⚠️ 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.
Induced draft fans earn their failures. They pull combustion gases, flue products, and process exhaust through systems that run hot, run dirty, and run continuously. The impeller takes the abuse directly — erosion from particulate, imbalance from buildup, and thermal stress from the gas stream itself. Then the bearings follow.
This checklist covers the inspection and maintenance tasks that catch IDF failures early — before the imbalance becomes a catastrophic event and before the bearing heat becomes a bearing failure.
For a full picture of what drives fan PM programs and where most of them fall short: fan and blower PM fundamentals your program is probably missing
How to Use This Checklist
Record what you find, not that you looked. "Bearing temp normal" means nothing three months from now. "NDE bearing: 168°F ambient 78°F, up from 152°F last cycle" means something. The same principle applies to vibration, current, and impeller condition — specifics build the trend that tells you when to act.
A good finding looks like this: Fan housing, inlet bell: light surface rust on upper casing seam, no cracks, no material loss, consistent with prior inspection. A bad finding looks like this: OK. One of those is a maintenance record. The other is evidence that you were present.
Visual Inspection Tasks
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Inspect fan housing, inlet bell, and discharge casing for cracks, corrosion, holes, or physical damage. Note any areas showing wear or material loss. | Every PM | MEC |
| Check inlet and discharge dampers for freedom of movement, correct position, and visible damage. Confirm actuator linkage is secure and not bent or binding. | Every PM | MEC |
| Inspect fan wheel (impeller) through the access opening for blade buildup, erosion, cracks, or missing material. Any imbalance indication should be flagged immediately. | Every PM | MEC |
| Check expansion joints (flexible connectors at inlet/outlet) for tears, delamination, or deterioration. Replace if cracked or leaking. | Semi-Annually | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Inspect fan housing, inlet bell, discharge casing, and accessible ductwork for cracks, corrosion, erosion, or physical damage. Document and compare to prior inspection records. | Every PM | MEC |
| Inspect fan wheel (impeller) through access opening for blade erosion, material buildup, cracks, or missing sections. Any imbalance symptom (elevated vibration, unusual noise) should prompt immediate shutdown for inspection. | Every PM | MEC |
| Inspect inlet and outlet dampers for correct position, binding, wear, or damage. Verify actuator linkage is secure and pivots move freely through full travel. Confirm control signal matches actual damper position. | Every PM | MEC |
| Inspect flexible connectors (expansion joints) at fan inlet and outlet for tears, delamination, stiffening, or leakage. Replace if deteriorated. A leaking expansion joint is both an air loss and a safety concern. | Quarterly | MEC |
| Perform full internal fan inspection with unit de-energized and LOTO applied. Inspect impeller, shaft, wear liners, and housing interior for erosion, cracks, or corrosion beyond normal wear. Photograph findings for trending. | Annually | MEC |
| Inspect fan shaft seals (labyrinth seals, lip seals, or packing) for leakage, wear, or deterioration. Replace if leaking product gas, dust, or process air in unacceptable quantities. | Annually | MEC |
Operational Checks
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Verify fan rotation direction is correct at startup. Verify airflow is present at the discharge. A fan spinning backward will move significantly less air. | Every PM | ALL |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Verify fan rotation direction at startup. Confirm airflow at discharge and compare to baseline. Reversed rotation or reduced airflow may indicate electrical or mechanical fault. | Every PM | ALL |
| Measure and record fan motor current on all phases using a clamp meter. Compare to nameplate FLA and prior readings. Investigate any upward trend or imbalance exceeding 2% between phases. | Every PM | ELE |
Mechanical Inspection
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Inspect drive coupling or belt drive for wear, cracking, misalignment, or looseness. For belt drives: check tension and sheave condition. For couplings: check flexible elements. | Monthly | MEC |
| Inspect all accessible fasteners on the fan — housing bolts, access doors, bearing pillow blocks, and motor mounting. Tighten any that are loose. | Quarterly | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Inspect drive coupling or belt drive — for couplings: check flexible elements for cracking or wear, verify spider/insert condition; for belt drives: measure tension, check belt condition and sheave groove wear. Document findings. | Monthly | MEC |
| Clean fan inlet screen, trash guards, and accessible interior surfaces of the housing. Remove any buildup or debris that could cause imbalance or restrict airflow. | Monthly | MEC |
| Inspect and re-torque all mechanical fasteners — bearing pillow block bolts, housing fasteners, access door hardware, motor mount bolts, and fan base anchor bolts. Use calibrated torque wrench where spec is available. | Quarterly | MEC |
| Perform vibration check on fan bearing housings and motor using a vibration pen or data collector. Record overall velocity (in/s or mm/s). Investigate any reading exceeding 0.2 in/s (5.0 mm/s) RMS on fan or motor. | Quarterly | MEC |
| Check fan shaft alignment to driven equipment (motor or gearbox) using dial indicators, laser alignment tool, or straightedge as applicable. Record and correct misalignment exceeding manufacturer tolerance. Document final alignment readings. | Annually | MEC |
| Review trending data from this and prior PM cycles — current draw, bearing temps, vibration levels, grease consumption, and any defect history. Identify deteriorating trends and adjust PM scope or frequency as warranted. Document in CMMS. | Annually | MEC |
Bearing Condition Monitoring
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Check fan shaft and bearing housings for excessive heat using an IR thermometer or contact probe. Elevated temperature above ambient + 40°C warrants investigation. | Every PM | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Check and record bearing housing temperatures on drive-end and non-drive-end bearings using an IR gun or contact thermometer. Acceptable limit: ambient + 40°C or manufacturer spec. Flag and trend any increasing readings. | Every PM | MEC |
| Perform vibration check on fan bearing housings and motor using a vibration pen or data collector. Record overall velocity (in/s or mm/s). Investigate any reading exceeding 0.2 in/s (5.0 mm/s) RMS on fan or motor. | Quarterly | MEC |
Lubrication
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Lubricate fan shaft bearings per the lubrication schedule — correct grease type and quantity. Do not over-grease. Check grease fittings for blockage. | Quarterly | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Lubricate fan shaft bearings per the lubrication schedule — verify correct grease type, quantity, and method. For purge-type fittings, run fan briefly after greasing to purge excess. Record lubricant type and quantity. | Quarterly | MEC |
| Lubricate motor bearings per manufacturer specification — type, quantity, and interval. Do not mix grease types. Record lubricant used. Check motor nameplate or motor data sheet for correct spec. | Quarterly | MEC |
Electrical Inspection
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Check fan motor for unusual noise, vibration, or heat. Inspect motor ventilation openings and clean of dust or debris. | Every PM | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Inspect all electrical connections at the motor terminal box and drive panel — check for looseness, corrosion, heat discoloration, or damaged insulation. Re-torque to spec. Apply anti-oxidant to aluminum connections if applicable. | Semi-Annually | ELE |
| Perform insulation resistance (megger) test on fan motor windings to ground. Test at 500V DC (for 480V motors) or 1000V DC (for 600V+). Record in MΩ. Values below 1 MΩ require immediate investigation; trend over time. | Annually | ELE |
Failure Modes This Checklist Targets
Impeller erosion and imbalance. IDF fans pull abrasive particulate through the wheel on every rotation. Material loss is uneven. Uneven material loss means imbalance. Imbalance means vibration — and vibration at speed destroys bearings faster than almost anything else on the failure list.
Blade buildup and asymmetric loading. The same particle-laden gas stream that erodes blades also deposits material on them. Buildup is rarely uniform. A fan running with uneven deposits is running out of balance, even if the blades are structurally intact. Visual inspection through the access opening catches this before the vibration signature does.
Bearing failure from heat and contamination. IDF bearings run in environments with elevated ambient temperatures, process gas infiltration, and variable loading. Grease degrades faster. Contamination accelerates wear. Temperature trending is the only way to know which direction things are heading before a bearing seizes.
Drive coupling and belt deterioration. Thermal cycling, vibration, and the occasional shock load from damper operation or duct restriction events wear couplings and belts faster than comparable fan applications. A flexible element that looks fine on the outside may be cracking through the core.
Damper failure and airflow restriction. An IDF fan running against a partially closed or binding damper is working harder than it should — drawing more current, generating more heat, and loading the bearings. Damper position verification is not optional.
Motor winding degradation. Hot, dirty environments accelerate insulation aging. Current imbalance between phases is an early indicator. A megohmmeter test annually gives you a number to trend rather than a surprise to react to.
Related Checklists
PM tasks for fans with similar operating environments and failure profiles:
