TESTS OF DRAINAGE PUMPING PLANTS. 7 



test is continued until the water is drawn down to a low level the 

 results may be divided into hourly periods in such a way as to show 

 the behavior of the plant throughout the range of lift. The reservoir 

 capacity per unit tested will determine the length of time required 

 for such a test. If it is desired to determine the behavior of a plant 

 under average lift, either the test must be comparatively short or 

 there must be a supply of water furnished by rain during the test, 

 though the water possibly may be siphoned back through a pump 

 that is not being operated. The latter plan is applicable only to 

 plants having more than one unit. In any case the test usually will 

 be more accurate if it extends over a considerable length of time. 

 Although many of the tests described covered only a comparatively 

 short period, the accuracy of fuel measurements is high because the 

 fuel has been oil. Tests made with this fuel used in internal- 

 combustion engines or burned in boiler furnaces are much more 

 accurate than those made for corresponding periods of time with 

 coal as a fuel. A boiler test with oil fuel can be made without dis- 

 turbing the normal operation of the plant. With coal as fuel there 

 are many irregularities introduced, due to the measurements neces- 

 sary to the test. Fortunately all the tests here recorded were made 

 with oil as fuel. 



The showing made by a pumping plant depends in some measure 

 on conditions surrounding the test. If a guarantee of efficiency and 

 fuel consumption has been made by the parties erecting the plant 

 and the test is made to show whether the guarantee has been met, 

 the plant is likely to make its best showing. If, however, the same 

 plant has been turned over to a careless operator and has not been 

 kept in first-class condition a casual test made without particular 

 preparation may show results quite different from those of the 

 a'-roptance test. The amount of this difference will vary greatly 

 with different types of plant and with the conditions of operation. 



Centrifugal pumps operate efficiently only at proper speeds. 

 There are, however, many instances where capacity and not efficiency 

 b 'he controlling element in a pumping plant. If an unusual rainfall 

 baa occurred it is desirable to remove the water before damage 

 lite fco crops, regardless of fuel cost. Steam pumping plants have 

 in general more overload capacity than internal-combustion engine 

 plants. Steam engines usually arc selected on a basis of size thai 

 enables them to force the pumps beyond normal capacity, while an 

 increase of steam pressure in case of liberal boiler capacity always 

 will insure overloads. On the other hand, the internal-combustion 

 engine usually may not be forced to an output of power greatly in 

 f its normal rating. When in the best possible condition ;i 

 maximum of 10 to \~> percent in exce of the rat ing may be expected. 



