Which condition indicates a balanced draft system in a boiler?

A balanced draft system in a boiler is characterized by having nearly atmospheric pressure in the furnace. In such a system, the combustion air supply and the flue gas removal work together effectively to maintain a neutral pressure environment within the furnace. This balance prevents excessive pressure that could lead to issues like blowback of flue gases or difficulties in fuel combustion, while also avoiding negative pressure that could draw in unwanted air or affect combustion efficiency.

Maintaining almost atmospheric pressure helps ensure optimal combustion conditions, which are crucial for the efficiency and safety of the boiler operation. It indicates that the draft fans and burners are operating harmoniously to create a controlled environment conducive to effective combustion.

In other scenarios, such as having a positive pressure in the furnace, there could be issues with fuel combustion efficiency or operation safety. Negative pressure can lead to the risk of flue gas leakage, which is undesirable. High pressure in the flue gas may indicate improper operation or blockage in the exhaust system, which could compromise boiler performance and safety. Overall, the near-atmospheric pressure in a balanced draft system ensures stable and efficient boiler operations.