What method is used for adding a new tube to a fire tube boiler?

The correct method for adding a new tube to a fire tube boiler is through the "Roll and bead" process. This method involves rolling the ends of the new tube and then creating a bead at the joint, which effectively seals the connection between the tube and the boiler shell. This technique is essential in ensuring that the tube is securely fixed in place, preventing leaks and allowing for efficient operation of the boiler.

The "Roll and bead" method is well-suited for fire tube boilers because it creates a strong mechanical connection that can withstand the high pressures typically encountered in such systems. Additionally, this method is favorable in terms of maintaining the integrity of the boiler structure while allowing for maintenance and replacement of tubes as needed.

The other methods mentioned, while they may be applicable in certain scenarios, do not align with the standard practices for fire tube boiler tube installation. Techniques like "Weld and bond" are more common in different types of boiler systems where welding is appropriate, while "Insert and fasten" does not provide the same level of securement and sealing required for high-pressure applications. Thus, rolling and beading is a specifically recognized procedure for efficiently and effectively adding tubes to fire tube boilers.