Centrifugal Pumps

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McGraw-Hill Book Company, Incorporated, 1915 - Pumping machinery - 192 pages
 

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Page 36 - Pumps," page 258. very similar in principle as all depend upon the combination of two fissures, the area of one remaining unchanged while that of the other varies. The method of operation is the same as that described in the preceding paragraph. If the shaft in Fig. 43(a) moves to the left, the variable fissure, v, closes up. This allows the pressure on the left-hand side of the piston to increase, while that on the right-hand side decreases. The resultant force on the piston is therefore directed...
Page 146 - 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 40 - Thus when this mixture is liberated either by too low a pressure or by an eddy, its corrosive action is greater than that of pure air. Aside from the question of the liberation of air, if the pressure becomes too low, water vapor is formed. Bearing in mind the fact that the pressure at the suction intake decreases as the flow increases, we see that the following state of affairs might exist. As vapor is liberated and fills part of the 'space, the rate of discharge decreases. This causes the pressure...
Page 128 - ... efficiency of a centrifugal pump set is often better than that of a reciprocating pump set. Even in cases where the efficiency is less, the cost of pumping, when interest on the investment is considered, may not be as much as for the displacement type. 92. Advantages of Displacement Pumps. — For very high heads, especially where the capacity is small, the displacement pumps have all the advantages in their favor. For other situations they may have a greater economy in some instances. Also they...
Page 6 - Fig. 11.) By a rising characteristic is meant that when the pump runs at constant speed the head increases as the discharge is increased from zero. After a certain value is reached, however, the head begins to fall again. A falling characteristic means that the head continuously decreases as the discharge increases from zero. The meaning of flat or steep is readily seen from the figure. Other less fundamental classifications will be made throughout the text. 3. Reaction Turbine vs. Turbine Pump....
Page 150 - ... the efficiency curve from values read from these curves rather than to attempt to draw efficiency curves through the points computed direct from the test data. 112. PROBLEMS 1. In a pump test the pressure gage read 50 Ib. per sq. in. and the suction gage recorded a vacuum of 10 in. of mercury. The center of the pressure gage was 2.0 ft. above the center of the pump shaft while the summit of the upper mercury column of the manometer was 1.0 ft. below the center of the shaft. The suction and discharge...
Page 103 - Characteristic diagram. which are shown in Figs. 77 and 78. In Fig. 77 we have the usual head-discharge curves at various constant speeds and upon these are superimposed iso-efficiency curves.1 In 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....
Page 112 - That this is so may he seen in Fig. 80. This curve was drawn for a number of pumps of all sizes and styles so that scarcely no two pumps differ only in this one respect. Since the efficiency is also affected by other factors so that the effect of "type" is sometimes offset by other considerations, the points plotted will not all lie on a single curve. If it is necessary to develop a high head per stage at a low rotative speed, it will be impossible to secure a low value Turbine Pumps Type-D/B 10....
Page 142 - ... and also the appearance of the curves will serve to indicate the accuracy of the test. Usually such a test as this will be run with one of the three variables, speed, head, or discharge constant. Of these the speed is the one that is most apt to be kept constant. The resulting curves will then be as shown in Fig.

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