What can Cause a Boiler Explosion?

Lori Kilchermann

Boiler explosions can result from a number of factors. The primary reason for them is a faulty pressure relief valve. Inner corrosion of the boiler plates is another primary reason a boiler will explode or suffer a catastrophic failure. Low water levels are responsible for many instances of boiler explosion and can happen when the water falls below the level of the firebox, causing it to overheat and occasionally burn through into the water chamber. Such explosions are typically linked to poor operator training and neglected maintenance procedures.

Inner corrosion of the boiler plates is a primary reason a boiler will explode or suffer a catastrophic failure.
Inner corrosion of the boiler plates is a primary reason a boiler will explode or suffer a catastrophic failure.

In a typical boiler design, water is heated and turned into steam, which is stored within the boiler's main chamber. The steam is under tremendous pressure and requires exact operating methods be followed in order to prevent a boiler explosion. If the steam is used according to the design, the typical boiler is able to provide many years of reliable service. Problems occur when operators take shortcuts instead of following maintenance protocol exactly. As in any type of pressurized system, a boiler explosion can be deadly to anyone near the vicinity of the explosion.

Most boiler designs utilize a pressure-relief valve to control the amount of internal pressure generated by the boiler. Commonly a spring-loaded valve that is pre-set to pop off or release at a given pressure level, the excess steam is allowed to escape through the pressure-relief valve and avoid a boiler explosion. Occasionally, these valves will become corroded and gummed up, preventing them from operating as designed. Most boilers have maintenance schedules to test and replace any inoperable pressure-relief valves.

Hot water creates scale and corrosion inside the boiler tank that can lead to faulty steel and, ultimately, a boiler explosion if left unattended. The inside of the boiler tank should be cleaned and examined periodically to monitor the condition of the boiler. If the scale and corrosion are allowed to remain inside of the tank, the metal can become weak, and even the rivets or welds used to seal the tank can develop weak spots. The minerals and natural products found within the makeup of the water itself can cause an explosion as well.

The reason a boiler explosion can be so damaging to the surrounding area is that steam takes up 1,600 times more room than water. When this power is given the smallest avenue through which to escape, it tries to leave the area all at once. The power of all of the steam pressure released at once during a boiler explosion is equal to that caused by detonating a huge amount of explosives or gunpowder.

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Discussion Comments


That's one reason why I had the boiler replaced in my older house when we bought the place. I didn't want something that potentially explosive sitting in my home. I remember when I was in school, we couldn't have any events at night unless a certified boiler mechanic was on duty. I thought if they needed someone to watch over a boiler at a school, then what could happen with an unsupervised boiler in my own house? I'm not trained to look out for things like water levels or heat settings.


I remember the guys at MythBusters tried to get water heaters and boilers to explode, but they had to make a lot of modifications before it happened. The pop-off valve had to be welded shut, for one thing. I think they also had to weaken the metal on the boiler tank as well.

At least they proved how well-constructed a lot of boilers and hot water tanks really are. It took a lot of work to make one fail. But when it finally blew up, the tank did go through the ceiling.

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