The Mechanical Handling and Storing of Material

CONTINUOUS HANDLING OF MATERIAL BY PNEUMATIC AND HYDRAULIC MEANS CHAPTER XIX THE HANDLING OF MATERIAL BY PNEUMATIC MEANS By the use of pneumatic conveyors material is carried without coming into contact with any mechanical appliances. It is, so to speak, floated in a current of air from which it is separated at the delivery point. To ensure the material floating more or less in and with the air, it is essential that it should not be of great specific gravity, and therefore pneumatic systems of transportation are mostly generally used for transporting such commodities as grain, malt, seeds and cotton, although potatoes, chemicals, cement, ashes, and even coal, can also be conveyed pneumatically. The greater the specific weight of the material, the greater must be the velocity of the air in the conveying pipes, otherwise the stock will have a tendency to separate from the air during travel, thus blocking the pipes, especially if these are horizontal or nearly so. Very considerable power, however, is required to propel air at great speed, and as pneumatic conveyors and elevators are probably the least economical type as regards the power necessary to work them, this excessive power is the more serious the heavier the material to be handled. About the year 1863 experiments were made with a view to elevating grain by means of air currents, and since then many patents have been taken out for appliances to solve this problem in different ways. Among the earliest and most important patents were those of Merrill, of Brooklyn, in 1873; of L. C. Renard and C. M. De La Haye, of Paris, taken out in America in 1879 ; of Jaacks & Behrns, of Lübeck, taken out in Germany in 1880 ; of Lyman Smith, taken out in America in 1882 and 1883 ; of Frederick W. Wiesebrock, of New York, taken out in the United States in 1884 ; of the Rev. George M. Capell, of Stony Stratford, Northampton, taken out in England in 1884 • of Oscar Bothner, of Leipzig, Germany, taken out in 1896. Most of the early inventors suffered disappointment because they strove to discover what might be termed a grain pump. The first practical application of pneumatic power to the conveying of grain was in 1887, when the Cyclone grain transfer barge was constructed at Cleveland by Lyman Smith, and used for transhipping grain from lake vessels to canal boats. An obvious advantage of such a system over a combination of ordinary elevators and conveyors is, that in unloading ships the suction pipe can be readily conducted within the hold so as to reach every corner and confined space therein; hence such appliances save a large amount of manual labour in trimming grain which is necessary with any other grain unloading appliance. The only valid objection to pneumatic elevators is the heavy initial cost of their installation, and the large expenditure for fuel necessary to produce the air current. In other words, like all other pneumatic methods of power distribution, it is notoriously 207