Without water to carry away heat, steel tubes and furnaces soften and sag, cast iron sections crack, and tube joints pull loose. Feeding cold water into a dry-fired boiler while it is still hot can crack it violently or cause a steam explosion. Low-water cutoffs exist to stop dry firing, and most dry-fire incidents involve a cutoff that was defeated, plugged or untested.
Somebody jumped out the low water and it dry fired over the weekend, the tubes are hanging like spaghetti.
If a boiler is found dry and hot, shut off the burner and let it cool on its own; adding water is what turns damage into an explosion.
Also heard as
- dry firing
Related terms
Low-water cutoff
A safety control that shuts the burner off when the boiler water level drops below a safe point.
Bag
A local bulge in a boiler tube, furnace or shell plate where overheated metal has been pushed out by pressure.
Thermal shock
Damaging stress from a sudden temperature change in boiler metal, such as cold water hitting hot iron.
Gauge glass
The glass tube or window on a steam boiler that shows the operator the actual water level.