TL;DR
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.
What you might see
- vibration alarm on the main drive gearbox
- periodic vibration at roll speed frequency
- spindle coupling grease thrown during operation
- strip surface showing a periodic thickness variation at roll pitch
Likely causes
Spindle coupling cross-pin or yoke wear creating backlash and impact loading
Coupling balance shifted from grease loss or uneven wear
Coupling operating angle above the design limit from incorrect roll or spindle alignment
Spindle liner worn causing radial clearance at the gear coupling
Required tools
- Spindle support stands rated for spindle weight
- Vibration meter
- Replacement coupling pins or gear coupling elements
- LOTO kit
Safety first
- Rolling mill spindles weigh several tonnes. Use rated support stands before any spindle coupling work.
- Lock out all main drives before disconnecting a spindle coupling. Unexpected rotation can cause severe injury.
Procedure
- 1
Stop the mill and lock out the main drives. Secure the spindles in a safe position before inspection.
Warning: Rolling mill spindles are extremely heavy. Use proper support stands before disconnecting any spindle coupling. - 2
Inspect the coupling cross-pins or crown gear teeth for wear, pitting, or fretting marks.[1]
- 3
Check the coupling grease. Grease thrown from the coupling indicates seal failure and dry running at the coupling teeth.[1]
- 4
Measure the coupling operating angle when the spindle is installed. The angle should be within the design specification for the coupling type.
- 5
If cross-pins are worn, replace the full pin set. Do not mix worn and new pins in the same coupling.
- 6
Regrease the coupling after any repair. Use the coupling manufacturer's recommended grease and filling procedure.
- 7
After reassembly, monitor vibration at the gearbox at the start of the next coil to confirm the vibration is resolved.
Sources
SMS group SMS X-Roll Hot / Cold Rolling Mill general technical documentation, SMS group
SMS group rolling mill spindle and coupling maintenance documentation (general)
More guides for SMS group SMS X-Roll
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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.
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