Centrifugal Pumps

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McGraw-Hill Book Company, Incorporated, 1915 - Centrifugal pumps - 192 pages
 

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Page 38 - N of gas is enclosed in a bulb of invariant volume \\ connected by a tube of negligible volume to a pipette of variable volume v which is kept at a constant temperature (say 0 C), the pressure being constant throughout the system and having the value po. The method of operation is the same as that described in the preceding paragraph except that the pressure is adjusted to po at each bulb temperature by adjustment of the volume of gas in the pipette. Let...
Page 148 - Francis formula slightly modified is q = 3.33(L - 0.1 nH) (H + oA,)1.8 where L is the length of the weir crest in feet, H is the head on the weir measured in feet, n is the number of end contractions or is zero for a suppressed weir, hv the velocity head in the weir channel, and aa factor varying from 1.0 to 2.0 according to circumstances.1 Experiments of Schoder and Turner indicate that for H = 0.1 ft. the factor 3.33 should be increased by 7 per cent., for H = 0.2 ft. by 3 per cent., and that it...
Page 142 - Factors.—Values of all the factors given in this chapter can be computed by theory, if the essential impeller dimensions are known. For practical use, however, it is better to compute them from test data. The uses of the factors have already been indicated. They serve to systematize the classification of centrifugal pumps and by their use one can determine the limits between which the choice of certain conditions for a centrifugal pump is possible. By their aid one can choose more wisely and with...
Page 94 - Pressures in case between first and second stages. peller, and consequently the impeller passages, is not completely filled with water. Thus the actual rate of discharge of the pump is decreased below the expected amount. This cavitation may make itself apparent even where the pump is tested at one speed only. It is indicated by an abrupt break in the smoothness of the curve or by a marked increase in the steepness of the curve for the larger discharges.
Page 148 - H = 0.1 ft. the factor 3.33 should be increased by 7 per cent., for H = 0.2 ft. by 3 per cent., and that it is correct when H = 0.3 ft. For small rates of discharge the triangular weir is better than the rectangular weir. Any angle of notch may be employed. For the 90 triangular notch the formula is q = 2.54 H™ The Venturi meter is very satisfactory and should be permanently installed in many pumping plants as it permits of the measurement of water without any interference in its flow. The extra...
Page 105 - Fig. 78 we have 105 something that is analogous to the characteristic curve for a hydraulic turbine as the coordinates are speed and discharge. (However, these coordinates represent actual values and not values under a unit head.) Upon this diagram we draw isohead, iso-power, and iso-efficiency curves. By the use of these diagrams it is possible to tell at a glance what the conditions of operation might be under any circumstances and it is easily seen what is the most economical field of operation....
Page 130 - ... favor. For other situations they may have a greater economy in some instances. Also they are able to lift water from below them at starting without being primed. The fact that there is no relation between head and discharge is often an advantage in their favor. Where either the head or the discharge are required to vary within wide limits and where they do not maintain definite relations with each other, the displacement pump will be found to be more flexible and more economical. 93. PROBLEMS...
Page 42 - ... liberated and fills part of the space, the rate of discharge decreases. This causes the pressure to rise, the vapor again becomes liquid, the pipe is filled with water and the discharge increases. But as it does so the pressure drops again and thus a pulsation of flow is set up. If there is just about a balance this pulsation will be perceptible to the ear only. If the pressure is further decreased the pulsation is sufficient to cause the suction line and pump to vibrate.
Page 171 - K, where 6 is the angle measured from the "cutwater," K is the radius to the "cutwater," and c is a constant. If the cross-section of the case is rectangular, the outer boundary curve should be a volute the diameter of whose base circle is 2K sin A, where K has the same meaning as in the former instance, and A is the angle with the tangent made by the stream lines entering the case. The smaller diameter of the "nozzle" will be v times the diameter of the base circle.
Page 22 - Various forms of clearance rings. Therefore the rings are placed as near to the "eye" of the impeller as possible. Sometimes both an outer and an inner set are employed. In order to impede the flow of water and at the same time permit of large clearances, labyrinth rings (Fig. 26E) are employed. It is of advantage not to have the clearances too close, otherwise vibration of the shaft or end play would bring the surfaces into contact. The rings are usually made of bronze. 11. Stuffing Boxes.

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