What type of boiler system operates under positive pressure during various load conditions?

A pressure-fired boiler is designed to operate under positive pressure, which means that the internal pressure is greater than the atmospheric pressure outside the boiler. This characteristic allows for better control over the combustion process and improved efficiency in heat transfer. The positive pressure environment helps to prevent the escape of combustion gases, thereby enhancing safety and maintaining proper operating conditions.

These boilers are commonly used in applications where consistent performance is required under various load conditions, such as in industrial settings or large commercial buildings. In contrast, other boiler types, like fire tube and water tube boilers, typically operate under different pressure conditions and are not primarily designed to maintain a positive pressure environment throughout their operational range. Low-pressure boilers, as the name implies, are specifically designed to operate at pressures below a certain threshold, which also distinguishes them from pressure-fired boilers.