162 STEAM BOILERS 



air holes in the bed of fuel. Fire evenly and regularly; be care- 

 ful not to fire too much at a time. Keep the fire free 

 from ashes and clinkers, and do not neglect the sides and cor- 

 ners while keeping the center clean. Do not, however, clean 

 the fires oftener than is necessary. Keep the ash-pit clear. 



Keeping Water Level Constant. In connection with the 

 maintenance of a constant water level, the following instruc- 

 tions should be followed : On starting to work, remember that 

 the first duty of the fireman is to examine the water level. Try 

 the gauge-cocks, as the gauge glass is not always reliable. 

 If there is a battery of boilers, try the gauge-cocks on each 

 boiler. 



PRIMING AND FOAMING 



Priming. The phenomenon called priming is analogous to 

 boiling over; the water is carried into the steam pipes and 

 thence to the engine, where considerable damage is liable to 

 take place if the priming is not checked in time. There are 

 several causes for priming, of which the most common ones are 

 the following: Insufficient boiler power; defective design of 

 boiler; water level carried too high; irregular firing; and sudden 

 opening of stop-valves. 



When the boiler power is insufficient, the best remedy is to 

 increase the boiler plant; the next best thing to do is to put in 

 a separator, which, obviously, will only prevent the entrained 

 water from reaching the engine, and will not stop the priming. 



Defective design of a boiler generally consists of a steam 

 space that is too small or a bad arrangement of the tubes, 

 which may be spaced so close in an effort to obtain a large 

 heating surface as to interfere seriously with the circulation. 

 In horizontal return -tubular boilers, a sufficiently large steam 

 space can be obtained by the addition of a steam drum; some- 

 times the top row of tubes can be taken out to advantage, 

 which permits a lower water level. Defective circulation in 

 horizontal fire-tube boilers is difficult to detect and to remedy; 

 if it is due to a too close spacing of the tubes, a marked better- 

 ment may be effected by the removal of one or two vertical 

 rows of tubes. The remedy for a water level that is too high 

 is to carry the water at a lower level. 



