Frequent web breaks are a common operational problem on paper machines. In the press section in particular, the cause is often related to several interacting process and equipment conditions rather than one isolated component.

A structured troubleshooting procedure should therefore progress from easily observable conditions toward more complex mechanical and process variables.

Operators should avoid changing several parameters simultaneously. Eliminating potential causes individually provides a clearer understanding of what is actually affecting web stability.

Press Felt Condition Should Be Checked First

The press felt or pickup felt is an important starting point.

Fillers, sizing chemicals, resin, stickies, fibers, fines and other papermaking deposits can gradually plug the felt structure.

As permeability and dewatering capacity decrease, water removal through the press nip can deteriorate. This can increase the possibility of sheet crushing, picking and unstable wet-web operation.

Felt age and mechanical condition should also be examined. Excessive wear, thinning, compaction and reduced resilience can affect void volume and water handling.

For seamed felts, confirm that the seam remains flat, properly closed, undamaged and stable during operation.

The cleaning system should be checked at the same time. Verify high-pressure shower operation, chemical cleaning performance, nozzle condition, water coverage and shower oscillation where applicable.

Include Dryer Fabric Condition in Overall Runnability Analysis

Although dryer fabrics operate downstream of the press section, their condition should be included when investigating overall paper machine runnability.

Inspect the dryer fabric for plugging, contamination, mechanical damage, uneven wear and unstable running.

Problems in downstream clothing can contribute to unstable sheet handling and web breaks elsewhere in the machine.

Verify Vacuum Conditions at Each Operating Position

Vacuum performance should be checked at the Suction Press Roll, Pickup Roll / Suction Pickup Roll, Vacuum Boxes and Uhle Boxes.

Excessive vacuum can increase the holding force acting on the sheet or felt and interfere with smooth transfer or release.

Insufficient vacuum can reduce dewatering and sheet support, leaving the wet sheet with excessive moisture and lower wet-web strength.

The objective is therefore to maintain the required vacuum for each machine position rather than simply maximizing vacuum.

Vacuum box wear surfaces should also be inspected for grooves, uneven wear and mechanical damage.

In addition, inspect vacuum piping, water-leg piping and drainage for blockages, leakage and poor drainage.

A vacuum pump can appear to operate normally while restrictions elsewhere in the system prevent stable vacuum at the machine position.

Examine Doctor Blade and Roll Surface Conditions

Doctor blades installed around press rolls, suction rolls and other relevant positions should be inspected carefully.

Important items include blade installation, holder operation, doctoring angle, loading uniformity, blade wear, movement and roll cleanliness.

When doctoring performance is inadequate, stock, fillers and stickies may accumulate on the roll surface.

Such deposits can interfere with sheet release and transfer and may eventually contribute to web breaks.

Doctoring performance should therefore be evaluated as:

Doctor Blade + Doctor Blade Holder + Blade Loading + Doctoring Angle + Roll Surface Condition

Use a Consistent Troubleshooting Sequence

A useful field sequence is:

Press Felt Condition → Felt Cleaning System → Vacuum Level → Suction/Pickup Roll → Vacuum Box and Piping → Doctor Blade and Holder → Roll Surface → Process and Machine Parameters

The purpose is to eliminate potential causes individually.

Changing several parameters simultaneously may temporarily restore operation, but it also makes the real cause difficult to identify.

A documented, step-by-step troubleshooting method makes future web-break analysis more efficient and repeatable.

More Web Break Troubleshooting

Press-section web breaks frequently involve multiple interacting factors.

The checks described here represent the first group of relatively direct inspections. Further troubleshooting can include additional process and equipment variables affecting wet-web stability and machine runnability.

Huatao Group – Paper Machine Equipment and Spare Parts

Since 2008, Huatao Group has been engaged in the production and export of pulp and paper machinery, paper machine clothing and spare parts.

Products include Press Felts, Pickup Felts, Dryer Fabrics, Spiral Dryer Fabrics, Forming Fabrics, Suction Press Rolls, Blind-Drilled Press Rolls, Jumbo Press Rolls, Pickup Rolls, Dewatering Elements, High-Vacuum Boxes, Low-Vacuum Boxes, Water-Leg Vacuum Boxes, Doctor Blades and Doctor Blade Holders.

Huatao Group
Website: www.huataolover.com
Email: service@huataogroup.com
WhatsApp / WeChat: +86 17778255675  

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