Saturday, December 25, 2010

Niagara Tunnel - Main Beam Cracks for Christmas

A 5.1 cm (2 inch) crack appeared at the top of the main beam (center spine support) of the TBM resulting in the immediate stoppage of mining. The main beam supports the TBM cutterhead, grippers and major hydraulics. In order to repair this crack, four 200 ton jacks have been utilized to lift the sections at the front of the crack and the rear of the crack in order to align the beam before it can be welded. 

Ernst Gschnitzer, Project Manager has said "she (the TBM ) has a crack in the Main Beam that we need to repair. After 9,107 meters of mainly difficult ground and more than 6,000 hours, we think she is just getting older and suffering from some correlated disease. We would have had to do some last repair anyway prior to the last reach of tunnel. Including these maintenance and repair works, we expect her back in service by December 27."

Well, I had a nice Christmas, no big killer earthquakes around the world.  Everybody got nifty toys, and I got some top-rack wine to compensate for nasty Google freezing me out.  :)

That's a heck of a load for that weld to hold!  Reminds me of try to glue things under a lot of stress.  It never works!  This machine expected a nice romp in the park, through soft shale, most of the trip.  But the shale proved to be a trap, and they had to move up into the very tough dolomite.  I'll bet if you did a scan on that steel you would find it riddled with fatigue cracks.  Still, we hope the weld holds, and doesn't crack immediately right beside it, which is what I would expect.  But I'm in a Christmas mood, and even if the whole beam just disintegrates, they can just inject another secret billion!  :)

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