TL;DR
A leaking pump seal shows as drips at the pump housing or a rising seal flush water flow. Isolate the pump, confirm the leak source, and replace the mechanical seal at the next outage or immediately if leaking is severe.
What you might see
- visible drips or spray at pump housing seal area
- rising seal flush water consumption
- white liquor or black liquor staining on pump pedestal
- increasing pump vibration
Likely causes
Mechanical seal face wear after extended service hours
Cavitation in the pump causing vibration damage to seal faces
Chemical attack on seal elastomers from high pH cooking liquor
Misalignment between pump and motor causing radial loading on the seal
Required tools
- Vibration meter
- Seal flush flow meter reading
- Full face shield and chemical-resistant gloves
- LOTO kit
- Replacement mechanical seal (cooking-liquor grade)
Safety first
- Cooking liquor is caustic and hot. Full face shield, chemical-resistant gloves, and splash suit are required when working near pump leaks.
- Lock out the pump motor before removing the back plate or touching the seal area.
Procedure
- 1
Observe the seal area from a safe distance. Note whether the leak is a steady drip or intermittent spray.
- 2
Check the seal flush water flow meter. A rise above the normal baseline confirms seal face wear.[1]
- 3
Measure pump vibration at the bearing housings. Vibration above 0.3 in/s suggests cavitation or misalignment contributing to seal wear.
- 4
If the leak is a steady drip or spray, switch to the standby circulation pump and isolate the leaking pump.
Warning: Cooking liquor is hot and caustic. Use full face shield, chemical-resistant gloves, and splash suit when isolating a leaking pump. - 5
Lock out the pump motor and drain the pump casing per the site SOP before starting seal inspection.
- 6
Remove the pump back plate and inspect the mechanical seal faces for scoring, cracking, or chemical degradation.[1]
- 7
Replace the mechanical seal with the correct grade for cooking liquor service. Verify elastomer and face material compatibility before installation.
Sources
Valmet Valmet KvaerComp / G2 Continuous Digester general technical documentation, Valmet
Centrifugal pump mechanical seal inspection and replacement, general industrial pump maintenance practice (general)
More guides for Valmet Valmet KvaerComp / G2
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Chip packing stalls the digester and causes uneven cooking. Reduce chip meter speed, increase steam to the chip chute, and confirm level sensors are reading correctly before resuming feed.
How to diagnose screen plate plugging on a Valmet KvaerComp G2 Continuous Digester
Plugged extraction screens reduce liquor withdrawal and cause cooking upsets. Confirm by pressure differential rise across the screen zone, then schedule a backflush or offline cleaning.
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