TL;DR
Rotor imbalance shows as elevated bearing vibration at running speed. Inspect the rotor for debris or broken segments, clean, and re-balance if needed.
What you might see
- high vibration at 1x rotor speed at bearing housings
- visible shaft wobble at low speed
- bearing temperature rising
- noise increasing under load
Likely causes
Fibrous debris or rags wrapped asymmetrically around the rotor
Broken or missing rotor wing/vane segment
Uneven wear on rotor vane surfaces
Material buildup on one side of the rotor from sticky furnish
Required tools
- Vibration meter (with frequency analysis)
- LOTO kit
- Cut-resistant gloves
- Tongs or hook for debris removal
- Replacement rotor vane segments (if available)
Safety first
- Pulper chests contain sharp contaminants. Use cut-resistant gloves and tongs when working inside the chest.
- Lock out and verify zero rotation before entering the pulper chest or touching the rotor.
Procedure
- 1
Measure vibration velocity at both bearing housings with a vibration meter. Record dominant frequency and amplitude.[1]
- 2
Confirm that the dominant vibration frequency matches rotor rotational speed. 1x speed vibration is the signature of unbalance.
- 3
Perform LOTO on the pulper drive. Drain the pulper chest to access the rotor.
- 4
Inspect the rotor for wrapped rags, wire, or other debris. Remove any wrapping with appropriate tools.
Warning: Pulper chests may contain sharp contaminants (wire, staples, baling straps). Use cut-resistant gloves and tongs, not bare hands, when clearing debris from the rotor. - 5
Inspect each rotor vane for breakage, cracks, or missing material. Replace any damaged vane segment.
- 6
Clean all vane surfaces of buildup and re-check for uniform surface condition.
- 7
If vibration persists after cleaning and vane inspection, schedule an in-situ dynamic balance measurement with a vibration analyzer.[1]
Sources
Valmet Valmet OptiFiner Pro Refiner / Pulper general technical documentation, Valmet
Pulper rotor inspection and vibration diagnosis, general rotating equipment maintenance practice (general)
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