Stoker
As a stoker , from engl. to stoke ( fanning ), a mechanical device for feeding the grate of a steam engine with solid fuel ( coal hereinafter).
development
The continuous increase in weight and speed of trains in connection with the steadily increasing grate dimensions in heavy locomotives brought manual lighting to the limit of its performance. The “Big Boy” in the USA had a grate area of almost 14 m² and a coal consumption of up to 9 t per hour, a quantity that cannot be handled manually by a heater without the support of a mechanical loading device.
At the turn of the 20th century, the development of the mechanical stoker began in the USA with various attempts at automatic grate loading. There are two ways to get the coal into the firebox. One possibility is the underfeed feeder. With it, the coal is simply pushed in at the level of the grate. The other option is the overfeed feeder on a plate at the height of the fire hole. The coal is pushed onto this by the screw conveyor and thrown onto the fire bed from above with the help of steam jets. The overfeed feeder with a screw conveyor and distribution with a steam jet on the fire bed has prevailed. The main supplier was the Standard Stoker Company from New York.
construction
The stoker consists of a screw conveyor that uses pipes to transport the coal from the tender to the fire box . The screw conveyor is driven with the help of a small steam engine, which was usually housed in the tender for reasons of space. The most common design was a three-part screw conveyor connected to cardan joints. The start and speed of the screw conveyor as well as the control of the steam jets are carried out by individually controllable valves. The steam engine is designed to be reversible in order to free the screw conveyor from trapped coal or foreign bodies. Since the coal is broken into smaller pieces by the stoker than is the case with manual firing, a special type of grate is required that allows enough combustion air to pass through despite smaller grate gaps.
The mechanized firing, which was on the one hand uniform and constant, and on the other hand flexibly adaptable to requirements, also made it possible, in conjunction with the other grate design, to use cheaper coal with a higher content of volatile components than with manual firing. Despite the almost double-digit higher consumption, operation and maintenance turned out to be more economical than with bucket firing. When using a Hulson shaking grate, it was possible to drive with a small but evenly high layer of fire.
In connection with a Hulson shaking grate and a double Kylchap suction system, there were several advantages:
- Grate loading that can be quantitatively controlled according to power requirements
- Even loading of the entire grate surface
- High power radiation and high boiler output due to the high temperatures of the surface embers
- Undisturbed and continuous burning process of the coal on the grate - no opening of the fire door means no penetration of cold or foreign air into the fire box
- Grate charging with coal of the same grain size, resulting in a homogeneous, evenly coated fire bed
- Reduction of coal consumption by 8–10% compared to hand-fired locomotives
- Relief of the stoker from heavy physical work, who can thus devote himself better to the monitoring and operation of the boiler and the route observation
distribution
While stokers were standard equipment on large locomotives in the USA - in 1938 at least 20,000 stokers were in use in the USA and Canada - they were not very common in Central Europe. The German Federal Railroad (DB) converted five machines of the DR series 45 with a new boiler and stoker device. Another five locomotives of the DRG Class 44 were converted in a similar manner in 1950 and ended in the early 1960s their service in Bw Ehrang.
In 1954 the Deutsche Reichsbahn (DR) made another, less successful attempt with a stoker on a prototype of the DR series 25 . The somewhat higher coal consumption of this facility, in addition to the introduction of oil firing, prevented further spread. Another disadvantage was the reduced water content of the tender when the devices for stoker firing were retrofitted.
In France , the development of its own stoker began as an American license in the 1930s at the Paris company Stein & Roubaix. The test locomotives included the 2'D1 'h3 locomotive series 241 of the Compagnie des chemins de fer de l'État (ETAT) and the SNCF 242 A 1, which was created from one of these machines through conversion . The French Northern Railway (NORD) initially tested a stoker of the type BK (two screw conveyors) in a machine of the Nord 3.1201 to 3.1290 series , later SNCF 2-231 C ("Superpacific") and in the Nord series 5.1201 to 5.1230 , later SNCF 2 -150 B. Then a stoker was to be installed in all new series at the SNCF, which was founded in 1937 , such as the 150 P , 141 P , 241 P or the coal-fired machines from the 141 R series . A total of more than 1200 locomotives with this mechanical lighting system of the type Stoker HT from Stein & Roubaix were in use.
At the former Czechoslovak State Railways (ČSD), this furnace had been developed to series production in the late 1940s. For example, the series 556.0 , 475.1 , 477.0 and 498.1 supplied by Škoda and ČKD Praha were equipped with stokers as standard, which resulted in a considerable increase in performance. The class 556.0 freight locomotives were nicknamed “Štokr” by the operations service due to the built-in firing system.
The stoker was widely used in southern Africa. Especially with more modern South African steam locomotives, e.g. B. in the GMAM and 25 series with grate areas of approx. 6 to 6.5 m², the stoker has proven itself very well.
literature
- Bernard Robinet: The stoker in France . In: Lok-Magazin . No. 80 . Franckh'sche Verlagshandlung, W. Keller & Co. , 1976, ISSN 0458-1822 , p. 370-378 .
Web links
Individual evidence
- ↑ J. Michael Mehltretter: Full steam ahead. Power and technology of steam locomotives . 1st edition. Transpress, Stuttgart 2013, ISBN 978-3-613-71469-4 , p. 31 .
- ↑ a b J. Michael Mehltretter: Full steam ahead. Performance and technology of steam locomotives , p. 72 f.
- ↑ Wolfgang Kreckler: The stoker locomotives in the Ehrang depot