What are the causes of paper breaks in the dryer section of a paper machine?

We all know that the wet end of a paper machine is easy to break. Therefore, the water filtering capacity of the pulp and the dewatering capacity of the paper machine itself have always been the focus of people’s attention. Let's take a look at the possible causes of paper breaks in the dryer section. The wet paper entering the dryer section has a dryness of over 32% and has a certain strength. But there will be broken ends in the drying part.

The reasons for the broken head can be the following main aspects:

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

For example, when the moisture content of the paper is too high and the knots of the dry cloth are not regular, it is easy to press knots on the paper, causing weak points and breaking the paper; the paper is folded in the press part, and in severe cases, it is in the late drying stage. When the tension is high, there will be broken ends, or there are horizontal cracks and holes on the wet part of the paper, which will also cause the drying part to break; when the basis weight of the paper fluctuates, the drying speed will be inconsistent, and the basis weight of the paper will be inconsistent. Small parts dry quickly, so drying is easy to cause the paper sheet to shrink too much, and breakage occurs at the end of the drying. When this happens, it should be solved for specific reasons.

2. Excessive tension of the paper causes end breakage

There are two reasons for excessive paper tension:

One is that the transmission ratio between each group of dryers is too large, and it often breaks when the paper is intensively received in the later stage of drying, or there are problems with the transmission components, such as belt slip, irregular gears, etc., which cause tension fluctuations. Will cause broken heads. Therefore, it is important to pay attention to adjusting the tension between the drying cylinders and to pay attention to the working decorations of the transmission at all times.

The second is that the drying cylinder temperature is too high, and the above-mentioned severe sticking of the cylinder will occur in the early stage of drying, and the paper will be over-dried during the drying process, which will cause the paper to shrink sharply and cause broken ends. Sometimes the end breakage takes a long time, and the temperature of the cylinder rises due to the long time no heat transfer to the paper sheet. This kind of end breakage will also occur when the paper is transferred again. Therefore, the drying department "watches the steam" should always pay attention to the changes in the steam pressure and the temperature of the dryer.

3. The debris between the dryers causes the paper to break

When there is a broken end, the damaged paper that has not been cleaned is easy to be broken when the paper sheet passes between the dry cloth and the dryer; when the scraper is not tight and the paper is leaked, it is easy to stick to the edge of the paper , Firstly damage the edges of the paper and cause breakage in the later stage of drying; some viscous substances brought in from the damaged paper in the paper material will also stick to the cylinder surface and cause breakage. Therefore, after breaking the ends, pay attention to using compressed air to clean up the damaged paper. At the same time, always pay attention to removing the paper foam at the scraper and pay attention to the working condition of the scraper.

4. Broken ends caused by dry cloth

Pleating the dry cloth will cause the paper sheet corresponding to the pleat to be poorly dried due to poor contact with the drying gap, causing it to break between the drying cylinder and the calender; the dry cloth joint is rough, which is easy to crush the paper sheet Broken ends; oil and resin sticking to the dry cloth will break the paper; even if the canvas edge is opened and shaken, it will open the edge of the paper and cause the full width to break. Therefore, in normal work, you should always pay attention to observe the working conditions of the dry cloth, and solve the problem in time.

The above is the cause of paper breaks in the dryer section of the paper machine.