ENGINE No. 78. 



Four valve (Corliss), 23" x 60." Speed, 74 rev. per min. 



These diagrams furnish another instance showing the in- 

 fluence, or want of influence, of leakage. In this case the 

 trouble was with the piston. Diagram No. 78a was taken with 

 the piston leaking, the packing ring being broken, and No. 7Sb 

 was taken when the ring had been renewed, and the piston 

 made tight. Feed- water tests made under both conditions 

 showed that the leaking engine used 34.5 Ibs. of steam per I. H. 

 P. per hour, and the tight engine, 27.7 Ibs. The difference is 

 about 20 %. The boiler pressure was higher after the repairs 

 than before, but this does not affect the general features. So 

 far as the expansion line is concerned, the leakage of the piston 

 had no appreciable effect. There is a noticeable difference in 

 the compression lines, but in the leaking engine this alone 

 would not prove the leakage in question. The diagrams are 

 from the crank end. 



ENGINE No. 78a 



ENGINE No. 78b 



-60 

 -40 

 -20 



- 

 -80 



-60 



-40 



-20 



- 



299 



