TL;DR
Plate gap vibration causes pulp quality variation and accelerates plate wear. Increase the gap slightly, check plate alignment, and verify the thrust bearing is in good condition.
What you might see
- audible grinding or chattering from the refiner
- motor current fluctuating in a rhythmic pattern
- elevated vibration at the refiner bearing housings
- inconsistent freeness at the refiner outlet
Likely causes
Plate-to-plate contact from gap set too close for the current consistency
Worn refiner plates with bar edges degraded and creating uneven contact
Thrust bearing wear allowing axial play that closes the gap intermittently
Pulp consistency too low reducing the fiber cushion between plates
Required tools
- DCS operator station access
- IR thermometer
- Dial indicator with magnetic base (for outage bearing check)
- LOTO kit
Safety first
- Refiners contain pressurized pulp at elevated temperature. Never open the plate housing without full LOTO and depressurization.
- Vibrating refiners can shift axially. Keep hands and tools away from the shaft area during operation.
Procedure
- 1
Open the plate gap by 0.1 mm increments from the control station until vibration subsides. Record the gap setting at which vibration stops.
- 2
Check motor current on the DCS. Stable current after gap increase confirms plate contact was the source.[1]
- 3
Measure thrust bearing temperature at the bearing housing with an IR thermometer. Temperature above 80 deg C indicates bearing wear.
- 4
Review the plate wear log. If plates are beyond the manufacturer's recommended minimum bar height, schedule a plate replacement.[1]
- 5
Verify consistency at the refiner inlet against the grade recipe. Low consistency reduces fiber cushioning and increases metal contact risk.
- 6
During the next planned outage, inspect the thrust bearing for axial play by measuring shaft endplay with a dial indicator.
- 7
Replace plates or bearings as indicated by inspection findings before returning to the target gap setting.
Sources
Valmet Valmet OptiFiner Pro Refiner / Pulper general technical documentation, Valmet
Disk refiner plate gap adjustment and vibration control, general pulp refining practice (general)
More guides for Valmet Valmet OptiFiner Pro
How to diagnose rotor imbalance on a Valmet OptiFiner Pro Pulper
Rotor imbalance shows as elevated bearing vibration at running speed. Inspect the rotor for debris or broken segments, clean, and re-balance if needed.
How to assess refiner plate wear on a Valmet OptiFiner Pro
Worn refiner plates reduce refining intensity and increase specific energy consumption. Measure bar height with a depth gauge and replace when below the minimum height in the plate specification.
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