How does "draft" relate to boiler operation?

The term "draft" in the context of boiler operation specifically pertains to the flow of air and exhaust gases through the boiler system. This flow is essential for ensuring that combustion occurs efficiently and that the byproducts of combustion (exhaust gases) are effectively vented from the boiler.

In a well-designed boiler system, draft helps maintain the necessary airflow required for efficient fuel combustion. Proper draft is crucial for ensuring that oxygen is supplied to the combustion process, and it also influences how well exhaust gases are removed from the combustion chamber. If there is insufficient draft, it can lead to incomplete combustion, increased emissions, and potential operational issues. Therefore, understanding and managing draft is vital for optimal boiler performance and safety.

The other options pertain to different aspects of boiler operation that do not directly relate to the concept of draft. For instance, the fuel supply mechanism deals with the delivery of fuel, while pressure levels refer to the internal steam pressure, and efficiency of heat transfer relates to how well the heat generated is utilized within the system.