PUMPS AND PUMPING. 544 PUMPS AND PUMPING. ton is but partially completed. The balance of the stroke is due to the expansion of the steam in the cylinder and is a gradually decreasing pressure." (See Steam Engine.) In the direct-act- ing pumps the piston speed is maintained through the whole stroke by means of a compensating device. One of the best known of these, the Worthington high-duty attachment, em|)loys an accumulator for this purpose, consisting of an oscillating piston. During the first part of the stroke the forward end of the jiump piston forces the oscillating piston against water pressure. When the steam is cut off' this pressure is auto- matically released, and, through proper mechan- ism, is utilized during the completion of the stroke, while the steam is expanding. In place of this device another manufacturer emploj's a portion of the high pressure of one side of a duplex engine to aid the expanding steam on the other side. Where a fly-wheel is employed it WORTHINGTON PLUNOEB AND EINQ PATTERN PCMP. affords all necessary compensation, exactly as in the steam engine. The Holly-Gaskill is the best- known type of a horizontal fly-wheel pumping engine and the Leavitt and Allis engines illus- trate the vertical type. The object of these various devices is to secure greater economy in the use of fuel, to which end an increased first cost of construction, or capital outlay, is imder- gone. Such engines are classed as high duty. The duty of a pumping engine was formerly expressed in millions of pounds of water lifted one foot high by the consumption of 100 pounds of coal. Since coal is variable in quality, there was sutistituted for it as a basis the work done by 1000 ])ounds of dry steam ; and as a further refinement, the work "done bv 1,000,000 British thermal units (B.T.U.). The two last give results that are fairly comparable for ordinary conditions, but, whereas 1000 pounds of dry steam, in a liigh-grade pumping engine, have yielded about 1.50,000,000 foot-pounds, the duty of the same engine, based on 100 pounds of coal, was about 108.000,000 foot-pounds. On tlie coal basis the duty of pumping engines has increased, in round numbers, from 6,000.000 foot-pounds for the Newcomen atmospheric pumping engine of 1709 to 178,000,000 foot-pounds for the best crank-and-fly-wheel triple-expansion pump of the present day. The wide range of efficiency of various types of pumps now used is shown by the following figures from Turneaure's ll'dfcr Supply, based on the duty per 1000 pounds of steam: High duty, 1G8-100 millions; ordinary pumping engines, 100-75 millions; steam pumps, 40-10 millions; direct-acting deep-well pumps, 0-2 millions; vacuum pumps. 8-2 millions; jet-pumps, 4-1 million foot-pounds. Power pumps, with <lirect connecting engines, the pumps alone having an elJieieney of 75 per cent., are ranked at 114 to 37 millions according to the type of engines. The air- lift pumps, with a pump elliciencv of 25 per cent., are figured to give duties of 31.000.000 to (i.OOO,- 000 foot-pounds per 1000 pounds of steam, with various styles of air compressors. The theoretical efficiencies of the above three classes of pumping apparatus (i.e. pump and motive power com- bined) lange from 20.6 per cent, for the high duty engines to 0.13 per cent, for the jet pumps, 14.7 per cent, for the triple-expansion condensing engines and power pmnps, 4.8 per cent, for sim- ple high-speed condensing engines and ])0ver pumps, and 4 to 0.77 per cent, for air-lift pumps. Historical Sketch. The earliest authentic record of a displacement pump, or of any im- provement over the water lifts, seems to be a description of the force pump of Ctesibius of. Alexandria, in Hero's Spiritalia. Two single- acting vertical pumps were operated alternately by a common beam, or brake, and the two dis- cliarge pipes were connected with an air cham- ber and the stream was then thrown from a movable nozzle. Hero also described another device for raising water, in which the expansive power of steam, acting in a closed vessel, was made to displace or lift water. In the fifteenth century there is evidence of the frequent use of hand pumps in wells, and. in fact, it seems that they may have been well knowni over a thousand years earlier, for a German translation of Vege- tins (Erfurt, 1511) contains an illustration of a suction-lift pump, with a rectangular barrel. The original of this work was dedicated to Valentinian II. (A.D. 375-392). The substitution of a plunger for a piston, in the ordinary force pump, is credited to Sir Samuel Jloreland. who obtained an English patent on the device in 1675. His plunger passed through a stuffing box on the upper end of the vertical pump cylinder, while a double-acting force pump, difl'ering somewhat in principle from the one just suggested, was de- scribed by La Hire in 1710, in the Memoirs of the French Acarlriini. The rotary piston pump dates from the sixteenth century, or earlier. Servifre (born at Lyons in 1593) describes a number of rotary pumps, including a double interlocking piston pump. The rotary displacement pump has been but little used, and when now employed it is generally for such service as fire protection, where economy of operation is a comparatively minor consideration. See Fire-Engine. The invention of the centrifugal pump is ascribed to Lemour. who, in 1732, sent to the French Academy a descri|)tion of a very elemen- tary hand pump of this type. An inclined tube was joined to the lower end of the axle and the whole was revolved by a crank at the upper end of the axle. One of the earliest centrifugal pumps to come into practical use was constructed in Massachusetts, in 1818, and was known as the Jlassachusetts pump. It was like a fan blower, with four right-angled blades. From this
