The Mechanical Handling and Storing of Material

22Ö THE MECHANICAL HANDLING OF MATERIAL Quite a number of these pneumatic conveyors are used in the power stations of the United States Government. Fig. 310 shows the 60-ton tank of the Central Power Plant, Norfolk Navy Yard. Provision is made for weighing the ashes taken from this tank, for the purpose of testing the quality of the coal. The connection with the exhauster is made through the large diagonal pipe. The 8-in. ash duct is led underground and then rises vertically to the top of the tank. The exhaust pipe is led to the tank via a dust collector, which latter is, however, not shown in the illustration. Pneumatic Coal Conveyors.—After many tedious attempts it is now possible to convey small coal from the size of dust to nut coal by pneumatic means. The first successful installation for this purpose has, as far as the writer is aware, been erected in a factory in Austria where twenty 10-ton truck-loads of coal per twenty-four hours have to be conveyed in order to feed the boilers in the two boiler-houses situated on both sides of the railway line (see Figs. 311 and 312). The continual demand for coal throughout the twenty-four hours cannot be regularly supplied by the railway, so that as a safeguard a stock pile of coal is kept in an open yard about 500 to 600 ft. from the boiler-house. Before the erection of this pneumatic plant the coal was conveyed in small trucks by hand labour from the wagons or the yard to the boiler-house. From the illustrations it will be seen that the pneumatic installation has been erected just above the railway siding and between the two boiler-houses. It is contained in a tall building /, and the coal is delivered from it by a cross worm conveyor to either or both of the two worms 5 and which distribute it to the coal bunkers. The component parts of this pneumatic plant are not unlike those already described, and consist of the receiver r, two filter chambers /and/p and twin air-pump the latter being in the engine-house. Two pipes