TL;DR
Smelt spout blockage stops flow and risks a dangerous water contact. Shut off wash water, clear the blockage mechanically, then restore wash water before resuming operation.
What you might see
- smelt flow reduced or stopped
- smelt spout glowing orange-red
- control room low-smelt-flow alarm
- smelt buildup visible at spout mouth
Likely causes
Solidified smelt bridging the spout opening during low-load operation
Reduced wash water flow allowing smelt to freeze at the spout tip
Scale or char accumulation narrowing the spout bore over time
Draft imbalance causing localized cooling at the spout
Required tools
- Long-handled smelt bar (1.5 m minimum)
- Full face shield rated for radiant heat
- Heat-resistant suit and leather gloves
- Two-way radio for control room communication
Safety first
- Smelt contacting water or wet surfaces causes explosive steam eruptions. Keep all water sources clear of the smelt flow path.
- Always approach smelt spouts from the side, never from directly in front of the spout opening.
- Confirm wash water is running before any personnel approach the smelt spout area.
Procedure
- 1
Notify the control room and confirm the boiler is in a stable low-load hold before approaching the smelt spout area.
Warning: Never approach smelt spouts without full face shield, heat-resistant suit, and leather gloves. Smelt contact with water causes explosive steam eruptions. - 2
Verify wash water flow to the smelt spout is running before approaching. If wash water is off, do not approach.
- 3
Using a long-handled smelt bar (minimum 1.5 m), probe the spout opening from the side, not directly in front, to locate the blockage.
- 4
Work the bar in a side-to-side motion to break the solidified smelt. Do not push straight in, which can dislodge a large plug suddenly.[1]
- 5
Once flow resumes, confirm smelt is running freely into the dissolving tank.
- 6
Increase wash water flow briefly to flush residual solids from the spout bore.
- 7
Inspect the spout for erosion or distortion after clearing. Schedule a spout replacement if wear is visible.[1]
Sources
ANDRITZ ANDRITZ HERB Recovery Boiler general technical documentation, ANDRITZ
Recovery boiler smelt spout maintenance and safety procedures, general industry practice (general)
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