TL;DR
A seized strand guide roll marks the billet surface and concentrates strand guide load on adjacent rolls. Replace failed rolls during the next planned stop and verify all rolls rotate freely after installation.
What you might see
- strand guide roll not rotating under load
- surface marking on the billet from a stationary roll
- roll bearing temperature above alarm threshold
- vibration spike in the strand guide section
Likely causes
Bearing contamination from secondary cooling water ingress past a degraded seal
Insufficient bearing grease interval in the secondary cooling environment
Bearing overloaded from incorrect roll gap setting reducing clearance excessively
Bearing fatigue from long service campaign without replacement
Required tools
- Roll rotation monitoring system or manual check tool
- Replacement strand guide rolls
- Roll gap measurement gauge
- LOTO kit
Safety first
- Residual hot strand in the guide retains extreme heat. Allow adequate cooling and use full PPE before working in the guide.
- Lock out all strand guide drive rolls before any manual roll access.
Procedure
- 1
Monitor strand guide roll rotation using the online roll rotation monitoring system if fitted. Flag any roll with zero or reduced rotation.[1]
- 2
During the next scheduled caster stop, stop the strand guide drives and lock out.
- 3
Manually rotate each roll in the suspect section. A seized roll will not rotate or will rotate with significant resistance.[1]
- 4
Replace seized rolls with spare units. Check the roll gap setting on adjacent rolls to confirm no misalignment is loading the new roll excessively.
- 5
Grease the new roll bearings to the specified interval before restarting.
- 6
After the caster restarts, inspect the next billet surface for roll marking. Clean roll rotation should eliminate surface marks.
Sources
SMS Concast SMS Concast CONROLL Continuous Caster general technical documentation, SMS Concast
General continuous casting strand guide roll maintenance and bearing inspection procedures (general)
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