What is the minimum air flow required during a purge on a prefiring cycle on an automatic system for a water tube boiler?

During the purge phase of a prefiring cycle for an automatic water tube boiler system, it is essential to ensure proper air flow to remove any potentially hazardous gases, such as unburned fuel or flue gases, from the combustion chamber. This step is critical for safety and operational efficiency.

A minimum air flow of 70% is required during this purge process to effectively dilute and carry away any harmful substances before ignition occurs. Achieving this level of air flow is crucial to prevent explosions or fires caused by accumulated gases. Adequate air flow ensures that there is enough oxygen available for the combustion process, promoting a safe and stable environment for the boiler to operate.

While higher levels of air flow may be beneficial for certain situations, the established minimum for purging is set at 70% to strike a balance between ensuring safety and maintaining operational efficiency. This allows for sufficient mixing and circulation of air within the combustion chamber. Therefore, the answer provided aligns with industry standards and best practices for boiler operations.