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Jammed TBM delays sewer drive


SEVERN TRENT Water is facing a bill of £1.5M and a four month delay after a Lovat TBM broke down on a major sewer scheme in Birmingham.

The Lovat 136 earth pressure balance machine stopped with suspected bearing failure in February while driving through fissured sandstone at the deepest part of a 5.5km tunnel between Perry Hall and Gravelly Hill near Spaghetti Junction.

Main contractor Amey Construction recovered the machine at the end of June after excavating a 30m deep shaft. It has been forced to open up a second tunnel face in the opposite direction using another Lovat TBM to minimise delay to the £20M scheme.

Severn Trent senior engineer Harry Driffill said greasing points around the perimeter of the main bearing became caked up and jammed during the drive. 'The bearing was getting very hot and shortly after that it failed,' he added.

The exact cause of the breakdown is now being investigated by independent consultants in the North of England.

The failure is the latest in a succession of high profile problems with the main bearings and seals of Lovat machines. The Canadian manufacturer was excluded from the shortlist of preferred suppliers for Channel Tunnel Rail Link after similar incidents at Port Hedland in Western Australia, the Jubilee Line Extension at North Greenwich and on the St Clair tunnel between Canada and the US.

But Lovat Europe general manager Steve Duncombe insisted that Lovat TBMs were 'just as reliable and robust' as other machines. 'We have sold 37 machines to UK customers and have completed over 300km of tunnels in the UK. Nobody buys just one machine, they all come back for a second, so we can't be doing everything wrong,' he said.

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