Steph, I agree with your translations. Umlaufblech is definitely a steel running board, such as around the boiler. Stehkessel is a vertical boiler, and if you recall early loco designs, the firebox was at the bottom of a vertical boiler design. A horizontal extension with boiler tubes to increase the heating surface eventually became the boiler proper, but the original Stehkessel remains around the firebox.

Jurgen