how to clean the press felt

1. Inspect the roller bearings to ensure they rotate freely; check the hardness and degree of aging of the roller shell. 2. Ensure that the supporting surfaces are free of abrasive debris. 3. Check the straightness of the rollers and the alignment system. 4. Verify that the pulp slurry contains no abrasive fillers. 5. Ensure that any shower pipes are free of sand or other abrasive substances. 6. Control dewatering on the wire section to reduce traction load and minimize abrasive wear; lower the vacuum levels to prevent wear on the forming fabric as it passes over the vacuum boxes. 7. Check the settings of the forming boards, ensuring sufficient clearance to achieve uniform, minimal dewatering at the breast roll.8. Proper maintenance-along with the correct selection and adjustment of dewatering and forming elements-can significantly reduce abrasive wear caused by traction. 9. Streaking in the paper sheet is typically caused by solid deposits on the forming boards or other stationary elements; these worn areas exhibit poorer dewatering performance than surrounding areas, resulting in visible streaks on the finished paper. 10. Check the load distribution between the couch roll and the drive roll.

Washing of Plugged Press Felts: During the papermaking process, fine fibers, fillers, sizing agents, pigments, and other substances present in the pulp-as well as impurities in the process water-can easily adhere to the press felts. This causes the felt pores to become clogged, thereby compromising the felt's absorbency and dewatering efficiency. Consequently, the effective washing of press felts is a critical factor in ensuring optimal dewatering performance in the press section and extending the service life of the felts. This is particularly important for needled felts; due to their long, dense surface nap and the small interstitial spaces between fibers, they are highly susceptible to clogging-and once contaminated and plugged, they are notoriously difficult to clean thoroughly.According to industry surveys, over 90% of felt replacements are necessitated not by abrasive wear, but by clogging. This underscores the fact that the key to maximizing felt performance and longevity lies in effective washing.
Felt washing methods generally fall into two categories: continuous washing performed during normal production, and washing performed during machine shutdowns. 1. High-Pressure Needle Shower Cleaning: This method utilizes water jets at pressures ranging from 1.47 to 2.45 MPa. Its advantages include minimal water consumption and the ability to reduce the need for chemical cleaning agents by leveraging the forceful impact of the high-pressure water jets. Its primary disadvantage, however, is the potential for significant mechanical damage to the felt structure. The cleaning surface corresponds to the side of the felt that contacts the paper web. A washing water temperature of approximately 50°C is recommended to enhance the descaling effect; however, the specific temperature may be adjusted based on actual production conditions.⑵. Intermittent On-Machine Chemical Cleaning: For intermittent cleaning, detergents, hydrochloric acid, or alkaline solutions may be used. These agents should be prepared to an appropriate concentration and applied across the entire width of the press felt. After allowing the concentrated chemical solution to act for the prescribed duration, use clean water to thoroughly rinse away any chemical residues remaining within the felt.
When using acid for cleaning, the concentration of the dilute acid must not exceed 5%; otherwise, exposure to a highly concentrated acid solution will cause the nylon fibers to stiffen, thereby impairing the press felt's dewatering performance.⑶. Continuous On-Machine Cleaning: This method ensures that the felt remains in an optimal state at all times, thereby maximizing papermaking efficiency. Continuous on-machine cleaning is considered the most effective cleaning method available.
Its primary objective is not merely to remove accumulated contaminants that have already clogged the felt, but rather to proactively remove impurities before they adhere to-or immediately as they begin to penetrate-the felt structure. The concentration of cleaning agents used in continuous cleaning applications typically ranges from 0.01% to 0.06%.
Although the cost of continuous cleaning agents is relatively high, the method offers significant advantages: it extends the service life of the press felt, consistently maintains the press felt in peak operating condition, helps reduce material consumption, minimizes paper web breaks and associated losses, and ultimately enhances the overall quality of the finished paper product.