56 BULLETIN 652, U. S. DEPARTMENT OF AGRICULTURE. 



of poppet valve using super-heated steam. Within the last three years a num- 

 ber of internal-combustion engines have been installed. These, too, vary in 

 character from the ordinary gasoline-burning engine to those which burn the 

 heavy crude oils. One plant close to New Orleans uses electric power. Both 

 the internal-combustion engines and the electric motors have great advantages 

 over the steam engines when used on intermittent service. There are consider- 

 able losses, both of fuel and labor, in starting a steam plant, while the other 

 types can be started without much loss of either. Although the total period of 

 operation of the average drainage pumping plant is about 20 days of 24 hours 

 each per year, the plant probably will operate on as many as 90 different 

 days. This means that the average period of operation for each time it is 

 fired up will be very short, perhaps less than 6 hours; therefore a large per- 

 centage of the fuel burned will be used in getting started. Owing to the famili- 

 arity of ordinary workmen with steam engines, and to the simplicity of such 

 engines, they still are very popular as a source of power for driving the pumps. 

 On the other hand, the great saving in labor and fuel obtained by the use of 

 engines burning crude oil has resulted in all the newer plants being driven by 

 oil engines. The depreciation of the steam plant, particularly of the boiler 

 because of bad feed water and the rapid corrosion of sheet metal in this climate, 

 is much greater in such intermittent service than is the depreciation of internal- 

 combustion engines. 



Cost of Pumping Plants. 



The cost of drainage-pumping plants, per indicated horsepower, varies widely 

 according to type of machinery, expense of transportation of machinery to site 

 of plant, character of foundation, and difficulty of erection. The last three items 

 will vary greatly according to local conditions. An accompanying diagram (fig. 

 16) shows comparative approximate costs of .single-unit centrifugal pumping 

 plants erected complete, inclusive of foundations, but exclusive of buildings, in- 

 take, discharge cauals, or flume. These costs are based on estimates for work in 

 Louisiana and Texas, and the diagram is published by courtesy of H. L. Hutson, 

 New Orleans, La. These figures are approximate, but are on the safe side; that 

 is, they take into consideration construction under unusual difficulties. In mak- 

 ing up these costs it was assumed that the effect of the three items mentioned as 

 varying according to local conditions would be a constant percentage of the cost 

 of the plant. It is obvious that this diagram should not be used in attempting to 

 determine accurately the cost of a drainage plant; its chief usefulness is in 

 showing the relative cost of the various types of machinery, for deciding upon 

 the most economical size of unit to be used in large plants, and for making ap- 

 proximate estimates of the total cost of plants. 



In making the diagram, the cost of the plant has been divided into the cost 

 of the "water end" (pump, pump foundation, and piping), and the cost of the 

 "steam end" (engines, boilers, and their foundations and auxiliaries). The 

 cost of the water end is given in terms of gallons per minute of rated capacity, 

 and that of the steam end in terms of indicated horsepower. Owing to the vari- 

 ation in costs it is necessary to use zones instead of lines to indicate them. 



The zone marked " steam end, compound condensing Corliss or 4-valve en- 

 gine " includes the cost of this type of engine and water-tube boilers. The zone 

 marked "Compound condensing slide valve" includes the cost of this type of 

 engine and either water tribe or return tubular boilers, according to the size of 

 the plant. The zone marked "Simple slide-valve noncondensing " includes the 

 cost of this type of engine and horizontal return tubular boilers. It will be 

 I that for the higher class engines the cost is not indicated below about 



