The Mechanical Handling and Storing of Material
Forfatter: A.-M.Inst.C E., George Frederick Zimmer
År: 1916
Forlag: Crosby Lockwood and Son
Sted: London
Sider: 752
UDK: 621.87 Zim, 621.86 Zim
Being a Treatise on the Handling and Storing of Material such as Grain, Coal, Ore, Timber, Etc., by Automatic or Semi-Automatic Machinery, together with the Various Accessories used in the Manipulation of such Plant
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224
THE MECHANICAL HANDLING OF MATERIAL
strong and costly, as lubrication is difficult or impossible. They are, therefore, rapidly
corroded.
Ashes have been dealt with on board ship, and disposed of overboard by pneumatic
or hydraulic means, but the credit of the introduction of a somewhat analogous system
for stationary boiler installations is due to the Darley Engineering Co., of Pittsburg, who
have erected upwards of thirty pneumatic ash-handling plants. Fig. 308 shows one of
these installations in diagrammatic form. The main ash duct a passes close in front of
the boilers and beneath the stokehole floor, but level with the floor are inlets before each
boiler, into which the ashes are raked or swept, and which are closed with a lid when
in use. The pipe leads to a large receptacle b with cone-shaped top and bottom, and
raised sufficiently high so that the lower end can deliver when opened into a railway
truck. The upper cone joins a suction pipe connected to an exhauster c, for small
installations, and for large ones to an air-pump. The outlet of this is connected with the
chimney whereby the draught is increased. At the top of the ascending pipe, and just
before the ashes reach the receptacle b, they are subjected to a water spray to avoid dust,
and consequently wear on the exhauster. In addition to this the air is withdrawn from'
the tank through a dust collector. The special rotary exhauster is simple and efficient
for small capacities, but for larger ones a cycloidal blower is used.
It is a known fact that in all pneumatic installations for grain, etc., the material
travels in the central portion of the pipe, so that no abrasion takes place at the sides of
the pipe, except where corners are negotiated, so it is necessary to make the bent portions
of the pipe not only of a fairly large radius, but also to fit them with renewable cheeks,
and as ashes and clinker are of a most cutting nature the wear on this part is reduced to
a minimum by having wearing blocks, d, of manganese steel, as shown in Fig. 309.
Suction conveyors have no moving parts in contact with the ashes. They are