TL;DR
Chock bearing overheating on a rolling mill is usually caused by low oil film bearing pressure or flow restriction. Check the oil supply pressure at the chock inlets and pull an oil sample before changing out the roll.
What you might see
- chock bearing temperature alarm active
- roll cooling water return temperature high
- bearing oil supply pressure below setpoint
- strip surface showing periodic roll marks
Likely causes
Oil film bearing supply pressure below the required value for the rolling load
Bearing oil filter blocked reducing supply flow
Oil contaminated with mill scale or cooling water reducing film strength
Roll chock seal worn allowing cooling water ingress into the bearing
Required tools
- Calibrated oil pressure gauge
- Oil sample kit
- LOTO kit
- Bearing bore measurement gauge
Safety first
- Hot rolling mills involve high-temperature strip and high-pressure hydraulic systems. Use appropriate PPE for hot metal work.
- Lock out roll drive and hydraulic systems before chock removal.
Procedure
- 1
Read the bearing supply oil pressure at the chock inlets from the mill monitoring system. Compare to the design value for the current rolling load.[1]
- 2
Check the oil filter differential pressure. Replace the filter if the differential exceeds the maximum.[1]
- 3
Pull an oil sample from the bearing supply line and analyze for water content and particle count.
- 4
If water contamination is confirmed, inspect the chock seals for wear or damage.
- 5
Reduce the rolling load or speed if the bearing temperature continues rising above the alarm setpoint.
- 6
If bearing temperature reaches the trip setpoint, stop the mill and roll change the hot stand.
- 7
Inspect the removed chock and bearing for damage and measure the bearing bore for wear before returning to service.
Sources
SMS group SMS X-Roll Hot / Cold Rolling Mill general technical documentation, SMS group
SMS group rolling mill oil film bearing and chock maintenance documentation (general)
More guides for SMS group SMS X-Roll
How to diagnose roll gap control deviation on a SMS X-Roll rolling mill
Strip thickness deviation despite AGC means the hydraulic capsule position sensor is drifting or the capsule is leaking. Verify sensor calibration and capsule pressure before blaming the rolling schedule.
How to diagnose spindle coupling vibration on a SMS X-Roll rolling mill
Spindle vibration at roll speed frequency is usually worn coupling cross-pins or unequal coupling balance from worn elements. Inspect the coupling teeth or cross-pins during the next roll change stop.
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