STEAM BOILERS 



335 



used only in stationary boilers. The water column 

 should be located so that the center of the column will 

 come to the point where the level of the water should be 

 above the tubes, or crown sheet. The column is gen- 

 erally of a casting about 3^2 inches in diameter and 15 

 inches long. Into this casting are secured the try cocks 

 and water glass. Some builders connect the steam gauge 

 to the upper end. 



By referring to Fig. 232 

 it will be noticed that the 

 lower end of the glass, the 

 lower try cock, and the 

 crown sheet are on a level 

 with each other, hence 

 when the water is out of 

 sight in the glass and also 

 will not flow from the try 

 cock the crown sheet is ex- 

 posed. The water should 

 be kept about in the middle 

 of the glass, and likewise 

 even with the center try 

 cock. It should not be 

 above the upper try cock, 

 or there will be trouble 

 from wet steam. 



456. Steam gauge. The mechanism of a steam gauge 

 (Fig. 233) usually consists of a thin tube bent in a circle. 

 One end of the tube is connected to the boiler, and the 

 other, by means of a link, to a small pinion which works 

 a needle indicator. Air is kept in the tube by means of the 

 siphon, and a cylinder of water lies between the air and 

 the boiler. When there is zero pressure in the boiler the 

 needle should set at o. As pressure begins to rise in the 



FIG. 232 WATER COLUMN, 



GAUGE GLASS, TRY COCKS 



AND STEAM GAUGE 



