Water gauge indicates the water level inside the boiler and is hence called as water level indicator. Usually two water gauges are fitted in front of boiler.

Description of water gauge:

It consists of a glass tube, two gun metal tubes and three cocks. The steam cock C1 is provided on the gun metal tube M1 which connects the glass tube with the steam space in the boiler. The water cock C2 is provided on the gun metal tube M2 which connects the glass tube with the water space. The gun metal tubes M1 and M2 are bolted to the boiler shell.

The drain cock C3 is used to drain the water from the glass tube at intervals to ascertain whether the gauge is in proper order or not. The glass tube is protected by means of a cover, made of specially toughened glass which will prevent any accident that may happen due to the breaking of glass tube.

Working of Water gauge:

The water gauge shows the level of water in the boiler drum. It warns the operator if the water level goes below a fixed mark, so that corrective action may be taken in time to avoid any accident.

For the observation of the water level in the boiler, the water and steam cocks are opened and drain cock is closed. The steam enters from the upper metal tube M1 into the glass tube and water enters from the lower metal tube M2 into the glass tube. Hence, water stands in the glass tube at the same level as in the boiler.

The junctions of the metal tubes and the glass tube are provided with two balls. In case the glass tube is broken, the balls are pushed to the top nd bottom ends of the glass tube. Thus the flow of both water and steam out of the boiler is prevented.

When the boiler is not working, the water gauge can be taken out from the boiler for cleaning purposes by removing the bolts.