Why Does Your Paper Machine Keep Breaking the Sheet? Start with These 4 Critical Systems

When repeated sheet breaks occur around the press section, replacing one component or immediately changing machine settings may not solve the underlying problem.

Press-section web stability can involve several connected systems, including the press felt, vacuum equipment, press rolls, doctoring system, sheet moisture and operating conditions.

Troubleshooting should therefore begin with visible, easily inspected items before progressing toward more complex process and mechanical factors.

1.Press Felt: Look Beyond Surface Appearance

A felt may appear mechanically intact while its internal structure has become loaded with fillers, sizing chemicals, resin, stickies, fibers and fines.

As contamination increases, permeability and dewatering performance may decrease.

The wet sheet can then become more difficult to handle through the press nip.

Inspect the felt for wear, thinning, compaction and reduced resilience. For seamed felts, examine the seam for raised areas, damage or poor closure.

The cleaning system is equally important. High-pressure shower pressure, nozzle condition, water coverage, oscillation and chemical cleaning performance should all be verified.

2.Vacuum: Correct Level Matters More Than Maximum Level

Vacuum should be evaluated according to the requirements of each operating position.

Excessive vacuum may increase holding force and interfere with sheet transfer or release.

Insufficient vacuum may reduce water removal and wet-web support.

Inspection should include the Suction Press Roll, Suction Pickup Roll, Vacuum Boxes, Uhle Boxes and associated vacuum piping.

Vacuum box covers should be checked for excessive wear, grooves, uneven surfaces and mechanical damage.

Water-leg piping and drainage should also be examined for leakage, restrictions and unstable flow.

3.Doctoring: Roll Cleanliness Can Affect Sheet Transfer

A doctor blade that does not maintain effective contact with the roll may allow stock, fillers or stickies to accumulate.

Inspect blade installation, doctor holder movement, doctoring angle, loading distribution and working-edge wear.

The roll surface should remain clean and stable.

Rather than evaluating only the blade, inspect the complete doctoring arrangement:

Blade + Holder + Loading + Angle + Roll Surface

4.Don't Forget Downstream Clothing

Dryer fabrics should also be checked during a broader web-break investigation.

Plugging, contamination, damage and uneven wear can affect downstream sheet handling and overall machine runnability.

5.Troubleshoot One Variable at a Time

A structured inspection sequence can begin with:

Press Felt → Felt Cleaning → Vacuum → Suction/Pickup Roll → Vacuum Box/Piping → Doctor System → Roll Surface → Operating Parameters

The purpose is not simply to restart the machine as quickly as possible, but to identify which condition actually caused or contributed to the break.

Changing several parameters together makes this much harder.

A systematic process provides better information for the next occurrence and helps build a more useful maintenance history.

Huatao Group

Huatao Group supplies paper machine clothing, rolls, dewatering equipment and doctoring components for pulp and paper mills.
Website: papermakingtech.com
Email: market@huataogroup.com
WhatsApp / WeChat: +86 18033763037

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