16 ENGINE TESTS. 



one hour) previous to the trial. When these are obstructed 

 a noticeable effect is produced upon the height of water shown 

 in the glass. 



It is also necessary to be assured of the tightness of the feed 

 valves and check valves concerned, that none of the water 

 measured escapes by leakage. 



The author has, in some instances, been able to obtain a 

 measurement of the feed-water by drawing it from the tank 

 which is often provided in mills for fire purposes and other 

 emergencies, and which is not regularly in use. This tank 

 being generally of uniform cross-section, the water it contains 

 is subject to accurate measurement. When such means is used 

 for measuring feed-water; it is absolutely necessary to be assured 

 that the water is not in the meantime used elsewhere than for 

 the test, and that the valves connected with the system of regu- 

 lar supply do not leak. 



The orifice method of measurement is one which the author 

 has found useful in a number of cases. One instance is that of 

 a 1000 horse-power compound condensing engine, in which tin- 

 water from the hot well was used in the customary manner tor 

 feeding. A test was required to determine the coal consumi- 

 tion of the plant per indicated horse-power per hour, under as 

 nearly as possible working practice. The quantity of feed-water 

 used was desired ; but it must be obtained without changing, 

 any more than necessary, the working conditions. Tin- lnt 

 well overflow pipe was too near the level of the suction pipe of 

 the pump to permit of using the ordinary process of weighing : 

 consequently, resort was had to orifice measurement. The feed- 

 tank was supplied from the overflow of the hot well through a 

 4-in. pipe. The elbow on this pipe, next to the tank, was 

 replaced by a 4-in. tee, one branch of which looked down and 

 the other looked up. To the lower branch a pair of flanges 

 was attached, in which was secured a horizontal plate having a 

 hole l|-in. diameter; and this served as the orifice. The plan- 

 was horizontal, and the discharge from it was therefore directly 

 downward into the tank. The upper branch of the tee con- 

 tained a stand-pipe 3 ft. high ; and to this pipe was attached a 



