VAC dryers are generally vacuum cylinder.The main function of the VAC cylinder is to make the drying section change from original upper and lower felts to one felt. The two-layer dryer paper is in an open state when running between the two dryers, without any support. When it is wet, the strength of the paper is relatively small, and the paper breaks easily.After the VAC cylinder is arranged, the paper will always run with the blanket. With entrustment, paper breaks and paper defects can be reduced. Generally, VAC cylinders are arranged in front of the drying section when the speed exceeds 400 meters.
Another advantage is that it is easy to handle if the paper breaks. When a paper break occurs, the damaged paper of the two-layer dryer will fall between felt and dryer, and sometimes wrap around guide roller, damaging blanket and making it difficult to handle. After arranged VAC cylinder,damaged paper falls directly to ground, and it can also be transported directly to the pulper with a conveyor belt. Therefore, high-speed paper machines generally adopt a single row arrangement of VAC cylinders.
