6.2 Preventive Maintenance (PM) Planning

Preventive Maintenance is not a suggestion; it is a rigid contract between Engineering and Operations. In high-precision electronics manufacturing, facility systems are active process variables. A 5% drop in compressed air pressure can cause a pick-and-place nozzle to drop a BGA component. We do not maintain systems to "look good"; we maintain them to stabilize the manufacturing process window.

Electrical Distribution & UPS

Dirty power corrupts logic. Voltage sags cause unexplainable SMT resets and corrupt server databases.

Thermographic Inspection (IR Scan)

• Frequency: Annual.
• Action: Scan all distribution panels and bus ducts under > 40% load.
• If Delta T is > 5˚C (above ambient) -> Then Schedule torque verification within 48 hours.
• If Delta T is > 20˚C -> Then Immediate Shutdown and Repair.

UPS Battery Health

• Frequency: Quarterly.
• Measure: Internal Impedance of every block.
• If Impedance deviates > 30% from baseline -> Then Replace the entire string.
• Physics: Mixing new and old batteries destroys the new ones via unequal charging currents.

Compressed Air Systems (ISO 8573 Class 1.4.1)

Pneumatic tools require energy, not water. Moisture acts as a solvent, washing away internal lubrication in solenoid valves and vacuum generators.

Filtration Logic

• Monitor: Differential Pressure (∆P).
• If ∆P > 0.7 bar (10 psi) -> Then Replace filter element immediately.
• Constraint: Never bypass a clogged filter "just to keep running." This injects contaminants downstream that require weeks to purge.

Oil Analysis

• Frequency: Quarterly.
• Test: Total Acid Number (TAN) and Particle Count.
• Rule: Change oil based on chemistry, not just hours. Acidic oil eats air-end bearings.

Pro-Tip: Verify "Zero-Loss" drains actually work. A stuck open drain wastes $2,000/year in energy. A stuck closed drain floods the dryer.

HVAC Hardware Integrity

The Building Management System (BMS) controls the setpoint, but the hardware delivers the reality.

Fan Belts & Drives

• Action: Check tension monthly.
• If belt is "glazed" or cracked -> Then Replace.
• Risk: Slipping belts cause airflow oscillation, disrupting the laminar flow required in cleanrooms.

Sensor Calibration

• Frequency: Annual.
• Standard: NIST-Traceable reference.
• If Drift is > 0.5˚C or > 2% RH -> Then Replace sensor. Do not use software offsets to "mask" the error.

Steam Humidifiers

• Action: Inspect cylinders monthly for scale.
• If Scale covers > 50% of electrodes -> Then Replace cylinder.
• Logic: Scale acts as an insulator, preventing the current required to boil water, leading to low-humidity alarms.

ESD Infrastructure Upkeep

The ESD floor is an electrical component, not just a surface to walk on.

Flooring Maintenance

• Chemicals: Use only ESD-Specific neutral cleaners.
• Prohibition: Never use standard floor wax. It creates an insulative dielectric layer (infinite resistance), rendering the conductive floor useless.
• Repair: Patch gouges with Conductive Epoxy, not standard filler.

Ionizers (Overhead & Benchtop)

• Action: Clean emitter pins monthly.
• Physics: Silicon dust accumulates on the needle tips ("Fuzzy Needles"), insulating the high-voltage emitter and stopping ion production.

Final Checklist

Parameter	Metric / Rule	Critical State
Electrical Panel	IR Hotspot Limit	< 5˚C Rise
UPS Batteries	Impedance Deviation	< 30%
Air Filters	Max ∆P	0.7 bar (10 psi)
Air Drains	Function Check	Weekly
HVAC Sensors	Max Drift	2% RH / 0.5˚C
ESD Floor	Cleaning Agent	No Wax / ESD Only
Ionizers	Emitter Status	Clean / Sharp
PM Scheduling	Trigger	Usage (Hours) > Calendar