166 ENGINE TESTS. 



Engine No. 42 is of the vertical cross-compound unjacketed 

 high-speed class. It is a duplicate of Engine No. 41, being 

 located in the same power house, and forming a part of the 

 same plant. It was supplied with steam from a different por- 

 tion of the service main, the water condensed in which returned 

 back to the boiler. Unlike engine No. 41 it was run non-con- 

 densing. The valves and pistons leaked to about the same 

 extent as in the other engine, and the load was of the same 

 character. The tests were two in number, one being made 

 with a very light load. 



These tests bring out very forcibly the wastefulness of a non- 

 condensing compound engine of this type when carrying an 

 extremely light load. In the case of the first test the load was 

 so small that the low-pressure cylinder contributed only about 

 10% of the whole power, which is so small as to be immaterial : 

 and consequently, the engine showed simply the economy d in- 

 to a non-condensing cylinder of this type carrying a high back 

 pressure, and working at a comparatively early cut-off. The 

 effect of valve leakage is revealed by the small proportion of 

 steam accounted for by the indicator. Compared with the con- 

 densing engine of the same type, No. 41, there is a marked 

 advantage due to the use of the condenser ; and this appears to 

 be especially true in the case of the light load. Comparing the 

 two heavy-load tests tlie reduced consumption of feed-water is 

 6.1 Ibs. per I. H. P. per hour, or about 24'/. In the light-load 

 test there is a remarkable increase in the steam accounted for 

 at release of the high-pressure cylinder over that shown at cut- 

 off. It is due largely no doubt to valve leakage. 



