paper-making forming fabrics
Paper-making dewatering fabrics (also known as paper-making forming fabrics) are critical and costly consumables on paper machines; their proper usage directly impacts paper quality, production efficiency, and operating costs. The following are detailed precautions for use, covering every stage from installation and operation to maintenance. I. Installation Precautions (Of Paramount Importance) Unpacking and Inspection: Careful Unpacking: Use unpacking pliers; strictly avoid using knives or other sharp tools that could scratch the fabric. Verify Information: Check the fabric model and specifications (length, width, circumference ) to ensure they match the order details and the requirements of the paper machine. Visual Inspection: Carefully examine the fabric surface for any obvious manufacturing defects, damage, stains, or creases. Installation Environment: Site Cleanliness: Ensure the installation area is clean and tidy; remove hard objects, welding slag, and other debris from the floor and equipment to prevent punctures or abrasion of the fabric. Adequate Space: Prepare a sufficiently spacious area to facilitate the unfolding and hoisting of the fabric. Installation Operations: Proper Hoisting: Use hoisting slings that are sufficiently wide and soft (the use of steel wire ropes is strictly prohibited); lift the fabric in a balanced manner to prevent excessive localized stress that could cause deformation or damage. Smooth Unfolding: Lay the fabric flat on the floor or on a dedicated support stand, ensuring it unfolds naturally without any forceful pulling or twisting. Verify Direction: Pay close attention to the fabric's running direction markings (usually indicated by arrows) to ensure correct installation. Coordinated Effort: Ensure multiple personnel work together under unified command to slowly and smoothly guide the fabric onto the paper machine. Verify that the fabric passes smoothly over all rollers, suction boxes, and other components without any scraping or collision. Use of Guide Mechanisms: Properly utilize fabric guide mechanisms to prevent the fabric from drifting off-center and sustaining damage. II. Operation and Commissioning Precautions Initial Tensioning: Low-Speed Tensioning: Start the paper machine at a low speed (e.g., "crawl speed"), then slowly and uniformly apply tension to the fabric. Avoid Over tensioning: The initial tension force should not be excessive; adhere to the recommended values provided by the equipment manufacturer or the fabric supplier. Over tensioning shortens the fabric's service life and increases the operational load. Drift Control: Timely Correction: During low-speed operation, closely monitor the fabric's running trajectory and use correction rollers to make fine adjustments, ensuring the fabric runs stably in a centered position. Avoid Abrupt Adjustments: When adjusting the corrector rolls, proceed slowly and in small increments to prevent sudden changes that could cause the wire to wrinkle. Uniform Dewatering: Vacuum Control: The vacuum level within the vacuum boxes should be adjusted gradually from low to high to ensure uniform dewatering and prevent localized, severe wear on the wire surface. Inspect Dewatering Elements: Ensure that the surfaces of the table rolls and vacuum box covers are flat, smooth, and free of wear or grooves. III. Normal Operation and Maintenance Considerations-Rinsing and Cleaning: High-Pressure Rinsing: The wire must be rinsed periodically and effectively using high-pressure fresh water. Particular attention should be paid to the contact side (the side in contact with the pulp slurry) and the running side (the side in contact with the dewatering elements) to remove fibers, fillers, and sticky substances clogging the wire mesh. Rinsing Pressure and Angle: Adjust the angle and pressure of the high-pressure shower nozzles to achieve optimal cleaning results without damaging the wire. Periodic Chemical Cleaning: Conduct periodic online or offline chemical cleaning to dissolve sticky substances that cannot be removed by water rinsing alone. Tension Control: Maintain Appropriate Tension: While meeting process requirements, aim to utilize the lowest possible operating tension. Excessive tension is a primary cause of premature fatigue failure in the wire. Avoid Mechanical Damage: Prevent Material Buildup: Promptly remove foreign objects from the pulp slurry to prevent them from becoming lodged between the wire and the rolls, which could lead to wire deformation or tearing. Equipment Maintenance: Periodically inspect all components in contact with the wire-such as vacuum box covers, table rolls, and guide rolls (particularly the couch roll and drive roll)-to ensure their surfaces remain smooth and flat, and are free of burrs, damage, or accumulated deposits. Shutdown Procedures: During planned shutdowns, release the wire tension and maintain slow-speed rotation or periodically "crawl" (jog) the wire to prevent deformation caused by prolonged static pressure at a single location. For extended shutdowns, the wire should be removed, cleaned, and stored properly. Process Control: Pulp Quality: Ensure the quality of pulp screening to minimize impurities. Chemical Additives: Carefully monitor the addition of fillers and chemical aids (such as defoamer and biocides) to prevent them from forming sticky deposits that could clog the wire mesh. IV. Common Problems and Prevention-Wrinkling: These issues are often caused by uneven tension, improper alignment,non-parallel rollers, or localized wear. Prompt adjustment is required to identify and resolve the underlying cause. Wear: Inspect the surface condition of all contact components to ensure they remain smooth. Clogging: Intensify flushing procedures and optimize the pulp and chemical systems. Longitudinal Tearing: Immediately shut down the equipment to locate and remove any hard objects lodged within the wire, and repair any mechanical defects.
