional optics for coating removal which use damageable scanner systems, we have developed a beam forming optics without moving parts. Thereby, a high-intensity line can be achieved that measures 15 mm x 70 µm.
The laser system used for tests on the British rail net delivers 400 kW pulsed laser power at pulse durations of 60 ns and a repetition rate of 25 kHz. The tests have proven the system’s applicability to clean railheads with 30 km/h (500 m/min) and a working distance of 200 mm.