The press roll is the main component of the press. There are many types of press rolls. The press section of the old paper machine uses a flat press roll. With the increase of the speed of the paper machine, the vacuum press roll is used, and then the grooved press roll is developed. In the 1970s, the blind hole was researched and developed. Pressure roller and controllable medium and high roller.
After absorbing the advantages of the vacuum press roll, the grooved roll and the blind hole roll, several other new press rolls appeared. In the 1980s and 1990s, wide nip presses and shoe presses for high speed paper machines were developed. Until now, researchers have not stopped developing new press rolls. The purpose of developing new press rolls is to improve dewatering efficiency, improve the quality of the paper sheets, and reduce the adverse effects of the press on the paper industry.
Classification of press rolls:
Flat roll press
Both plain and positive presses are pressed with a flat roll. The structure of the flat roll press, the upper roll is a stone roll, the lower roll is a rubber roll, and both rolls have a smooth and smooth roll surface.
Stone rolls are a common flat press roll. Stone rolls are usually made of materials that are easily peeled off from paper, mostly using granite. The main feature of granite is that it has many tiny pores in its structure, which stores a certain amount of air, which is beneficial to the peeling of wet paper sheets. Its disadvantages are high cost and easy brittleness. During operation, if the rotation speed is too fast or the load is too large, the shaft head may be overheated, causing axial or annular cracks on the surface of the stone roller. When the high temperature expansion is serious, the shaft core may fall off.
With the increase in the speed of paper machines, the limitations of granite rolls are becoming more and more obvious. Most of today, artificial stone made of rubber and quartz sand is used instead of natural granite as the upper pressure roller.
The lower roll of the flat roll press is a rubberized cast iron roll. In addition to providing the corrosion resistance of the press roll, it is more important to provide good elasticity, to ease the pressing action of the upper press roll on the wet paper and the felt, thereby prolonging the life of the felt and reducing the “pressing” of the wet paper. The elastic under-sealing roller can also impart good contact and uniform dehydration between the two rolls and compensate for the high error in the lower press roll.
The rubber hardness of the rubber roller when producing general paper is usually 70 to 90 Shore hardness. The hardness of the rubber rollers used in each press of the press section increases as the pressure of each press line increases, and the hardness of the rubber roller also increases accordingly.