Chimney (steam locomotive)

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A typical spark arrester chimney
The "Seguin" with a chimney at the back and fans to fan the fire

The chimney or chimney of a steam locomotive is called a chimney . The name is derived from the chimney used in the same way in stationary combustion systems, for example in forges .

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It is usually located above the smoke chamber . The blowpipe and, if available, the auxiliary blower are placed directly below . This was not the case with the first steam locomotives, as the advantages of this arrangement had not yet been recognized at the time.

The chimney is primarily used to remove the flue gases that arise when the fuel is burned. The additional discharge of the exhaust steam from the cylinder through the chimney has technical advantages. The current common position on the side of the boiler facing away from the driver's cab is primarily due to technical reasons. When arranging the chimney, however, care must be taken that the smoke, especially in tunnels, is directed over the driver's cab, as otherwise the smoke makes it impossible to see the route (the smoke gases are of course not wanted in the driver's cab). This problem was solved in the cab-forward locomotives by turning the actual locomotive structure.

Because some fuels have a more or less tendency to form embers and sparks, which can be carried away by the flue gases, a spark arrester is sometimes necessary. This can be installed both in the smoke chamber and in the chimney itself. This special design with a spark arrester in the chimney is also called a spark arrester chimney . This is mainly installed in steam locomotives with wood combustion and has a pronounced conical shape. Wood-fired locomotives usually have two spark arresters (one in the smoke box and an additional one in the smoke box). In the case of coal-fired locomotives, it is sufficient to install the spark arrester in the smoke chamber, which is why they have an almost cylindrical design, as this is easier to manufacture. However, these chimneys also generally have a slightly conical shape on the inside, as this allows a better draft to be achieved through the blowpipe.

Since the possible construction height of the chimney is limited, there is often no natural draft, so fans began to be installed. Initially, for example, these were fans driven by the axles. It quickly became apparent, however, that the simplest solution is to divert the used steam from the cylinders through the chimney, which creates a negative pressure in the smoke chamber, which sucks the smoke gases out of the heating pipes, and so that of high chimneys can replace the resulting natural train. Modern steam locomotives have auxiliary blowers for standstill, with which the locomotive crew can regulate the draft in the chimney. In the case of condensation locomotives, a fan had to be installed in the chimney due to the lack of exhaust steam.

The chimney and the blowpipe must be coordinated with one another, as this is the only way to create a suction effect that additionally ignites the fire through the resulting draft. This fanning is directly dependent on the strength of the exhaust blow, and thus on the work of the steam engine. The kindling of the fire is therefore desirable, as it automatically regulates the steam engine's power within certain limits.

In order to ensure better evacuation of the smoke gases outside the chimney at higher speeds, the shape of the chimney has always been decisive. Initially, an appropriately adapted crown on the fireplace was sufficient. The upper end was also not cut horizontally, but sloping towards the front . However, with increasing power and increasing speeds, this was no longer sufficient, and additional smoke deflectors were started , which can have a positive effect on the extraction of the flue.

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