The XI HT was developed as a heavy tank locomotive for freight trains on mountain routes to replace the older, weaker machines. It had similarities with the recently appeared Prussian T 16 and weighed about the same, but was faster despite smaller wheels.
By using the wheel arrangement 0-10-0T, the locomotives could be designed to be powerful and the entire weight was available as adhesive weight. A distinction is made between two types, each of which had an axle load of 15 and 16 tonnes and were suitable for different lines. While only ten of the lighter variant were built in 1910, 17 of the heavier variant were built in 1908 and 1909 and 136 other slightly heavier ones between 1915 and 1923. The locomotives benefited from modern technical achievements and were given Schmidt smoke tube superheaters, among other things. Thanks to a well-designed chassis and engine, the heavier variant could travel 60 km/h, while the lighter one reached a speed of 45 km/h, which was sufficient for freight trains and shunting services on branch lines.
Braking was initially done with a steam brake, but the later locomotives received a continuous Westinghouse brake from the factory. In addition, some were equipped with a Riggenbach counter-pressure brake so that they could also be used on steep stretches. In the last year of production, the locomotives received a surface feedwater heater to increase their efficiency. Air brakes and feedwater heaters were often retrofitted on older locomotives as well.
After the First World War, some of the older locomotives were sent to France as reparations, but were replaced as production progressed after the war. The Reichsbahn assigned the lighter engines to class 9419 and the heavier ones to class 9420-21. After 1945 there were still more than 110 units, all of which came to the GDR. The first were replaced by diesels from 1966, but the last pairs were not expendable until 1978.
