When is a boiler typically classified as a watertube boiler?

A watertube boiler is typically classified as such when water is contained within the tubes. This design allows water to be heated as it flows through the tubes, which are exposed to hot gases generated by combustion. The fundamental operation of a watertube boiler distinguishes it from a firetube boiler, where the hot gases pass through tubes that are submerged in water.

In the watertube design, the heat transfer occurs efficiently as the water circulates in the tubes, making it effective for high-pressure applications. The tubes, typically arranged in a way that maximizes surface area, are crucial to the boiler's ability to safely operate under high temperatures and pressures because they can handle thermal stress better than larger water-filled sections. Understanding the fundamental principle that defines watertube boilers is essential for recognizing their applications and advantages in various heating scenarios.