SAR class 25

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SAR class 25/25 NC
Condenser 3511
Condenser 3511
Numbering: 3451–3540
3401–3450 (25 NC)
Number: 90 + 50 (25 NC)
Manufacturer: Henschel , North British
Year of construction (s): 1953-1954
Retirement: 1980s – 1990s
Type : 2'D2 'h2
Gauge : 1067 mm ( cape track )
Length over coupling: 32,750 mm
27,900 mm (25 NC)
Service mass: 124.3 t
Friction mass: 75 t
Wheel set mass : 18.8 t
Top speed: 90 km / h
Indexed performance : approx. 3400 PSi
Driving wheel diameter: 1,524 mm
Impeller diameter front: 762 mm
Rear wheel diameter: 762 mm
Cylinder diameter: 690 mm
Piston stroke: 711 mm
Boiler overpressure: 156.96 N / cm²
Grate area: 6.5 m²
Superheater area : 59 m²
Evaporation heating surface: 290 m²
Train brake: Suction air brake

The class 25 of the South African Railways (SAR) is a steam locomotive with a condensing system , the most powerful and longest-running locomotive of this type. The series was also supplied as class 25 NC ( Non Condensing , without condensing device).

Development and trials

On the long stretches through the Karoo Desert, the water consumption of the locomotives was a serious problem. In some cases, the water had to be brought to the supply points by tank car trains, so that in particularly dry years there were more water trains than freight trains.

Even before the Second World War, SAR became aware of the condenser locomotives designed by Richard Roosen and built by the Henschel works for Argentina, Iraq and the Soviet Union. This technology, which was able to reduce water consumption by up to 90%, could have solved the problem.

The idea could only be pursued after the war and Henschel delivered the first test tender in 1950 . It was a conversion of a still existing war engine condenser tender 3'2'T16. The tender had been lengthened in order to adapt it to the increased performance and the special conditions in South Africa (higher temperatures, lower air pressure because of the routes that were sometimes very high). In addition, it received two three-axle Cape gauge bogies , modified couplings and suction air brakes in order to adapt to the South African conditions .

The condensation tender was intended for the one-off class 20 unit built by SAR itself , a 1'E1 'locomotive, but could also be coupled to the class 19D and 24 locomotives . The attempts were successful; the locomotive had a range of more than 1000 km under favorable conditions and there were no major technical problems.

The SAR then ordered 90 class 25 locomotives and another 50 class 25 NC locomotives, which were supplied by the Henschel works and the North British Locomotive Company in 1953 and 1954 . They were given road numbers 3451 to 3540 (class 25) and 3401 to 3450 (class 25 NC). At SAR, until the E7 electric locomotives were built, the company numbers were only assigned once and thus had a fixed reference to the series.


Although the class 25 locomotives were built for the Cape Gauge prevalent in southern Africa , they are heavier and more powerful than almost all standard gauge steam locomotives outside of North America. The main lines of the SAR were designed for an axle load of approx. 20 t at that time ; The eight-axle locomotives with the 2'D2 '( Northern ) wheel arrangement were able to develop a correspondingly large amount of power (approx. 2500 kW) and tractive power .

The locomotives were state-of-the-art and had cast steel frames, roller bearings on all axles and rods, as well as stokers and a steam-operated reversing device . The driving wheel diameter was five feet (1524 mm), which means that the locomotives could be used for both passenger and freight trains. Both the condensing and conventional tenders had two three-axle bogies, but the condensing tenders were significantly longer.

The blower and fan turbines were operated with the exhaust steam, from which an output of approx. 125 kW was taken. The steam escaping from the safety valves was also fed into the condensation. The exhaust pipe leading from the cylinders to the tender ran - as with the class 52 - on the left side of the locomotive.

The smoke chambers were self-cleaning (“self-cleaning front end”), whereby the gas routing ensured that the extinguishers could not settle but were blown out of the chimney together with the exhaust gases.

25 NC No. 3465 with converted tender in the De Aar locomotive depot (1979)


After the operation of the condensing locomotives was no longer necessary due to the use of diesel and electric locomotives , they were converted into class 25 NC in 1978 in the workshops in Salt River / Cape Town due to their higher operating costs . Only two of them kept their condensing tenders.

The converted locomotives could be recognized not only by their company number but also by the unusually long tenders that were rounded at the top. The tenders were converted from the condenser tenders, the cast steel frame of which could not be shortened.

End of operational use

25 NC No. 3405 (with missing boiler cladding)

The class 25 NC locomotives were among the last steam locomotives used on main lines in South Africa and were in regular use until the early 1990s.

A locomotive no. 3450, was in 1981 in the class 26 rebuilt. The goal was to significantly reduce water and coal consumption while increasing performance. However, this one conversion remained, as the end of steam locomotive operation was also in sight in South Africa. This locomotive, named "Red Devil" after its red color, is one of the most modern steam locomotives in the world.

Some of the locomotives, some of which are still in working order, are still preserved today, with the last run of one of the two unmodified condenser locomotives (No. 3511) taking place in 1992 . The locomotive has been preserved in a museum to this day. Locomotive No. 3405 was brought back to England shortly after its retirement in 1991 and is located in the Buckinghamshire Railway Center near Aylesbury (see picture).

See also


  • Leith Paxton, David Bourne: Locomotives of the South African Railways. A Concise Guide. C. Strui (Pty) Ltd., Cape Town 1985, ISBN 0-86977-211-2 .
  • John N. Middleton: Railways of Southern Africa. Locomotive guide. 5th edition. Beyer-Garratt Publications, Rickmansworth 1994, ISBN 0-620-18548-1 .

Web links

Commons : SAR Class 25 (Henschel)  - Collection of images, videos and audio files
Commons : SAR Class 25NC  - Collection of Images, Videos and Audio Files
Commons : Railroad  - Collection of images, videos and audio files

Individual evidence

  1. Richard Roosen : A Life for the Locomotive. From the memories of a steam locomotive and machine engineer. Franckh, Stuttgart 1976, ISBN 3-440-04309-6 .