TL;DR
Motor overload on a dry pump means mechanical resistance has increased. Check for solid polymer deposits inside the pump body before attempting a restart.
What you might see
- motor overload fault on pump controller
- current above nameplate full-load amps
- pump trips shortly after restart
- solid buildup visible at pump inlet
Likely causes
Solid polymer or crystalline deposits restricting rotor clearances
Liquid slug ingestion causing hydraulic lock
Rotor contact from thermal expansion due to cooling failure
Motor electrical fault, winding degradation or phase loss
Required tools
- Clamp ammeter
- Multimeter
- LOTO kit
- Manual rotation tool (if supplied with pump)
- Process inlet valve lockout
Safety first
- Pump inlet may contain process solvent or toxic gas at the time of fault. Lock out the process inlet valve and purge with nitrogen before opening the pump.
- Never force a locked rotor. Diagnose the cause first. Forced rotation can worsen internal damage.
- Cool the pump to ambient temperature before opening casings if a thermal event is suspected.
Procedure
- 1
Stop the pump. Lock out and tag out the drive and the process inlet valve.
- 2
Record the motor current at the time of fault from the control log.
- 3
Rotate the pump shaft by hand using the provided manual rotation port. Resistance or full lock indicates internal contact or solids.[1]
- 4
Inspect the pump inlet connection for visible solid or liquid accumulation.[1]
- 5
Check the cooling water supply flow and temperature for water-cooled pump models.
- 6
If internal solids are suspected, perform a thermal soak procedure per the general maintenance guide to soften deposits before attempting to turn the shaft.
Warning: Do not force the shaft if it will not turn by hand. Forced rotation can damage rotor contact surfaces permanently. - 7
Measure motor winding resistance on all three phases. Compare readings. Phase imbalance above 5% or resistance below 1 MO indicates a winding issue.
- 8
After clearing the mechanical resistance, restart and monitor current for the first 30 minutes.
Sources
Edwards (Atlas Copco) Edwards GXS / iH dry pumps Vacuum Pump (Industrial) general technical documentation, Edwards (Atlas Copco)
Edwards GXS / iH dry pump general rotor inspection and motor load procedures (general)
More guides for Edwards (Atlas Copco) Edwards GXS / iH dry pumps
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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.
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.
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