New or changing noises from a rotary screw compressor are always worth investigating. The airend, motor, belts, and coupling all have wear components that announce failure before it happens—if you're listening.
Grinding or rumbling usually points to bearing wear. Squealing often means belt slip or tension issues. Knocking can indicate coupling problems or internal damage. Catching these early prevents catastrophic failures and expensive repairs.
Rotary Screw Troubleshooting
Unusual Noise – Rotary Screw Air Compressor Troubleshooting
Abnormal sounds like grinding, knocking, squealing, or rattling during operation—typically indicating bearing wear, mechanical damage, belt issues, or alignment problems.
Industrial systems
Field-tested diagnostics
Independent & unbiased
Safety Notice
Lock out/tag out before inspecting rotating components, belts, or couplings. Let the compressor cool before touching bearings or oil system components. Never remove guards while the compressor is running.
What this problem usually means
Check these first
5–10 minute checks before diving deeper
- Identify the noise type—grinding, knocking, squealing, rattling, or hissing?
- When does it occur—startup only, running loaded, during unload transition, or constant?
- Bearing temperature—use infrared or careful touch to compare motor vs. airend bearings
- Belt condition and tension if belt-driven—cracks, glazing, proper deflection?
- Coupling alignment and condition—rubber element wear, set screws tight?
- Loose bolts, panels, guards, or piping that could vibrate
- Isolate motor noise from airend noise—disconnect belt/coupling if safe to test motor alone
- Oil level and condition—low oil or contamination can cause airend noise
Common root causes
Why this happens in rotary screw compressors
Worn airend bearings
Grinding or rumbling from the airend that progressively worsens. Often accompanied by rising discharge temperature. Requires airend rebuild or replacement.
Belt problems
Squealing on startup, during load changes, or constantly. Caused by worn belts, incorrect tension, or misaligned sheaves. Check for glazing and cracks.
Coupling misalignment or wear
Knocking or vibration at the connection point between motor and airend. Rubber coupling elements wear out and allow movement. Check alignment with straightedge.
Motor bearing failure
High-pitched whine or growl from the motor. Isolate by disconnecting the drive—if noise continues, it's the motor. Often detectable by comparing bearing temperatures.
Loose components or resonance
Rattling from guards, panels, piping, or mounting bolts. Sometimes caused by operating at a speed that creates resonance. Check all fasteners and mounts.
What NOT to do
Don't ignore new noises or assume they'll go away on their own. Don't continue running a compressor with obvious bearing noise—damage escalates quickly and can destroy the airend. Don't replace parts without first identifying the noise source.
Full Rotary Screw Troubleshooting Manual
Step-by-step diagnostics, root cause logic, and practical fixes for oil-injected rotary screw compressors. Save time and reduce downtime with proven methods.
- Step-by-step diagnostics for common failures
- Root cause analysis techniques
- Practical fixes with parts notes
- Works across all major brands