TL;DR
Web breaks on the winder are usually caused by edge cracks, incorrect tension, or reel defects carried from the paper machine. Check the tension profile and inspect incoming reel edges before each set.
What you might see
- web breaks at winder unwind or rewind
- edge tears visible before the break
- tension variation on the winder tension meters
- wrinkles forming ahead of the break point
Likely causes
Edge cracks in the incoming reel propagating under winder tension
Tension set point too high for the paper grade or basis weight
Winder alignment out of specification causing cross-web tension variation
Reel defects from the paper machine, caliper variation, or moisture streaks, creating weak zones
Required tools
- Tension meter or winder tension display
- Tape measure for break CD position measurement
- Alignment tools (straightedge, laser level)
Safety first
- Running nips on winders are severe pinch-point hazards. Never reach into a moving nip under any circumstance.
- Broken web tails flap at high speed and can cause lacerations. Stand clear when re-threading after a break.
Procedure
- 1
Record the break location on the web width and note whether breaks repeat at the same CD position. Consistent CD location points to a reel defect or alignment issue.[1]
- 2
Inspect the incoming reel edges for visible cracks or damage before threading the next set.
- 3
Verify the tension profile settings against the grade recipe. Confirm entry tension, draw, and nip load are within the approved range for the current grade.[1]
- 4
Check winder alignment. Verify the unwind and rewind spool axes are parallel within the tolerance specified in the winder maintenance manual.
- 5
Inspect winder rolls and rider roll surface for contamination or damage that could create a localized tension spike.
- 6
If breaks are concentrated at reel ends, check the pope reel winding parameters on the paper machine for the last few reels.
- 7
Log all break locations with time stamp and grade for trend analysis. Three or more breaks with the same CD location warrant a machine alignment check.
Sources
Valmet Valmet OptiCalender / OptiWin Calender / Winder general technical documentation, Valmet
Winder web break analysis and tension control, general paper machine winding practice (general)
More guides for Valmet Valmet OptiCalender / OptiWin
How to inspect and respond to hot roll surface damage on a Valmet OptiCalender
Surface damage on a hot calender roll shows as streaks or embossing in the paper. Stop the nip, reduce roll temperature, and inspect visually. Grinding is required for anything beyond minor marking.
How to diagnose roll nip vibration on a Valmet OptiCalender
Nip vibration produces CD caliper bands and audible chatter. Check roll surface condition and nip load first, then measure roll roundness with a profilometer at the next outage.
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