⚠️ Disclaimer: These tasks are guidelines only. They do not include lockout/tagout (LOTO), energy isolation, or other safety requirements. Review and verify suitability for your specific equipment and application. Add all required safety procedures per your company's policies and regulatory requirements before use. You are responsible for the safe and appropriate execution of all maintenance activities.
Forced draft fans push. That's the job. They move air into a process — a furnace, a boiler, a cooling tower, a dryer — and when they fail, the process fails with them. The failure modes aren't exotic. Bearing wear. Imbalance from blade buildup. Coupling deterioration from misalignment that nobody caught. Motor overloads that ran hot until the insulation gave out.
None of that is sudden. All of it is findable — if the PM checklist is built around what actually fails.
For the full picture on fan PM strategy, see industrial fans and blowers.
How to Use This Checklist
Record what you find, not just whether the box gets checked. "Bearing noise — slight roughness at DE, consistent with last quarter" is information. "OK" is a checkbox. One of those gets acted on before the failure. Note what changed since the last PM — new vibration, different noise, temperature trending up. That delta is the finding. A concrete example: "Belt tension at 60 lbs, sheave showing uneven groove wear right side" tells the next tech something. "Checked" tells them nothing.
Field Checklist — Critical Tasks
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect fan housing exterior for cracks, corrosion, dents, or signs of physical damage. | Every PM | MEC |
| Check fan inlet and outlet for obstructions, debris buildup, or foreign material that could restrict airflow. | Every PM | MEC |
| Verify access doors, inspection ports, and covers are properly secured and gasketed after any inspection. | Every PM | MEC |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Listen and feel for abnormal bearing noise, vibration, or roughness while fan is running. Flag any change from baseline. | Every PM | MEC |
| Inspect fan shaft and coupling for visible misalignment, looseness, or wear. Check coupling element or spider insert for deterioration. | Monthly | MEC |
| Inspect fan impeller/wheel through access door or inspection port for blade erosion, cracking, or debris accumulation. Clean if needed. | Quarterly | MEC |
| Check motor mounting bolts and fan base anchor bolts for tightness. Retorque to spec if loose. | Quarterly | MEC |
| Inspect V-belt drives (if applicable) for tension, cracking, fraying, or glazing. Check sheave alignment and groove wear. | Monthly | MEC |
| Inspect ductwork connections at fan inlet and outlet for air leaks, loose flanges, or damaged gaskets. | Quarterly | MEC |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Lubricate fan shaft bearings per manufacturer spec and site lubrication schedule. Do not over-grease — follow quantity and interval guidelines. | Quarterly | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Verify motor electrical connections at terminal box are tight and free of corrosion or heat discoloration. | Semi-Annually | ELE |
| Check motor nameplate data against operating voltage and amperage under load. Record actual amps and compare to FLA. | Semi-Annually | ELE |
Reference Checklist — Full Task Library
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Perform overall visual inspection of fan unit: housing, inlet, outlet, ducting connections, and motor. Note any corrosion, physical damage, or leaks. | Every PM | MEC |
| Verify fan inlet is free of obstructions. Check inlet cone or bell mouth for damage or distortion that could affect airflow. | Every PM | MEC |
| Check fan housing drain (if equipped) for blockage. Inspect housing interior if access allows — look for condensation, corrosion, or material accumulation. | Semi-Annually | MEC |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Check fan for abnormal vibration using a vibration meter or handheld analyzer. Record overall velocity (in/s or mm/s) and compare to baseline. Flag readings above alarm threshold. | Monthly | MEC |
| Inspect motor and fan bearings for noise and temperature. Use a contact thermometer or IR thermometer — compare drive-end and non-drive-end temperatures. Investigate if delta exceeds 20°F (11°C) from baseline. | Monthly | MEC |
| Check V-belt tension using a tension gauge. Verify sheave alignment with a straightedge. Inspect belts for cracking, fraying, glazing, or matching wear. Replace as a matched set. | Monthly | MEC |
| Inspect shaft coupling: check element/spider/disc condition, fastener torque, and shaft hub security. Check for rubber dust or debris indicating wear. | Quarterly | MEC |
| Inspect impeller/fan wheel through access door for blade erosion, cracking, fatigue cracks at the hub, or material buildup. Clean blades if accumulation is present — uneven buildup causes imbalance. | Quarterly | MEC |
| Inspect motor mounting base, anchor bolts, and vibration isolation pads or mounts for cracks, deterioration, and proper torque. | Quarterly | MEC |
| Verify damper operation at inlet vane or outlet damper (if equipped): full open and close travel, actuator linkage condition, and positioner calibration. | Quarterly | MEC |
| Inspect ductwork at all fan connections: flanges, flexible connectors, and expansion joints for air leaks, cracking, or loose fasteners. Inspect for corrosion along seams. | Semi-Annually | MEC |
| Verify shaft alignment using dial indicators or laser alignment tool. Correct if parallel or angular misalignment exceeds equipment manufacturer tolerance. | Semi-Annually | MEC |
| Verify fan performance against design: confirm airflow (CFM/m³/hr), static pressure, and motor amperage are consistent with baseline. Investigate if airflow has dropped >10% from design. | Annually | MEC |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Lubricate fan shaft bearings and motor bearings per lubrication schedule. Document grease type, quantity, and date. Do not mix grease types without purging. | Quarterly | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Measure and record motor operating current on all three phases under load. Compare to nameplate FLA. An imbalance >2% or consistent high amps warrants investigation. | Monthly | ELE |
| Inspect motor terminal connections and junction box for tight terminations, insulation integrity, and evidence of heat (discoloration, melted insulation, carbon tracking). | Semi-Annually | ELE |
| Test motor winding insulation resistance using a megohmmeter (500V DC for <1kV motors). Record MΩ values for each winding to ground. Investigate readings below 1 MΩ or a significant trend decline. | Annually | ELE |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Review and update fan PM history log. Note bearing temperatures, vibration readings, belt/coupling condition, and any corrective actions taken. Flag trends for reliability review. | Every PM | ALL |
Failure Modes This Checklist Targets
Bearing Wear and Failure Forced draft fans run continuously under thermal and mechanical load. Bearings erode from inadequate lubrication, over-greasing, contamination, or misalignment-induced overloading — and they announce the problem through noise, heat, and vibration long before they seize.
Impeller Imbalance Blade buildup from process dust, debris, or moisture is asymmetric by nature. Even small accumulation on one blade shifts the center of mass. The result is vibration that accelerates bearing wear, fatigues the shaft, and transmits load to the housing structure.
Belt and Coupling Deterioration V-belt drives degrade from improper tension, sheave misalignment, and heat. Coupling elements crack or compress over time, especially under misaligned shafts. Either failure mode loads the bearings in ways the equipment wasn't designed to handle.
Shaft Misalignment Misalignment is a bearing killer that hides behind vibration. Thermal growth, base settling, and soft-foot conditions all shift alignment over time. A fan that aligned correctly at installation may not be aligned six months later.
Motor Electrical Failure Overcurrent from restricted airflow, high ambient temperature, and phase imbalance degrade winding insulation. The motor runs until it can't. Amperage trending and periodic insulation resistance testing are the only early warning available.
Ductwork Air Leaks Leaks at fan discharge reduce system airflow without reducing motor load. The fan works harder against a different pressure curve. Energy consumption climbs. Process outcomes degrade. And because the motor keeps running, nobody notices until the problem is severe.
