REVIEW OF FEED -WATER TESTS. 253 



These proportions of cylinder condensation and leakage can 

 better be examined by referring to the accompanying chart on 

 which they are plotted, ordinates or verticals representing per- 

 centages of cut-off, and abscissae or horizontals, percentages of 

 condensation and leakage. The curved line drawn through 

 them represents the mean curve of condensation and leakage 

 deduced from these results. It clearly shows that the percent- 

 age rapidly increases as the point of cut-off becomes earlier, 

 and at the very earliest cut-off the condensation and leakage 

 bears a very large proportion to the total consumption of 

 steam. 



The best series of tests on this subject, using the same 

 engine, are those made on Engine No. 31, which was a pair of 

 Corliss non-condensing engines having cylinders 16 in. diameter 

 and 4^ in. stroke. This engine was practically tight, and the 

 percentages of condensation (and leakage) over a range of cut- 

 off from 4% to 32% was from 62% down to 20%. 



That leakage has an important effect upon the economy of 

 an engine is well shown by a comparison of the results obtained 

 from engines which leaked excessively with those shown on 

 the chart. For example, in Engine No. 19, which is of the 

 single-valve type showing considerable leakage compared with 

 Corliss engines, the proportion of steam accounted for is .706 

 at 30% cut-off, giving condensation and leakage of 29.4%. 

 The condensation and leakage shown on the average curve of 

 the chart at that cut-off is about 20%, so that the difference 

 between 20 and 29.4 must be due in a laige degree to leakage. 

 In Engine No. 2J a test with a leaking exhaust valve showed 

 condensation and leakage of 30.8%. When the valve had been 

 repaired and made tight, the condensation and leakage dropped 

 down to 25.5%, the difference being due almost entirely to a 

 reduction in leakage. The saving in actual feed-water con- 

 sumption was about 10%. 



In the compound engine tests which can be compared for the 

 purpose of studying cylinder condensation, the range of cut- 

 off in the high-pressure cylinder is hardly sufficient to serve 

 as a basis for satisfactory conclusions. The tests which can be 



