The Mechanical Handling and Storing of Material

THE HANDLING OF MATERIAL BY PNEUMATLC MEANS 213 It consists of an Fig. 285 Duckham’s Suction Nozzle. iron piping for the straight lengths and flexible hose for the bends. . The hose is armour- plated inside and covered with india-rubber with insertion to keep it air-tight. Experiments have shown that the construction of the nozzle is not of very great importance provided that it is easily adjustable, its essential function being to adjust the proportion of grain to a given quantity of air passing through the pipe, and as the proportion of grain must be smaller when the pipes are longer, or the grain heavier or lighter, it is important that the adjustment should be easy to make. For the sake of completeness the very simple delivery nozzle which is used in con- nection with the combined system is here also given in Fig. 286. iron pipe about two or three times the diameter of the supply pipe, and the length five to ten times the diameter of the latter. The pipe which leads from tank m (Fig. 283) is connected to the delivery nozzle, and as soon as the air which carries the grain expands in the wider nozzle, the velocity of the grain is reduced, and it runs out of the pipe in a uniform stream. This method of delivery has been successfully applied in several instances, the most important being the floating elevator “ Garryowen ” at Limerick and the “ Leitrim ” at Sharpness. The combined suction and blast system can only be used effec- tively in cases where the grain has been sufficiently freed from dust before delivery, or in cases where the dust would be no objection. With the Duckham system a partial vacuum of 7 to 10 in. of mercury is necessary to work the conveyor. With this vacuum the grain travels in the pipe at the rate of 30 to 50 ft. per second. One pipe has then a capacity of 30 to 40 tons of grain per hour. As one of the vacuum tanks is fed by at least two pipes, the capacity of a single installation through one air trap is 50 to 60 tons per hour. The power consumed in driving such an installation is about 3 H.P. per ton of grain to be conveyed per hour. This is exceedingly high in comparison with ordinary bucket elevators. It means that a Duckham plant with a capacity of 100 tons per hour and a 60 ft. lift would consume 300 H.P. A bucket elevator would lift the same quantity of grain with only 10 H.P. Fig. 286. Duckham’s Delivery Nozzle. Figs. 287, 288, and 289 show a complete installation of the Duckham elevator for discharging grain ships. It was built by G. Luther, of Brunswick, for the Hamburg- American Line. It has a capacity of 150 tons of grain per hour, and has proved capable of very good work. A dust collector which is here employed is marked in the drawing. It is intended for the purification of the air before it goes to the exhausters. Haviland & Farmers System.—This firm, after abandoning their original system, now work on the same system as that of Duckham. They claim to have made a number of improvements, and certainly some of their innovations are very noteworthy. They have paid special attention to the purification of the air between the vacuum chamber and the exhausters. In order to prevent wear and tear and consequent loss of driving power owing to the leakage of the air past the exhauster pistons, they have also