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Show INTER-MOUNTAI- MINING REVIEW. N 5 9 electricity vs. compressed air. Actvril Results in' a Mine of the Colorado Fuel and Iron Co. By Lewis Scaring. recent resurrection of compressed air as a pi ;sible rival of electricity as a motive power mal s a practical test of both systems, under sim ar conditions, of special interest. y st year the writer was called upon to invest igate the compressed air system in operation at one of the largest coal mines of the Colorado Fuel & Iron Co., to ascertain the T e prol able saving that could be made by substi- tuting electricity. The result of the investigation showed such a possibility for saving by the use of that the Fuel Company decided to have The installation was made a plant installed. great elec-tric- iy feet per hundred, continuing downward a distance of 3300 feet. The workings ramify from this main slope and connect with another mine known as No. 3 in which there were two small pumps operated by air. At the time of the test of the air plant these pumps were shut down. Air is conducted to No. 3 mine by a 4 inch pipe down No. 1 slope about 1,400 feet, from which point a 3 and 4 inch pipe crosses to No. 3 through the workings. The compressors being 400 feet from the mouth of No. 1 slope, the total length of 4 inch pipe to pump near No. 1 face is 3600 feet. Pipe to No. 3 has 5000 feet 4 inch and 800 feet 3 inch, a total of 5800 feet. The air pipes are laid under ground as far as mouth of No. 1 slope and from there continue down the mine unprotected. The pump at bottom of No. 1 slope on which the test was made, discharged water to the surface through 700 feet of 10 inch pipe and 2,550 inter-connect- ed A pressure guage was placed on the water discharge pipe at the pump at the bottom of the mine. Air pressure was measured at receiver. Crosby steam engine indicators were attached to the steam cylinders of the air compressors. Observers were stationed at various points to take readings. Readings were taken through the day commencing at 10 a. m. and ending at 5 p. m. At one time in the afternoon one minute readings were taken for ten minutes. At another time one of the compressors was shut down and the pumping done by two compressors as a check on the indicator measurements. The results are somewhat surprising: .... ..80 lbs. Average steam pressure 50 lbs. Average air pressure Average revolutions per minute: 64 Three compressors 110 Two compressors Average gallons discharged by pump COMPOUND ENGINE. 150 II. P., Coupled to 550 Volt Generator. Rouse Pumping Plant. under the personal supervision of the writer feet of 6 inch pipe, the pipe being laid up the afterwards operated under his direction for over a month, during which time tests were made and the workings of both systems noted. The above mentioned mine is located at Rouse, Colorado, at an altitude of 6000 feet. The compressed air plant is employed only for pumping and comprises three Norwalk Air Compressors, each 13 inch high pressure air cylinder, 22 inch low pressure ain and 20 inch steam cylinder, all of 24 inch stroke. The air cylinders are water jacketed. The air receiver stands outside of the compressor house and is 4 feet in diameter, by 12 feet high, having no covering. The air is conducted down No. 1 mine by a four inch pipe to a Deane duplex direct acting pump 18 steam by 'l.i water cylinder with 12 inch stroke, local ed near the face of the slope. 1 mine enters on a slope of an average 5.3 and slope in a practically straight line. The boilers supplying steam to the compressors consist of a battery of two 60 inch by 16 feet horizontal tu bulars and six plain cylinder boilers, 36 inch by 36 feet all of which are set in brick. The boiler and compressor houses are adjacent to each other, making the connecting steam pipe comparatively short. The test of the compressed air system was confined to the one pipe in No. 1 slope to obtain the total efficiency between the steam cylinders of the compressors and the water discharge of the pump. This test was not supposed to be an exhaustive one, but made simply to get a good estimate of the efficiency of the system. The per minute 400 Average strokes of pump per minute.. 176 Average pressure per sq. inch pumped 120 lbs. against Average indicated horse power at steam 312 cylinders of compressors As the theoretical horse power required to force 400 gallons per minute against 120 pounds is 28, it follows that the efficiency of the system between the points measured is less than nine fercent. It will be observed that this is the efficiency of the plant as found under actual working conditions and includes every loss which may occur between the steam cylinders of the compressor and the water discharge of the pump, amount of water discharged was measured by a and due to wear of apparatus and to inherent weir at the end of the water discharge pipe on and other defects in the system. the surface. This weir was 16 inches wide with As there are many mines in the state that are forced to employ a similar method of pumping measuring stake four feet up stream. |