Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of two leading wheels, ten powered and coupled driving wheels, and two trailing wheels. In the United States and elsewhere the is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.
Overview
The wheel arrangement evolved in the United States from the 2-10-0 Decapod of the Atchison, Topeka and Santa Fe Railway (ATSF). Their existing 2-10-0 tandem compound locomotives, used as pushers up Raton Pass, encountered problems reversing back down the grade for their next assignments since they were unable to track around curves at speed in reverse and had to run very slowly to avoid derailing. Consequently, the ATSF added a trailing truck to the locomotives which allowed them to operate successfully in both directions. These first locomotives became the forerunners to the entire family.
The 's inherent problem was the low speed restriction on the type, which was about . Further, the had other inherent restrictions. The massive cylinders that were required on locomotives in the United States for high tractive effort had the result that no reasonably sized valves could admit and exhaust steam at a sufficient rate to permit fast running. In addition the , like the 2-6-2|, had its main rod connected to the middle coupled axle, very near to the centre of gravity, which created a violent nosing (waddling) action when operating at speed. The peak of the design limitations was reached in the United States in 1926 and was overcome with the advent of the superior 2-10-4 design.
Belgian Congo
Two classes of locomotives were used in the Belgian Congo.
- Two locomotives were built by Forges, Usines et Fonderies de Haine-Saint-Pierre for the in 1937, numbered 60 and 61. They had cylinders and coupled wheels, with a working order mass of .
- One locomotive was built for the by Société Anonyme John Cockerill in 1947, numbered 901 and later renumbered 802. It had cylinders and coupled wheels, with a working order mass of , a grate area of and a tractive effort at 65% boiler pressure of .
Canada
In 1916, Canadian Government Railways (CGR) took delivery of ten built by ALCO. After CGR became part of Canadian National Railways (CNR) in 1918, these locomotives were designated Class . Ten more were delivered from the Montreal Locomotive Works in 1918, and another 25 slightly modified in 1920 that were lighter. Canadian Locomotive Company produced five in 1924. Ten ALCO's named were acquired from the Boston and Albany Railroad in 1928. Canadian Locomotive Company produced the last series of for CNR, a batch of 15 in 1929, and 18 in 1930.
The began to be scrapped in the mid-1950s, with the last models being used until 1961. There are two surviving CNR locomotives. One is No. 4008, on display at the CNR Station in Rainy River, Ontario, and the other is No. 4100, on display at the Canadian Railway Museum in Delson, Quebec.
China
thumb|The first QJ class locomotive
The mainstay of Chinese steam was their locomotives. This was the wheel arrangement of the Chinese QJ class locomotives that were based on the Soviet locomotive class LV and built by Datong Locomotive Works from 1959. They were produced until 1988 and were still in widespread service until the final steam runs in 2005.
After retirement, some of these QJ class locomotives found their way to the United States, where they are used in revenue freight and excursion service. In Train Festival 2011, Multipower International restored two Chinese locomotives to Federal Railroad Administration (FRA) Part 230 specifications and delivered them to the Railroad Development Corporation.
Germany
thumb|[[Prussian T 20, class BR95]]
Examples on the German railway systems included classes BR84 and BR85, both standard tank locomotive designs built in 1935 and 1937 respectively, and class BR95, a tank locomotive built in 1922 by the Prussian State Railways as the Prussian T 20.
From 1936, the German railways built 28 three-cylinder tender freight locomotives of class BR45, which were the most powerful steam locomotives on the system.
Further examples, still in regular service, are the metre-gauge DR Class 99.23-24 on the Harz Narrow Gauge Railways and the 750 mm-gauge DR Class 99.77-79 on the Rügen narrow-gauge railway.
Greece
thumb|SEK class Μα
SEK (, Hellenic State Railways) class Μα (or class Ma; Mu-alpha) was a class of 2-10-2 steam locomotives built by Ansaldo and Breda in 1953. They were numbered Μα 1001-1020.
The Μα locomotives were the last steam locomotives acquired by SEK before conversion to diesel traction. They were designed and built in Italy by Breda (10 units) and Ansaldo (10 units) in 1953–1954, while some parts (including whole tender underframes) were made by Nuove Reggiane. The length of the locomotive with the tender was 24.93 m, the maximum height 4.51 m and service weight 136 t. The boiler operated at , and their rated power was . Maximum speed was 90 km/h.
Due to various technical problems, only two years after introduction they were modified by Henschel (1957–1958). The boilers were converted to burn heavy fuel oil.
These locomotives were based at Aghios Ioannis Rentis and Thessaloniki depots and were used mainly for freight trains and for some express passenger trains on Piraeus–Thessaloniki and Thessaloniki–Idomeni mainlines until the early 1970s, when they were withdrawn by the Hellenic Railways Organisation (successor of SEK) due to complete conversion to diesel traction.
Only two examples survived the 1984-1985 steam locomotives scrappings. One of them, 1002 was set on display as part of the theatre , at Rouf station in Athens. The other one is at Thessaloniki old railway station, not preserved.
India
The Bombay Port Trust had a pair of 2-10-2 tank locomotives, numbered 25H and 26H, for hump shunting, weighing in at 105.5 tons. Built by Nasmyth, Wilson and Company in 1922, they had driving wheels, and cylinders. Both were withdrawn and scrapped in 1976.
Mozambique
thumb|CFM Class 250 No. 252
While the wheel arrangement was not very common in Africa, the Lourenco Marques system in Mozambique ( or CFM) had altogether 37 locomotives of this type, in three classes.
- Nine locomotives of the Series 200, numbered 201 to 209, were built by Baldwin Locomotive Works between 1915 and 1919.
- Six more Santa Fe type locomotives of the Series 214, numbered 214 to 219, were built by Henschel and Son in 1951.
They were serviced to haul heavy freight trains on the South Main Line between Manila and . This class also had one of the largest cylinders of any unarticulated Cape-gauge locomotive according to Alco, but it comparatively had small boilers and grills. Their arrival also called for larger turntables in both ends of the line, making them some of the largest and most powerful locomotives that entered Philippine service.
Out of ten locomotives, four managed to survive World War II, all of which were still in active service in 1952. However, these locomotives were retired after the MRR turned to upgrading its fleet to diesel locomotives in 1956. Not a single unit was preserved.
Poland
thumb|PKP Class OKz32
Twenty-five OKz32 2-10-2 tank locomotives were built by H. Cegielski – Poznań and delivered to PKP between 1934 and 1936. They were used mainly to work passenger trains between Kraków and Zakopane, a difficult railway line, steep in places, with many sharp curves, and requiring three direction changes. One has been preserved in working condition.
Two of these locomotives were built by the Malaxa Works in 1939 and 1941, numbered 151.001 and 151.002. Number 151.002 was preserved.
South Africa
thumb|[[South African Class 18 2-10-2|SAR Class 18]]
On , this wheel arrangement was first used by the South African Railways (SAR) in 1927. Two Class 18 steam locomotives, the most powerful non-articulated locomotives to see service on the SAR, were introduced on the line between Witbank and Germiston in an attempt to ease problems that were being experienced with increasingly heavy coal trains. It was designed by Colonel F.R. Collins DSO, Chief Mechanical Engineer of the SAR from 1922 to 1929, and built by Henschel and Son in Germany. They were three-cylinder locomotives, with the two outer cylinders using Walschaerts valve gear and the inner cylinder using Gresley conjugated valve gear, actuated by the motions of the outer cylinders.
thumb|left|[[South African Class 20 2-10-2|SAR Class 20 as experimental condensing locomotive]]
One more locomotive, the Class 20, was designed for branch line work on light rail by A.G. Watson, Chief Mechanical Engineer from 1929 to 1936. Only one locomotive was built by the SAR at its Pretoria Mechanical Shops at Salvokop in 1935.
thumb|left|[[Soviet locomotive class FD in Brest museum]]
The FD class was developed from ALCO and Baldwin heavy freight locomotives that were imported to the Soviet Union, where they were designated as the Ta and Tb classes respectively. The first FD class locomotive was built at the Voroshilovgrad Locomotive Plant in 1931.
In 1932, the Voroshilovgrad plant began with the mass production of FD20 locomotives. In the process of production, their construction was improved constantly. Production was interrupted at the outbreak of the Great Patriotic war in 1941 and was only resumed in 1942, when four locomotives were built in Ulan Ude. The total production was 2,927 locomotives of FD20, and 286 locomotives of FD21. The two subclasses only differed in respect of their types of superheater.
thumb|right|OR18-01 at [[Lebyazhye, Lomonosovsky District, Leningrad Oblast|Lebyazhye Railway Museum]]
In 1958, 1,054 FD class locomotives were sold to China, where they worked until the 1980s. A much lesser number were sold to North Korea at around the same time.
The Soviet locomotive class LV was developed from the previous L class 2-10-0 locomotive by the Voroshilovgrad plant. It used a feedwater heater to increase thermal efficiency and was the most efficient freight steam locomotive in the Soviet Union, with thermal efficiency of 9.3%. The first prototype was named OR18-01 (October Revolution plant, 18 ton axle load). A total of 522 LV class locomotives were built. Several were preserved, including the first, OR18-01, and the last, LV-0522.
Spain
thumb|RENFE 151.5001 at [[Railway Museum of Catalonia]]
In Spain, the wheel arrangement was represented by one series of 22 locomotives. They were initially ordered for the , but RENFE kept the entire series in reserve. Built between 1941 and 1944 in the factory in Barcelona for hauling heavy coal trains, they were amongst the most powerful steam locomotives in Europe. They had three cylinders, but used simple expansion and were known as Santa Fe locomotives.
United States
thumb|left|[[Atchison, Topeka and Santa Fe Railway|AT&SF No. 3932]]
In the United States, the type was produced between 1903 and 1930. The first were the Atchison, Topeka and Santa Fe Railway (AT&SF) engines of the 900 and 1600 series, which were an early type with few advantages over the Decapod, save their ability to operate in reverse without derailing. By 1919, the AT&SF was building the definitive type, with the trailing truck supporting a large firebox. These were of the AT&SF 3800 class. One of them, AT&SF engine No. 3829, was equipped with an experimental two-axle trailing truck to become the first Texas type.
Of the built for the Santa Fe, only one has been preserved. AT&SF No. 940 is on static display outside the Santa Fe depot, now a Visitor Center, in Bartlesville, Oklahoma.
thumb|[[Southern Railway (U.S.)|Southern Railway USRA Light Santa Fe No. 5200]]
The Baltimore and Ohio Railroad ordered its first from Baldwin in 1914. From 1914 to 1956, their bore numbers commencing with 6, hence the nickname "Big Sixes". Designated the S class, there were several sub-classes. The first of the Big Sixes was retired in 1951 and were all scrapped by 1960. The second batches of twenty-five (Nos. 6350–6374) were built by the American Locomotive Company's (ALCO) Richmond Works in 1918 originally for SOU's Cincinnati, New Orleans and Texas Pacific (CNO&TP) division. Of these, only one locomotive survives; Union Pacific 5511 was donated to the Railroading Heritage of Midwest America, who are restoring the locomotive to operation.
The Denver and Rio Grande Western rostered ten locomotives, under the class designation of F-81, rostered as Nos. 1400–1409, and purchased from Alco in 1916. None survived into preservation, all of them being scrapped between 1952 and 1955.