TL;DR
Lining wear beyond the minimum thickness is a breakout risk. Track the lining thickness every campaign and stop the furnace for relining when wear reaches the manufacturer's minimum allowed thickness.
What you might see
- lining thickness gauge approaching minimum
- coil temperature rising during melt
- lining wear rate faster than historical campaign average
- refractory cracks visible through the inspection port
Likely causes
Normal erosion of the refractory lining over successive heats
Slag chemistry attacking the lining material, accelerating erosion beyond normal rate
Lining not sintered correctly at the beginning of the campaign
Operating temperature above the lining design maximum
Required tools
- Calibrated lining thickness gauge
- Lining log for campaign tracking
- Refractory rammer or pouring form
Safety first
- A lining breakout releases molten metal at temperatures above 1500 degC. Never continue operating beyond the minimum lining thickness.
- Ensure the furnace pit area is clear of water or moisture before any melt. Water contact with molten metal causes a violent steam explosion.
Procedure
- 1
Measure the lining thickness at the crucible bottom, mid-wall, and top using a calibrated lining gauge at the end of each campaign heat target.[1]
- 2
Record all measurements in the lining log and compare to the minimum allowable thickness from the furnace documentation.[1]
- 3
If any measurement is at or below the minimum, stop the furnace for relining. Do not continue the campaign.
- 4
Inspect the lining surface for cracks, erosion channels, or hot spots after the furnace is cooled and the charge removed.
- 5
During a planned stop, pour or ram a new lining using the specified refractory material and sinter it per the furnace manufacturer's sinter schedule.
- 6
After relining, confirm the coil temperature is back within the normal range during the first heat before increasing to full power.
Sources
Inductotherm (Inductotherm Group) Inductotherm VIP-I / Power-Trak Induction Melting Furnace general technical documentation, Inductotherm (Inductotherm Group)
General induction furnace refractory lining monitoring and campaign management procedures (general)
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