i used one to clean locomotive engine blocks, before painting them. you have to be careful with them, as they can actually blow through gaskets, and do some real damage. strips a locomotive diesel block to bare metal, in a very short time. traction motors use a gear lube, that is similar to warm tar, in viscosity. a steam jenny will cut through decades of the stuff, baked onto the gearbox, and slung all over the underside of the frame, where it leaks out. awesome for getting stains off the driveway, but again, the ability to actually damage the concrete is possible. high pressure steam, is really a super cleaning tool.