Can Press Felt Cause Paper Breaks in the Paper Machine Press Section?

When paper breaks in the press section of a paper machine, we usually think about where the break is. Whether the press felt is off-center or the vacuum level is too low are all important operations, but it is easy to make premature judgments based on a single phenomenon. A paper breakage in the press section does not necessarily mean that there is a problem with the pressing section equipment. The press felt may not be off-center, but that does not mean that dehydration and transfer are normal. A low vacuum value cannot be directly equated with press felt blockage. The best approach is to map the break location, press felt condition, and vacuum fluctuations onto a unified timeline, then trace back while considering the sheet’s behavior at the time.

Where Exactly Does The Paper Break Occur?

Did the paper break before suction, fall during suction, or break after entering the pressing section? Does the break originate from the operating side, the drive side, or the center? These factors can all influence the direction of the investigation.
If the paper is soft or cracked at the edges before it is sucked in, check the wire section dehydration and wet paper strength first. If the paper sheet does not adhere to the press felt after leaving the mesh section, or if it adheres but drifts away, both suction displacement and the condition of the press felt need to be monitored. If the paper has entered the pressing zone steadily but breaks later, it is necessary to check the pressing zone, traction, and transmission operation.

A Properly Tracking Press Felt May Not Always Be in Good Condition

Assessing press felt condition requires looking beyond mere positioning; one must also check for creases, fuzzing, wear, seam irregularities, edge damage, and frequent corrective adjustments. It is also necessary to consider the paper’s performance, such as whether the paper transfer is stable, whether the press section inlet is loose, whether it is peeling or wrinkling, and the state of the paper after pressing. Even if the press felt does not show obvious deviation, the water permeability and drainage may have deteriorated. If the vacuum level gradually decreases before the paper breaks, accompanied by paper dehydration or deterioration in transfer performance, the press felt and its related vacuum system should be checked first. However, a drop in vacuum does not automatically indicate press felt plugging; issues could also stem from suction boxes, piping, seals, drainage systems, or measurement signals, all of which require systematic verification.

Vacuum Readings Must Match The Actual Situation On Site

When reviewing the vacuum, do not just observe one value. Observe the continuous decrease, short-term fluctuations, and changes after paper breakage. At the same time, check the operation of other relevant measuring points, pumps and pipelines, as well as the drainage and paper condition on site.
If the vacuum trend is stable, but the paper transfer is obviously unstable, it cannot be ruled out that the measuring point position is inappropriate, there is a problem with the instrument signal detection, or the vacuum is not effectively applied to the paper. Conversely, if the vacuum reading fluctuates but the paper movement on-site does not change accordingly, it cannot be concluded that the paper breakage is caused by the vacuum alone. The order in which the trends change is crucial: if the vacuum changes first and the paper condition changes later, or if the vacuum changes only after the paper breaks, the direction of the investigation will be different.

Connect The Observations of The Paper Break Location, Press Felt and Vacuum Degree

• Determine the paper break location, record whether the paper break occurred before suction, during transfer or near the pressure zone, and indicate which side or which part has the problem.
• Review the condition of the sheet prior to the break, checking for signs of softening, edge loss, wandering, wrinkling, or localized tearing.
• Check the condition of the press felt. Observe for deviation, wrinkles, joints, wear, cleaning and drainage conditions, and pay attention to whether the calibrator operates frequently.
• Compare with the vacuum trend to confirm the time of change, check the relevant equipment and measuring points, and determine whether it is synchronized with the paper abnormality.
• Examine the draw and equipment status in the press section; if no significant anomalies are found regarding the press felt, vacuum, or sheet transfer, verify speed relationships, draw settings, the roll arrangement, and drive signals.

Post-adjustment Verification

After making checks and adjustments, do not simply verify that the paper sheet has been re-established; you must also observe the press felt position, vacuum trends, sheet displacement, and the stability of the press section operation. Confirm that no alarms recur and determine whether any temporary adjustments need to be reverted. If adjustments are made simultaneously to vacuum, traction, and machine speed, it becomes difficult to identify which specific measure was effective, even if the sheet break is temporarily resolved. Whenever conditions permit, verify each item according to the machine’s operating procedures and record the phenomena and trends observed before and after the adjustments. If equipment alarms persist or conditions continue to deteriorate, manage risks in accordance with on-site protocols; do not simply keep increasing the draw or forcing the machine to run in an attempt to maintain operation.

The key to dealing with paper breakage in the paper machine press section is not to quickly find a “point of responsibility,” but to analyze and reconstruct the process by which the paper breaks. Breakpoints tell us where to start investigating, press felt and vacuum system provide clues, and trends help determine which events occurred first and which were the result. This way, it’s less likely that seemingly abnormal parameters will be mistaken for the real cause during the investigation.