Vibration alone won't predict your next bearing failure

Vibration is the default signal for rotating equipment monitoring, and for good reason: it is well understood, the failure signatures are documented, and the sensors are cheap. It is also, on its own, a noticeably weaker predictor than most reliability programmes assume.

What vibration sees late

Bearing degradation produces a vibration signature reliably, but often well after other channels have moved. Lubrication breakdown shows in oil debris first. Electrical faults in the driving motor show in current signature analysis first. Thermal shows in a rising temperature differential before the mechanical looseness that vibration detects.

The case for multi-modal

Each channel has a different lead time and a different false-positive profile. Combining them does two things: it extends the warning horizon to the earliest channel that moves, and it suppresses the false alarms that any single channel produces on its own, because a genuine degradation shows in more than one place.

• Vibration — mechanical looseness, imbalance, late-stage bearing wear
• Thermal — friction and lubrication problems, often earlier than vibration
• Motor current signature — rotor bar and electrical faults invisible to vibration
• Oil debris and particle count — the earliest indicator on lubricated assets
• Process context — load, speed, and duty, without which every other channel is ambiguous

Process context is the one most often missing

A vibration reading without the load it was taken under is close to meaningless. The same amplitude at 40% load and 95% load describe entirely different conditions. Reliability programmes that plateau usually have good sensor coverage and no connection to the process data that would make the readings interpretable.

Where to start

If you have vibration and nothing else, add thermal and process load before adding more accelerometers. It is cheaper, and it does more for the forecast than doubling the density of the channel you already have.