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TBM failure costs £1.5M

SEVERN TRENT Water is facing a bill of £1.5M and a delay of four months after a Lovat tunnel boring machine broke down with suspected bearing failure on a sewer scheme in Birmingham.

The Lovat 136 earth pressure balance machine failed in February while driving through fissured sandstone at the deepest part of a 5.5km tunnel sewer between Perry Hall and Gravelly Hill near Spaghetti Junction. It is expected to be put back in the ground this week.

Main contractor Amey Construction recovered the machine at the end of June after excavating a 30m deep shaft in private gardens. But it has since opened up a second face working in the opposite direction with 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. He added: 'We got to a stage where the bearing was getting very hot and shortly after that it failed.'

The exact cause of the break-down is now being investigated by independent consultants. Severn Trent hopes to have the refurbished machine back on site next week

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 the Channel Tunnel Rail Link (NCE 1 May 1997) after similar recent 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 Lovat TBMs were 'reliable and robust'.

He added: '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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