42 in. × 10 in. stroke × 30 strokes × 60 minutes
353
= 815 gal. per hour. About 10 per cent. is deducted for loss. The horse-power required is the number of lb. of water delivered per minute, multiplied by the height raised in ft., and divided by 33,000. Thus:—
815 gal. × 10 lb. × 30 ft. lift = 7·4 H.P.
33,000
6. Lift Pump.
Fig. 6 shows a vertical section of the simple lift-pump. a is the working barrel, bored true, to enable the piston or bucket b to move up and down, air-tight. The usual length of barrel in a common pump is 10 in. and the diameters are 2, 2½, 3, 3½, 4, 5, and 6 in.; a 3 in. barrel is called a 3 in. pump. The stroke is the length of the barrel; but a crank, 5 in. projection from the centre of a shaft, will give a 10 in. stroke at one revolution; but in the common pump shown, use is made of a lever pump handle, whose short arm c d is about 6 in. long, and the long arm or handle d e is usually 36 in., making the power as 6 to 1; f is the fulcrum or prop. Improved pumps have a joint at f, which causes the piston to work in a perpendicular line, instead of grinding against the side of the barrel. The head g of the pump is made a little larger than the barrel, to enable the piston to pass freely to the barrel cylinder; in wrought-iron pumps, the nozzle is riveted to the heads, and unless the head is larger than the barrel these rivets would prevent the piston from passing, and injure the leather packing on the bucket. The nozzle h, fixed at the lower part of head, is to run off the water at each rise of the piston. There is 1 valve i at the bottom of the barrel, and another in the bucket b.
The suction pipe k should be ⅔ the diameter of the pump barrel. A rose l is fixed at the end of the suction pipe to keep out any solid matter that might be drawn into the pump and stop the action of the valves. The suction pipe must be fixed with great care. The joints must be air-tight: if of cast flange-pipe, which is the most durable, a packing of hemp, with white and red lead, and screwed up with 4 nuts and screws, or a washer of vulcanised rubber ⅜ in. thick, with screw bolts, is best. If the suction pipe is of gas-tube, the sockets must all be taken off, and a paint of boiled oil and red-lead be put on the screwed end, then a string of raw hemp bound round and well screwed up with the gas tongs, making a sure joint for cold water, steam, or gas.
Many plumbers prefer lead pipe, so that they can make the usual plumbers’ joint. The tail m of the pump is for fixing the suction pipe on a plank level with the ground. Stages n are fixed at every 12 ft. in a well; the suction pipe is fixed to these by a strap staple, or the action of the pump would damage the joints. There are two plans for fixing the suction pipe; (1) in a well o directly under the pump; (2) the suction pipe p may be laid in a horizontal direction, and about 18 in. deep under the ground (to keep the water from freezing in winter) for almost any distance to a pond, the only consideration being the extra labour of exhausting so much air. In the end of such suction pipe p it is usual to fix an extra valve, called a “tail” valve, to prevent the water from running out of the pipe when not in use. The action is simply explained. First raise the handle e, which lowers the piston b to i; during this movement the air that was in the barrel a is forced through the valve in the piston b; when the handle is lowered, and the piston begins to rise, this valve closes and pumps out the air; in the meantime the air expands in the suction pipe k, and rises into the barrel b through the valve i; at the second stroke of the piston this valve closes and prevents the air getting back to the suction pipe, which is pumped out as before. After a few strokes of the pump handle, the air in the suction pipe is nearly drawn out, creating what is called a vacuum, and then as the water is pressed by the outward air equal to 15 lb. on the sq. in., the water rises into the barrel as fast as the piston rises: also the water will remain in the suction pipe as long as the piston and valves are in proper working order.