494 CONSTRUCTION, FARM ENGINEERING, MECHANICS 



Barometric pressure at different altitudes, as affecting pumps 

 With equivalent head of water and the vertical suction lift of pumps 



Altitude 



Sea level . . 

 imile, 1,320 ft. 

 imile, 2,640 ft. 

 fmile, 3,960 ft. 



1 mile, 5,280 ft. 

 li mile, 6.600 ft. 

 l^mile, 7,920 ft. 



2 miles, 10,560 ft, 



Barometric 

 Pressure 



14.70 

 14.02 

 13.33 

 12.66 

 12.02 

 11.42 

 10.88 

 9.88 



Equivalent 

 Head of 

 Water 



33.95 

 32.38 

 30.79 

 29.24 

 27.76 

 26.38 

 25.13 

 22.82 



Practical 



Suction Lift 



OF Pumps 



25 

 24 

 22 

 21 

 20 

 19 

 18 

 16 



Windmill Figures 



Windmills for pumping (Rayner). 



Windmills vary in type and efficiency from a four-arm direct-con- 

 nected paddle wheel, erected on a single post, to the modern curved 

 blade, back-geared, steel windmill, erected on a scientifically con- 

 structed steel tower. 



To select a proper-sized windmill for the purpose required, the speed 

 of the wind in the particular locality should be considered. In the 

 United States, this information can be readily secured from the nearest 

 weather bureau station. When the average speed is above eight 

 miles per hour, throughout the year, the following table may be fol- 

 lowed safely : — 



Lift (ft.) 



8-ft. diameter windmill 3 -inch diameter pump, 40 



8-ft. diameter windmill 2i^-inch diameter pump, 70 



10-ft. diameter windmill 3 -inch diameter pump, 70 



10-ft. diameter windmill 2J^-inch diameter pump, 120 



12-ft. diameter windmill 3 -inch diameter pump, 100 



12-ft. fiiameter windmill 2J/^-inch diameter pump, 180 



12-ft. diameter windmill 2*^ -inch diameter pump, 200 



12-ft. diameter windmill 2 -inch diameter pump, 300 



When the average speed of the wind is less than given above, a pro- 

 portionally larger diameter windmill should be chosen. 



In the lift that is required of the pump, the elevation above the 

 ground to the top of the elevated tank or cistern should be added to 

 the depth of the well. 



