Electricity takes the path of least resistance, not the shortest path. It CAN go through the crane but if your welding something big enough to need a CRANE, then no. Especially if it has pieces welded together already. The ground will go through the weld straight to the ground. Like JR said, your making a mountain out of a pimple (funny saying btw
). You probably have a better chance of lightning coming into your shop and striking you while you're welding because of the ionic charge that can be emitted from the electrical current making an electromagnetic field that can create an attraction to the storm.
This is a thoughtful and very good question, but it's almost like asking: if you weld in the garage next to a little puddle of water coming out of the hose on the concrete floor, can the current get sucked into the water hose and follow the water into the piping inside the house and shock someone in the house washing their hands or someone doing dishes.
I'm not making fun, just saying that you probably don't need to be all THAT cautious. Just use common sense when doing something. Don't over-psychoanalyze the situation.
-Hillbilly