What is the last step to be performed when shutting down a boiler?

The last step in shutting down a boiler is closing the feedwater supply valve. This action is crucial because it effectively disconnects the water source from the boiler system, preventing any further water from entering the boiler. By doing this last, it ensures that residual water in the boiler can be accounted for and managed, minimizing risks associated with water over-pressurization or leftover water causing unexpected reactions.

In a shutdown procedure, there are several necessary steps to ensure safety and proper handling of the boiler. While releasing the pressure is essential to reduce risks of bursts or leaks, this should occur before the feedwater supply is closed. Turning off the burners is also critical but should happen prior to the closure of the feedwater valve to ensure no water is introduced while the burner is still operational, which could result in dangerous conditions. Securing the flue is an important step for ensuring that exhaust gases do not pose a safety hazard, but this is also typically done earlier in the shutdown process.

Overall, closing the feedwater supply valve last helps ensure that the boiler is safely transitioned out of operation, making it an essential final step.