High Pressure Spray Added to The Back of The Press Felt

Is it feasible to install a high-pressure spray system on the non-contact surface of paper making press felts? Is it an important measure to achieve deep cleaning and maintain optimal felt performance? Sun Hong will analyze this from several aspects below.

Why Install High-Pressure Spray System on The Back of Paper Making Press Felt?

During the production and operation of press felts, dirt can be present in two places: on the surface and deep inside. The surface, which is the contact surface with the paper, often contains fibers, fillers, and adhesives. Fine fillers, adhesives, and oil stains are forcibly pressed into the deep fiber structure of the felt under vacuum suction. Simply rinsing the front side cannot completely remove this deep-seated dirt. Installing a high-pressure spray system on the back of the press felt can effectively solve the problem of deep contamination.

Methods and Main Functions of Cleaning Press Felts

Front Side High Pressure Spray:

This spray is applied from the paper surface towards the inside of the press felt, removing surface slurry and most loose impurities, maintaining a smooth surface. The cleaning direction is the same as the direction of impurity penetration. It cannot effectively wash impurities embedded inside the felt and may even cause them to become more compacted.

Back Side High Pressure Spray:

This spray is applied from the back of the press felt towards the paper surface (reverse impact), loosening and flushing out deeply embedded impurities (fillers, adhesives), restoring the felt’s porosity and air permeability. However, precise control is required; otherwise, it may affect the paper sheet and cause nozzle to disperse.

Advantages of Adding High Pressure Spray on The Back of The Press Felt

• Significantly improves the air permeability of the paper making press felt: This part is crucial for the pressing section. After the deep blockages are removed, the internal void channels are restored to unobstructed flow, and the dehydration efficiency is greatly improved.
• Stabilizes paper moisture content: Maintaining stable and efficient dewatering performance means more stable paper dryness in the press section, laying the foundation for reduced energy consumption in the subsequent drying section.
• Extends the lifespan of the paper felt: Effectively extends the lifespan by 30% or more. Deep contaminants accelerate fiber wear and fatigue; regular deep cleaning prevents the felt from hardening and losing elasticity.
• Improves paper quality: A clean felt surface is uniform, reducing felt marks, holes, and other problems.
• Reduces downtime: The press felt remains in good condition for longer during operation, reducing the frequency of downtime and replacement due to blockages.

Precautions and Installation Plan for Paper Making Press Felts

While installing a high-pressure back spray system offers good benefits, it requires more meticulous design and management; otherwise, it may backfire.

• Selection of Installation Location: Typically, the press felt should be installed before leaving the vacuum suction box or after the vacuum rollers, before entering the next press zone. Additionally, make sure the back of the press felt is touchable, and that the wastewater flushed out after spraying has a suitable collection and discharge path, preventing splashing onto the paper, other critical parts, or equipment.
• Control of Spray Pressure and Flow Rate: Higher pressure is not always better. Excessive pressure can damage the press felt base fabric, and in severe cases, may even penetrate the felt and splash onto the paper edge, causing paper breakage. The pressure needs to be adjusted according to the press felt’s weight, material, condition, and machine speed. Generally, it should be slightly lower than or equal to the pressure of the front-side cleaning spray. A pressure control system can also be used for flexible application.
• Nozzle Type and Angle: Needle nozzles are typically used, with a oscillating mechanism for slow, reciprocating motion to avoid creating fixed “water lines” on the press felt, achieving uniform, full-coverage cleaning.
• Water Quality: High-pressure water on the back should be clean water, not plain water. Plain water contains impurities, which may be flushed deep into the press felt during reverse rinsing, causing secondary contamination.
• Intermittent Use: Continuous operation is not required. An “intermittent mode” can be used, for example, running for 30 seconds per minute. This achieves the cleaning effect while reducing water consumption and impact on the press felt. (When changing materials or producing paper types prone to adhesive residue, the cleaning frequency and intensity on the back can be increased.)

Adding a spray system to the back of the paper making press felt is feasible. It does not replace front cleaning, but works in synergy to ensure efficient and stable operation of the paper machine, improve production quality, and reduce press felt consumption.