WELL PUMPS
The pumps intended for raising water from wells are practically the same in construction as the house pump, except that they are intended to deliver a greater volume of water and sometimes to work under a different condition, as that of the deep well pump. Well pumps have, therefore, assumed certain standard forms that differ only in the styles of mechanism employed by different manufacturers.
The one shown in Fig. 133 furnishes a good example of a general-purpose iron pump which may be used either as a force pump or a lift pump. It represents also the general construction of a deep-well pump, where the water must be lifted from a level, below that at which a lift pump will work.
The piston and valves are enclosed in the cylinder C, placed below the surface of the water in the well. This cylinder also appears in section in the small drawing, showing the details of the valve. The operation of this pump is identical to that of the lift pump already described, but the addition of an air chamber gives it the necessary facility to produce a continuous flow of water. In order to prevent the air in the air chamber from escaping, the pump rod is surrounded with the necessary stuffing-box which is usually packed with candle wicking to assure a good joint. In deep wells the tube is elongated sufficiently to place the cylinder C below the surface of the water in the well. Such pumps are operated either by hand or by power.
Wooden Pump.
—The wooden pump of Fig. 134 furnishes a good illustration of a type that was formerly used in great numbers. It is an inexpensive and efficient pump made almost entirely of wood except the cylinder which is quite generally made of iron, lined with enamel. The valve and the piston with its valves are made of wood, but faced with leather to insure tight joints. The piston is also provided with leather packing to make it tight in the cylinder. The action of the pump is the same as that already described. The wooden tube is made in sections joined together by taper joints that are driven into place.
Fig. 133.—Sectional view of a well with an iron cylinder pump, placed for deep-well pumping.
Fig. 134.—Sectional view of a well and wooden pump for shallow pumping.
The piece at the side of the pump is provided to drain the water from above the piston, as a precaution against freezing during extremely cold weather. The rod, when raised, opens an orifice that leads to the inside of the pump and permits the water to drain into the well.
Pumps for Driven Wells.
—The method of constructing driven wells—that of driving a pipe into the earth to the water-bearing stratum of sand or gravel—requires a special end to prevent the pump tube from becoming stopped. In order that the fine material may not enter and fill the lower end of the tube, a sand-point is used, such as that shown in Fig. 128. It is made of perforated brass tubing and provided with a sharpened end to facilitate driving. The perforations act as a strainer that keeps out all but the fine particles which will pass the pump valves. Sand-points are made with strainers of various degrees of fineness to suit the different conditions of soils. These strainers may in the course of time become filled with particles of the soil that lodge in the perforations and the outside become so encrusted as to prevent the entrance of the water. In such case, the pipe must be pulled out of the ground and the point replaced by a new one. In Fig. 128 is shown a driven well with the sand-point in the water-bearing stratum. If the small particles of earth clog the strainer the pump will “work hard” and yield only a portion of the water the soil is capable of giving when the strainer is clear.
Deep-well Pumps.
—The principle of operation as described in the lift pump takes advantage of the atmospheric pressure to lift the water above the first valve. The limiting distance to which water can be lifted by the atmospheric pressure will depend on the altitude and the atmospheric pressure. With the normal atmospheric pressure at sea level, water can be lifted, theoretically, 34 feet, but in practice the limiting value is never even approximated. The pump is usually placed within 10 of 12 feet of the water and 20 feet is about the limit of distance. The reason for this is because of the impossibility of keeping the joints tight in the valve and tubing.
Where water is to be raised from a deep well, the cylinder with its piston is placed near the water and the tube and rod, as that of Fig. 133, connects the cylinder with the pump stock. After the water has passed the valve in the piston, it may be readily lifted to the pump stock. In this way water is raised from wells of great depth.
Fig. 135.
Tubular-well Cylinders.
—Tubular wells that are cased with iron pipe are provided with a special type of pump cylinder that admits of deep-well operation. The casing of the well being in place, the cylinder shown in Fig. 135 is forced down the casing to its proper place, the spring S holding it in place until it is firmly secured. A special seating tool is now lowered into the casing and attaches at T to the coupling; as the tool is turned, rubber packing R is expanded, locking the cylinder firmly to the casing. This makes a complete pump cylinder, which with the piston P in place is operated as any other pump.
Chain Pumps.
—In shallow wells and other sources of supply, where water is to be lifted only a short distance, chain pumps have been used to a great extent, because of their quick action. This pump, as shown in Fig. 136, elevates the water by an endless chain being drawn through the tube, the lower end of which is below the surface of the water. The chain is provided at intervals with discs or rubber or iron, that fit the bore of the tube and form pistons which elevate the water as they ascend. The chain passes around a wheel in the upper part of the box and is worked by the crank. Chain pumps are not usually employed to elevate water a greater height than 20 feet. They are not efficient pumps and are not sanitary because of the opportunity they give for admitting polluting material to the well. Their one advantage is that of quick action in elevating water short distances.
Fig. 136.—Chain pump often used in shallow wells.