The “Seraing” was one of the four locomotives that took part in the Semmering competition. Its name came from the Belgian city where its manufacturer was based. It had two complete boilers which met in the middle at the firebox. Two power plants were each in a bogie. The locomotive thus anticipated the design of the Double Fairlie and is said to have basically met the requirements.
The biggest problem, however, was that the manufacturing methods for the flexible steam pipes at that time were not yet mature enough to remain permanently leak-proof. The amount of dry steam that could be extracted from the boiler was also said not to have been sufficient. It eventually finished third in the competition and was not used for long.