Arkansas Boiler Operator Practice Exam

In a water tube boiler, what passes through the tubes?

1. Fire

2. Water

3. Steam

4. Air

The correct answer is: Water

In a water tube boiler, water is the fluid that circulates through the tubes. The design of a water tube boiler involves water being contained within tubes that are heated externally by combustion gases. As a result of this heat, the water inside the tubes transforms into steam, which then rises to the top of the boiler. This setup allows for efficient heat transfer from the high-temperature flue gases to the water, enabling faster steam production and better pressure management. With the water passing through the tubes, the boiler benefits from greater scalability and efficiency compared to fire tube boilers, where hot gases pass through the tubes instead. Understanding this fluid dynamics is crucial when operating a water tube boiler, as it directly impacts performance, safety, and energy efficiency.