The first four examples of the type 18a were built in 1900 by Hartmann in Chemnitz for the Norwegian Northern Railway. Another four followed the next year, which were also to be used on other routes, and in 1903 two more followed, which were manufactured in Norway by the Hamar iron foundry. These were saturated locomotives with a 4-6-0 wheel arrangement and two-cylinder compound engine. The axle load of the coupled axles was almost twelve tonnes each and the top speed was 60 km/h. In 1907, six more locomotives followed, which were a bit heavier and were therefore designated as Type 18b.
A total of 19 examples of the Type 18c were produced between 1910 and 1919 as a result of a major revision. They were designed using superheated steam technology and had a simple two-cylinder engine without compound action. At the same time, the boiler pressure was reduced from 13 to 12 bars and the speed could be increased to 65 km/h. Almost all of the type 18a and 18b locomotives were subsequently converted, some of which did not happen until 1948. From this point on, it wasn't long before the locomotives were relegated to lower roles and retired in the 1960s. The 18c with the number 255 from 1913 is still operational today after being refurbished between 1980 and 1992.
