The National Board records boiler failures throughout the nation. Most boiler failures are caused by a low water condition or poor maintenance.
When water is heated and converted into steam, it expands at a rate of 1600 times its volume, at atmospheric pressure, when compared to what it was as a liquid. This huge expansion, when released, causes the enormous forces evidenced in the pictures shown below .....
Failures are often the result of an improperly maintained or faulty level control which fails to shut the burner off at the proper low water point. When the water level drops below the top of the furnace the metal overheats and loses tensile strength, resulting many times in a rupture of the furnace and tube sheet causing a steam explosion, rocketing the boiler great distances across the room.