Paper Machine Drying Fabric FFI Ratio Design
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Solution Overview
Problem
Existing drying fabrics in paper machines face challenges with cleanability on the paper side and abrasion resistance on the machine side, leading to impaired drying effects and reduced paper quality due to deposits and shortened service life.
Innovation Solution
The design of the drying fabric increases the ratio of Fabric Fineness Index (FFI) on the machine side to the paper side by enhancing the contact area and number of contact points on the machine side, achieved through increased warp knuckles, longer warp thread floats, and more weft threads, while maintaining sufficient contact area on the paper side for effective drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the contact area on the machine side is increased to improve abrasion resistance, then the service life is extended, but the cleanability on the paper side deteriorates due to deposits accumulation
Solution Approach 1:
The patent applies different Fabric Fineness Index values to different sides of the dryer fabric. The machine side has a higher FFI (≥1.25 times the paper side) to provide increased contact area and abrasion resistance, while the paper side maintains a lower FFI to reduce deposit accumulation and improve cleanability. This local differentiation of fabric properties resolves the contradiction between durability and cleanability.
2Duration of action of stationary object
If the contact area on the machine side is increased to improve abrasion resistance, then the service life is extended, but the drying effect on the paper side deteriorates due to reduced contact area
Solution Approach 1:
The patent optimizes the FFI ratio to ensure the paper side maintains sufficient contact area (lower FFI) for effective drying, while the machine side has increased contact area (higher FFI) for abrasion resistance. The minimum ratio of 1.25:1 ensures both requirements are met simultaneously, resolving the contradiction between drying performance and service life.
3Reliability
If the contact area on the paper side is increased to improve drying effect, then the heat transfer is enhanced, but the cleanability deteriorates due to increased deposit accumulation
Solution Approach 1:
The patent optimizes the paper side FFI to provide sufficient contact area for effective drying and heat transfer, while keeping it lower than the machine side FFI (ratio ≥1.25:1) to minimize deposit accumulation. This local optimization ensures both drying performance and cleanability are achieved.
4Duration of action of stationary object
If the fabric weave is optimized for abrasion resistance on the machine side, then the service life is extended, but the fabric complexity increases
Solution Approach 1:
The patent achieves improved abrasion resistance by changing the FFI parameter on the machine side to be at least 1.25 times the paper side FFI. This parameter optimization, rather than complex structural modifications, extends service life while maintaining manageable fabric complexity. The approach uses quantitative parameter adjustment rather than qualitative structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design improves cleanability and extends the service life of the drying fabric by allowing faster and more thorough removal of deposits, while maintaining effective drying performance and paper quality.
Implementation Method 1
The paper web is then fed to the drying section, in which the paper web is guided over heated drying cylinders, as a result of which the paper web is thermally dewatered
Data Source
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AI summary
The invention relates to a drying screen for paper machines with a fabric consisting of woven threads (2 to 5; 7 to 10; 12 to 15; 22 to 25; 27 to 30; 32 to 39), which has a paper side and a machine side, each having contact points, contact surfaces (16, 17; 40, 41) formed by the woven threads (2 to 5; 7 to 10; 12 to 15; 22 to 25; 27 to 30; 32 to 39), which sum to a total contact area on the paper side and on the machine side, with a contact area fraction of the total area, wherein a Fabric Fineness Index for the machine side (FFI-MS) and a Fabric Fineness Index for the paper side (FFI-PS) can be calculated from the contact area fraction, the number of contact points and the fabric thickness of the drying screen according to the following formula: FFI = contact area fraction % × number of contact points per cm² tissue thickness mm and wherein the ratio of FFI-MS to FFI-PS is at least 1.25:1, preferably at least 1.5:1.