The Mechanical Handling and Storing of Material

CHAPTER XX CONVEYING MATERIAL BY HYDRAULIC MEANS In the United States experiments have been satisfactorily conducted, in which small coal was mixed with and conveyed in a stream of water through pipes, and at the destination the coal was allowed to settle whilst the water was led away. What has been said in connection with pneumatic conveyors applies also to this system, viz., the material to be conveyed should not have a specific gravity much greater than the medium in which it travels, otherwise the speed of the mixture in the pipes must be greater, and therefore the expenditure of driving power higher. This rule applies to the conveyance of coal by means of currents of water. The flow must be swift enough to prevent the coal from separating and depositing, thereby blocking up the pipes, particularly where these are laid horizontally. Material from dredgers, such as sand and mud, is frequently conveyed by such means, water being mixed freely with the material, which is thus conveyed on to waste land. This fact can only be briefly mentioned without going into details, as it would be beyond the scope of this work, in which also dredgers and power shovels have been omitted, as digging and excavating, and not conveying, are the primary and more important objects of these appliances. Hydraulic Conveying at the Hammersmith Borough Council’s Electric Light Installation.—The first installation of this kind was erected for the Hammersmith Borough Council 'for their electric light installation, the power house being situated some 600 yds. from the river Thames, where the coal is received in barges. The capacity is from 30 to 60 tons of coal per hour, which is pumped, as it were, through 8-in. Mannesmann tubes. The mains are laid in the streets in the form of a large S-bend. Both delivery and return pipes are placed close together; these are socket and spigot pipes in lengths of approximately 30 ft. At the coal wharf a large mixing tank is erected, which is fed by a grab that lifts the coal from the barges, and after it is passed over an automatic weighing machine, it is deposited in a tank in the proportion of ’15 per cent, of coal to 85 per cent, of water. A powerful electrically driven pump, built by Messrs Gwynnes, Ltd., forces this mixture at a high velocity through the pipes to the receiving tank at the electricity works. Here the coal sinks to the bottom of the tank, and a second and similar pump drives the water through the return pipes to the mixing tank, while another grab lifts the coal out of the reception tank and deposits it in huge storage tanks capable of holding 6,000 tons of coal. The pipes are laid approximately level, but rise about 15 ft. near the delivery terminal. The process is automatic, and the same water is used over and over again. The installation was estimated to cost ^15,600, but as previously the coal had to be conveyed by cart at a cost of approximately 7d. per ton, it is estimated that an annual saving of ^1,577 may be effected. The installation was designed by Mr G. G. Bell, electrical engineer of the Hammer- smith Borough Council, and erected about the end of 1914. 228