Chemical Age Volume 8 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 edition. Excerpt: ...Steam Pump, Water End, Fig. 5. Steam Pump, Water End, Outside Ring and Flunger Pattern. Packed Pattern. the question is one rather of corrosion and repairs than of economy of power and ball valves are extensively used. As a general rule, it may be said that for the best results the valves must open freely under a light pressure, and return quickly and without shock when the current has ceased to pass through them, and must close tight. They should have a small lift, offer as direct a passage as possible, and have a net area sufficient to limit the water passing through them to a velocity of 240 feet per minute. The valves and seats must be durable and easily repaired and replaced when worn out. In even double acting pumps, there is an interruption of the flow of liquid at the end of each stroke, when the piston changes the direction of its motion. This, of course, causes the moving column of water to stop also, and this column must therefore be started with each stroke. If the pipe is long, the force necessary to do this will be great and there will also be a certain amount of shock to the pump. To overcome this trouble and make the flow of liquid more continuous and steady, air chambers (see A, Fig. 3) are provided, which are attached to the discharge of the pump. The air in these acts as a sort of reservoir of power, being compressed with the forward stroke of the piston and acting as a spring giving it out with the return stroke. For an ordinary pump the air chamber should be at least three times the piston displacement for each 100 lbs. pressure per square inch under which the pump works. Centrifugal pumps depend for their action, as we have said, upon the pressure produced by the centrifugal force of a quantity of water rotated rapidly by...