TL;DR
Rising vibration with a bearing temperature increase means bearing wear. Log baseline readings, plan a bearing change at the next outage, and do not run past the high-temperature alarm.
What you might see
- elevated vibration at rotor speed
- noise from bearing housing
- bearing temperature rising
- motor current creeping upward
Likely causes
Lubrication breakdown in the timing gear or rotor shaft bearings
Rotor contact from contamination causing thermal expansion beyond clearances
Extended operation beyond the recommended bearing replacement interval
Solids or polymer deposits increasing drag on rotor clearances
Required tools
- Vibration meter
- IR thermometer
- LOTO kit
- Gearbox oil (correct grade for pump model)
- Replacement bearings per pump model
Safety first
- Dry pumps handling toxic or flammable process gases must be purged with nitrogen before opening. Confirm safe atmosphere before disassembly.
- Rotor shafts can retain solvent condensate. Wear chemical-resistant gloves and face protection when opening the pump casing.
- Lock out the pump and the nitrogen purge supply before opening the bearing housing.
Procedure
- 1
Record the pump vibration level and bearing temperature from the instrument display.
- 2
Lock out the pump. Remove the bearing housing access cover and inspect for grease leakage or discoloration.[1]
- 3
Check the oil level in the gearbox sight glass. Low oil accelerates bearing wear significantly.[1]
- 4
Inspect the nitrogen purge flow rate at the purge inlet. Low purge allows solids to migrate into the bearing area.
- 5
Connect a vibration meter to the bearing housing. Velocity above 4.5 mm/s indicates significant bearing degradation.
- 6
If temperature is within normal range but trending up over weeks, schedule bearing replacement at the next planned outage.
- 7
If bearing temperature exceeds the alarm setpoint or vibration exceeds 4.5 mm/s, stop the pump and replace bearings immediately.
Sources
Edwards (Atlas Copco) Edwards GXS / iH dry pumps Vacuum Pump (Industrial) general technical documentation, Edwards (Atlas Copco)
Edwards GXS / iH dry pump general maintenance and bearing inspection procedures (general)
More guides for Edwards (Atlas Copco) Edwards GXS / iH dry pumps
How to fix an exhaust restriction on an Edwards GXS / iH dry vacuum pump
Exhaust backpressure above the design limit forces the pump to work harder and reduces vacuum depth. Locate and remove the restriction in the exhaust train.
How to diagnose a motor overload fault on an Edwards GXS / iH dry vacuum pump
Motor overload on a dry pump means mechanical resistance has increased. Check for solid polymer deposits inside the pump body before attempting a restart.
Stop fixing the same fault twice.
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