Which feature is characteristic of immersion boiler tube bundles?

The characteristic feature of immersion boiler tube bundles being easily removable for maintenance purposes is essential because it facilitates efficient servicing and repair without the need for extensive disassembly of the boiler system. This design aspect means that if there is a need to replace or clean the tubes, maintenance personnel can access them directly, minimizing downtime and ensuring that the system can be returned to operation quickly.

This ease of removal is particularly important in industrial applications, where boiler efficiency and uptime are critical. Tubes that can be easily serviced allow for routine inspections and cleaning, which contribute to the longevity and reliability of the boiler.

Considering the other choices, while conducting current through the boiler water, withstanding extremely high temperatures and pressures, and having negligible electrical resistance relate to different operational features, they do not encapsulate the primary maintenance advantage that immersion boiler tube bundles provide. Hence, the focus on the capacity for maintenance distinguishes this choice as the correct answer.