Boiler soot blower nozzles are installed not greater than every third tube if the axis of the element is at right angles to the axis of the tubes or not greater than how many inches if the axis of the element is parallel to the tubes?

Boiler soot blower nozzles are designed to effectively clean the surfaces of boiler tubes by discharging high-pressure steam or water to remove soot and other deposits. When the axis of the soot blower element is parallel to the tubes, the spacing of the nozzles is crucial to ensure adequate cleaning without leaving any tube sections unaddressed.

In this case, the correct answer indicates that the nozzles should be installed no greater than 3 inches apart when positioned parallel to the tubes. This specific distance allows for effective cleaning coverage, ensuring that the sooting buildup can be adequately addressed throughout the entire heating surface of the boiler.

This spacing is established based on operational experience, engineering practices, and the need to maintain boiler efficiency. If the nozzles were spaced too far apart, areas between them might not receive sufficient cleaning, which could lead to reduced performance and efficiency due to soot accumulation. Thus, maintaining a maximum separation of 3 inches is essential for effective soot removal and overall boiler operation.