SA3 couplers are railway rollingstock couplings used primarily in Russia and states influenced by the former Soviet Union, such as Finland, Mongolia, Ukraine,... Russian railways originally used EU+UK legacy Buffers And Chain couplers, however these had several disadvantages: their draft load was limited, they were not semi-auto like North AmericanJanney couplers, and the required buffers could lock and cause accidents. It took a while to find a replacement: the two basic options were, convert to Janney couplers, as did Japan and Australia starting in the 1910s and 1920s, or devise something else. The Willison coupler was patented by John Willison from Derby, England. It was patented in 1916, and in Germany. The company Knorr bought it and it started to be used in Germany for some heavy trains and some suburban trains in Paris. In the 1930s, the Soviets improved upon and then decided to make this coupler standard across the Russian broad gauge railway system.
Experimentation
In the late 1920s, the UIC had established a working group for the replacement of the chain link coupler, which restricts the efficiency of freight railroads in a major way. Many railroads ran prototypes. In Germany, coal trains with Scharfenberg couplers yielded unfavourable results in winter weather, other railroads did similar tests. But the UIC was not able to agree on one replacement. This failure of the UIC, which hampers freight operation in Europe even today, led to the decision by the Soviet Union to move forward without a standard being achieved in the talks. The coupler was developed in and named SA-3 and was an improved version of Willison coupler, with better design of lock parts and mechanics. In 1935, the conversion of the vehicles began gradually. The Second World War delayed the introduction, so that the conversion was completed only 1957.
Operation
Helper locomotives at the end of the train are rarely used in the countries of the former Soviet Union. The load of the freight per train is not as heavy as on American railways. Although the SA-3 coupler is primarily used in the countries of the former Soviet Union, they are visible every day at the transshipping stations, at the eastern borders of the European Union. Since bogie-changing technology has progressed, this allows for cars with SA-3 coupler to regularly operate on the standard gauge tracks. A special converter car is inserted between standard and broad gauge cars for this operation, with different couplers on either end. Although these coupling freight cars have room for cargo, they are always operated empty. If the vehicle fitted with the SA3 retains its buffers, then a special adapter allows that vehicle to couple to another vehicle fitted with buffers and chains, provided that the buffers have the same spacing or gauge. This appears to be done in Iran. On the Uzhhorod–Košice broad-gauge track between Košice and Uzhhorod, Ukraine, of which the major part is on Slovakian territory, SA3 couplings are used exclusively. The railway is used for ore and coal transports from Kryvyi Rih, Ukraine to the US Steel mill in Košice and coal to the power plant of Vojany. In addition, the heavy iron ore trains on the Swedish Malmbanan began to use SA3 couplings in 1969 after problems with snapping chain couplers and a need for ever increasing capacity with higher train weights. Today, IORE locomotives haul trains of 68 hopper cars of with a total weight of over over gradients of 10 per-mille in harsh weather conditions, from the LKAB mine in Kiruna to the ice-free harbour of Narvik, Norway using couplings of the SA3 type without any problem. They tried out Janney couplers, too, when moving beyond 8,000 tons because SA-3 hasn't seen much use at such loads before that: in the SU, freight trains rarely exceeded 6,000 tons. The earlier SJ Dm3 locomotives have buffers fitted; therefore, they can couple with cars with a chainlink coupler. The longest and heaviest train with SA3 couplings ran on 20 February 1986 from Ekibastuz to the Urals, Soviet Union. The composition consisted of 439 coal wagons and several diesel locomotives distributed along the train with a mass of 43,400 tonnes and the total length of 6.5 kilometres.
Future
The new European Automatic Center Coupler has been based on this coupler, with the extended features of automatic brake and electric couplings. It also has vertical stability added, so that the coupling cannot fall down and damage the tracks or cause a derailment. It is compatible with the standard SA3 coupler and will have buffers needed for use with the standard buffers and chain couplers under the long transition period. The electric plugs would be most useful with electronically controlled pneumatic brakes.
