In Turneaure & Russell's "Public Water Supplies," the formula given as "commonly used for determining the relation of the various factors in an air lift problem" is-

q=

125 A

h

in which q gallons of water per minute.

Acu. feet of free air per minute.

h=height of lift in feet from water surface to point of discharge.

Fig. 5 shows three commonly used methods of arranging the discharge and air pipes in an air lift.

AIR DISPLACEMENT PUMPS.

In this device for raising ground water, the air acts as a piston upon the upper surface of the water in a discharge chamber, depressing it to a given level and discharging it through an eduction pipe to the desired point. In wells of small bore the discharge chamber consists of a vertical pipe or barrel to which is connected the air pipe at the upper end and the discharge pipe at the lower end as illustrated in outline in Fig. 6. The discharge chamber fills either by gravity or by suction. The air is admitted by a reversing valve that is actuated either by trip valves located in the discharge chamber, which in turn are operated by floats when the water has reached a predetermined level; or by the increase and decrease of pressure in the air line due to the rise and depression of the water surface in the discharge chamber.

In some types the air is exhausted into the atmosphere while in others the air is led back to the suction of the compressor under gradually diminishing pressure. The water flows into the discharge chamber by gravity as the air is displaced and if the compressor forms a partial vacuum the discharge chamber will be filled by suction to a level above that of the water in the well.

In wells of large bore, two discharge chambers are sometimes placed side by side, from which the discharge takes place alternately with a practically constant flow. The same result is accomplished by connecting two or more wells with the same delivery pipe and the same reversing valve which admits air into the several discharge chambers alternately.

CONDITIONS GOVERNING SELECTION OF TYPE AND EFFICIENCY.

It is beyond question that all the devices for raising deep ground water described have their particular field of usefulness. The intermittent flow plunger pumps undoubtedly have a low efficiency. In both the single and double-acting types, the column of water in the vertical discharge pipe comes to rest at the end of each stroke. The shock of overcoming the inertia of the column of water at the beginning of every stroke is necessarily violent and leads to great loss of power. The speed is limited to about 100 feet of piston travel per minute to prevent

undue injury to the mechanism, and this limits the yield of the well to the actual displacement capacity of the pump at this speed. In the "constant flow" or "non-pulsating" type," much higher speeds are practicable and the loss of efficiency due to the violent shock of stopping and starting the column of water is largely overcome.

Where the desired output is small and the lift is relatively low, the reciprocating pump undoubtedly has a wide field of usefulness. The first cost of installation is relatively small and the interest and depreciation charges are therefore correspondingly low. At water stations having a small output the fuel consumption, which is the factor most influenced by low efficiency, is a small part of the total cost of operation; the greater part of the operating cost usually represents the attendance and the interest and depreciation charges. However, this pump is simple and reliable and is giving good results where the yield per well or the desired quantity is small. The output can be increased approximately 100 per cent by the use of the double-acting type as compared with the single-acting, with some increase in first cost. High efficiencies are shown by the "nonpulsating" type and an increased yield is obtained on account of the higher practicable speeds. A test made by the Engineering Experiment Station at the University of Illinois with a motor-driven pump of the “non-pulsating" type showed an overall efficiency for motor and pump of 47-7 to 49.2 per cent. Subsequent experiments indicated that the efficiency of the motor was about 70 per cent. and the pump efficiency was therefore also about 70 per cent., which is unusually high.

The reciprocating plunger pump does not lend itself well for operating scattered wells unless electric power is available. The maintenance of separate steam plants is impracticable and where the character of the water-bearing formation requires a wide spacing of wells for good results, the loss in steam transmission is necessarily large; such wells, however, may be located in a straight line and be operated from a single shaft or may be located at random and operated by the device familiar in oil-producing territory, a description of such plant for a water station being given in the 1911 Proceedings.

Where the yield per well is large and large quantities are desired at a constant rate, pumps of the centrifugal and propeller types offer particular advantages. Units of this type are simple and compact, and their output is perhaps larger than that of any other device for raising deep ground water except the air lift. Relatively high efficiencies result where the type and design selected are made to fit the quantity of discharge, lift and other conditions of service. Where electricity is available scattered pumps of this type can be operated by individual motors at a minimum expense for supervision. This pump also possesses the particular advantage of successfully handling waters that contain considerable sand which in the reciprocating pump will soon destroy the wearing parts of the working barrel, but its use in wells that are not straight is not successful on ac

count of the necessary bending and distortion of the shaft with every revolution. The maximum practical length of vertical shaft does not usually exceed 200 feet.

AIR LIFT AND AIR DISPLACEMENT PUMPS.

The air lift is not an efficient device, but it is capable of raising a larger amount of water from a small hole than any other deep well pumping method. The comparatively poor method of power application and many energy transformations can only result in limited efficiencies. However, it lends itself very well to serve scattered wells from one central power station, provided the spacing of wells is not so large as to result in excessive cost for piping the air supply. Its principal objections are the low efficiency and the disadvantage of providing the necessary submergence for best results, which under certain conditions is impracticable. The efficiency falls off so rapidly with a submergence decreasing below 60 per cent. that any wide departure from this submergence renders the loss of energy practically prohibitive. In the air displacement pump a fixed submergence for good results is not required, as it is only necessary to have the discharge chamber sufficiently submerged to insure its filling by gravity or by suction.

The air lift offers particular advantages in handling wells that contain considerable sand, as there are no valves to be affected, also in operating wells that are so crooked that the ordinary pump rod or vertical shaft cannot be used and in holes of too small bore for other methods, but unless the wells are located in the immediate vicinity of the tank, a second pump is necessary to elevate the water into the tank as the air lift will not convey water horizontally, which, however, is true only of the air lift and not the air displacement pump.

Respesctfully submitted,

COMMITTEE ON WATER SERVICE.

Appendix A.

TRACK TANKS.

BY GEORGE W. VAUGHAN, ENGINEER MAINTENANCE OF WAY, NEW YORK

CENTRAL & HUDSON RIVER RAILROAD.

HISTORICAL INTRODUCTION.

*Railroad construction in this country was practically in its infancy between the years of 1830 and 1840. At that time the freight schedule of a road usually included from one train a week to one a day, and the passenger schedule was not much better. The locomotives were very small and consumed little water. As might be expected, the question of water supply was about the least important one encountered.

At that time storage tanks with a capacity of 2,000 to 5,000 gallons were ample and it was many years before tanks with a capacity of 15,000 gallons became standard on the New York Central & Hudson River Railroad. The water supply, when not obtainable by gravity, was usually furnished through hand pumps, which were operated by switchmen during their spare moments. As the railroads were extended and the traffic increased the hand power for pumping was superseded by horse-power, windmills, hot-air engines, and finally by steam and electricity. The pump log gave way to the cast-iron pipe, which would stand a higher pressure and be more durable, the storage tanks were enlarged to 50,000, and even to 100,000 gallons capacity, and the old leather hose was replaced by standpipe, so that the locomotives could be watered more quickly and conveniently.

At the present time, at many of our stations, we find it necessary to provide for a consumption approaching an average of 1,000,000 gallons per twenty-four hours. The public demands an eighteen-hour schedule service between New York and Chicago, and proportionate schedules between other points. Fruit and other perishable freight must be transported at a high rate of speed. Such service does not permit frequent stops and water must be supplied to the locomotives while running at or near full speed. The cost of pumping such large quantities of water, together with fixed charges on the large investment required in equipment, reaches such a high figure that we are warranted in making expensive investigations into the methods of producing the desired results with the greatest economy.

The railroad corporations of England felt the need of supplying water to moving trains as far back as the middle of the nineteenth century,

See "Historical Notes on Water Supply on the New York Central & Hudson River Railroad," by C. H. Rice. Bulletin 100, June, 1908, American Railway Engineering and Maintenance of Way Association.

See "Trautwine's Civil Engineers' Pocket Book," subject "Track Tanks," also Tratman's "Railway Track and Track Work."

and for this purpose J. Ramsbottom invented in 1861 an outfit, including a track tank between the rails and a scoop on the locomotive tender. The track tank or trough was of cast-iron, in lengths of about 6 ft., these sections being bolted together by means of flanges and the ends separated by strips of vulcanized rubber.

*It has been supposed that this was the first track tank ever put in service, but a few years ago Mr. F. W. Webb, Chief Mechanical Engineer of the London & Northwestern Railway, claimed that they were introduced on that road in 1857, and that he was engaged in preparing the first equipment.

The first track tank in the United States was built at Montrose, between New York and Albany, on the Hudson Division of the New York Central & Hudson River Railroad, and put in service in 1870. It was for the use of the fast Saratoga trains at that time and was supplied with water by a hand pump, no provision being made to prevent freezing, as its use was discontinued in the winter. Mr. Wm. Buchanan designed the first scoop, then called a "jerk water." It was attached back of the rear trucks and the conductor pipe placed back of and outside of the tender tank. The first track tank on the Mohawk Division was installed at Palatine Bridge about 1889 and the first one on the Western Division at Churchville in 1892. They were first installed on each of the four main line divisions of the Lake Shore & Michigan Southern Railway in 1893, and at Forks Creek, Tilbury and Waterford on the Michigan Central Railroad in the same year.

The use of track tanks on the main divisions of the New York Central Lines has now become quite general. There are fourteen on the New York Central & Hudson River Railroad, between New York and Buffalo, ten on the Lake Shore & Michigan Southern Railway, between Buffalo and Chicago, and fourteen on the Michigan Central Railroad, between Buffalo and Chicago, so that trains can now run from New York to Chicago without making a single stop for water, except at the terminals, where the locomotives are regularly changed.

Many articles have been published in the Proceedings of the American Railway Engineering and Maintenance of Way Association and various periodicals on the subject of "General Water Supply," discussing the advantages of various sources of supply, the proper location of water stations, the equipment connected therewith, the relative merits of steam and gasolene, water treatment, etc., but little has been said about the details of construction of track tanks, and it is the purpose of this article to collect what data is obtainable regarding that phase of the water question.

*See "Modern Water Supply Stations for Locomotives" by F. M. Whyte, "American Railway Master Mechanics' Association Proceedings" of 1902.

†See "Railroad Gazette," March 13, 1908, article "Railroad Track Tanks" by H. H. Ross. Also report by Mr. S. Rockwell, Chief Engineer Lake Shore & Michigan Southern Railway, dated January 27, 1908.