What is the correct procedure for adding a new tube to a fire tube boiler?

The procedure for adding a new tube to a fire tube boiler is best described by the method known as "Roll and bead." This process involves rolling the tube into its designated seat followed by creating a bead around the end of the tube. The rolling action forms a tight initial seal between the tube and the boiler shell, establishing a good physical connection.

The beading process further enhances this joint by providing additional mechanical strength and a more reliable seal against the hot gases inside the boiler. This is crucial for maintaining the operational efficiency of the boiler as it prevents leaks and ensures that the boiler can withstand pressure and temperature variations during its operation.

In contrast, other methods might not provide the same level of integrity or might not be applicable to the design of fire tube boilers. For instance, rolling and expanding typically refers to processes that are more suited for different types of tubing or applications, which may not ensure the optimal seal required for fire tube boilers. Therefore, the "Roll and bead" method is the preferred and correct approach for this specific boiler type.