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
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