TESTS OF DEAINAGE 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 
acceptance 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 
is the controlling element in a pumping plant. If an unusual rainfall 
has occurred it is desirable to remove the water before damage 
results to crops, regardless of fuel cost. Steam pumping plants have 
in general more overload capacity than internal-combustion engine 
plants. Steam engines usually are selected on a basis of size that 
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 
excess of its normal rating. When in the best possible condition a 
maximum of 10 to 15 per cent in excess of the rating may be expected. 
