6.3 Predictive Maintenance (PdM)

Predictive Maintenance is not about fixing machines; it is about buying time. While Preventive Maintenance relies on statistical guesses (replacing parts "just in case"), PdM interrogates the asset for physical signatures of distress—heat, vibration, and noise. This shifts the operational reality from "Run-to-Failure" to "Run-to-Managed-Intervention." We do not wait for the bearing to seize at 2:00 AM; we detect the 10-micron defect three weeks prior and schedule the changeover during lunch.

Vibration Analysis (The Heartbeat)

Rotating assets (Reflow blowers, Wave impellers) speak before they fail. By the time you hear a noise, the damage is already catastrophic.

• Metric: Velocity (mm/s RMS).
• If Vibration is < 2.8 mm/s -> Then Asset is Healthy.
• If Vibration is 2.8 – 4.5 mm/s -> Then Flag as Warning.
  • Action: Increase monitoring frequency to Daily. Order spare parts immediately.
• If Vibration is > 4.5 mm/s -> Then Asset is Critical.
  • Action: Schedule downtime within 24 hours. Failure is imminent.
  • Diagnostic: 1x RPM amplitude spike = Imbalance (Dirty Fan). Non-synchronous spike = Bearing Defect.

Infrared Thermography (The Fever)

Resistance creates heat. In electrical systems, heat is the precursor to fire. In mechanical systems, heat is the signature of friction.

Electrical Panels & Busbars

• If Delta T is > 5˚C (vs. Reference Phase) -> Then Re-torque connection.
• If Delta T is > 20˚C -> Then Immediate Shutdown. The component is failing.

Mechanical Drive Systems

• If Motor Housing > 80˚C -> Then Inspect winding insulation and ventilation.
• Physics: For every 10˚C rise above rated temperature, insulation life is cut by 50%.

Ultrasonic Leak Detection (The Hiss)

Compressed air and Nitrogen (N2) leaks are expensive and invisible. A "quiet" facility can still be bleeding thousands of dollars in gas costs.

Compressed Air Lines

• Target: Overhead distribution and regulator drops.
• Frequency: Semi-Annual scan.

Nitrogen (N2) Reflow Plumbing

• Target: N2 is a direct cost of goods sold (COGS). Leaks here compromise the inert atmosphere and increase solder defects.
• If Ultrasonic Signal is > 10 dB above background -> Then Tag and Seal.

Motor Current Analysis (The Load)

Current draw is a direct proxy for mechanical load. A conveyor motor pulling high amps is fighting a jam or a seized bearing.

• Baseline: Establish a "Golden Trace" for normal operation.
• If Baseline shifts Upward -> Then Check belt tension and lubrication.
• If Current Spikes > 120% -> Then Trigger PLC "Over-Torque" Shutdown.
  • Logic: Cut power before the motor burns out or the PCBA is crushed.

Final Checklist

Parameter	Metric / Rule	Critical State
Vibration Limit	ISO 10816-3	> 4.5 mm/s RMS
Reflow Fans	Check Frequency	Monthly
Electrical Heat	Delta T (Phase-to-Phase)	> 20˚C = Shutdown
Motor Heat	Housing Temp	> 80˚C
N2 Leaks	Ultrasonic Threshold	> 10 dB
Conveyor Protection	Current Limit	120% Nominal
Scan Schedule	Electrical IR	Annual