The above pictures show what can happen when a welding tank is brought near a magnet. The flying tank destroyed the phantom sitting in the magnet. This site was lucky, nothing happened to the magnet itself, however............

My Favorite Horror Story

Here's one I heard from an Oxford Magnets engineer which was later independently verified by a technologist who had been hired to work at this site.

A brand new magnet had just finished being installed into a brand new building. All of the acceptance testing had been completed and the magnet was to be turned over to the customer the very next day. There was only one minor problem to be dealt with first. One of the sprinklers in the scan room had a tiny leak. A welder was brought in to fix the leak but somebody forgot to tell him that the magnet was at field. So..... in walks this welder with his acetyene torch system. His tank flies into the magnet, the valve breaks off, sparks and catches fire. Since he was in there to fix a leak in the sprinkler system, it had been turned off first. The brand new building burned to the ground!

Sorry, I don't have any pictures.

If anyone knows if I have any of the details wrong, I'd appreciate them letting me know.