Stationary Transfer Device for Pulp Web in Extended-Nip Press
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Solution Overview
Problem
Conventional methods for transferring a pulp web in paper or tissue machines with low basis weight are prone to breaks and production downtime due to the web's low wet strength, especially during unsupported transfers in extended-nip press units, where the transfer area is often lengthy and unreliable.
Innovation Solution
A method for supported, closed transfer of the pulp web using a stationary transfer device within a clearly defined area, where the pulp web is transferred from a revolving press belt to a transfer fabric assisted by suction, with a short and precisely defined transfer zone, and the press belt is stabilized using pneumatic pressure and supporting elements to minimize friction and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pulp web is transferred unsupported from the press belt to a roll or fabric in the extended-nip press unit, then the transfer process is simpler, but the web breaks frequently due to low wet strength
Solution Approach 1:
A stationary transfer fabric is introduced as an intermediary medium between the press belt and the suction roll. The transfer fabric is fed onto the suction roll and contacts the press belt in a defined transfer zone, enabling reliable web transfer through a mediating surface that provides both support and friction for effective transfer while preventing web breaks
Solution Approach 2:
The mechanical unsupported transfer system is replaced with a supported transfer system using a stationary transfer fabric on a suction roll. The suction force creates a controlled mechanical environment that supports the web during transfer, replacing the unreliable direct mechanical contact between press belt and receiving surface
2Ease of operation
If a lengthy transfer area is used for web transfer, then the transfer zone is more gradual, but the web is more prone to breaks due to extended exposure and handling
Solution Approach 1:
The transfer fabric is designed with specific local properties in the transfer zone: a rougher surface structure provides increased friction for effective web transfer, while the localized application of suction force only in the defined transfer area creates optimal transfer conditions without extending the web's vulnerable exposure area
Solution Approach 2:
The transfer process is segmented into a clearly defined transfer zone where the transfer fabric contacts the press belt, separated from other process areas. This segmentation concentrates the transfer function in a specific location, reducing the overall length of the transfer area while maintaining effectiveness through focused design elements
3Reliability
If the press belt is not stabilized in the transfer area, then the friction and contact pressure are higher for better transfer, but the press belt wear and energy consumption increase
Solution Approach 1:
Pneumatic pressure is applied to stabilize the press belt in the transfer area, dynamically adjusting the belt's physical state. This parameter change allows the belt to maintain optimal contact characteristics for transfer while reducing mechanical wear and energy consumption through air support that minimizes friction and stabilizes the belt position
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
Ensures reliable web transfer with reduced risk of damage and downtime by maintaining a short, defined transfer area and applying suction to the transfer fabric, while stabilizing the press belt to enhance transfer efficiency and service life.
Implementation Method 1
The transfer fabric is fed onto a suction roll or a stationary transfer device, to which suction is applied, and which receives the pulp web in a transfer area
Data Source
AI summary
A method for treating a pulp web in a paper or tissue machine with an extended-nip press unit. This extended-nip press unit includes a shoe press roll with a revolving press belt and a backing roll, where the pulp web is dewatered in the extended press nip between the backing roll and the press belt and where the pulp web is carried on the revolving press belt of the press roll after the extended press nip to a transfer fabric that receives the pulp web. The transfer fabric is guided over a stationary transfer device in the transfer area. A corresponding device for treating the pulp web.