Do You Know The Function of Paper Machine Breast Roll ?

The Breast Roll on the Foudrinier Paper Machine

The breast rollis the first roll in the paper machine, located at the beginning of the wire section.

Its main role is to support the forming fabric. As the forming fabric moves around the breast roll, it changes direction, and after passing through the roll, the non-working side of the fabric becomes the working side. In many cases, the breast roll also plays a role in dewatering within the forming section, allowing some or most of the pulp that is spread onto the wire to lose moisture on the breast roll.

To ensure proper function, the breast roll must be rigid and have minimal deflection to prevent the forming fabric from wrinkling.

To reduce the load on the breast roll, it should be lightweight. Typically, breast rolls on small and medium-sized, low-speed paper machines are not very tall, while those on larger, high-speed machines are slightly taller.

Previously, breast rolls were commonly made from thin-walled steel tubes covered with either 3-4mm thick copper or 8mm thick rubber (Brinell hardness of 12-17 degrees).

Some were also covered with fiberglass ladles. These rolls are required to pass both static and dynamic balance tests.

To prevent fiber clumps from getting trapped between the breast roll and the forming fabric, a doctor blade made of HDPE, glass fiber, or epoxy resin is installed on the surface of the roll to clean it.

A water spray pipe is also placed between the breast roll and the lower lip plate to keep the roll surface clean. Usually, an extension plate is located behind the doctor blade, which helps direct the white water removed from the wire into the first white water tray.

The breast roll also contributes to dewatering, and the amount of water removed can be controlled by how the pulp flows onto the roll.

If the pulp stream lands directly on the breast roll, a significant amount of water is removed, which can slightly shape the paper. However, if the pulp is sprayed onto the forming board, the dewatering effect on the breast roll is less, and the shaping of the paper sheet is mainly controlled by the table roll or dewatering plate.

In modern high-speed paper machines that produce thin paper using free pulp, water-absorbing breast rolls are used for stronger dewatering.

In these cases, most of the water is removed by the breast roll. The dewatering process of the breast roll works in a similar way to that of the table roll.