What should you do when adding a new tube to a water tube boiler?

When adding a new tube to a water tube boiler, the appropriate action is to roll and expand the tube. This process is essential for ensuring a proper fit and a tight seal between the tube and the headers of the boiler. Rolling refers to the technique of deforming the tube ends against the header to create a mechanical bond, while expanding involves using a tool to increase the diameter of the tube end slightly, ensuring it fits securely into the header.

This method is vital because it helps maintain the integrity of the boiler system, preventing leaks and ensuring efficient heat transfer. A well-rolled and expanded tube can withstand the operational pressures and temperatures typical within a water tube boiler, contributing to the overall safety and performance of the boiler.

Other options such as welding and sealing, flaring and securing, or simply inserting and locking may not provide the same structural reliability or thermal connection necessary for high-pressure operation in a boiler. These methods might be applicable in different contexts but do not align with the standard practice required when adding tubes to a water tube boiler.