Track and signalling

First ever rail-mounted milling machine trials on UK railway

Trans Plant and Schweerbau are starting the first ever trials of an on-track rail milling machine on a UK railway network following successful demonstrations to London Underground safety officials and other rail industry figures.

Running rails on two stretches of the Northern line – above ground between Colindale and Golders Green and in the tunnel from Mornington Crescent to Warren Street – will be milled at night using the specially developed machine.

Rail milling makes passenger journeys smoother and reduces the long-term wear of rails and train wheels by restoring rail head geometry and removing gauge corner cracks and corrugations from the head of each running rail. Until now, such benefits could only be reaped by replacing rails – a highly time-consuming and expensive process – or by grinding rails, which takes a lot longer than milling in the conditions on the Underground.

“This machine takes the principles of milling and applies them in a larger context, as the machines which have been trialled before have been much smaller,” says Jonathan Bray, track development manager at Tubelines.

“In the past, the norm was to use grinding machines, but these did present problems. As well as being faster and more efficient than other grinding, milling is also much cleaner and safer as the machine collects all the metal milled from the rails.

“In contrast, grinding causes a shower of red-hot metal filings which have to be watched in case they cause fires and cleaned up so that they do not cause signal failures. For us to now be able to mill the line will also be much better for a variety of other reasons. There is also the issue of speed. About 200m of rails needing significant treatment can be ground in an hour using an on-track rail grinding machine, compared with between 600-1200m of milling, depending on the track formation.”

Schweerbau, a German company which has been supplying on-track rail milling machines to German surface railways for fifteen years, worked with Trans Plant to build a train specially suited to urban metros like the Tube. It is small enough to fit down the small diameter tunnels lying deep below London and has special features to ensure it meets the rigorous safety and performance requirements of the network.

“The machine uses a rotating cutting head, which could be compared to a larger scale plaining device, which has cutting teeth built in which remove the excess metal on the track. These teeth are set to the correct profile of the rail,” continues Jonathan.

“This is also not a cheap piece of kit. To produce it costs several million pounds. However, we are leasing the machinery as a service from Schweerbau. This arrangement provides value for money for Tube Lines.

“Of course we are also benefiting from the various features which the milling machine has to offer, in that because it usually only requires one pass over the track to remove the required amount of metal and that it removes more metal comparatively to grinding, we are increasing our productivity, which in turn adds value for money.

“Other features that the milling machine offers include its diesel engine technology, which is state of the art; it is also a self propelled vehicle and produces the lowest amount of fumes possible, whilst also being incredibly energy efficient. In terms of rail management, it also has the latest guidance and measuring systems as well, so it is a great all round package which is also state of the art.”

Dr Stuart Grassie, renowned expert on wheel-rail interface issues and rail corrugation who advises Schweerbau and Tube Lines, says: “The London Underground has a lot of rail with poor transverse profile. Although the root causes of this must be addressed in the long term, this rail-milling machine offers the Underground an excellent means of correcting profile quickly, cleanly and safely both now and in the future. Transverse profile can be restored and corrugation removed to the most stringent levels demanded by LU or European standards.”

So will this machine be rolled out onto light rail networks throughout the country?

“That is an interesting question,” says Jonathan. “Whilst Schweerbau built the machine originally in a way where it could be adapted to fit most networks, it was calibrated specifically to the London Underground pneumatic loading gauge, so when you look at it, the machine closely resembles two underground carriages. However, I do think that it was the manufacturer’s intention to make the machine in such a way that it could be rolled out further with some modifications to the design.”

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