File:Machinery for metalliferous mines - a practical treatise for mining engineers, metallurgists and managers of mines (1902) (14766096315).jpg

Identifier: machineryformeta00davi (find matches)
Title: Machinery for metalliferous mines : a practical treatise for mining engineers, metallurgists and managers of mines
Year: 1902 (1900s)
Authors: Davies, E. Henry (Edward Henry)
Subjects: Mining machinery
Publisher: London : Crosby Lockwood New York : Van Nostrand
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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eration is dependent only on the practical speedat which the steam engine may be operated. Speed Governor.—In addition to the usual speed governor, it isnecessary to provide one that shall control the speed of the compressorin exact accordance with the amount of compressed air required,the speed governor only acting when the limit of safe working hasbeen reached. To accomplish this result a floating lever is added tothe ordinary governor, one end of which is attached to the cut-offmechanism, and the other to a plunger working in an oil cylinder. Thisarrangement will be seen by reference to fig. 119. The position of thisplunger is controlled by the air pressure working against a spring. Shouldthe air pressure exceed the normal limit, the plunger moves upwardsagainst the spring, and thereby alters the cut-off on the steam cylinderto an earlier point. Similarly should the air pressure fall below the normal,the spring lowers the plunger and increases the speed of the engine. ^ ^ w^ -5 Q
Text Appearing After Image:
i8o MACHINERY FOR METALLIFEROUS MINES. There is thus constantly exerted a force on either side of the con-trolhng plunger, assisted by the greater or lesser resistance in the aircylinder itself; and the speed of the machine is thereby automaticallyvaried to suit the amount of compressed air required. Compound Air Cylinders.—The merits of compounding in steamcylinders hardly need recapitulating here, though it may be stated that evencompounding in steam cylinders is hardly to be advocated for air com-pressing, when fuel is moderately cheap and less than loo I.H.P. requiredand sufficient water for condensing not available. The reason for this isthat with a duplex air compressor either side may be used independentlyof the other. This it would be difficult to do with a compound engine,as it would require a low pressure cylinder of unusual strength and specialvalves and connections for modifying the steam pressures. If, however, the power required exceeds 150 I.HT^., then there isa fourf

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