TL;DR
Grinding from the airend signals bearing wear. Check mounting bolt torque first (easy fix), then run a bearing inspection if noise persists.
What you might see
- grinding or rumbling from the airend
- knocking noise varying with speed
- rattling from the enclosure panels
- vibration felt through the floor
Likely causes
Airend bearing wear, typical after 16,000+ operating hours or oil starvation
Loose mounting bolts allowing the compressor to vibrate on its base frame
Anti-vibration mounts degraded or missing, transmitting mechanical noise to the structure
VFD-induced resonance at certain operating speeds causing structural panels to rattle
Required tools
- Torque wrench and socket set
- Elektronikon controller access (operating hours)
- IR stethoscope or vibration meter
- LOTO kit
- Replacement anti-vibration mounts (if needed)
Safety first
- Lock out before touching any fasteners while the compressor is running. Rotating components are present inside the enclosure.
- Depressurize fully before opening the oil drain to inspect for metal particles.
Procedure
- 1
Listen carefully to locate the noise source. Airend noise is from the front of the unit; panel rattles are from the enclosure. This distinction determines the next steps.
- 2
Lock out the compressor. Torque-check all base mounting bolts and enclosure panel fasteners.[1]
- 3
Inspect the anti-vibration mounts under the base frame. Cracked or collapsed mounts need replacement.
- 4
Check the operating hours on the Elektronikon controller. If above 16,000 hours since last service, bearing replacement is due.[1]
- 5
If the noise correlates with a specific VSD output frequency, identify that frequency and program a skip frequency band in the Elektronikon to avoid sustained operation at that speed.
- 6
If bearing noise is confirmed and the compressor is under 16,000 hours, drain the oil and inspect for metal particles with a magnetic drain plug.
- 7
Metal particles in the oil confirm bearing failure. Schedule an airend overhaul or replacement.
Sources
Atlas Copco GA VSD+ Air Compressor User Manual, Atlas Copco
Atlas Copco GA VSD+ IOM, bearing service intervals and noise diagnostic procedures (general)
View source
More guides for Atlas Copco GA VSD+
How to find and fix air leaks on an Atlas Copco GA VSD+ compressor installation
Walk the system with a sonic leak detector at every joint, fitting, and drain. Prioritize leaks by flow rate. A 3 mm orifice leak at 7 bar wastes roughly 60 SCFM continuously.
How to fix overheating on an Atlas Copco GA VSD+ air compressor
Overheating almost always means a blocked intercooler or aftercooler. Clean both coolers and verify the thermostatic bypass valve opens at the correct temperature.
How to fix excessive vibration on an Atlas Copco GA VSD+ air compressor
Excessive vibration is most often loose foundation bolts or collapsed anti-vibration mounts. Torque the foundation bolts first, then check the mounts before suspecting the airend.
How to fix low pressure output on an Atlas Copco GA VSD+ air compressor
Low pressure output is most often worn inlet valve plates allowing blow-by. Check separator delta-P first, then do a compression efficiency test.
Related learning guides
Electrical Fault Finding
Step-by-step electrical fault diagnosis for plant technicians.
Read guideVibration Analysis Basics
What your equipment is telling you before it fails.
Read guideBearing Replacement: When, Why, and How
The right-way guide to bearing replacement — and the warning signs you should never skip.
Read guideStop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.