Although Prussia had already built a superheated freight locomotive with the G 8 from 1902, they were not yet completely convinced of the superheater technology and thus designed the G 9. The G 7 was used as the basis for the development, but one could now Install a larger boiler due to the meanwhile higher permissible axle loads.
Initially the engines were also put into service as the G 7, but the new designation G 9 was soon assigned. This made sense, since the new engines were significantly more powerful than the G 7 due to the larger boiler, a cylinder diameter increased by 30 mm and a weight increased by a little more than five tonnes. Nevertheless, the power remained noticeably below that of the G 8, which in turn demonstrated the power of a locomotive of about the same weight in the superheated version, which was not yet fully developed.
The first ten pieces received internal Allan valve gear, but the rest used the usual external Walschaerts valve gear. Between 1908 and 1911, Schichau and other works produced exactly 200 of these, which were mainly used to transport ore from the North Sea to the Ruhr area. A few years later, only 133 engines came to the Reichsbahn, which were assigned to class 5523-24. Of these, 36 were superheated in the years that followed, bringing them closer to the G 8 in terms of power and speed.
Schematic drawing with dimensions
Locomotive Magazine, October 1910
After the war, the engines of the former G 9 were used in both parts of Germany, with the exception of a few examples that remained abroad. In the western zones, there was no need for these saturated steam locomotives and they were retired by 1949. This was different in the Soviet occupation zone, which is why the engines were included in the inventory of the Reichsbahn. Road number 55 2361 was the last to be retired there in 1961.