Water gauge

  



Definition
A sight glass or water gauge is a transparent tube through which the operator of a tank or boiler can observe the level of liquid contained within.

Regulation
Every boiler is to be fitted with at least 2 independent means of indicating the boiler level in it: one of which is to be a glass gauge. The other means is to be either an additional glass gauge or an approved equivalent device.
Water tube boiler are to be fitted with 2 systems of water level detection which are independent of any other mounting on the boiler. Both the system are to operated audible alarm and automatic shut off device.

Tubular Gauge Glass
suitable for pressure below 17.5 bar
Safety feature include a steel valve valve on the water side connection to shut off the water in event of glass breaking and a wire insert glass cage to prevent injury to the personnel

Reflex Plate Gauge Glass
suitable for pressure below 34 bar
Make use of refraction of light so that when illuminated, the series of ribs at the back of glass plate cause the light rays to be reflected back from steam space and absorbed in the water space. This gives a bright silvery appearance to the steam side while water side appears dark

Double Plate Gauge Glass
For pressure > 34 bar
The assembly consists of a hollow centre piece fitted with 2 plates of toughened glass held in place by means of a clamp plate.
A louvre plate at the back of the glass
Directs the light rays at an angle to
make the meniscus of water
level glow

Gauge Glass test
Close the steam and water side valves and open the drain valve
Blow through the steam side by opening the upper valve for 1 ~2 sec and close.
Blow through the water side by opening the lower valve for 1 ~2 sec and close.
Close the drain valve
Open both steam and water side valves by turning them slowly