⚠️ 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.
A lobe blower has two moving parts and no internal lubrication in the airstream. It looks simple. It isn't. The lobes rotate in close proximity to each other and to the casing — measured in thousandths of an inch. Contaminated inlet air, restricted backpressure, a worn shaft seal, or a gear oil level that drops two inches below the sight glass will turn that clearance into contact. Contact means metal. Metal means failure. And lobe blower failures don't signal loudly before they go.
This checklist covers lobe blowers used in industrial applications — conveying, aeration, pneumatic conveying, and vacuum service. It applies to belt-driven and direct-coupled units. Field technicians use the Field Checklist to execute PMs efficiently. Maintenance managers use the Reference Checklist to build, audit, or expand a program.
Start with the full picture of what lobe blowers demand from a PM program: Industrial fan and blower preventive maintenance and where PM programs miss the failures that matter
How to Use This Checklist
Record what you find, not what you assume. "Checked — OK" is not a finding. "Gear oil at full mark, no metal particulate visible in drain plug area, seal showing light weep at drive end — within tolerance, will monitor" is a finding. One tells you nothing in twelve months. The other starts a trend.
Compare every reading against baseline. Lobe blowers that have been in service develop a signature — pressure, temperature, sound, and vibration that defines normal for that unit in that application. A discharge pressure reading three PSI above baseline is not a curiosity. It is a conversation.
If the inlet filter hasn't been touched in three months and discharge pressure is trending up, that's your answer before you spend any time diagnosing the blower itself.
Field Checklist — Critical Tasks
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect blower inlet and discharge connections for air or oil leaks. Note any wetness, staining, or odor at flanges and fittings. | Every PM | MEC |
| Inspect inlet filter or strainer for loading, damage, or bypass. Clean or replace per site schedule. A restricted inlet causes overheating and reduced output. | Monthly | MEC |
| Inspect blower shaft seals for oil weeping or leakage. Light film is normal on some designs; active dripping or pooling indicates seal replacement is needed. | Monthly | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Check blower body and housing for unusual heat. Surface temperature should not be hot to the touch within the normal operating range for the unit. | Every PM | MEC |
| Listen for abnormal sounds during operation — knocking, grinding, squealing, or rhythmic thumping. Note any change from baseline noise levels. | Every PM | MEC |
| Verify blower relief valve is operational — confirm it is not stuck open or bypassing. A failed-open relief valve causes pressure loss and overheating. | Quarterly | MEC |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Check drive belt condition and tension (belt-driven units). Inspect for fraying, glazing, or cracking. Verify sheave alignment is within 1/8" per foot of span. | Monthly | MEC |
| Inspect coupling or direct drive connection for looseness, wear, or misalignment. Tighten hardware to spec; replace worn elastomeric elements. | Semi-Annually | MEC |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Check gear oil level in gearbox sight glass or dipstick (if equipped). Oil should be at the full mark. Add correct grade if low — do not overfill. | Monthly | MEC |
| Change gear oil per manufacturer interval or site schedule. Drain fully, flush if contaminated, and refill with the correct grade and quantity. | Semi-Annually | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect all electrical connections at motor terminals and control panel for tightness, corrosion, or heat discoloration. | Annually | ELE |
Reference Checklist — Full Task Library
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect blower exterior for air or oil leaks at inlet, discharge, shaft seals, and all flanged connections. Mark any active leaks for follow-up. | Every PM | MEC |
| Inspect and service the blower inlet filter or strainer. Measure differential pressure across filter if instrumented — replace at manufacturer threshold or when flow restriction is evident. | Monthly | MEC |
| Inspect blower shaft seals (both drive-end and non-drive-end) for oil leakage. Active dripping indicates seal failure — schedule replacement. Document seal condition in equipment history. | Monthly | MEC |
| Inspect inlet and discharge piping for cracks, corrosion, unsupported spans, or thermal stress. Verify piping is not loading the blower flanges — pipe strain causes casing distortion and lobe contact. | Semi-Annually | MEC |
| Remove blower inspection cover (if accessible) and inspect lobe clearances, lobe surfaces, and interior of casing for contact marks, scoring, or buildup. Any metal-to-metal contact evidence requires immediate removal from service. | Annually | MEC |
| Review equipment history for recurring faults, bearing replacements, seal failures, and oil consumption trends. Identify patterns that indicate underlying issues — escalate to reliability if no root cause has been addressed. | Annually | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Monitor blower operating temperature using an IR thermometer or thermocouple. Compare against baseline. Elevated temperature may indicate restricted inlet, excessive backpressure, or bearing wear. | Every PM | MEC |
| Listen and note any abnormal sounds during operation — knocking, grinding, squealing, or thumping. Document and compare to baseline audio or vibration data if available. | Every PM | MEC |
| Verify operating pressure at the discharge gauge is within the rated working range for the application. Excessive pressure causes overheating and can damage lobes. | Every PM | MEC |
| Verify relief valve set point and operation. Manually test valve operation if design allows — confirm it opens at rated pressure and reseats fully. A failed-open valve bypasses flow and masks pressure problems. | Quarterly | MEC |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Check belt drive condition and tension (belt-driven units). Measure tension with a belt tension gauge; compare to nameplate or engineering spec. Check sheave alignment with a straightedge or laser tool. | Monthly | MEC |
| Check direct drive coupling for wear, cracking, or looseness of elastomeric insert. Verify coupling hub set screws are torqued to spec. Replace worn spider elements before they fail. | Monthly | MEC |
| Take hand-held vibration measurements at drive-end and non-drive-end bearing housings (horizontal, vertical, and axial planes). Compare to ISO 10816 limits or established baseline. Increasing trend warrants bearing inspection. | Quarterly | MEC |
| Inspect all mounting fasteners — base bolts, inlet/discharge flanges, and motor mount hardware. Torque to spec. Loose mounts contribute to vibration and misalignment. | Quarterly | MEC |
| Verify blower-to-motor alignment using dial indicator or laser alignment tool. Correct angular and parallel misalignment to within 0.002" TIR or manufacturer spec. Misalignment accelerates bearing and seal wear. | Semi-Annually | MEC |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Check gear oil level at sight glass or dipstick. Record current level. If low, identify source of loss before adding oil. Use only the manufacturer-specified grade and viscosity. | Monthly | MEC |
| Take oil sample from gearbox for analysis (if oil analysis program is active). Submit for particle count, viscosity, and metal content. Results guide oil change interval and bearing/gear condition. | Quarterly | MEC |
| Perform gear oil change. Drain fully while warm for maximum contaminant removal. Inspect drained oil for metal particles, water, or milky appearance. Refill to correct level with specified lubricant grade. | Semi-Annually | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Measure motor running current on all phases with a clamp meter. Compare to nameplate FLA. Imbalance greater than 5% between phases or current consistently above 90% of FLA warrants investigation. | Semi-Annually | ELE |
| Inspect all motor and control wiring for condition — insulation, routing, and connection tightness. Confirm terminal block torque and check for heat discoloration at terminations. | Annually | ELE |
| Perform motor insulation resistance test (megger) at 500V DC. Record PI or DA results and compare to previous readings. Declining trend or reading below 1 MΩ requires investigation before returning to service. | Annually | ELE |
Failure Modes This Checklist Targets
Lobe Contact and Casing Damage The lobes maintain their clearance by design. That design depends on clean inlet air, correct backpressure, and gear oil that keeps timing intact. When any of those conditions drift, the clearance goes with them — and the first sign is often a sound that should have been documented three PMs ago.
Gear Oil Failure The timing gears synchronize the lobes and carry the load. No oil film means metal on metal inside the gearbox. Gear oil doesn't announce its own degradation — oil analysis and change intervals are the only way to stay ahead of it.
Bearing Wear Lobe blower bearings carry radial and axial loads across a wide RPM range. A worn bearing changes lobe position. A changed lobe position changes clearance. Vibration trending catches bearing wear before it becomes a lobe clearance problem.
Inlet Restriction A loaded inlet filter chokes the blower. The unit runs hotter, works harder against the same discharge pressure, and degrades faster. It is also the most fixable problem on this checklist — and the one most often ignored between major PMs.
Shaft Seal Leakage Seal failure on a lobe blower moves oil into the airstream or lets process air contaminate the gearbox. Either one is a secondary failure waiting to happen. Documenting seal condition at every PM creates the trend that tells you when "light weep" becomes "scheduled replacement."
Drive Misalignment and Belt Wear Belt drives are forgiving up to a point. Past that point, misalignment degrades belt life, loads the bearings, and puts the blower shaft in a position it was not designed to operate in. A laser alignment and a tension gauge take fifteen minutes. A failed shaft takes weeks.
