This is the pipe that 9 and 7 escape through while being chased by the Spiderbots.

   When 9 and 7 blow up the factory, they toss an oil can with a lit fuse into the tunnel, exploding, and destroying seekers, spiderbots, and various other robots the Fabrication Machine created.  When the oil can is rolled into the tunnel, it drags a seeker into the tunnel also.