Engine Test.—Cylinder diameters : high-pressure, 30 in. ; low-pressure, 60 in.; water, 27 in. Length of stroke: nominal, 4 ft. ; average during trial, 41625 ft. Average steam pressure at engine, 10516 lbs.; average pressure in force main, 95.67 lbs.; average vacuum in suction main. '2•38 lbs. ; pressure equivalent to difference between the two gauges, 26;13 lbs. ; net load on plungers, per sq. in., 12418 lbs. ; mean effective pressure : high-pressure cylinder, 48.82 lbs.; low-pressure cylinder, 14.666 lbs. Average piston speed per minute. 133.3 ft.; net work done in the 24-hour test, 26,779,100,000 ft. lbs.; duty per 1,000 lbs. feed water, 117,325.000 ft. lbs. ; capacity in 24 hours, as calculated from plunger displacement, 11.202,000 gallons. Average indicated horse-power developed by steam cylinders, 605.88 horse-power ; horse power calculated from work done, 563.5 horse-power; efficiency of engine, 93 per cent.; dry coal actually burned per indicated horse-power per hour, lbs.; pounds of water evaporated from feed at 153 26° F. to steam at 110.06 lbs., per indicated horse-power per hour, 15'70 lbs.
The Gaskill Pumping-engine, made by the Holly Manufacturing Co., Lockport, N. Y., is shown in Fig. 3.
On a heavy iron bed-plate are mounted two pumps, and m direct line therewith two low pressure steam-cylinders, with the piston-rods of the low-pressure steam-cylinders connected to the piston-rods of the pumps. Between the pumps and steam-cylinders are placed two beam supports, which carry the beam shafts and beams, the lower end of the latter being connected to the cross-heads of the low-pressure cylinders by means of links. On the top of the pumps are placed the main shaft bearings, which support the shaft, fly-wheel, and cranks, the latter being keyed to the shaft at right angles to each other. On the top of the low pressure steam-cylinders are mounted the two high-pressure steam-cylinders, with their centers in the same horizontal plane as the center of the main crank shafts. Two cross heads for the high-pressure steam-cylinders are connected by means of links to the upper ends of the beams, and the beams are in turn connected by means of connecting-rods to the crank-pins. From the high-pressure steam-cylinders heavy cast-iron girders extend to the pillow blocks. On the inner end of each of the beam centers an arm is keyed, from which the air-pumps are driven. The valves of the steam-cylinders are operated by means of eccentrics keyed on a shaft, which is at right angles with and driven by the main shaft through small bevel gears. The admission valves to the high-pressure steam-cylinders are of the double-beat puppet pattern, so arranged as to open at the proper time and to close at any desired point of the stroke. The exhaust valves from the high-pressure cylinders serve
also as admission valves to the low-pressure steam-cylinders, and are of the ordinary slide valve type, and are set so as to remain open somewhat less time than is required to make a complete stroke. The exhaust valves from the low-pressure cylinders are also plain slide valves, operating in the same manner as the high-pressure exhaust valves. The plungers are arranged to work through glands in the centers of the pumps, and are accessible from the covers at the ends of the pump cylinders. The pump valves are placed on horizontal plates below and above the line of the plunger travel. The glands above mentioned divide the valves of one end of the pump from those of the other end, at the center of the valve plates.
Test of a Gaskill Pumping-engine.—The following is condensed from a report by Prof. D. M. Greene, of the Rensselaer Polytechnic Institute, of a test made by him of the Gaskill Duplex Compound Engine, at Saratoga Springs, in 1889 ; The principal dimensions of the engine and pumps are as follows : Diameter of high pressure cylinders. 27 in. Diameter of low-pressure cylinders, 54 in. Diameter of pump plungers, 25 in. Stroke of steam-pistons and pump plungers, 40 in. Diameter of high pressure piston-rods (steel), 3.5 in. of low piston-rods (2) (steel), 4.5 in. Diameter of pump rods, 5 in. Diameter of crank shaft (fagoted iron), in. Diameter of hub of crank, 22.5 in. Depth of crank, 11 in. Diameter of crank-pins (steel), 7-5 in. Length of crank-pins (steel), 9 in. Length of beam between centers, 63 in. Length of upper beam pin. 14 in. Diameter of upper beam pin, 6 in. Length of lower beam pin, 6 in. Diameter of lower beam pin, 6 in. Diameter of fly-wheel. 16 ft. Depth of rim of fly-wheel, 16 in. Width of face of fly-wheel, 14 in. Weight of fly-wheel, about 28,000 lbs.
The clearance space in all of the cylinders is small, and is taken at 2.7 per cent. and 3 per cent. in the high- and low-pressure cylinders, respectively. The pumps, which are double-acting, are each fitted with 700 " Troy" valves, each of about 14- in. diameter and in. lift. At each end of each pump, therefore, there are 175 induction and 175 eduction valves, giving an aggregate valve opening for the reception and discharge of the water equal to more than 0.6 of the effective area of the plunger. The loss of head due to the passage of the water through the pumps is probably not greater than of a foot.