30 May 2003
A pulsed Nd:YAG laser will clean railway lines in the UK this autumn.
LaserThor, a UK-based company that has developed a laser system to blast leaf residue off of railway lines, has sold two production units to Network Rail, the company that looks after the UK’s rail infrastructure.
Malcolm Higgins came up with the brainwave to use lasers for removing leaf contamination in 1999. Since founding LaserThor, he has worked with, the Fraunhofer Institute for Laser Technology in Aachen, Germany, and the Rutherford-Appleton Laboratory in the UK on the development of a fully-fledged system.
Higgins told Optics.org: “I still find it difficult to really believe the idea has been turned into reality! I guess I will really feel we have cracked it when Network Rail has taken delivery of their units in the autumn, tested them, and declared that they are happy.”
The units sold are due for delivery in September 2003 and will be in operational service for full evaluation by Network Rail from October onwards.
In the most recent trials, performed last autumn, the laser unit was fitted to a Network Rail multi-purpose vehicle (MPV) and operated by a non-specialist crew in the MPV’s cab. A two-mile section of track was tested with the LaserThor equipment. With the MPV travelling at 20 mph, the laser removed leaf residue and other contamination, leaving a clean, dry rail.
Higgins’ original idea was to fit lasers to passenger trains and although this has proved impractical in the short term, he believes that recent developments in laser technology will eventually see this become a reality.
Since genuine track trials are necessarily limited to the autumn period, LaserThor has built a test rig to simulate a moving rail travelling between 1 and 50 mph. Using the rig, rail samples could be exposed to bilions of pulses and analyzed for any ensuing damage. According to the company, there has been no damage to rails in the tests so far.
The current system features a fiber-delivered Nd:YAG Q-switched laser emitting an average power of 1 kW in 80 ns bursts at 25 kHz. It is powered by a 3-phase supply drawing 32 A and weighs half a tonne in all.
The next step is to prove that laser-cleaning works at 40 mph, the speed of operation demanded by Network Rail’s predecessor Railtrack. According to Higgins, the most recent trials were successful enough for them to specify a more powerful laser system to operate at the higher speed. This system is currently being built and will be delivered to Network Rail in the autumn.
LaserThor is also looking at the possibility of ice removal with the laser. The same system could be used, simply switching from leaf contamination in autumn to de-icing in the winter.
Michael Hatcher is technology editor on Opto & Laser Europe magazine.