How are the tubes secured in a firetube boiler?

In a firetube boiler, the tubes are rolled and then beaded at the ends to create a secure and leak-proof connection to the tube sheets. The rolling process involves expanding the ends of the tubes against the tube sheets, which creates a tight fit that can withstand the pressures and temperatures typically experienced in a boiler. After rolling, beading involves adding a slight deformation at the tube ends to further prevent any potential leaks that could occur due to thermal expansion or pressure changes.

This method ensures that the connection remains strong and reliable, allowing for efficient heat transfer from the combustion gases to the water in the boiler. The combination of rolling and beading provides a durable solution that mitigates the risk of heat damage while maintaining the structural integrity of the system. Other methods, such as using nuts and bolts or clamps, do not provide the same level of reliability or integrity required in high-pressure steam applications.