STEAM BOILERS 163 



Evidences of Priming. Priming manifests itself first by a 

 peculiar clicking sound in the cylinder of the engine, due 

 to water thrown against the heads. In cases of very violent 

 priming, the water will suddenly rise several inches in the gauge 

 glass, thus showing more water in the boiler than there really 

 is. When priming takes place, it can be checked temporarily 

 as follows: Close the damper, and thereby check the fires until 

 the water is quiet ; the engine stop-valve should also be partly 

 closed to check the inrush of water. Observe whether the 

 water drops in the gauge glass, and then, if more feed is needed, 

 increase the feed. To prevent damage to the engine, open the 

 cylinder drains. Regular and even firing tends to prevent 

 priming. 



Foaming. The phenomenon called foaming is not the same 

 as priming, though frequently considered so. Foaming is the 

 result of dirty or greasy water in the boiler; the water foams 

 and froths at the surface, but does not lift. A boiler may prime 

 and foam simultaneously, but a foaming boiler does not always 

 prime. Foaming while taking place is visible in the gauge 

 glass and is best remedied by using the surface blow-off. If 

 no surface blow-off is fitted, the bottom blow-off may be used 

 in order to get rid of the dirty water. Like foaming, priming, 

 will cause a wrong level to be shown, and hence the first thing 

 to do in case of foaming is to quiet the water by checking the 

 outrush of steam, either by slowing the engine down or by 

 checking the fire, or by both. 



SHUTTING DOWN AND STARTING UP 

 Preparations l : or Shutting Down. Before shutting down for 

 the night it is advisable to fill the boiler to the top of the glass, 

 so as to be sure to have sufficient water to start with in the 

 morning. The presence of possible leaks through the valves, 

 tube ends, or seams necessitates this course of action. Even 

 if no leaks exist, it is good practice to do this, if for no other rea- 

 son than to admit of blowing out a portion before raising steem 

 in the morning. All the gauge cocks should be tried and the water 

 column should be blown out to insure their being free and clear. 

 Banking of Fires. The fires may be banked at such a time 

 that there will be about enough steam to finish the day's run, 



