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VIEW PRODUCTSToo Wet, Poor Formation or Too Much Filler? 6 Upstream Causes Behind Paper Machine Web Breaks
Oct 01,2026
Repeated press-section web breaks are not always the result of a press roll, felt or mechanical setting.
Sometimes the press section is simply the place where an upstream weakness finally becomes visible.
A more complete diagnosis should therefore consider what happens to the stock and wet sheet before pressing begins.
1. Low Sheet Dryness
The sheet leaving the forming section must have sufficient dryness and wet strength for subsequent transfer.
If moisture remains excessively high, the wet sheet may not withstand the mechanical conditions of the press nip.
The problem is not limited to low dryness.
Unstable dryness can be equally disruptive because fluctuations in forming-section dewatering continuously change the strength and behavior of the incoming web.
2. Poor Sheet Formation
Fiber distribution should remain sufficiently uniform throughout the sheet.
Poor formation can produce local basis-weight variations and structurally weaker zones.
These weak areas may become the first locations to fail when the sheet is subjected to press dewatering and transfer forces.
3. Insufficient Wet-Web Strength
Before drying, the web depends heavily on the structure developed from the furnish and refining process.
Review the degree of refining / freeness and determine whether the wet web has enough strength to withstand transfer and pressing.
When the cause remains uncertain, wet-web strength can be evaluated before the sheet enters the press. 断纸排查1001 英文
4. Excessive Short Fiber in the Furnish
Fiber composition directly affects sheet structure.
If the proportion of short fibers becomes too high, fiber-to-fiber bonding may be negatively affected.
The resulting reduction in wet strength can make the sheet more sensitive to press-section stresses.
Therefore, any recent change in fiber source, furnish ratio or blending strategy deserves attention.
5. Excessive Filler Content
Fillers such as calcium carbonate (CaCO₃) and kaolin clay are commonly used in papermaking.
However, excessive filler content can reduce direct bonding between fibers.
As the sheet's mechanical strength decreases, its ability to withstand pressing and transfer may also decline.
Filler dosage should therefore be reviewed as part of the web-break investigation rather than treated only as a paper-quality parameter.
6. Stickies, Pitch and Stock Contamination
Contaminants create a different type of risk.
Stickies, pitch, dirt and other materials present in stock preparation or approach flow can deposit on machine surfaces.
Potential locations include:
Forming Fabrics + Press Felts + Rolls + Other Contact Surfaces
These localized deposits can cause uneven sheet adhesion and release.
Once sheet release becomes inconsistent across the machine width, the risk of tearing and web breaks can increase.
Look Upstream Before Making More Press Adjustments
When press-section equipment appears normal, repeated adjustment of the press may not address the actual problem.
Instead, evaluate the process as a chain:
Stock Properties
→ Fiber Bonding
→ Sheet Formation
→ Forming-Section Dewatering
→ Sheet Dryness
→ Wet-Web Strength
→ Press-Section Runnability
This approach helps connect what happens upstream with what operators eventually observe at the press.
A press-section web break may therefore be the final symptom of an upstream sheet or stock condition, rather than the original source of the problem.
Reduce Web Breaks and Improve Paper Machine Runnability
Since 2008, Huatao Group has focused on pulp and paper machinery, paper machine equipment and spare parts.
We provide equipment and solutions covering stock preparation, forming, pressing, dewatering, cleaning and doctoring, supporting applications related to dewatering efficiency, sheet transfer stability and paper machine runnability.
Huatao Group
Website: huataogroup.com
Email: team3@huataogroup.com
WhatsApp / WeChat: +86 19322109200
20 Tags
#PaperMachine #WebBreak #SheetBreak #PressSection #WetWebStrength #SheetFormation #SheetDryness #FiberFurnish #ShortFiber #PapermakingFiller #CalciumCarbonate #StockPreparation #ApproachFlow #Dewatering #PressFelt #PaperMachineRunnability #PulpAndPaper #PaperMill #Papermaking #HuataoGroup
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