SOME NOTED PUMPING ENGINES
In considering the development of the modern pumping engine for public water supply, with especial reference to the crank and flywheel type, it is interesting to note how closely its progress in economic performance has been associated with the advance of the steam engine itself apart and aside from the pumping of water. The compound, receiver steam engine came into marine practice about 1857; the development and employment of the re ceiver making it possible to set the cranks at any desired angle. The Woolf compound type with its exactly alternating pistons had up to that time either confined the crank pin posttions to 180 degrees, or made necessary the use of side levers or of beams; but the receiver having once entered the field, the 90 degree or quarter crank compound engine came into marine work, comparatively soon after followed by the three-cylinder and four-cylinder triple-expansion marine engine with crankpins at angles of 90 and of 120 degrees; and the type of three-cylinder triple marine steam end, formed the steam end for the triple-pumping engine. The first triple-expansion waterworks pumping engine designed was of the vertical crank and flywheel type. It followed the general idea in design of the vertical direct connected marine engine with the steam cylinders overhead, the crank shaft bearings in the main bedplates, and was built in 1886 for the high service station of the Milwaukee waterworks. The simple and very effective, outside packed, single acting plunger pump well known in principle for many years as boiler feeders and for factory purposes formed the water end of the then new design of municipal waterworks pumping machinery, although it had also been used previously to 1886 in waterworks engines. In the new triple machine there were placed three pumps, one pump directly beneath each steam cylinder, and with the plun gers driven directly by means of rigid connections from the steam pistons. The chief dimensions of this engine are as follows: High pressure cylinder, 20 l/4-in. diameter; intermediate pressure cylinder, 35-in. diameter; low pressure cylinder. 49-in. diameter; each pump plunger, 21 1/2-in. diameter; stroke of all pistons and plungers, 36 in.; daily capacity, 6,000.000 U. S. gal. per twenty-four hours. A general view of the steam end of this engine is given in tig. t, which is a half tone reduction from a photograph of the original triple pumping engine, taken in 1887. There is one feature of this engine not generally known, and that is, the intermediate engine and main pump form an entirely self-contained pumping engine proper, containing the bedplates and main shaft bearings, resting on and secured to the suction and discharge chambers and without any support from foundation piers; thus, so far as any available evidence goes to show, forming the first instance of the self-contained vertical pumping engine now so generally used where applicable. In 1889 a triple-expansion pump ing engine of this type was built for the Omaha waterworks, having daily capacity of 18,000,000 gal. per twenty-four hours, and a view of the steam end of which is shown in fig 2. This is the first example of an all self-contained vertical pumping engine w-herein the complete engine is carried entirely upon the main pump chambers; and where the self-contained engine of the double flow class can be economically used it is well adapted for locations where the quantity of water to be handled is very large, or where the pressure is very high, as it has the effect of reducing the valve chambers to the smallest possible diameter. A suction pipe common to both sides of the engine, enters the building and forks towards either side. there being separate inlets to each of the six suction chambers. The water from the six discharge chambers is brought together by a “Y” pipe, and delivered through one discharge main. The steam cylinders are of the usual construction, having Corliss valves on the high pressure cylinder throughout; on the intermediate cylinder there are Corliss steam valves and poppet exhaust valves; and on the low pressure there arc fitted poppet steam and poppet exhaust valves. The valve gear is driven by a lay shaft, the lay shaft being driven by bevel gearing, a not unusual method in steam engine practice. The chief dimensions of this engine are as follows: High pressure cylinder, 40-in. diameter; intermediate pressure cyinder, 70-hi. diameter; low pressure cylinder, 104-in. diameter; each pump plunger. 32-in. diameter; stroke of all pistons and plungers. 60 in.: daily capacity. 18.000.000 U. S. gal. per twenty-four hours. Total water load against engine, 310 ft. Another 18,000,000-gal. pumping engine of this type was built in 1890 for the Milwaukee waterworks, and enjoys _ the distinction oi being the first semi-self-contained vertical pumping engine, in which one end of the bedplates is supported on the pump chambers and the other end carried on a masonry pier. This design is very convenient and economical in construction, coming very near to being the best form for vertical engines where the building is deep enough to admit of the suction and delivery valve chambers being placed one above the other. It costs less to build than the entirely self-contained machine, is very accessible and thoroughly efficient in all respects. In balancing proposals, however, covering first cost, it is important for the buyer to ascertain the total cost of this type including necessary foundation pier, as against the apparently higher cost of the wholly selfcontained machine with the masonry pier omitted. The chief dimensions of this engine are as follows: High pressure cylinder, 28-in. diameter; intermediate pressure cylinder, 48in. diameter; low pressure cylinder, 76-in. diameter; each pump plunger, 32-in. diameter; stroke of all pistons and plungers, 60 in.; daily capacity, 18,000,000 U. S. gal. per twenty-four hours; total water load against engine, 153 ft. The first vertical pumping engine with selfcontaining frames is shown in fig. 3, and is a compound machine of 30,000,000-gal. daily capacity, built for the St. Louis low service station in 1893. There was a special reason for this construction of this particular class of engine; it had to go into a pit or basement al ready in existence and of rather limited dimen sions, having been built for a smaller engine. There was no room for the usual foundation piers and hence the self-containing framing. The engine is of very large capacity and has a low lift, so there is no objection to large valve chambers, and no necessity on account of pressure of dividing the valve chambers into pairs, as is frequently done with large capacity and high lift or head. The engine being of the compound class permitted the use of the valve chambers outside of the bedplates at opposite ends of the construction as shown in the illustration. The chief dimensions of this engine are as follows: High pressure cylinder, 27-in. diameter; low pressure cylinder. 52in. diameter; each pump plunger, 48-in. diameter; stroke of all pistons and plungers, 108 in.; daily capacity, 30,000,000 U. S. gal. per twentyfour hours; total water load against engine, 55 ft, When St. Louis installed triple-expansion pumping engines for the high or regular service in 1896, the self-contained type was preferred, and the valve chambers being smaller in the triples than in the compound above referred to, permitted the valve chambers in the triples being placed upon the lower bedplates between the frames. Regarding the merits of this form of construction, the supporting of the steam end of the vertical pumping engine on independent lower framing, although sometimes apparently attractive from some points of view, entails an extra cost of construction, and there are really very few locations which justify the use of such designs, especially when it is considered that the main pumps are less accessible with the lower framing than with the valve chamber form of support. The valve gear of this engine is similar in general features to that on the Omaha engine already referred to; but in this St. Louis engine the lay shaft is operated by means of small drag cranks actuated from the main crank pins of the high and low pressure portions of the machine, as may be seen in fig. 5 illustrating the Boston engine. The St. Louis class of self-contained vertical triple, pumping engines, were the first machines in which the crank-actuated lay-shaft was used. See fig. 4 for the self-contained triples with the lower framing. The chief dimensions of this engine are as follows: High pressure cylinder, 34-in. diameter; intermediate pressure cylinder, 62-in. diameter; low pressure cylinder, 92-in. diameter; each pump plunger, 29½-in. diameter: stroke of all pistons and plungers, 72 in.; daily capacity, 15.000,000 U. S. gal. per twentyfour hours; total water load against engine. 290 ft. One of these engines holds a record for duty per 1,000 lbs. of steam, of 181,068.000 ft. lbs. Fig. 5 shows the triple-expansion pumping engine in the Boston high service station at Chestnut Hill reservoir of 30,000,000gal. daily capacity, installed in 1897 and which holds the world’s record for efficiency in the use of steam. The steam consumption of this engine on the official test was 10.33 lb. per indicated horsepower per hour; the coal consumption being 1.06 lb. per indicated horsepower per hour, although the coal consumption involves the boilers as well as the engine, and the high efficiency of the boilers being indicated by the fact that the annual coal duty is about 80 per cent, of the steam duty obtained at the official test, whtch makes it quite evrdent that the most possible is not generally made of the situation in obtaining actual tuel economy and high boiler efficiency in the usual run of pumping stations. Others have exceeded this Boston engine in steam duty on test, but due to lower proportionate friction as they all operate against higher heads than the Boston machine, the latter working against a total head of only 140 ft., such a low head naturally resulting in a higher percentage of friction. The chief dimensions of this engine are as follows: High pressure cylinder. 30-in. diam eter; intermediate pressure cylinder, 56-in. diameter; low pressure cylinder. 87-in, diame ter; each pump plunger, 42-in. diameter; stroke of all pistons and plungers, 66 rn.; daily capa city, 30,000,000 U. S. gal. per twenty-four hours; total water load against engine, 140 ft. The main pumps of the Boston engine are of the double flow class, having two sets of suction and two sets of discharge chambers paced at opposite sides of a plunger barrel common to both chambers. The steam valve gear is all Corliss on the high pressure cylinder; Corliss steam and poppet exhaust on the intermediate; and all poppet valves on the low pressure cylinder. The valve gear is driven by a crankactuated lay-shaft clearly shown in the illustra tion. So far as the records show, and so far as is authentically known, no steam engine has ever produced a horsepower with all steam accounted for and charged to the machine, on as low a consumption of saturated steam as this pumping engine.