What is the purpose of boiler handholes?

The purpose of boiler handholes is primarily to allow for inspection and maintenance of the boiler shell or drum. Handholes are small access points that facilitate entry into various components of the boiler system. By utilizing the handholes, operators can visually inspect critical areas within the shell or drum for signs of wear, corrosion, or other issues that could impact the safety and efficiency of the boiler. This access is crucial for maintaining the integrity of the boiler and ensuring that it operates effectively and safely.

In contrast, the other options refer to areas that are not typically accessed through handholes. Entry into the furnace or uptake usually requires larger openings due to the equipment and structures involved, while the windbox is a different part of the system associated with air distribution and is not generally accessed through handholes either. Thus, handholes serve a specific and important function related to the boiler shell or drum.