TESTS OF DBAISTAGE PUMPING PLANTS. 



43 



The test showed an average efficiency at 6-foot lift of 50.55 per 

 cent. At a lift of 6.32 feet and while pumping more than 76,000 

 gallons per minute the guaranteed efficiency of 52£ per cent was 

 attained. 



TESTS OF 12-FOOT WOOD SCREW PUMP, NEW ORLEANS DRAINAGE SYSTEM. 



The drainage of New Orleans and the sanitary sewers are separate 

 systems. The area drained amounts to 25,000 acres, or a little more 

 than 39 square miles. The capacity of pumping plants for drainage 

 will eventually be equal to 7.33 inches of run-off removed in 24 hours. 

 The pumping units include eleven 12-foot screw pumps. (See fig. 4.) 



Tests were made of one of the 12-foot Wood screw pumps at New 

 Orleans pumping plant No. 1, on November 17, 1916, and January 



Jt/cfion Basin. yy X 



Fig. 4.— Section through 12-foot screw pump, New Orleans drainage pumping plant. 



17, 1917. In the test of November 17 the flume was divided into 10 

 equal areas. As the bottom was V-shaped the width of these sections 

 was greatest at the sides of the flume and least near the middle. 

 Velocities were observed at 0.2, 0.6, and 0.8 depth in each area, and 

 the mean velocity for an area was taken to be the mean of the three 

 velocities observed. The sum of the 10 separate areas multiplied 

 each by it- mean velocity gave the total discharge and this divided by 

 the total area gave I he mean velocity. 



In the tesl on January 17, L917, observations were taken of velocity 

 at tlir -;iim<- sections as in the previous lest but at one-sixth, live- 

 tenths, and five-sixths depth. The mean of three readings was used 

 ; '- the mean velocity of the vertical section, and the total discharge 

 was obtained by 3umming up the discharges <>f the 9eparate sections. 

 Table 37 gives the re ul1 of the ti 



