TL;DR
A hot spot on the kiln shell means the refractory lining has cracked. Schedule a refractory repair at the next planned stop before the crack propagates and threatens the shell.
What you might see
- kiln shell hot spot detected on external scan
- heat loss in one zone higher than design value
- refractory crack visible through inspection window
- draft (air ingress) felt at a kiln seam or joint
Likely causes
Thermal cycling over many heating and cooling campaigns fatiguing the refractory
Rapid kiln startup causing thermal shock in the refractory
Kiln shell flexion from an uneven support frame causing the refractory to crack
Refractory anchor failure allowing the lining to detach from the shell
Required tools
- IR thermometer or thermal camera
- Confined-space entry equipment (gas monitor, harness)
- Refractory gunning machine or mortar
- LOTO kit
Safety first
- Confined-space entry into the kiln requires a formal permit, CO and O2 monitoring, and a rescue standby.
- Residual CO in the kiln after a shutdown. Full atmospheric testing before entry.
- Thermal radiation from residual kiln heat. Verify the kiln is below the safe entry temperature before any person enters.
Procedure
- 1
During operation, scan the kiln shell with an IR camera or IR thermometer. Mark any zone above 60 degC on the shell exterior.[1]
- 2
Correlate hot spots to the refractory sections inside the kiln by position and zone number.[1]
- 3
During a planned shutdown, allow the kiln to cool fully before entering for inspection.
- 4
Inspect the identified refractory zones for cracks, delamination, or anchor failure.
Warning: Confined-space entry into the kiln requires a permit, atmospheric testing, and a rescue standby. The kiln interior can contain CO after shutdown. - 5
Repair cracks with refractory gunning or mortar appropriate for the kiln temperature zone. Follow the refractory supplier's application guidelines.
- 6
After repair, heat the kiln up at the approved ramp rate. Do not rush the heat-up, as rapid heating cracks new refractory.
Sources
Sacmi Sacmi FMS / FMA Roller Kiln (Ceramics) general technical documentation, Sacmi
Sacmi roller kiln refractory inspection and repair maintenance documentation (general)
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