Check to make sure you have enough oil in your Gear Boxes. You also need to do some oil analysis from time to time to check for wear and foreign particulates. Check your seals to see if they are leaking. Examine backlash and endplay to make sure all shafts, gears, and hardware are working correctly.
Structural components are also areas of great concern. Older Cooling Towers often have aging wood components, whether it be structural, stairways, walk ways, etc. Deteriorating framework and wood members can cause serious problems if left unaddressed. Loose or missing bolts and fasteners are an indication of an accident just waiting to happen