Train 32N was traveling about 47 mph at the time of the derailment, which was less than the maximum authorized timetable speed of 50 mph.
Train 32 was operating with a dynamic brake application, The wayside defect detector, or hot bearing detector (HBD), as the train passed a wayside defect detector on the east side of Palestine, Ohio, at milepost (MP) 49.81 transmitted a critical audible alarm message instructing the crew to slow and stop the train to inspect a hot axle.
Train 32N passed three HBD systems on its trip before the derailment.
At MP 79.9, the suspect bearing from the 23rd car had a recorded temperature of 38°F above ambient temperature.
When train 32N passed the next HBD, at MP 69.01, the bearing’s recorded temperature was 103°F above ambient.
The third HBD, at MP 49.81, recorded the suspect bearing’s temperature at 253°F above ambient.
NS has established the following HBD alarm thresholds (above ambient temperature) and criteria for bearings:
Between 170°F and 200°F, warm bearing (non-critical); stop and inspect
A difference between bearings on the same axle greater than or equal to 115°F (non-critical); stop and inspect
Highlights include the following: