Have You Ever Met These Problems While Using The Press Felt

In the papermaking process, press felt plays an important role in maintaining paper quality and preventing paper defects. Therefore, proper use of press felt is essential for stable paper machine operation. During operation, however, press felt may encounter various problems that can affect its running stability and service life. This article discusses some press felt problems you may encounter and overlook.

Press Felt Fiber Loss

Press felt fiber loss refers to the shedding of surface fibers from the press felt during operation, caused by mechanical stress, external forces, or wear.

This phenomenon reduces the lifespan of the press felt. It also affects the quality of the final paper sheets and the stability of the paper machine operation.

Paper Machine Spare Parts Wear

During the operation of the press felt, if the surface of the paper machine spare parts in close contact with the felt, like guide rolls, is rough or worn. Or, if the rollers’ rotation speed is not synchronized with the felt, uneven friction will be applied to the felt, resulting in shedding of the felt fibers.

Chemical Damage

If the press comes into contact with strong acids, strong alkaline cleaning agents, or other unsuitable chemicals during the cleaning process, it will corrode the felt fibers, causing them to become brittle and hardened, reducing the fiber bonding strength, and ultimately leading to the shedding of the pile.

Water Jet Damage

Improper operation of the high-pressure spray system on the paper machine can also cause the press felt to lose its fibers.

For instance, excessive spray pressure, incorrect spray angle, nozzle blockage, dry abrasion during spraying, or poor water quality can all damage the surface fibers of the press felt, accelerating fiber shedding.

Improper Press Felt Operating Parameters

The running tension of the press felt has a significant impact on its service life.

If the operating tension is too high, the press felt fibers are under significant stretch for a long time. And then it can easily cause felt fatigue and wear, accelerating the shedding of fibers.

And if the tension is too low, the press felt is also prone to problems such as misalignment and wrinkles, causing abnormal friction in local areas, leading to fiber loss.

Press Felt Design Flaws

During the operation of the press felt, problems such as pulp fragments entering the pressing zone, pulp entanglement on the guide roller surface, blanket weaving defects, and unreasonable design of the stretching roller can all lead to uneven stress on the felt in some areas, which will aggravate wear in some areas and eventually cause shedding.

Press Felt Standard Line Deformation

Press felt standard lines are an important reference for judging the operating status of felts. When the standard line changes abnormally, it usually means that there is a problem with the lateral force on the press felt or its operating condition.

During press felt use, the deformation of the standard line can be roughly divided into the following categories: the standard line is slanted to the left or right, the standard line is convex in front, the standard line is concave in back, the standard line is S-shaped, and other irregular deformations.

Causes of Press Felt Standard Line Misalignment

• The tension on the two sides of the papermaking press felt is uneven, with one side being greater and the other less.
• The linear pressure on both sides of the press roller is inconsistent.
• The eccentricity of the two sides of rollers, such as press rollers, flat rollers, and dewatering rollers, is inconsistent.
• The height setting of the press roller is unreasonable.
• The slurry residue on the roller surface was not cleaned in time.
• The rollers may be worn or misaligned, or the bearings may be damaged and not replaced in time.

How to Correct Press Felt Standard Line Deformation

If the standard lines of the press felt become deformed, adjustments should be made promptly to avoid further affecting the felt’s dehydration performance and dimensional stability.

If left untreated for a long time, it may cause the felt to wrinkle or even fold, affecting the stability of the paper machine operation.

It is important to note that when adjusting the standard line of the press felt, you should use the crawling speed to make gradual adjustments to prevent the felt from shifting or folding due to too rapid a change.

 

Press Felt Edge Serpentine Movement

Serpentine movement of the press felt edge involves continuous side-to-side movement during operation, resulting in an unstable running path.

The causes of a press felt swaying in a serpentine manner usually include problems with the quality of the felt itself, uneven cutting edges, and inconsistent lateral tension.

Serpentine movement of the press felt edge can destabilize felt running on the paper machine, resulting in sheet threading difficulties and paper breaks. 

Continuous edge movement can also accelerate wear on other paper machine components, including vacuum boxes, vacuum rolls, and felt guiding systems.

The key to reducing press felt serpentine movement at its source is to choose felts manufactured by marking a reference line and cutting the edges precisely along the line.

Precise edge trimming improves the smoothness of the press felt edges, making the felt run more stably and extending its service life.