Equipment Hours

since the rebuild involved inspecting the gears and replacement of the bearings you should zero out the run hours. most rebuild involve reusing the gear sets unless there is major wear. what you should do is a complete flush and filter of the box if possible and then track as a new unit paying attention to the type break in wear observed thru your anaylisis.
oil on dude!!!!

The gearbox hours should in my opinion not be set to zero.

The maintenance intervention was an inspection with the bearings being replaced as per procedure.

Component hours have to be trended with regard to maintenance significant items. A simple spur gear set consist of at least 4 bearings and 2 shafts & gears - a bundle to trend and not always possible due to various reasons (fow of information etc). In a perfect world it would be ideal.

The gearbox can be classified as a maintainable item to be trended. If the gearbox is changed out, in it's entirety, as an operational unit then the hours can be reset to zero e. g. screen mechanisms, small worm drive gearboxes, conveyor gearboxes etc.

Large industrial gearboxes where the internals are usually replaced but the housing is fixed it is best to trend the internals and zero only if the internal parts have physically been changed out - not merely inspected since this will not reflect compnent life and will adversely affect calculations of MTTF etc.

The operational criticality, capital investment, lead time on new parts etc. all influence prioritisation in determining the significance of each item. An RCM (reliability Centered Maintenance) matrix should be drawn up amd FMECA (Failure Mode Effect and Criticallity Analysis) conducted to establish the significance and your maintenance structured accordingly. This would dictate what should and should not be trended.

Hope this helps ..... well, that is my que!