10 of 20
Cleaning Glass in Steam Service
Proper cleaning and maintenance of flat glass gages in steam service is vital for enhanced
performance and service life. The gage glass must be kept clean to ensure the visible water
level in the chamber accurately represents the water level in the boiler. Note that the
frequency and method of blow-down may affect service life and performance of glass level
gages.
A glass gage on a boiler enables the operator to visually observe and verify the actual water
level in the boiler. However, if not properly cleaned and maintained, a glass gage can appear
to show a normal water level when the boiler may actually be operating in a “low” or “low-low”
water condition. A stain or coating can develop on the inside of the glass where it is in contact
with boiling water. After time, this stain gives the appearance of water in the boiler, especially
when the glass gage is completely full or empty.
Also, the connection lines to the glass gage can become clogged with sediment, causing an
apparent normal water level when the boiler water may be low. After performing the blow-
down procedure, if the water level does not return to the normal level promptly, the connecting
piping may be partially clogged and require cleaning.
Clark-Reliance recommends the following blow-down procedure:
1. Close both the (top) steam and (bottom) water valves between the boiler drum and the
gage.
2. Open the drain valve fully on the bottom of the gage.
3. Slightly open the water valve to clean the pipe and valve of any blockage or sediment.
Once clear, close the water valve.
4. Slightly open the steam valve and allow a
gentle
rush of steam to pass through the
gage.
The steam should not pass through for longer than 20 seconds.
5. Close the steam valve.
6. Inspect the gage to ensure that all foreign matter is flushed from the glass or mica.
7. If the gage is not visually clean, repeat steps 3 and 4.
8. Close the drain valve, open the steam valve ¼ - ½ turn, then open the water valve ¼ -
½ turn, slowly bringing the equipment back to its normal operating level. Once the
level has equalized, fully open both valves. See Bringing Gage into Service for further
instructions.
9. When bringing the gage into service, liquid should quickly enter the glass gage. This
indicates that the lines are free of sludge, sediment or scale buildup.
