Fig. 98.—Pulsometer Steam Vacuum Pump.
A section of a Pulsometer is shown in Fig. 98. It consists of two bottle-shaped chambers A and B with their necks communicating at the top and each opening into the outlet chamber O through a check valve. Steam is admitted at the top and enters chamber A or B according to the position of the steam valve C as shown. This steam valve is a ball which is free to roll either to the right or left and forms a steam-tight joint with whichever seat it rests upon. In normal operation chamber A would be filled with water as the steam enters the cylinder. At the same time a check valve at the top opens to admit a small quantity of air which forms a cushion insulating the steam from the water, reduces the condensation of the steam, and serves as a cushion for the incoming water on the opposite stroke. The pressure of the steam depresses the surface of the water without agitation and forces the water through the check valve F into the discharge chamber O. When the water falls to the level of the discharge chamber the even surface is broken up and the intimate contact of the steam and water condenses the former instantaneously. This forms a vacuum in chamber A which, assisted by a slight upward pressure in chamber B caused by the incoming water, immediately pulls the ball C over to the other seat and directs the steam into chamber B. The vacuum in chamber A now draws up a new charge of water through the suction pipe into the chamber.
Fig. 99.—Emerson Steam Vacuum Pump.
A section of the Emerson pump is shown in Fig. 99. The pump consists of two vertical cylinders B and C. Each chamber has a suction valve L at the bottom, opening upward from a common chamber from which the discharge pipe U extends. On the top of each chamber is a baffle plate G which operates to distribute the steam evenly to the two chambers and to prevent it from agitating the surface of the water in the chambers. A condenser nozzle F is connected with the bottom of the opposite chamber by a pipe into which a check valve opens upward. As the pressure in the chamber alternates water will be injected through F into the opposite chamber and condense the steam therein, promptly forming a vacuum. An air valve P admits a small quantity of air while the chamber is filling with water, the air acting as an insulating cushion as in the Pulsometer. Valve O, just above the top connection S is used to regulate the amount of steam that enters the pump. The top connection S has two ports, one leading to each chamber. An oscillating valve enclosed in it admits the steam through these ports to the two chambers alternately. This valve is driven by a small three-cylinder engine, the crank shaft of which extends into the top connection in the center of the bearing on which the valve oscillates. A positive geared connection is made between the valve and the engine and so arranged that the engine will run faster than the valve.
The action of these pumps consists of alternately filling and emptying the two chambers. They will continue operation without attention or lubrication so long as the steam is turned on. In view of the simplicity of their operation and make-up, their ability to handle liquids heavily charged with solids, and their reasonable steam consumption these pumps are widely used for pumping water in construction work. They have an added advantage that no foundation or setting is required for them as they can be hung by a chain from any available support.
These pumps are manufactured in sizes varying from 25 to 2500 gallons per minute at a 25–foot head, and with a steam consumption of about 150 pounds per horse-power hour. They reduce about 4 per cent in capacity for each 10 feet of additional lift. They will operate satisfactorily between heads of 5 to 150 feet, with a suction lift not to exceed 15 feet. Lower suction lifts are desirable and the best operation is obtained when the pump is partly submerged. The steam pressure should be balanced against the total head. It varies from 50 to 75 pounds for lifts up to 50 feet, and increases proportionally for higher lifts. The dryer the steam the lower the necessary boiler pressure.
141. Centrifugal and Reciprocating Pumps.—The details of these pumps, their adaptability to various conditions, and their capacities are given in Chapter VII. The centrifugal is better adapted to trench pumping as it is not so affected by water containing sand and grit, but for clear water, high suction lifts and fairly permanent installations, reciprocating pumps can be used with satisfaction.
142. Well Points.—In dewatering quicksand a method frequently attended with success is to drive a number of well points into the sand and connect them all to a single pump. Figure 100 shows a well point system used on sewer work in Indiana. The well points are 3 feet apart and are connected to a 2½-inch header which in turn is connected to six Nye pumps, each with a capacity of 200 gallons per minute for a lift of 50 feet. The number and size of well points and pumps to use will depend on conditions as met on the job. On a piece of work in Atlantic City[[88]] the equipment consisted of two complete outfits each comprising one hundred 1½ inch by 36–inch No. 60 well points, one hundred 6–foot lengths of rubber hose, about 600 feet of suction main, one hundred valved T connections, and a 7 × 8–inch Gould Triplex Pump with a capacity of 200 gallons per minute, belted to a 7½ horse-power motor.