TL;DR
A hot spot on the EAF shell means the refractory lining is thin or damaged at that point. Stop the heat if the shell temperature approaches the critical limit and apply gunning refractory during the next planned stop.
What you might see
- elevated temperature on the furnace shell infrared scan
- visible discoloration on the outer shell
- refractory inspection showing thin lining in that zone
- cooling water temperature rise in adjacent panels
Likely causes
Refractory lining worn thin from erosion by liquid steel and slag over the campaign
Arc hot spot in the dead zones of the furnace from incorrect electrode centering
Slag line erosion from fluctuating bath chemistry causing acidic or basic dissolution of the lining
Thermal shock cracks in the refractory from rapid temperature changes during charging
Required tools
- IR thermometer or thermal camera
- Refractory gunning machine and mix
- Radiant-heat PPE
- LOTO kit
Safety first
- Extreme thermal radiation inside the EAF even during a planned stop. Radiant-heat PPE is mandatory for any access to the furnace interior.
- Residual molten slag in the shell. Never step onto the furnace hearth without confirming it is fully solidified.
Procedure
- 1
Conduct a thermal scan of the furnace shell with an IR camera or handheld IR thermometer at the start of each shift.[1]
- 2
If a shell temperature above the defined alarm threshold is found, mark the zone and increase monitoring frequency.[1]
- 3
If the shell temperature approaches the critical limit, stop the heat and allow the furnace to cool before inspection.
- 4
During the planned maintenance stop, inspect the hot-spot zone internally using a visual inspection through the slag door or an access port.
- 5
Apply refractory gunning to repair the thin lining in the hot-spot zone. Match the gunning material to the original lining specification.
Warning: Thermal radiation inside the EAF during hot repair work. Use radiant-heat PPE and limit exposure time. - 6
After gunning repair, allow the refractory to sinter at low temperature before returning to full power.
Sources
Danieli Danieli Q-One / Digimelter Electric Arc Furnace (EAF) general technical documentation, Danieli
General EAF refractory monitoring and hot repair best practices (general)
More guides for Danieli Danieli Q-One / Digimelter
How to respond to electrode breakage on a Danieli Q-One / Digimelter EAF
An electrode break stops melting on one phase. Stop the heat, raise the electrodes to the retracted position, and recover the broken stub from the scrap charge before jointing and continuing.
How to detect and respond to water-cooled panel leaks on a Danieli Q-One / Digimelter EAF
Water entering a molten steel bath causes a violent steam explosion. If a panel leak is suspected, stop the heat immediately. Never continue melting with a confirmed water leak into the furnace.
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