2026-04-21 · TWH Team

Factory Preventive Maintenance Checklist for Thai Manufacturing

A monthly/quarterly/annual PM checklist covering electrical, HVAC, plumbing, and structural maintenance for Thai factory operators.

Preventive maintenance (PM) is the single most effective lever factory operators have for controlling maintenance costs, reducing unplanned downtime, and meeting the safety and environmental standards required by industrial estate authorities in Thailand. Yet many factories — particularly in the Eastern Economic Corridor (EEC) provinces of Chonburi and Rayong — still operate on a reactive “fix when broken” model that costs significantly more over a 3–5 year horizon.

This checklist is designed for production and facilities managers in Thai manufacturing. It covers building systems — electrical, HVAC, plumbing, and structural — and is structured around monthly, quarterly, and annual cycles. Process equipment (CNC machines, presses, conveyor systems) is out of scope; this guide focuses on the facility shell and building services.

How to Use This Checklist

Each item lists the inspection task, what to look for, and the action trigger — the condition that warrants a repair or replacement work order. Assign each task to a responsible role (in-house technician, outsourced vendor, or licensed inspector) before going live.

For factories in EEC industrial zones (Amata City Chonburi, Map Ta Phut Rayong, Laem Chabang), some tasks are mandatory under industrial estate authority regulations and must be documented and available for inspection. These are marked [Regulatory].

Monthly Checks

Monthly checks should take no more than half a day for a facility team of two. They focus on items that degrade quickly in Thailand’s climate — high humidity, heat, and (in Chonburi/Rayong) salt-laden coastal air.

Electrical Systems

• Panel visual inspection: Open all distribution boards. Look for burn marks, corrosion on bus bars and terminals, loose connections, and tripped breakers that have been reset without investigation. Action trigger: Any discolouration, burning smell, or hot spot detected by thermal feel warrants an electrical contractor visit within 48 hours.
• Emergency lighting test: Activate each emergency light and confirm minimum 3-hour battery hold. In Thailand, this is a fire safety requirement. Action trigger: Any unit failing to hold charge must be replaced within 7 days.
• Outdoor lighting and security light check: Walk the perimeter at dusk. Note any failed luminaires, particularly in loading dock and gate areas. Action trigger: Replace or repair within 14 days.
• Generator fuel and oil level: Check diesel level, coolant, and engine oil. Run the generator under no-load for 15 minutes and observe for warning lights, unusual vibration, or exhaust smoke colour. Action trigger: Abnormal smoke or vibration — stop and call service engineer.
• Earthing system visual check: Inspect earthing rods and cables at panel room level for corrosion or damage. Action trigger: Corroded connections — clean or replace.

HVAC and Ventilation

• Air handling unit (AHU) filter inspection: Check pressure drop across filters if differential gauges are installed; otherwise, visually inspect for clogging. Action trigger: Pressure drop exceeds design maximum or filter visually clogged — replace filter media.
• Split-type and cassette AC filter cleaning: Remove and clean filters in all office, control room, and breakroom units. In coastal Chonburi/Rayong factories, salt corrosion on fins accelerates at 12–18 months — inspect fins monthly. Action trigger: Damaged fins — call air-conditioning technician.
• Exhaust fan check: Verify exhaust fans in production areas, spray booths, and chemical storage are operational. Check belt tension where applicable. Action trigger: Noise, reduced airflow, or belt slippage — service within 3 days.
• Condensate drain check: Inspect drain pans and drain lines for algae buildup and blockage. Action trigger: Standing water in drain pan — clear immediately and dose with biocide tablet.

Plumbing

• Sprinkler head visual check: Walk all production bays and storage areas. Look for painted-over, corroded, or mechanically damaged sprinkler heads. Action trigger: Any obstruction or damage — fire protection contractor within 24 hours. [Regulatory]
• Sanitary fixture inspection: Check all toilet blocks and handwashing stations for leaks, blocked drains, and broken fixtures. Action trigger: Leak or blockage — repair within 24 hours.
• Water storage tank level and pump operation: Confirm tanks are at correct levels, float valves are functional, and booster pumps operate without unusual noise or vibration. Action trigger: Unusual noise — call plumbing contractor.

Structural and Common Areas

• Roof drainage check: After any significant rain, walk the roof perimeter and check drain outlets and gutters for debris accumulation. In monsoon season (May–October), this shifts to after every major rainfall. Action trigger: Blocked drain outlet or visible standing water on roof — clear within 24 hours.
• Door and gate mechanism check: Verify all fire escape doors open fully and are not obstructed. Check motorised gates and roller doors for smooth operation. Action trigger: Fire door obstruction — immediate corrective action. [Regulatory]

Quarterly Checks

Quarterly tasks go deeper than monthly visual checks. They often require a specialist contractor and generate a service report — important for insurance documentation and industrial estate compliance.

Electrical

• Thermographic (infrared) scan of panels: Use an IR camera or engage an electrical contractor with IR capability to scan all distribution boards under load. Hot spots above 10°C above ambient on any connection indicate a developing fault. Action trigger: Hot spot found — repair during next maintenance window or immediately if delta T exceeds 30°C. [Regulatory in factories with 200kVA+ demand]
• Generator load bank test: Run the generator at 75–100% rated load for 1–2 hours. Verify voltage and frequency stability, oil pressure, water temperature, and automatic transfer switch (ATS) response. Action trigger: Voltage or frequency deviation outside 5% — service engineer.
• Earthing resistance measurement: Use a ground resistance tester to measure earth electrode resistance. Thai standard PEA requirement: below 5 Ohms. Action trigger: Above 5 Ohms — install additional earth electrodes. [Regulatory]

HVAC

• Chiller or centralised AC system service: Full coil wash (evaporator and condenser), refrigerant pressure check, bearing lubrication, and controls calibration. For factories with central chilled water plants, this is a specialist job requiring certified refrigeration engineers.
• AHU belt, bearing, and motor check: Inspect V-belts for wear and cracking, grease bearings, and measure motor current draw against nameplate. Action trigger: Belt wear beyond 20% of original thickness — replace.
• Ventilation duct inspection: Internal inspection of main ductwork for dust accumulation, mould, or vermin evidence. Action trigger: Visible mould or significant dust — schedule duct cleaning.

Plumbing

• Underground drainage CCTV inspection: For factories with underground process wastewater drains, quarterly CCTV inspection identifies root intrusion, sediment buildup, and pipe deformation before blockage occurs. In Rayong and Chonburi, petrochemical-adjacent factories face accelerated pipe degradation. Action trigger: Deformation or >25% cross-section blockage — schedule excavation repair.
• Backflow preventer test: Test all backflow preventers on potable water supply lines. [Regulatory where applicable]
• Wastewater treatment system check: Verify aeration blowers, settling tanks, and effluent quality monitoring equipment are operational. [Regulatory — EEC factories with WWT systems]

Structural

• Roof membrane and waterproofing inspection: Full visual walk with a focus on membrane laps, penetrations (pipe sleeves, conduit entries), and expansion joints. Action trigger: Delamination, blister, or cracked sealant — schedule repair before next monsoon.
• Cladding and curtain wall inspection: Check external wall cladding panels, particularly at bracket connections. Salt air in Chonburi/Rayong corrodes steel fixings in 3–5 years without protective coating. Action trigger: Visible corrosion at fixings — engage general maintenance or structural contractor.

Annual Checks

Annual checks address systems that degrade over a full seasonal cycle and require specialist certification or regulatory submission.

Electrical

• Full electrical safety inspection by licensed engineer: Thai law (Ministerial Regulation on Electrical Safety) requires periodic inspection by a licensed electrical engineer for factories above defined power consumption thresholds. The inspection produces a formal report submitted to the Department of Industrial Works (DIW). [Regulatory]
• Lightning protection system inspection and continuity test: Measure resistance of lightning conductor system and inspect air terminals, down conductors, and earth connections. Target: under 10 Ohms total. Action trigger: Above 10 Ohms — repair and retest.
• UPS battery capacity test: For factories with UPS protecting control systems, annual capacity discharge test confirms battery state of health. Action trigger: Capacity below 80% of rated — replace battery string.

HVAC

• Full refrigerant system leak detection: For systems containing HFCs (R-410A, R-134a), annual leak testing is aligned with Thailand’s F-Gas commitments. Factories in EEC are subject to increasing regulatory attention on refrigerant management. [Regulatory — increasingly enforced]
• AHU coil replacement or deep clean: Depending on coil condition from quarterly checks, annual deep clean or replacement of severely corroded coils.
• Cooling tower annual service: Full basin clean, fill media inspection, nozzle check, and Legionella risk assessment for factories using cooling towers. [Regulatory — industrial estate requirements]

Plumbing and Fire Protection

• Fire suppression system annual inspection: Sprinkler system annual inspection by a licensed fire protection engineer, including flow test, pressure test, and inspection of all heads, valves, and pumps. Required for submission to local fire authority and industrial estate. [Regulatory]
• Water tank internal inspection and clean: Drain, enter, and clean all potable water storage tanks. Inspect for cracks, liner condition, and inlet/outlet valve condition. [Regulatory — food-adjacent and pharmaceutical factories]

Structural and Civil

• Facade and structural joint inspection: Engage a civil engineer for annual review of building expansion joints, column base conditions, and any visible cracking. In EEC coastal zones, carbonation and chloride ingress in concrete structures may require cores to be taken after year 10.
• Welded joint inspection on mezzanines and racking: Annual visual and, where required, NDT inspection of structural welds on in-house fabricated mezzanines and heavy racking. For weld repairs and new structural welds, see our welding services.

Documenting PM Work

The checklist is only as good as the records it generates. For EEC industrial estates and DIW compliance, inspectors expect:

• A PM log (digital or paper) with date, task, finding, and action taken
• Service reports from any outsourced contractor, on company letterhead with technician’s name and qualifications
• Regulatory inspection certificates filed and readily retrievable
• A forward schedule showing the next PM date for each item

If your factory does not currently have a documented PM system, the lowest-friction starting point is to implement the monthly checklist first, establish a simple log, and add quarterly and annual tasks in subsequent quarters.

For specialist tasks requiring certified contractors — electrical, fire protection, structural — TWH’s vendor network covers EEC industrial zones with verified, experienced contractors who issue proper tax documentation for each job. Explore maintenance services for B2B factory clients.