The Mechanical Handling and Storing of Material

602 THE MECHANICAL HANDLING OF MATERIAL Some establishments have found it expedient to erect extensive silo or bin systems for storing coal, and have equipped the same with complete mechanical plants.1 Figs. 935 to 939 illustrate the coal store which has been used by Messrs Possehl & Co., Altona, since 1896. This store was designed to receive coal coming by boat up the Elbe, screening it, and then dispatching it either by rail for inland use, or by vehicular traffic for local con- sumption. Small coal is discharged from steamers, by means of a ship’s elevator, of a capacity of 60 to 70 tons per hour, whilst large coal is unloaded by a crane and grab of a capacity of 40 to 50 tons per hour. The small coal which has been unloaded by the ship’s elevator is stored in fifteen silos. These silos are hopper-bottomed, and the whole of their contents can therefore be withdrawn with a minimum of labour. Six of the fifteen silos are set apart for such coal as require screening. Fig. 939. Elevation of Coal Store, Altona. The main store contains six silos 69 ft. in height, reaching down to the level of the ground, and nine silos of a height of 50 ft. The former measure 27 ft. 6 in. by 21 ft. 6 in., and hold 1,000 tons, whilst the latter have a floor area of 27 ft. 6 in. by 28 ft. 6 in., and hold 800 tons. On the quay is an iron tower containing an elevator, and connected with the main store by two gantries. The ship’s elevator is suspended from one end of a derrick which is supported from the tower. The elevator discharges the coal on to a band conveyor which has been erected within the derrick. This band in turn discharges its load on to a second band running on the lower gantry, delivering into an automatic weighing machine, whence it slides down a shoot to the well of an inner elevator which takes it to the top of the building, and to another band conveyor which is provided with a throw-off carriage to the various silos, almost identical with a granary installation. 1 For installations of this class, but solely for feeding boilers, see “ Coal, Coke, and Ash Handling Plants for Boiler-Houses, Gasworks, etc,,” page 630.