Which tube should be removed for analysis to determine if the boiler needs acid cleaning?

Removing the screen tube, which is typically located 2/3 of the way down the furnace depth, is the correct choice for analyzing the need for acid cleaning in a boiler. This tube is strategically positioned to accumulate deposits from the combustion process and water chemistry over time. By inspecting the screen tube, you can obtain a clear indication of the extent of fouling and scaling present in the boiler system.

This specific tube allows for a representative analysis of the boiler's overall condition without having to remove more critical components that could disrupt the boiler's operation and require a more extensive shutdown for maintenance. In addition, the screen tube provides data on the effectiveness of the existing water treatment program and identifies whether the deposits have reached levels where acid cleaning is necessary to restore efficiency and prevent potential operational issues.

Other tubes, such as the top header tube or the bottom header tube, may not present a comprehensive view of the deposits formed throughout the boiler system, as they are less critical in capturing the overall conditioning of the furnace compared to the screen tube.