Hot box
Hot box turns up in 2 fields: asphalt, railroad. Here is what it means to the people in each one.
Hot box in asphalt
A heated, insulated hopper on a truck or trailer that keeps mix hot all day for patching.
A patching unit with an insulated body heated by a diesel burner, propane or electric elements, used to carry hot mix and keep it workable for hours. Crews load it at the plant in the morning and work through pothole and utility-cut repairs without the mix cooling. Some hot boxes also recycle chunks of cold asphalt by reheating them overnight.
"Load the hot box with four tons of 9.5 and grab the plate tamper, there's utility cuts all over the east side."
Hot box in railroad
An overheated wheel bearing on a railcar, a defect that can burn the end off an axle if missed.
The name comes from the journal box on a plain-bearing truck, where oil-soaked packing that runs dry starts to smoke and burn. Roller bearings run far cooler but still fail, and an overheating bearing can climb hundreds of degrees and burn the journal off the axle, dropping the car onto the track. Wayside detectors exist mainly to catch hot boxes before that happens.
"Detector called a hot box on the rear, conductor shot it with the temp gun and it's reading 300 over ambient."