London’s Crossrail programme has chosen to maintain the profile of rails in its tunnels using a rail milling train.
Rail milling uses a large wheel-shaped cutter fitted with tungsten carbide inserts to machine off the top of a damaged rail, restoring the original profile and removing surface flaws such as cracks from rolling contact fatigue.
A £12 million contract has been placed with Austrian rail-milling specialist Linsinger for a 48-metre long milling train, to be delivered in spring 2018.
The model MG31 train will be the first of its type in the UK, although the technology is already being used on the continent, and will work at up to three metres per minute, or one kilometre every five-and-a-half hours.
Rail millers are favoured for use in tunnels over traditional rail grinders due to the lack of sparks generated by the process, a hazard in underground systems. A strong suction device removes both the chips from the milling process and also the few sparks from small grinding wheels which are used to perfect the surface finish of the rail head.
The new rail milling train, which will be powered by a low-emission 1,125 bhp diesel engine, will be housed at the Plumstead infrastructure maintenance depot close to the south-eastern tunnel portal. It will be able to travel at up to 50 mph (80 km/h) and will be fitted with the CBTC signalling system that will be used in the Crossrail tunnels.
Rail Milling has already been trialled in the UK. An articulated road-rail vehicle, operated by Strabag and also manufactured by Linsinger, ran trials with both Network Rail and Docklands Light Railway in 2011, and a small machine shaped for London Underground’s tunnels and manufactured by Schweerbau has been used on the Northern and Victoria lines since 2009. However, Crossrail’s new train will be the first large-scale rail miller to be based in Britain.
Report by Nigel Wordsworth