Generally, once the equipment is installed, the baseplate and foundation are not a concern. There is not much preventative maintenance, and as long as the startup and inspection was approved, what could possibly go wrong? Plenty. The baseplate and foundation of rotating equipment needs to be inspected regularly, sometimes daily.

This is where the difference between flexible foundations and rigid mounts can effect the operation. Flexible installations, as most centrifugal blowers and exhaust fans use, can be a bit more forgiving as they will accept a little more vibration. The rigid mounts of most pumps and gearboxes, as well as some grouted in blowers, often requires a better rotor balance by the factory to minimize overall vibration levels. The purpose of the rigid mount is to reduce vibration, since fastening it tight to the earth has got to keep it from moving.  

Flexible installations generally use vibration isolation pads, or spring isolators, between the baseplate and the foundation/floor. Vibration pads can wear out to the point they are no longer absorbing the motion. They can fill with stones and dirt, or be chemically compromised by ambient gas. A more common cause is stones or other hardware becoming jammed beneath the baseplate, which prevents the pad from isolating, and allows the vibration to increase leading to premature bearing wear.

Spring isolators, often used on fan baseplates, can simply break. More than once, I have been called in to do a balance on a rooftop fan and found 1 or more of the spring isolators were damaged. I can't balance a fan unless the mounting is adequate. All they had to do is look first. Sometimes the spring isolators are supporting the concrete foundation pad that the equipment is fastened to. The concrete has to be closely inspected for cracks and/or deterioration.

Rigid mounts can have broken bolts that you may not be able to see is loose without actually putting a wrench on it. Rust is a big factor in steel baseplates bolted to steel, or concrete, foundations. Sometimes you can't see any cracks in the concrete floor, but if you stand in a certain spot, you can feel the increase in vibration. Concrete floors are notorious for developing "weak spots", in the gravel/stone base beneath the concrete. These sinkholes can cause a resonance that activates a critical frequency in the equipment. The resulting vibration can lead to premature bearing wear.

So the preventative maintenance for foundations and baseplates consists primarily of a visual inspection. Keep the area clean, the hardware free of rust, and the isolators as good as new. Invest in PM, it will save you money!