Which of the following techniques are used for predictive maintenance?

Predictive maintenance involves techniques that monitor the condition of equipment to anticipate failure before it occurs. Common predictive techniques include:

Vibration monitoring (1) – Detects imbalance, misalignment, or bearing wear.

Oil analysis (2) – Identifies contamination, wear particles, or breakdown in lubricants.

Ultrasound (4) – Detects leaks, arcing, and mechanical friction.

PM frequency analysis (3) is part of preventive maintenance, not predictive maintenance.