Class 20 to be one of their best locomotives since it was free-steaming, more than usually trouble-free and able to handle any load they gave it. Condensing trials The arid nature of a large part of South Africa and the consequent difficulty to ensure adequate and suitable water supplies for steam locomotives led to a decision to experiment with condensing locomotives. Such locomotives had by then already been built by Henschel and Son for use in Argentina, 240 Kriegsloks for the Eastern Front in Germany in the 1930s and more than 4,000 units of the Russian SOK class, mainly for use in Turkestan and other arid regions of the Soviet Union. In the pre-war years, the SAR considered modifying a Class 12A into a condensing locomotive, but this never happened. In 1950, the Class 20 was modified to an experimental condensing locomotive in the Pretoria workshops, fitted with German Witte-style smoke deflectors, an extension to the chimney and a Type CL condensing tender which had been ordered from Henschel in 1948. This condensing tender, with Henschel works no. T28388, was designed for a Deutsche Reichsbahn Class 52 condensing locomotive. It was modified slightly and was equipped with a pair of Buckeye three-axle bogies instead of the German arrangement of one six-wheeled and one four-wheeled bogie. It had an coal capacity, a water capacity and a axle load. The total weight of the modified engine and Type CL tender in full working order was . The Type CL tender was designed in such a way that it could also be used on a modified Class 19D or Class 24, but this was never done. The tender was capable of condensing of exhaust steam per hour in maximum operating temperatures of between . As on the later Class 25 condensing locomotives, the pipe to feed spent steam back to the condensing tender was mounted on the left side of the engine. It was run back from the smokebox above the running board to a box that contained a centrifuge and filters to remove cylinder lubricant from the exhaust steam, then below the running board and underneath the cab to the tender. The tender had six large radiators on each side, cooled by three exhaust steam-driven roof-mounted fans which drew air from outside through the radiators. Beginning in 1951, tests with the condensing Class 20, named Pretoria, were conducted in the Eastern Transvaal