The function of the water gauge (Fig. 166) is to register the height of the water in the boiler. It consists of a small cast iron drum placed in an upright position in front of the boiler, provided with a glass gauge, cocks, water and steam connections. Pipe connections are arranged so that steam enters the top and water enters the bottom. Water gauge and cocks are essential to the safety of the boiler and should be blown out frequently to prevent clogging. Water should stand halfway in a gauge glass cock while working, and at night should be raised to the top gauge cock. The first duty of a fireman in taking charge of his boiler is to see if the water is at a proper level. To tell if the glass is registering correctly, the gauge cocks must be tried. The water column should be blown out at least once a day, and sometimes three or four times, depending upon the quality of the feed water. The gauge cocks should be opened after blowing out the water column to see that the level in the glass coincides with the level indicated by the gauge cocks. The water has to be kept at about the same height all the time, and the engineer can tell whether it is right or not by opening the gauge cocks. One of these is below the water line, and one is above it. If the water in the boiler is right, steam will come out of the upper one and water out of the lower one; if it is too low, steam will come out of both.
Fig. 166. - Water Gauge.
Fig. 167. - Cross-Section of a Boiler Pump.