What device is used to expand boiler tubes from the inside?

The device used to expand boiler tubes from the inside is known as a tube roller or expander. This tool is specifically designed to fit inside the boiler tubes and applies a controlled amount of pressure to the tube’s walls, effectively increasing the diameter of the tube to achieve a tight and secure fit against the tube sheet.

This process is critical because a proper seal is necessary to ensure the efficiency and safety of the boiler during operation. By expanding the tubes properly, the tube roller or expander helps prevent leaks and maintains the structural integrity of the boiler system.

Other tools mentioned, such as a pipe bender, are used for different purposes like shaping pipes rather than expanding them inside. Boiler cleaners are utilized for maintenance to remove debris and buildup from the boiler system, while flare tools are used to create a flare in the end of pipes to ensure a tight connection in piping systems, not for expanding tubes within a boiler. Therefore, the tube roller or expander is the correct answer as it fulfills the specific need for tube expansion in boiler maintenance.