Because the column connects above and below the waterline, water inside it stands at the same level as in the boiler, but with calmer surface and easy access. The gauge glass, try cocks and often the float-type low-water cutoff mount on it. A drain valve at the bottom lets the operator blow the column down to clear sludge from the connections, which keeps the level readings true.
Blow down the water column and watch how fast the glass comes back, if it's lazy the lower connection is plugging.
Blow down the column and the glass separately; a plugged lower connection can make the glass hold a false level.
Also heard as
- column
- water column assembly
Related terms
Gauge glass
The glass tube or window on a steam boiler that shows the operator the actual water level.
Try cocks
Small valves at set heights on a water column, opened by hand to check whether water or steam sits at each level.
Low-water cutoff
A safety control that shuts the burner off when the boiler water level drops below a safe point.
Blowdown
Draining some boiler water on purpose to remove concentrated dissolved solids and settled sludge.