How to unload coal from railway wagons?

Answer 1

There are numerous techniques to unload coal from wagons. The methods are determined at the design stage of the wagon. Historically the wooden wagons were simply tipped individually with their wheel sets attached as part of the wagon. The tipping could have been along the wagon or to the side using very promitive systems of derricks & ropes. Loading of barges was often achieved by simply tipping the wagons sideways at a height with the material falling into the barge from an elevated rail system. An alternative was to lift the wooden hopper of the wheel sets with a crane to then rotate in the air and discharge the contents - used for early ship loading of coal. It is of note that current versions are used of wagon side tipping for certain large terminals.

In more recent history there are "Tipplers" which rotate one or two wagons at a time around their coupler to dump them, after which the whole train is "indexed" along the track until the next set is aligned ready to be tippled. This is not a continuous process due to the indexing. Another current technique is to design the wagons for bottom dumping with doors on the wagons that can be opened at the destination to dump into a hopper below the rails. These doors may across the wagon or along the wagon. Opening techniques were historically manual opening, however for high volume operations these operations are automated.