After being hit by a detector for a hot wheel or hot journal, how many axles ahead of and behind the indicated axle must you inspect to ensure adjacent axles are not overheated?

• A. 6
• B. 12
• C. 2
• D. 4

Answer: (B)

When a detector flags a hot wheel or hot journal, heat can affect not just the indicated axle but nearby ones as well. To make sure there isn’t an additional overheated axle nearby, you inspect a window of axles around the detector hit. The standard approach is to look six axles ahead and six behind the indicated axle, for a total of twelve axles. This range accounts for how heat can transfer and for the possibility of multiple hot bearings within a short span, giving a reliable check that no adjacent axles are overheated. If you inspect fewer axles, you might miss another hot axle and miss a growing problem; inspecting a larger window isn’t necessary for typical conditions and would waste time.