Did Your Paper Machine Occur Paper Blowing?

Paper Sheet Blowing

Blowing refers to the phenomenon where air entrained by the pulp or felt partially accumulates between the felt and the paper sheet, forming bubbles that cause the paper sheet to bulge or result in local delamination and blistering between wet paper sheet layers. It primarily occurs on the cylinder mould of multi-wire paper machines, at the entrance of the press nip, and in the dryer section.

Causes and Solutions of Bubble Formation:

1. There is a large amount of air trapped in the pores of new felt. Due to factors such as uneven surface, excessive air permeability, insufficient vacuum, and high moisture content in the new felt, it cannot meet the requirements of normal production, making it easy for bubbles to form between the paper sheet and the felt at the entrance of the press zone.

2. During the production of board paper, the beating degrees of the pulp materials in each layer vary greatly, leading to differences in the interlayer bonding.

3. Improper adjustment of the pressure on the couch roll line; improper control of the approach flow amount on each wire, the liquid level of the sizing material on the wire, and the water level difference inside and outside the wire; excessively low vacuum degree in the vacuum suction box, resulting in significant differences in moisture content among the wet paper sheets formed between the approach flow layers, thus causing bubbling in the wet paper sheets.

4. Local dirt on the wire section and felt causes poor local dewatering and poor air permeability; when the doctor blade of the couch roll is partially blocked, or the water retaining cloth is uneven or has holes, the pressed water may exhibit moisture regain.

5. The angle of the wet paper sheet before entering the press is incorrect, and the eccentricity and linear pressure adjustments of each press are not correct.