I always find it interesting that you can always tell a welder that has used an engine driven welder. They'll always tap the work with the electrode first before they start welding. Regardless of what they are using. It's a reflex action.
I tap the work to make sure I have a ground. Same with a electric machine
In the power house it wasn't necessary. Mostly we used grid type machines which had one central ground, meaning the entire boiler/ piping/ structural was grounded
