What are the common problems with an open headbox

What are the common problems with an open headbox
Open flow boxes may encounter various common problems in the papermaking process, which mainly involve equipment performance, stability, and pulp quality. Here are some common problems and their possible causes:
1、 Uniformity issue
Large horizontal quantitative difference and vertical quantitative fluctuation: This may be caused by stability issues in the short cycle system and discharge valve, insufficient supply of compressed air in the pulse attenuator, or unstable liquid level in the headbox. In addition, dirt in the flow area or lip area of the slurry may also cause this problem.
Large banner fluctuation: Despite the automatic adjustment of the banner, the banner fluctuation is still significant, which may be caused by dirt in the pulp flow area or lip area, incorrect calibration between the banner control system's actuator and the paper banner detection system, or changes in the position of the paper edge.
2、 Fiber arrangement issue
Poor horizontal fiber arrangement: This may be caused by issues with the lip plate banner, imbalanced pressure in the main inlet pipe of the headbox, blockages in the edge flow channel or incorrect valve settings, or dirt in the slurry flow channel or lip plate area.
3、 Flow and pressure issues
The flow rate at the lip outlet is not within the calculated range: this may be caused by inaccurate flow control or malfunction of the flow measurement device.
Unreliable pressure and liquid level: This may be caused by interference from short cycles, unsuitable pressure, liquid level, and flow settings for product grade requirements, and actuators not within their operating range.
4、 Operation and maintenance issues
The inclination of the lip slurry spraying line may be caused by factors such as the deviation between the slurry baffle and the chest roller, or defects in the lip opening banner.
The flipping of the upper lip or headbox cannot reach the correct position or is trapped: this may be caused by transmission gear or motor failure, sticking at the connection of the upper lip, or the upper lip being blocked by the walls on both sides.
5、 Cleaning and hygiene issues
Scaling inside the headbox: This may be caused by the use of excessively hard water quality, incomplete cleaning, and other reasons. Long term non cleaning or improper cleaning can lead to severe scaling inside the pulp box, affecting the fluidity and uniformity of the pulp.
Bacteria and microbial growth: If the interior of the flow box is not cleaned for a long time or not thoroughly cleaned, it may lead to the growth of bacteria and microorganisms. This not only affects the quality of the pulp, but may also cause corrosion and damage to the equipment.
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To address the above issues, the following solutions can be taken:
Inspection and cleaning: Regularly inspect all components of the headbox to ensure that there are no blockages or contamination. If dirt or scaling is found, it should be cleaned promptly.
Calibration and adjustment: For issues such as large quantitative differences and fluctuations in banners, it is possible to check and calibrate the calibration between the execution mechanism of the banner control system and the paper banner detection system. At the same time, adjust the various parameters of the headbox, such as pressure, liquid level, flow rate, etc., to ensure that it meets the requirements of the product grade.
Repair and replacement: If damage is found to the transmission gear, motor or other components, timely repair or replacement should be carried out. At the same time, regularly inspect and replace vulnerable parts, such as sealing gaskets.
Optimization operation: Operators should receive professional training and master the correct operating methods and processes. At the same time, optimize operating parameters and processes to reduce equipment wear and failure.
Improving water quality: If the water quality is too hard and causes severe scaling inside the headbox, it can be considered to improve the water quality or use chemical cleaning agents for cleaning.
In summary, open flow boxes may encounter various common problems during the papermaking process. Regular inspections, cleaning, calibration, adjustment, maintenance, and replacement measures can ensure the normal operation of equipment and extend its service life. Meanwhile, optimizing operations and improving water quality also contribute to improving the quality and stability of pulp.