What Are The Reasons for Paper Breakage in The Dryer Section of Paper Machine?

What are the reasons for paper breakage in the dryer section of paper machine?

It is well known that the wet end of paper machines is prone to breakage, so the filtration capacity of pulp and the dewatering capacity of the paper machine itself have always been the focus of people's attention. Even if it enters the dryer end, there is still a possibility of paper breakage, which cannot be ignored. Let's take a look at the reasons why the dryer section paper end may cause paper breakage. The wet paper entering the dryer section has a dryness of over 32% and has a certain strength. But there may still be breakage in the dryer section.

There are several main reasons for the occurrence of paper breakage, including:

1. The strength of the paper itself is insufficient or there are weak points

For example, when the moisture content on the paper is too high and the dryer fabric knots are irregular, it is easy to press knot marks on the paper, causing weak points and resulting in paper breakage;

Paper sheets are folded in the press section, and in severe cases, they may break when the tension is high in the later stage of drying, or there may be horizontal cracks and holes on the wet section of the paper sheet, which can also cause paper sheet breakage in the dryer section;

When there is a fluctuation in the basis weight of the paper, the drying speed will be inconsistent. In areas with small basis weight, the drying process will be faster, which can lead to excessive shrinkage of the paper and breakage at the end of the drying process. When such a situation arises, it should be addressed based on the specific reasons.

2. Excessive tension on the paper causes breakage

There are two reasons for excessive paper tension:

One reason is that the transmission ratio between each group of dryer cylinders is too large, which often leads to breakage when the paper sheets are collected violently in the later stage of drying, or when there are problems with the transmission components, such as belt slippage, irregular gears, etc., causing tension fluctuations and also causing breakage. Therefore, it is important to pay attention to adjusting the tension between each dryer and to constantly monitor the working condition of the transmission.

The second issue is that the temperature of the dryer is too high, which can cause serious sticking of the dryer during the early stages of drying, resulting in broken ends. During the drying process, it can cause the paper to become excessively dry, causing severe shrinkage and resulting in broken ends. Sometimes the cutting time is even longer, as the cylinder temperature rises due to the prolonged lack of heat transfer to the paper sheet. This type of cutting can also occur during paper transfer operation. Therefore, the dryer section should always pay attention to the changes in steam pressure and temperature of the dryer.

3. The paper fragment between the dryer cylinders caused paper breakage

When there is a damaged paper that has not been cleaned up due to breakage, it is easy for the paper sheet to be padded and broken when it passes between the dryer fabric and the dryer; When the doctor blade is not tight and paper fragment  leaks, it is easy to stick to the edge of the paper, which first damages the edge and causes breakage in the later stage of drying; Some viscous substances brought in by damaged paper in the paper material can also stick to the cylinder surface, causing breakage. Therefore, after cutting the head, pay attention to cleaning the damaged paper with compressed air, and regularly remove the paper fragment at the doctor blade, and pay attention to the working condition of the doctor blade.

4. Broken paper ends caused by dryer fabric

Folding dryer fabric can cause poor drying of the paper corresponding to the pleats due to poor contact with the dryer, resulting in breakage between the dryer and the calender; The dryer fabric seam joint is rough and prone to crushing paper pages, resulting in broken paper ends; Dryer fabric with oil and resin sticking on it can break the paper sheet; Even if the dryer fabric edge is sewn and tossed back and forth, it can cause openings in the paper edge, resulting in full width breakage and other issues. Therefore, in normal work, attention should be paid to observing the working condition of the dryer fabric at all times, and any problems should be promptly resolved.