Arkansas Boiler Operator Practice Exam

In a fire tube boiler, what flows through the tubes?

1. Water

2. Fire

3. Steam

4. Gas

The correct answer is: Fire

In a fire tube boiler, the correct answer is that fire, or more specifically, combustion gases, flows through the tubes. In this type of boiler design, the hot gases produced from fuel combustion inside the furnace pass through tubes that are surrounded by water. As the combustion gases travel through the tubes, they transfer heat to the water in the shell or outer layer of the boiler, causing the water to heat up and eventually produce steam. The critical aspect of the fire tube boiler is this heat exchange process. The tubes contain the fire (combustion gases), while water fills the space surrounding these tubes. This design allows for efficient heat transfer and is a common configuration used in many industrial and commercial applications. The fire must be contained within the tubes to provide effective heating to the water surrounding them, making this option the fundamental principle behind the operation of fire tube boilers. While other answers might relate to various aspects of boiler operation, they do not accurately describe what flows through the tubes in a fire tube boiler. Water is indeed present but is outside the tubes, while steam is the product generated as a result of heating the water, and gas does not accurately describe the state of the combustion products in this context.