Massachusetts 2nd Class Fireman's Practice Exam

A tube in a fire-tube boiler is primarily surrounded by what substance?

1. Water

2. Air

3. Flue gases

4. Steam

The correct answer is: Water

In a fire-tube boiler, the tubes are specifically designed to carry the hot flue gases produced from the combustion of fuel. The primary function of this design is to transfer heat from these gases to the surrounding water. Water is utilized in this context because it absorbs the heat, leading to the production of steam or heated water, which is then used for heating, power generation, or other industrial processes. The water surrounding the tubes is crucial for efficient heat transfer and overall boiler operation. As the flue gases pass through the tubes, the heat causes the temperature of the water to rise, transforming it into steam or hot water that can be utilized in various applications. While air, flue gases, and steam play roles in the operation of a fire-tube boiler, they do not encompass the primary substance that surrounds the tubes. Air serves a role in the combustion process, flue gases result from combustion itself, and steam may be produced as a byproduct, but it is the water that is consistently in direct contact with the tubes, facilitating the heat transfer necessary for the boiler's function.