What is an "overfire" in boiler terminology?

An "overfire" in boiler terminology refers specifically to a condition where excessive air enters the combustion zone of the boiler. This situation can lead to inefficient combustion, potentially causing elevated temperatures and increased emissions. When too much air is introduced, it disrupts the optimal air-to-fuel ratio required for efficient burning, which can hinder the boiler's performance and lead to wastage of fuel. Maintaining the right balance of air is crucial for efficient operation and to prevent issues related to combustion efficiency and emissions control.

In contrast to other options, a coolant leak relates to equipment malfunctions and is not classified as an overfire condition. Low water levels would indicate a different issue entirely, often leading to boiler damage or failure, while safety features designed to prevent overheating are preventative measures rather than conditions resulting from improper air flow during combustion. Understanding the concept of overfire helps in maintaining proper operational standards for boiler efficiency.