MOTOR AND CENTRIFUGAL PUMP.
Fig. 241is intended to show the application of the electric motor to a centrifugal pump; these two machines are mounted on one bed plate, directly connected by a flange coupling between them. The motor shown, is almost identical with the machine illustrated,Fig. 217, and described onpage 251. The pump is so arranged that the discharge can be turned in any direction desired. Wherever electric power is available and the centrifugal pump is the form best adapted to the work, this combination presents advantages over a steam engine operated by a plain slide valve such as is generally used.
Fig. 241.
Fig. 241.
Fig. 242shows a double pump driven directly, without gears or belt, from the shaft of an electric motor. The pump crossheads are connected directly to cranks at each end of the motor shaft. The cranks are set at right angles and each pump is double acting, or has two plungers connected by outside rods and with outside packed stuffing-boxes, so that this portion of the pump is always accessible.
The plungers are 31⁄2inches diameter and 51⁄2inches stroke. The pump and motor are mounted upon a rigid box girder frame: this unit is self-contained and occupies a relatively small floor space.
Electric Drive for Fire Pumps.The importance of instantly operating fire extinguishing apparatus can scarcely be exaggerated. The largest conflagrations are but little flames at the beginning, and if caught at the critical moment they make no record of destruction; for such service the electric current is the ideal agent. A notable installation of electric-driven pumps for fire service is in the Marshall Field store, Chicago, a building occupying an entire city block. The outfit consists of a Laidlaw-Dunn-Gordonduplex Underwriter pump connected by single reduction gearing to a waterproof electric motor.
Fig. 242.
Fig. 242.
The pump cylinders, 8 × 12 inches, have a computed capacity of 700 gallons per minute at 140 pounds water pressure. The pump, besides its other special features, is claimed to be rust proof throughout so that it will not get out of ready running condition.
Fig. 243.
Fig. 243.
The electric system has especial conveniences for mine pumping because of its adaptability to long transmissions of power; electric power can be transmitted to almost any distance, and the pumps can be supplied with either direct or alternating current motors. A mining outfit can be easily divided into a number of parts, to facilitate lowering into a mine, after which the assembling of the parts is a simple operation.
Stationary pumps for mine use are made in two classes: first, vertical pumps having cylinders in a vertical position in which the over all height is comparatively great and the horizontal dimensions as small as possible; second, horizontal pumps with cylinders in a horizontal position and having for cross dimensions the over all length. The class of pump to be selected, of course, depends upon the limitations of the location. In either case, the motor used for driving the pump is mounted on an extension of the pump base, making a self-contained and compact outfit.
Engraving,Fig. 243, represents a Quintuplex pump used principally in mining operations, or wherever large quantities of water are to be delivered under high pressure in the shortest possible space of time. The pump here shown was designed to deliver 225 gallons of water per minute under a head of 1,200 feet. It has five plungers 4 inches in diameter each and having a uniform stroke of 12 inches.
These pumps driven by electric motors it is said represent the most economical method of transmitting power, as compared with the best designs of steam pumps. An efficiency of 80 per cent. is claimed for these pumps.
Note.—It is interesting to know that in one of the largest electric pumping installations which has ever been made for mining work, the power is carried 2,500 feet underground at a potential of 3,500 volts and then transformed into 220 volts at the motors. No trouble has thus far resulted from the high voltage or any other cause; in regard to danger from underground electric pumps, it can be stated that accidents due to the use of electricity in such installations are almost unknown.Induction motors are arranged to operate without moving contacts.They are therefore free from sparks and can be used in mines where the presence of gases compels the use of safety lamps.
Note.—It is interesting to know that in one of the largest electric pumping installations which has ever been made for mining work, the power is carried 2,500 feet underground at a potential of 3,500 volts and then transformed into 220 volts at the motors. No trouble has thus far resulted from the high voltage or any other cause; in regard to danger from underground electric pumps, it can be stated that accidents due to the use of electricity in such installations are almost unknown.Induction motors are arranged to operate without moving contacts.They are therefore free from sparks and can be used in mines where the presence of gases compels the use of safety lamps.
Fig. 244exhibits an electric induction motor operating a 51⁄2× 8 portable track pump.
Portability is an important feature in all pumps for mine use; and, as track pumps may be put into service immediately at any point on a system of tracks, they meet this requirement better than pumps of any other form.
Such an outfit can be hauled to any point in the mine and there operated from some convenient circuit such, for instance, as the circuit supplying power to mine locomotives.
Fig. 244.
Fig. 244.
The pump and motor shown inFig. 244are mounted on an iron truck, no wood whatever being used in construction, so that adjustment cannot be affected by moisture and an easy running and durable pump is assured. The pumps are made as compact and strong as possible for mine service, which is usually exceptionally rough and continuous. They are of the horizontal type which is best adapted for low passageways and are designed so as to afford easy access to all parts. The pumps are single acting and the plungers are provided with outside stuffing-boxes, which can be packed, and being in sight, any leakage can be quickly detected. Access to all valves is made easy by the removal of one large hand-hole cover on the valve chest.