In which component of a boiler are tube holes typically found?

The correct answer identifies the tube sheet as the component of a boiler where tube holes are typically located. The tube sheet serves as a critical junction that holds the boiler tubes in place and provides a structural barrier between different sections of the boiler.

In operation, water or steam flows through these tubes, facilitating efficient heat exchange between the heated gases produced during combustion and the water or steam in the tubes. Tube holes in the tube sheet allow for the installation and maintenance of the tubes, ensuring proper alignment and sealing to prevent leaks.

The other components mentioned do not contain tube holes; for instance, the boiler drum serves as a reservoir for water and steam but does not have the fittings for tube insertion. The water leg is designed to provide structural support and stabilize the boiler but is not associated with tube installation. The firing chamber is where combustion occurs and does not accommodate tube holes either. Therefore, the presence of tube holes is distinctly characteristic of the tube sheet, making it the correct answer.